Artificial Immune Systems (AIS) are intelligent algorithms derived on the principles inspired by human immune system. In this research work, electroencephalography (EEG) signals for four distinct motor movement of human limbs are detected and classified using Negative Selection Classification Algorithm (NSCA). For this study, a widely studied open source EEG signal database (BCI IV - Graz dataset 2a, comprising 9 subjects) has been used. Mel Frequency Cepstral Coefficients (MFCCs) are extracted as selected feature from recorded EEG signals. (...) Dimensionality reduction of data is carried out by applying two hidden layered stacked auto-encoder. Genetic Algorithm (GA) optimized detectors (Artificial Lymphocytes) are trained using Negative Selection Algorithm (NSA) for detection and classification of four motor movements. The trained detectors consist of four sets of detectors, each set is trained for detection and classification of one of the four movements from the other three movements. The optimized radius of detector is small enough not to mis-detect the sample. Euclidean distance of each detector with every training dataset sample is taken and compared with optimized radius of detector as a non-self detector. Our proposed approach achieved a mean classification accuracy of 86.39% for limb movements over 9 subjects with a maximum individual subject classification accuracy of 97.5 % for subject number eight. (shrink)

In biology, the ‘ecological orientation' rests on a commitment to examining systems, and the conceptual challenge of defining that system now employs techniques and concepts adapted from diverse disciplines (i.e., systems philosophy, cybernetics, information theory, computer science) that are applied to biological simulations and model building. Immunology has joined these efforts, and the question posed here is whether the discipline will remain committed to its theoretical concerns framed by the notions of protecting an insular self, an entity demarcated from (...) its environment, or will shift its focus of interest to a wider context. An ecological perspective emphasizes the interchange between the organism and its environment, the processing of information, and the regulation arising from responses to this larger context. Moving from the first attempts at modeling the immune system as a closed network, immunologists have joined the general interest in systems analysis, and that move might portend a significant shift to an open, more holistic consideration of immune regulation. *Received December 2006; revised August 2007. †To contact the author, please write to: Center for Philosophy and History of Science, Boston University, 745 Commonwealth Ave., Boston, MA 02215; e-mail: [email protected]. (shrink)

Behavioral immune system describes psychological mechanisms that detect cues to infectious pathogens in the immediate environment, trigger disease-relevant responses and facilitate behavioral avoidance/escape. BIS activation elicits a perceived vulnerability to disease which can result in conformity with social norms. However, a response to superficial cues can result in aversive responses to people that pose no actual threat, leading to an aversion to unfamiliar others, and likelihood of prejudice. Pathogen-neutralizing behaviors, therefore, have implications for social interaction as well as (...) illness behaviors and responses to health communications. In this study, we investigate how PVD influences conformity, attitudes to other people and to lockdown regulations through the lens of the Reinforcement Sensitivity Theory. RST describes personality in terms of biologically-driven approach and avoidance motivations which support personal goals. Participants from the United Kingdom public completed an RST personality questionnaire and then read either coronavirus morbidity-mortality statistics and current United Kingdom government lifestyle regulations, just the regulations, or no information at all. They all completed the Perceived Vulnerability to Disease scale to assess BIS-relevant Germ Aversion and Perceived Infectability, followed by questions measuring social conformity, warmth toward others and attitudes toward lockdown measures. Significantly lower PVD scores were observed in the no-information condition, with the other conditions showing no difference. In terms of RST, approach behaviors related to goal-drive persistence work alongside fear in explaining conformity to social norms. Reward related approach behaviors partially explained warmth toward others, indicating that social rewards gained through interaction continue to be strong drivers of behavior. We found no role for RST traits in attitudes toward lockdown. Overall, coronavirus-related behavior is not driven purely by fear, but also by social and/or protection goals regulated by approach motivation. This study presents new insights into public perceptions of coronavirus and government regulated lifestyle restrictions, helping to explain social behaviors in terms of biologically driven mechanisms. Such understanding is vital if we are to successfully motivate public behavior to constrain spread of the virus. (shrink)

In the following pages we propose a theory on cognitive systems and the common strategies of perception, which are at the basis of their function. We demonstrate that these strategies are easily seen to be in place in known cognitive systems such as vision and language. Furthermore we show that taking these strategies into consideration implies a new outlook on immune function calling for a new appraisal of the immune system as a cognitive system.

