High frequency of circulating gamma delta T cells with dominance of the V(delta)1 subset in a healthy population

TCR gamma delta(+) cells constitute <5% of all circulating T cells in healt hy, adult Caucasians, and V(delta)1(+) cells constitute a minority of these cells. In contrast to TCR alpha beta(+) cells, their repertoire is selecte d extrathymically by environmental antigens, Although increased frequencies of V(delta)1(+) cells are found in several diseases, their function remain s obscure. Here we show that the frequency of peripheral blood gamma delta T cells in healthy West Africans is about twice that of Caucasians, mainly due to a 5-fold increase in V(delta)1(+) cells, which is consequently the d ominant subset. No age dependency of V(delta)1 frequencies was identified a nd the V(delta)1(+) cells in the African donors did not show preferential V -gamma chain usage. Analysis of the CDR3 region size did not reveal any par ticular skewing of the V(delta)1 repertoire, although oligoclonality was mo re pronounced in adults compared to children. The proportions of CD8(+), CD 38(+) and CD45RA(hi)CD45RO(-) cells within the V(delta)1(+) subset were hig her in the African than in the European donors, without obvious differences in expression of activation markers, No significant correlations between l evels of V(delta)1(+) cells and environmental antigens or immunological par ameters were identified. Taken together, the evidence argues against a CDR3 -restricted, antigen-driven expansion of V(delta)1(+) cells in the African study population. Our study shows that high frequencies of TCR gamma delta( +) cells with dominance of the V(delta)1(+) subset can occur at the populat ion level in healthy people, raising questions about the physiological role of V(delta)1(+) T cells in the function and regulation of the immune syste m.