Steele EJ, Rothenfluh HS, Ada GL, Blanden RV. Affinity maturation of lymphocyte receptors and positive selection of T cells in the thymus.
Immunol Rev 1993;
135:5-49. [PMID:
8282316 DOI:
10.1111/j.1600-065x.1993.tb00642.x]
[Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In this review we have re-evaluated the dominant paradigm that TcR V genes do not somatically mutate. We highlight the many structural and functional similarities between Ig and TcR antigen-specific receptors on B and T cells. We have reviewed the factors influencing the somatic and germline evolution of IgV regions in B cells, have evaluated in detail various models which could be invoked to explain the pattern of variation in both transcribed and non-transcribed segments of germline IgV-gene DNA sequences, and applied this perspective to the TcR V beta and V alpha genes. Whilst specific TcRs recognize a complex of a short antigenic peptide bound to MHC Class I or II glycoprotein, and Ig receptors can recognize both oligopeptides and conformational determinants on undegraded polypeptides, they both employ heterodimer variable regions (Fabs) utilizing all three CDRs in epitope binding. We conclude that a plausible case can be made for the possibility that rearranged TcR V genes may undergo some type of somatic hypermutation process during T-cell development in the thymus (concurrent with or after the positive selection phase) thus allowing a repertoire of TvR alpha beta heterodimers to be both positively and negatively selected by the same set of ligands (self MHC + self peptide) in the thymus.
Collapse