The principal focus of this paper is to consider the implications of head and neck transplantation surgery on the issue of personal identity. To this end, it is noted that the immune system has not only been established to impose a level of self-identity on bodily cells, it has also been implicated in mental development and the regulation of mental state. In this it serves as a paradigm for the mind as the product of cephalic and extracephalic systems. (...) The importance of bodily systems in identity is then discussed in relation to phantom tissue syndrome. The data strongly indicate that, even if surgically successful, head and neck transplantation will result in the loss of the continuity of personal identity. (shrink)

A Bayesian mind is, at its core, a rational mind. Bayesianism is thus well-suited to predict and explain mental processes that best exemplify our ability to be rational. However, evidence from belief acquisition and change appears to show that we do not acquire and update information in a Bayesian way. Instead, the principles of belief acquisition and updating seem grounded in maintaining a psychological immune system rather than in approximating a Bayesian processor.

Graphical AbstractMHC II, a major feature of the adaptive immune system, is lacking in Atlantic cod, and there are different scenarios (metabolic cost hypothesis or functional shift hypothesis) that might explain this loss. The lack of MHC II coincides with an increased number of genes for MHC I and Toll-like receptors (TLRs).

Stress-induced brain-mediated immunoregulation is effected by two pathways: autonomic outflow and (neuro)endocrine outflow. Particular attention is given to the interaction-effects of chronic an acute stress. Recent data have established that cells of the immune system produce neuro-peptides and hormones. In concert with cytokines released by these immune cells the brain can be informed on the nature of ongoing immune activity. The significance of conditioning of immune responses is discussed.

In recent years, immune systems have sparked considerable interest within the philosophy of science. One issue that has received increased attention is whether other phyla besides vertebrates display an adaptive immune system. Particularly the discovery of CRISPR-Cas9-based systems has triggered a discussion about how to classify adaptive immune systems. One question that has not been addressed yet is the transgenerational aspect of the CRISPR-Cas9-based response. If immunity is acquired and inherited, how to distinguish evolutionary from immunological (...) adaptation? To shed light on this issue and obtain conceptual clarity, I will investigate the inheritance of small RNA responses to pathogens in the nematode C. elegans as a further potential instantiation of a transgenerational adaptive immune system. I will explore how to make sense of systems that lie at the crossroads between genetic, immunological, and evolutionary spheres and explore the consequences of a transgenerational perspective on immune systems for immunology and its philosophy. (shrink)

One of the fundamental questions of life sciences is one of whether there are genuinely random biological processes. An affirmative or negative answer to this question may have important methodological consequences. It appears that a number of biological processes are explicitly classified as random. One of them is the so-called somatic hypermutation. However, closer analysis of somatic hypermutation reveals that it is not a genuinely random process. Somatic hypermutation is called random because the exact outcome of this process is difficult (...) to predict in practice. The case of somatic hypermutation suggests that there may be no scientific evidence of a single case of ontologically random process in the biological world. (shrink)

In this interdisciplinary article, we investigate the relationship between creativity and the immune system; the creative features of the immune system and how the immune system and its role in regulating homeostasis might be related to creative cognition. We argue that within a multivariate approach of creativity, the immune system is a contributing factor. New directions for research are also discussed. When astronauts and cosmonauts venture into the new and extreme environment of (...) outer space, their immune system needs to instantly adapt and find new answers to survive biologically and psychologically. Many astronauts report interest in creative activities and therefore represent an interesting group to investigate creativity in relation with the immune system. Little is known regarding how the immune system interacts with and supports creative cognition and behavior, if an individual’s immune system, interacting with cognition, adapts more originally to a new environment compared to another’s; in other words, if there is creativity in the domain of the immune system, and the creative properties and functions of the immune system itself. (shrink)

: Despite the development of a vast body of literature pertaining to feminism and science, examples of how feminist philosophies might be applied to scientific theories and practice have been limited. Moreover, most scientists remain unfamiliar with how feminism pertains to their work. Using the example of the immune system, this paper applies three feminist epistemologies--feminist empiricism, feminist standpoint theory, and feminist postmodernism--to assess competing claims of immune function within a feminist context.

