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Nature Reviews Immunology 6, 79–84 (1 January 2006) | doi:10.1038/nri1749

Co-evolution of a primordial peptide-presentation system and cellular immunity

Thomas Boehm

How did early vertebrates survive when their lymphocytes began to use antigen receptors with random specificities, despite their potential for extensive self-reactivity? Here, I propose that the quality-control mechanisms that tame self-reactivity in the adaptive immune system were derived, at least in part, from an ancient mechanism that guided sexual selection on the basis of evaluating genetic relatedness.