It is increasingly suggested that shortages in the supply chain for human blood could be met by the development of techniques to manufacture human blood ex vivo. These techniques fall broadly under the umbrella of synthetic biology. We examine the biopolitical context surrounding the ex vivo culture of red blood cells through the linked concepts of alienation, immunity, bio-value and biosecuritization. We engage with diverse meanings of synthetic blood, and questions about how the discourses of biosecurity and privatization of risk (...) are linked to claims that the technology will address unmet needs and promote social justice. Through our discussion we contrast communitarian ideas that culturing red blood cells ‘extends the gift’ of adult blood donation with understandings of the immunitary logics that underpin the cord-blood economy. (shrink)