Immunity by William Paul is an overview of fundamental principles of immunology and their experimental basis. The book includes not only well- established facts about the immune system but also recent findings (the role of Th17 cells, regulatory T cells, inflammasomes, etc.), which are skillfully incorporated into the framework of immunological understanding. The presentation is clear and emotionally charged, which makes the reading of Immunity enjoyable. Despite the original intentions, though, the book may appear too challenging for a (...) lay reader to serve as a popular introduction to immunology. Instead, it may help to put already acquired immunological knowledge in order benefiting advanced biology students and researchers. At a deeper level, Immunity provokes questions concerning what counts as relevant and what counts as a landmark in immunology. (shrink)

Despite the availability of safe vaccines against SARS-CoV-2, some people will remain vulnerable because they will not be vaccinated. Who are these non-vaccinated people? We can distinguish two groups: (i) persons who cannot be vaccinated for clinical reasons and who, despite having been vaccinated, have not achieved immunity; (ii) persons who voluntarily refuse to get vaccinated. These groups have in common an immune system that will make them vulnerable to COVID-19. The reasons for their vulnerability and the ethical (...) judgment they deserve are different; the solutions offered to them are also different. In the case of those who voluntarily avoid vaccination, States are not compromised to introduce new protective policies. In the case of people who remain involuntarily vulnerable, instead, the response should be articulated on the same rules and principles that inform the social model of disability because they will live with an organic disability. (shrink)

Biological boundaries are important because of what they reveal about the evolution of a lineage, the relationship between organisms of different lineages, the structure and function of particular subsystems of the organism, the interconnection between an organism and its environment, and a myriad of other important issues related to individuality, development, and evolution. Since there is no single unifying theory for all biological sciences, there are various possible theoretical characterizations of what counts as a biological boundary. Theoretical specificity is crucial (...) for the full characterization of a boundary; to this end, it is useful to begin with general properties and then to compare these to those properties specific to a particular biological boundary. This dual heuristic approach—top-down and bottom-up—can then be repeated to increase the robustness of the boundary characterization. In what follows, I explore both the general structural and functional aspects of biological boundaries and those specific to a biological subsystem, which itself is critical to boundary formation, maintenance, and evolution—the vertebrate immune system. It is a remarkable and sobering regularity of nature that organisms remain whole because their parts are constantly being built up and broken down, and this is no less true of their boundaries. The vertebrate immune system is at the center of this process of biological boundary maintenance and breakdown. (shrink)

One of the characteristics of all somatic cells is a finite life span. Cells may proliferate until they reach a point after which, although they are metabolically active, they can no longer produce daughter cells. This observation is central to the clonal exhaustion hypothesis, a mechanism cited to explain age-associated immune dysfunction. In this hypothesis, repeated division of lymphocytes leads to a replicative limit, after which they enter the senescent phase but are not lost from the pool of T (...) cells. Advancing age would then be associated with an increase in the number of T cells that are unable to proliferate to a stimulus which induces a proliferative response in T cells from younger individuals. This hypothesis seems both logical and reasonable and is supported by data from both humans and mice with the demonstration of an age-related accumulation of senescent T cells in both species. However, there is an apparent paradox. The paradox arises because the onset of immunosenescence appears to be more closely linked to the life span of the animal rather than the life span of the lymphocyte. BioEssays 21:519–524, 1999. © 1999 John Wiley & Sons, Inc. (shrink)

Physical exercise is seen as the main ally for health promotion, preventing and protecting the organism from several diseases. According to WHO, there is a tendency of constant growth in the elderly population in the coming years. The regular practice of exercises by the elderly becomes relevant to minimize the deleterious effects of the aging process and to increase the fitness index. Recently, the world population started a confrontation against Corona Virus Disease (COVID-19), which is the most significant public health (...) challenge globally. Although social isolation is a reasonable measure in an attempt to stop contamination by COVID-19, this measure has limited the ability of individuals to exercise outdoors or in gyms and health clubs, which increased the risk of developing chronic illnesses related to a sedentary lifestyle. The critical point is that the recent recommendations on exercise prescription to combat the potentially harmful effects of COVID-19 failure to adequately address resistance exercise interventions as home-based exercise strategy. Thus, in this paper, we discussed the physical exercise as medicine if the training status is enough to protect the elderly against COVID-19 infection, about the role of physical activity on immunosuppression. Possible risks for COVID-19 infection, and the old training methods, such as no-load resistance training as possible resistance exercise strategies and high-intensity interval training, as new proposals of home-based exercise interventions, could perform during the current COVID-19 pandemic. (shrink)

