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Evolution of vertebrate adaptive immunity: Immune cells and tissues, and AID/APOBEC cytidine deaminases
Author(s) -
Hirano Masayuki
Publication year - 2015
Publication title -
bioessays
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.175
H-Index - 184
eISSN - 1521-1878
pISSN - 0265-9247
DOI - 10.1002/bies.201400178
Subject(s) - hagfish , biology , apobec , vertebrate , acquired immune system , immune system , cytidine deaminase , receptor , evolutionary biology , immunity , genetics , t cell receptor , immunology , antibody , gene , t cell , genome
All surviving jawed vertebrate representatives achieve diversity in immunoglobulin‐based B and T cell receptors for antigen recognition through recombinatorial rearrangement of V ( D ) J segments. However, the extant jawless vertebrates, lampreys and hagfish, instead generate three types of variable lymphocyte receptors (VLRs) through a template‐mediated combinatorial assembly of different leucine‐rich repeat (LRR) sequences. The clonally diverse VLRB receptors are expressed by B‐like lymphocytes, while the VLRA and VLRC receptors are expressed by lymphocyte lineages that resemble αβ and γδ T lymphocytes, respectively. These findings suggest that three basic types of lymphocytes, one B‐like and two T‐like, are an essential feature of vertebrate adaptive immunity. Around 500 million years ago, a common ancestor of jawed and jawless vertebrates evolved a genetic program for the development of prototypic lymphoid cells as a foundation for an adaptive immune system. This acquisition preceded the convergent evolution of alternative types of clonally diverse receptors for antigens in all vertebrates, as reviewed in this article.