Evolutionary implications of a third lymphocyte lineage in lampreys

M Hirano, P Guo, N McCurley, M Schorpp, S Das… - Nature, 2013 - nature.com
M Hirano, P Guo, N McCurley, M Schorpp, S Das, T Boehm, MD Cooper
Nature, 2013nature.com
Jawed vertebrates (gnathostomes) and jawless vertebrates (cyclostomes) have different
adaptive immune systems,. Gnathostomes use T-and B-cell antigen receptors belonging to
the immunoglobulin superfamily,. Cyclostomes, the lampreys and hagfish, instead use
leucine-rich repeat proteins to construct variable lymphocyte receptors (VLRs), two types of
which, VLRA and VLRB, are reciprocally expressed by lymphocytes resembling
gnathostome T and B cells,,. Here we define another lineage of T-cell-like lymphocytes that …
Abstract
Jawed vertebrates (gnathostomes) and jawless vertebrates (cyclostomes) have different adaptive immune systems,. Gnathostomes use T- and B-cell antigen receptors belonging to the immunoglobulin superfamily,. Cyclostomes, the lampreys and hagfish, instead use leucine-rich repeat proteins to construct variable lymphocyte receptors (VLRs), two types of which, VLRA and VLRB, are reciprocally expressed by lymphocytes resembling gnathostome T and B cells,,. Here we define another lineage of T-cell-like lymphocytes that express the recently identified VLRC receptors,. Both VLRC+ and VLRA+ lymphocytes express orthologues of genes that gnathostome γδ and αβ T cells use for their differentiation, undergo VLRC and VLRA assembly and repertoire diversification in the ‘thymoid’ gill region, and express their VLRs solely as cell-surface proteins. Our findings suggest that the genetic programmes for two primordial T-cell lineages and a prototypic B-cell lineage were already present in the last common vertebrate ancestor approximately 500 million years ago. We propose that functional specialization of distinct T-cell-like lineages was an ancient feature of a primordial immune system.
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