An enlarged subpopulation of T lymphocytes bearing two distinct gamma delta TCR in an HIV-positive patient

Although T cell clone monospecificity is ensured by several allelic exclusi on processes operating at either the genotypic or phenotypic levels, clones expressing two distinct alpha beta or gamma delta TCR have been described in several instances. Thus far, the origin of dual TCR-expressing cells and the homeostatic mechanisms controlling the size of this subset in the peri phery remain poorly understood. In the course of a phenotypic analysis of g amma delta T cells in HIV-infected patients, we detected the presence of a T cell subset stained by both V(delta)2- and V(delta)3-specific mAb, which represented a large fraction (up to 16.5%) of gamma delta peripheral blood lymphocytes (PBL) in one HIV patient. The presence of two distinct function al delta chains on these cells was confirmed by phenotypic and molecular an alysis of TCR transcripts expressed by V(delta)2(+)V(delta)3(+) T cell clon es derived from this patient. For 18 months, the absolute number of these c ells varied similarly to the other PBL subsets, before becoming undetectabl e in blood samples. Moreover, most of these cells expressed CD8 receptors, which are classically found on activated, but not resting, gamma delta T ce lls. Taken together, these data suggest that dual TCR-expressing T cells ar e subjected to peripheral expansions and contractions presumably following antigen recognition, which would argue against a systematic counter-selecti on of these cells during peripheral antigen-driven responses.