title: Evolution of two prototypic T cell lineages.
abstract: Jawless vertebrates, which occupy a unique position in chordate phylogeny, employ leucine-rich repeat (LRR)-based variable lymphocyte receptors (VLR) for antigen recognition. During the assembly of the VLR genes (VLRA, VLRB and VLRC), donor LRR-encoding sequences are copied in a step-wise manner into the incomplete germ-line genes. The assembled VLR genes are differentially expressed by discrete lymphocyte lineages: VLRA- and VLRC-producing cells are T-cell like, whereas VLRB-producing cells are B-cell like. VLRA(+) and VLRC(+) lymphocytes resemble the two principal T-cell lineages of jawed vertebrates that express the αβ or γδ T-cell receptors (TCR). Reminiscent of the interspersed nature of the TCRα/TCRδ locus in jawed vertebrates, the close proximity of the VLRA and VLRC loci facilitates sharing of donor LRR sequences during VLRA and VLRC assembly. Here we discuss the insight these findings provide into vertebrate T- and B-cell evolution, and the alternative types of anticipatory receptors they use for adaptive immunity.
authors.affiliation: Emory Vaccine Center and Department of Pathology and Laboratory Medicine, Emory University, 1462 Clifton Road North-East, Atlanta, GA 30322, United States.
authors.forename: Sabyasachi
authors.initials: S
authors.lastname: Das
authors.affiliation: Emory Vaccine Center and Department of Pathology and Laboratory Medicine, Emory University, 1462 Clifton Road North-East, Atlanta, GA 30322, United States.
authors.forename: Jianxu
authors.initials: J
authors.lastname: Li
authors.affiliation: Emory Vaccine Center and Department of Pathology and Laboratory Medicine, Emory University, 1462 Clifton Road North-East, Atlanta, GA 30322, United States.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Hirano
authors.affiliation: Emory Vaccine Center and Department of Pathology and Laboratory Medicine, Emory University, 1462 Clifton Road North-East, Atlanta, GA 30322, United States.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Sutoh
authors.affiliation: Emory Vaccine Center and Department of Pathology and Laboratory Medicine, Emory University, 1462 Clifton Road North-East, Atlanta, GA 30322, United States.
authors.forename: Brantley R
authors.initials: BR
authors.lastname: Herrin
authors.affiliation: Emory Vaccine Center and Department of Pathology and Laboratory Medicine, Emory University, 1462 Clifton Road North-East, Atlanta, GA 30322, United States. Electronic address: mdcoope@emory.edu.
authors.forename: Max D
authors.initials: MD
authors.lastname: Cooper
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D005075:Biological Evolution; D019070:Cell Lineage / Q000276:immunology; D006196:Hagfishes / Q000145:classification / Q000235:genetics / Q000276:immunology*; D007798:Lampreys / Q000145:classification / Q000235:genetics / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D010802:Phylogeny; D011947:Receptors, Antigen, B-Cell / Q000276:immunology*; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology*; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D011947:Receptors, Antigen, B-Cell; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta
keywords: Adaptive immunity; Jawless vertebrates; Leucine-rich repeat; Variable lymphocyte receptor; αβ and γδ T-cell receptor