Characterization of T Cell Receptor Gamma Chain Expression in a Subset of Murine Thymocytes

Abstract

While much information exists about the structure and function of the clonally distributed T cell receptor (TCR) alpha beta heterodimer, little is known about the gamma protein, the product of a third rearranging TCR gene. An antiserum to a carboxyl-terminal peptide common to several of the murine gamma chain constant regions and a monoclonal antibody to the murine T3 complex were used to identify products of this TCR gene family in a subpopulation of Lyt2-, L3T4- thymocytes. This subpopulation does not express TCR alpha or full-length TCR beta messenger RNA. The gamma chain is a 35-kilodalton (kD) protein that is disulfide-bonded to a 45-kD partner and is associated with the T3 complex. Analysis of the glycosylation pattern of this thymic gamma chain revealed that the major variable region gamma (V gamma) gene transcribed in activated peripheral T cells is absent from this subpopulation. The cells that bear this second T cell receptor may therefore represent a distinct lineage differentiating within the thymus.

Predominant variable region gene usage by gamma/delta T cell receptor-bearing cells in the adult thymus.

“…To determine the approximate frequency of 8 rearrangements in thymic y/8 cells, we analyzed the rearrangements present in DNA from an enriched population of such cells (50-80% y/8 cells) isolated by short-term (3 d) culture in a lymphokine cocktail (4) . Because most of these cells express a y/8 receptor, quantitation of various 8 rearrangements represents an approach to determining the usage and diversity of V8 genes in the population .…”

Involvement of the interleukin 2 pathway in the rearrangement and expression of both alpha/beta and gamma/delta T cell receptor genes in human T cell precursors.

“…In contrast, TCRa/Q expression increases throughout T cell ontogeny concomitantly with the acquisition of CD4 and/or CD8 molecules by mature T cells, expression of TCRy/S being restricted to a small population of CD4" CD8 -adult thymocytes and peripheral T cells (3,4) . These findings suggest that y/8-bearing CD4 -CD8 -cells may define a separate T cell lineage whose intrathymic development precedes that of classical a/a mature T cells (21,22) . Nonetheless, the presence of y gene rearrangements in mature a/0-bearing T cells (23), as well as the finding of partial a gene rearrangements in TCRy/S+ cells processes remain poorly understood, and precursor-product relationships involving the various intrathymic subpopulations continue to be disputed, making it difficult to establish direct correlations between the described patterns of TCR gene expression and a functional pathway of T cell development.…”

T cell receptor gamma/delta chain diversity.

“…Results and Discussion Six TCR-7/6-expressing hybridomas (1C6.F11 and 1H11 .B9 of C3H/HeN origin and DN12 .1, DN7.1, DN7 .3, and DN2 .3 of C57BL/6 origin) were used in this study. Earlier studies (2,6,12,13) have indicated that all these hybridomas express glycosylated y chains that are not derived from Vy-Cy4 transcripts since the antiserum used to detect these y chains does not react with Cy4 chains (nomenclature according to Garman et al, [10]). Furthermore, since the Cy3 locus is a pseudogene (8) and, at least for the C57BL/6 mice, V71 .2-C"y2 transcripts would result in nonglycosylated y chains (19), these hybridomas most likely express y chains derived from Vy-CyI transcripts.…”