The behavioral immune system (BIS) includes perceptual mechanisms for detecting cues of contamination. Former studies have indicated that moisture has a disgusting property. Therefore, moisture could be a target for detecting contamination cues by the BIS. We conducted two experiments to examine the psychophysical basis of moisture perception and clarify the relationship between the perception of moisture and the BIS. We assumed that the number of high luminance areas in a visual image provided optical information that would enable (...) the visual perception of moisture. In two experiments, we presented eight images of dough that contained different amounts of moisture as experimental stimuli. The amount of moisture shown in the images was increased in eight steps, from 28.6% to 42.9% of the total weight of the dough. In Experiment 1, the images were randomly presented on a computer display, and the participants (n = 22) were asked to rank the images in the order of the visually perceived moisture content. In Experiment 2, the participants (n = 15) completed pairwise comparisons based on the perceived moistness of the images. Furthermore, to examine the BIS responses, the participants rated the strength of disgust evoked by the stimuli, their motivation to avoid touching the stimuli, and the estimated magnitude of the risk of contamination by physical contact with the stimuli. The results indicated that the moisture content and the numbers of high luminance areas in the images accurately predicted the perception of moisture, suggesting that the detection of visual moisture was highly accurate, and the optical information served as an essential perceptual cue for detecting moisture. On the other hand, the BIS responses peaked in response to stimuli having approximately 33% to 39% moisture content. These results show that objects containing a moderate amount of moisture could be the target of visually detecting pathogens by the BIS. (shrink)

The immune system has evolved to detect and remove foreign or non‐self molecules from the body. To perform this task, the system has coupled together specific recognition with non‐specific effector mechanisms in at least two distinct fashions, as outlined in this review.

Despite the development of a vast body of literature pertaining to feminism and science, examples of how feminist phifosophies might be applied to scientific theories and practice have been limited. Moreover, most scientists remain unfamiliar with how feminism pertains to their work. Using the example of the immune system, this paper applies three feminist epistemologies feminist empiricism, feminist standpoint theory, and feminist postmodernismtoassess competingchims of immune function within a feminist context.

The authors attempt to show that certain forms of behavior of the human immune system are illuminatingly regarded as errors in that system's operation. Since error-ascription can occur only within the context of an intentional/teleological characterization of the system, it follows that such a characterization is illuminating. It is argued that error-ascription is objective, non-anthropomorphic, irreducible to any purely causal form of explanation of the same behavior, and further that it is wrong to regard all errors (...) of the immune system as due to malfunction or maladaptation. <br>. (shrink)

In an instant classic paper ; 2002: 179–182) biologist Yuri Lazebnik deplores the poor effectiveness of the approach adopted by biologists to understand and “fix” biological systems. Lazebnik suggests that to remedy this state of things biologist should take inspiration from the approach used by engineers to design, understand, and troubleshoot technological systems. In the present paper I substantiate Lazebnik’s analysis by concretely showing how to apply the engineering approach to biological problems. I use an actual example of electronic circuit (...) troubleshooting to ground the thesis that, in engineering, the crucial phases of any non-trivial troubleshooting process are aimed at generating a mechanistic explanation of the functioning of the system, which makes extensive recourse to problem-driven qualitative reasoning possibly based on cognitive artifacts applied to systems that are known to have been designed for function. To show how to translate these findings into biological practice I consider a concrete example of biological model building and “troubleshooting”, aimed at the identification of a “fix” for the human immune system in presence of progressing cancer, autoimmune disease, and transplant rejection. The result is a novel immune system model—the danger model with regulatory cells— and new, original hypotheses concerning the development, prophylaxis, and therapy of these unwanted biological processes. Based on the manifest efficacy of the proposed approach, I suggest a refocusing of the activity of theoretical biologists along the engineering-inspired lines illustrated in the paper. (shrink)

The immune system, to protect the body, must discriminate between the pathogenic and non-pathogenic microbes and respond to them in different ways. How the mucosal immune system manages to make this distinction is poorly understood. We suggest here that the distinction between pathogenic and non-pathogenic microbes is made by an integrated system rather than by single types of cells or single types of receptors; a systems biology approach is needed to understand immune recognition.

