How innate immunity gave rise to adaptive immunity in vertebrates remains unknown. We propose an evolutionary scenario beginning with pathogen-associated molecular pattern(s) (PAMPs) being presented by molecule(s) on one cell to specific receptor(s) on other cells, much like MHC molecules and T cell receptors (TCRs). In this model, mutations in MHC-like molecule(s) that bound new PAMP(s) would not be recognized by original TCR-like molecule(s), and new MHC-like gene(s) would be lost by neutral drift. Integrating recombination activating gene (RAG) transposon(s) in a TCR-like gene would result in greater recognition diversity, with new MHC-like variants recognized and selected, along with a new RAG/TCR-like system. MHC genes would be selected to present many peptides, through multigene families, allelic polymorphism, and peptide-binding promiscuity.

先天免疫如何引起脊椎动物的适应性免疫仍是未知的。我们提出了一种进化方案，从一个病原体相关的分子模式（PAMP）开始，一个分子上的分子呈现给其他细胞上的特定受体，就像MHC分子和T细胞受体（TCR）一样。在该模型中，结合了新的PAMP的MHC样分子中的突变将不会被原始的TCR样分子识别，而新的MHC样基因将因中性漂移而丢失。将重组激活基因（RAG）转座子整合到TCR样基因中将导致更大的识别多样性，并识别和选择新的MHC样变体，以及新的RAG / TCR样系统。通过多基因家族，等位基因多态性和肽结合滥交，将选择MHC基因来呈递许多肽。