No abstract

The T cell response to many self-MHC-restricted nominal Ag involves limited use of the TCR repertoire. The status of the TCR repertoire in allogeneic responses remains unclear. In this report, we have studied the TCR V beta gene repertoire involved in the rejection of cardiac allografts disparate for major and minor histocompatibility Ag in rats. Graft-infiltrating lymphocytes (GIL) were isolated from rejecting heart allografts and analyzed for the expression of the V beta repertoire using a cDNA library and a semiquantitative polymerase chain reaction (PCR). We report here that GIL isolated at early stages of the rejection reaction preferentially use the V beta 4 gene. First, V beta 4 comprised 36.4% (8/22) of randomly sequenced cDNA clones isolated from a TCR-beta chain-specific cDNA library established from GIL harvested 3 days posttransplantation. The V beta 4 gene in these clones was found in conjunction with several different J beta and N regions, suggesting a dominant role for the V beta 4 encoded domains in the recognition of allograft Ag. Second, the V beta 4 message comprised 56.6 to 65.7% of the transcripts expressed by the 20 rat V beta genes in three T cell lines established from GIL isolated 2 days posttransplantation. Third, fresh, unmanipulated GIL harvested at days 2 and 3 posttransplantation predominantly expressed the V beta 4 gene. Fourth, the expression of V beta 4 in naive splenocytes constituted only 5.4% of the V beta detected, suggesting that the predominant use of the V beta 4 gene by GIL was not a consequence of its high level of expression in the periphery. The limited use of the TCR repertoire in allograft rejection may provide the opportunity to interrupt the rejection process and induce donor-specific tolerance by targeting a select population of T cells for inactivation or elimination.

We have sequenced 22 TCR-alpha clones isolated from two cDNA libraries derived from rat thymocytes and heart allograft-infiltrating lymphocytes. Sixteen different V alpha and 17 J alpha genes were characterized in these clones. The V alpha genes could be divided into nine subfamilies, each containing from one to three members. Nucleotide sequence comparisons to mouse alpha genes revealed the existence of mouse homologues for all the J alpha s and 8 of 9 V alpha subfamilies. One of the rat V alpha subfamilies appeared to have no known mouse counterpart. Southern blot analysis of germ-line DNA with cDNA probes specific for six different subfamilies demonstrated the existence of two to nine V alpha genes per subfamily. A minimum number of 35 V alpha genes was estimated for the nine rat subfamilies characterized. These analyses also detected two different RFLP patterns among five different inbred rat strains, including strain-specific loss of hybridization bands for some V alpha, indicating that deletion events may have occurred in the rat alpha gene locus. The characterization of rat TCR V alpha genes should facilitate a better understanding of T cell role in pathologic conditions such as autoimmune diseases and graft rejection.

No abstract

No abstract