Insular populations have traditionally drawn a lot of attention from epidemiologists as they provide important insights regarding transmission of infectious diseases and propagation of epidemics. There are numerous historical instances where isolated populations showed high morbidity once a new virus entered the population. Building upon that and recent findings that the activation of the behavioral immune system depends both upon one’s vulnerability and environmental context, we predicted that, during the COVID-19 pandemic, place of residence explains a significant proportion (...) of variance in preferred interpersonal distances, animosity toward strangers, and willingness to punish those who do not adhere to COVID-19 preventive measures. With 48 populated islands, Croatia provides a fruitful testing ground for this prediction. We also opted to explore relations among BIS-related variables and social cognitions in a more natural context than has previously been done. The study was conducted online, on Croatian residents, during April and May 2020. As expected, the BIS variables contributed significantly to preferred interpersonal distances, negative emotions toward strangers, and willingness to punish those who do not adhere to COVID-19 preventive measures. Furthermore, our results showed that geographical location explained a significant amount of variance in preferred social distances and negative emotions toward foreigners. As Croatian islands are extremely frequent travel destinations, these differences between mainlanders and islanders cannot be explained by the lack of exposure to foreigners. Additionally, we found that scores on preferred interpersonal distances, pathogen disgust, and germ aversion were significantly higher compared to those obtained in Croatian samples before the COVID-19 pandemic. Furthermore, men scored higher in perceived infectability than before the COVID-19 pandemic, and women did not, which reflects the objectively higher risk of SARS-CoV-2 for men than for women. Taken together, our results support the notion that BIS is a highly adaptive and context-dependent response system, likely more reactive in more susceptible individuals. (shrink)

Immunologists use psychological and cognitive terms to describe and explain the behavior of our immune system. Do they use them metaphorically or literally? In this paper I show that on the grounds of some psychophysical assumptions, the uniqueness of each person as an individual organism necessarily corresponds to the singularity of each person as a psychological subject. On the basis of these assumptions, immunologists, irrespective of their various conceptual frames, are entitled to ascribe psychological and cognitive traits to (...) our immune system and its behavior. Immunologists are allowed to do so because each immune system of any higher, unique individual organism corresponds to psychological traits, which are ascribable only to persons, each of whom is a singular being. This correspondence is necessarily compatible with the psychophysical unity or inseparability. Furthermore, the psychological or cognitive traits pertain to the immune system require no consciousness. In the case of artificial immune systems, in contrast, the application of psychological or cognitive terms is only metaphorical, for each such system is not unique but it is duplicable or replicable. Only the immune system of unique individual organisms that as psychological subjects are singular beings—i.e. persons—can be subject, literally or non-metaphorically, to psychological and cognitive terms. (shrink)

In the 1940s, Georges Canguilhem has established the concept of biological normativity on the level of the organism in his key work on “ The Normal and the Pathological ”. We would like to present a contemporary analysis of Canguilhem’s work, set it in context with more recent results from the field of complexity and immunology, and evaluate the problematic whether normativity is a genuine capacity of the organism. Based on Canguilhem’s conditions of the definition of biological normativity, we show (...) that the immune system as one of the complex systems of the living equally shares the capacity to be normative. We will then conclude that normativity can also be conceptually independently displayed on the level of complex systems of the living. (shrink)

A mathematical model of the dynamics of the immune system is considered to illustrate the effect of its response to HIV infection, i.e. on viral growth and on T-cell dynamics. The specific immune response is measured by the levels of cytotoxic lymphocytes in a human body. The existence and stability analyses are performed for infected steady state and uninfected steady state. In order to keep infection under control, roles of drug therapies are analyzed in the presence of (...) efficient immune response. Numerical simulations are computed and exhibited to illustrate the support of the immune system to drug therapies, so as to ensure the decay of infection and to maintain the level of healthy cells. (shrink)

Studies of the activation of the behavioral immune system triggered by the coronavirus disease-2019 pandemic have demonstrated that evolutionary explanations of individual differences in self-protection should not be based only on parental investment and sexual selection theory. An evolutionary model must also incorporate individual differences that arise within each sex as a result of life history strategies and attachment patterns.

It has long been thought that the central nervous system is able to influence the progression of disease. Furthermore, there is now overwhelming evidence that the communication pathways are bidirectional. A variety of immune system peptides are now known to be capable of transmitting information from the immune system to the central nervous system. These immunotransmitters include interleukins, interferons and thymosine peptides which have the capability of modulating slow‐wave sleep as well as the release (...) of neuro‐ and pituitary peptides. In some instances, release of these peptides during early development may have long lasting, if not permanent effects upon the normal development of neuro‐endocrine circuits. Collectively these various brain mediated events appear to contribute in various and diverse ways to defense against pathogens. It is becoming more and more apparent that certain abnormalities within the immune system may be the consequence of a neurological abnormality. The converse is also true. (shrink)

