In a series of patients transplanted with HLA-matched allogeneic bone marrow grafts (alloBMT), we previously showed that a few T-cell receptor (TCR) V alpha and V beta gene segment transcripts were overexpressed in skin compared with blood at the time of acute graft- versus-host disease (aGVHD). Here, in one selected patient with overexpressed V beta 16 and V alpha 11 transcripts in skin, we analyzed the junctional variability of these transcripts in donor blood, patient blood, and skin collected at aGVHD onset. A unique junctional region sequence accounted for 81% of in frame V beta 16 transcripts (13 of 16) in skin and 59% (13 of 22) in patient blood. Similarly, two recurrent junctional region sequences were found in skin V alpha 11 transcripts, one accounting for 66% (21 of 32) and the other for 16% (5 of 32). These recurrences were also found in patient blood (36% and 15% of V alpha 11 transcripts, respectively). To extend our analysis, a polymerase chain reaction (PCR)-based method was used to precisely determine TCR beta transcript length in run-off reactions using uncloned bulk cDNA samples. All V beta-C beta PCR products analyzed in donor blood, as well as the majority of those analyzed in patient blood, included transcripts with highly diverse junctional region sizes. As expected from the sequence data, most V beta 16-C beta PCR products in skin and patient blood were of the same size (ie, same junctional region). In addition, V beta 3, V beta 5, and V beta 17 transcripts in skin were shown to display highly restricted size variability. The clonality of the V beta 16-C beta and V beta 17-C beta transcripts was further supported by the results of run-off reactions using 13 J beta specific primers. We have identified several recurrent TCR transcripts in skin, some of them also present in patient blood. These data support the view that several T-cell subpopulations are clonally expanded in vivo at the time of aGVHD onset in this case of related HLA-matched alloBMT.
Human leukocyte antigen (HLA)-dependent selection mechanisms exerted during thymic maturation are supposed to be main contributing factors to the genetic predetermination of the TCR repertoire and may have a detectable effect on adult peripheral blood lymphocyte V segment frequencies. Here, we analyzed whether polymorphic or non-polymorphic HLA determinants are associated with selected expression of some V gene segment specificities. We first examined the reactivity of 17 V segment specific mAb on purified CD4+ and CD8+ cell fractions in 10 unrelated people. We found a significant overexpression of only three V segment products (V beta 2, V beta 5.1 and V beta 6.7) in CD4+ and none in CD8+ cell fractions in most individuals. Skewing of certain V beta segments by non-polymorphic HLA determinants (i.e. class II for CD4+ and class I for CD8+ cells) is therefore more limited (3/17) than previously thought. Considering the effects of polymorphic HLA determinants, we compared TCR V segment frequencies in HLA-identical siblings to sibling pairs who differ at one or both HLA haplotypes, using 13 V beta specific mAb. In pairwise comparisons, we found that the HLA complex had no detectable effect on TCR repertoire in five large families with multiple siblings. Together, these observations suggest that HLA-predicted selection mechanisms exerted during thymic maturation might not have a predominant influence shaping the TCR repertoire of normal adults.
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