THE T-CELL RECEPTOR V-BETA-6 GENE USAGE IN ALLOREACTIVE T-CELL RESPONSES

To analyze the role of TCR V beta gene elements in allorecognition, we have determined frequencies of the TCR V beta G elements expressed by allospecific T cells as compared to randomly activated T cells. Limit ing dilution analysis was applied to estimate the usage of TCR vp elem ents in CD4(+) T cells polyclonally stimulated by immobilized anti-CD3 or specifically activated with HLA-DR disparate allotargets. In a foc used alloresponse of HLA-DRB1()0401(+) responders to HLA-DRB1(*)0404 stimulator cells, V beta 6(+) T cells were preferentially recruited. T o map the functional domain of allogeneic HLA-DR molecules involved in the recruitment of V beta 6(+) T-cell specificities, CD4(+) T cells f rom HLA-DRB1()0401(+) donors were activated with allogeneic stimulato rs sharing either the first and second or the third HVR of the HLA-DRB 1 gene. Stimulation with allotargets sharing the sequence of the HVR3 caused a twofold to fourfold enrichment of V beta 6(+) CD4(+) T cells, while sequence variations in the HVR3 was sufficient to abrogate the preferential usage of V beta 6(+) T cells. These data suggest that seq uence variations mapped to the alpha-helical loop of the HLA-DR beta c hain impose structural constraints that shape the alloreactive TCR V b eta repertoire.