Secondary lymphoid organs form in utero through an inherited and well‐established developmental program. However, maternal non‐heritable features can have a major impact on the gene expression of the embryo, hence influencing the future health of the offspring. Recently, maternal retinoids were shown to regulate the formation of immune structures, shedding light on the role of maternal nutrition in the genetic signature of emergent immune cells. Here we highlight evidence showing how the maternal diet influences the establishment of the (...) immune system, and we also discuss how unbalanced maternal diets may set the response to infection and vaccination in the progeny. (shrink)

An extensive, and controversial, literature concluding that prolactin (PRL), growth hormone (GH), insulin-like growth factor-I (IGF-I), and thyroid hormones are critical immunoregulatory factors has accumulated. However, recent studies of mice deficient in the production of these hormones or expression of their receptors indicate that there are only a few instances in which these hormones are required for lymphocyte development or antigen responsiveness. Instead, a case is made that their primary role is to counteract the effects of negative immunoregulatory factors, such (...) as glucocorticoids, which are produced when the organism is subjected to major stressors. The immunoprotective actions of PRL, GH, IGF-I, and/or thyroid hormones in these instances may ensure immune system homeostasis and reduce the susceptibility to stress-induced disease. These immuno-enhancing effects could be exploited clinically in instances where the immune system is depressed due to illness or various treatment regimens. BioEssays 23:288–294, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

The mammary gland is a skin gland unique to the class Mammalia. Despite a growing molecular and histological understanding of the development and physiology of the mammary gland, its functional and morphological origins have remained speculative. Numerous theories on the origin of the mammary gland and lactation exist. The purpose of the mammary gland is to provide the newborn with copious amounts of milk, a unique body fluid that has a dual role of nutrition and immunological protection. Interestingly, antimicrobial enzymes, (...) such as xanthine oxidoreductase or lysozyme, are directly involved in the evolution of the nutritional aspect of milk. We outline that xanthine oxidoreductase evolved a dual role in the mammary gland and hence provide new evidence supporting the hypothesis that the nutritional function of the milk evolved subsequent to its protective function. Therefore, we postulate that the mammary gland evolved from the innate immune system. In addition, we suggest that lactation partly evolved as an inflammatory response to tissue damage and infection, and discuss the observation that the two signaling pathways, NF‐kB and Jak/Stat, play central roles in inflammation as well as in lactation. BioEssays 28: 606–616, 2006. © 2006 Wiley Periodicals, Inc. (shrink)

According to Mohan Matthen and Edwin Levy, certain immunological processes require explanations in which the immune system is attributed intentional states. This, they think, strengthens the scientific credentials of intentional psychology and undermines the position of those who argue that the scientific treatment of human action should involve the elimination of intentional description. In this paper, I argue that immunology does not and need not employ intentional explanation or description and consequently has nothing to offer those who seek (...) to defend the scientific standing of intentional psychology by looking for other disciplines that "accommodate the intentional". (shrink)

The thymus has been an enigmatic organ for centuries. Its true function was revealed only in 1961 when it was shown to be responsible for the proper development of the immune system. This finding has revolutionized the science of immunology and has led to a better understanding of the mechanisms involved in resistance to infections and of the pathogenesis of autoimmune and immunodeficiency diseases.

Genetic and environmental factors leading to Alzheimer's disease (AD) converge in a pathogenic pathway that leads to the accumulation of mis‐folded amyloid peptide (Aβ) in the brain. Removal of Aβ from the brain has thus been the focus of academic and industrial research in the last decade. The concept of immunization therapy could be proven in animal models mimicking amyloid pathology but a multicenter clinical trial in which AD patients were vaccinated with aggregated Aβ has resulted in somewhat unanticipated and (...) partially conflicting results. The occurrence of meningoencephalitis in 6% of vaccinated individuals forced the discontinuation of the clinical study, preventing the generation of sufficient data for an unequivocal statement about the effectiveness of such a therapy approach. This study, however, clearly showed that vaccination induced the production of antibodies against Aβ in some immunized patients. Moreover, circulating anti‐Aβ antibodies are found in healthy humans suggesting a protective role of such physiological antibodies. Nonetheless, the physiological role of the immune system in preventing AD is not fully understood. This article summarizes crucial animal and clinical data underscoring the potential of the immune system for AD treatment. BioEssays 29:927–932, 2007. © 2007 Wiley Periodicals, Inc. (shrink)