gamma delta T cells increase with Mycobacterium avium complex infection but not with tuberculosis in AIDS patients

The aim of the present study was to better characterize the expansion of do uble-negative (DN) T cells in vivo in AIDS patients and to ascertain the di screpant response of an immunodepressed immune system towards two distinct mycobacterial infections. In a large cohort of HIV-1 seropositive patients with low CD4(+) T cell counts (<100/mm(3)), we have recently reported on an expansion of DN T cells which was observed only in patients with dissemina ted Mycobacterium avium infection, toxoplasmosis and Kaposi sarcoma, but no t in patients with tuberculosis. The potential differential gamma delta T c ells response observed in vivo in AIDS patients with tuberculosis or dissem inated M. avium complex infection was investigated by collecting the concom itant or the closest T lymphocyte counts performed within 2 weeks of bacter ial diagnosis of 112 disseminated M. avium infection and 41 tuberculosis pa tients. The DN and gamma delta T cell percentages were different between th e two groups (P < 10(-4)) and the expansion of this compartment was found o nly with disseminated M. avium infections. An analysis of the variable delt a 2 segment versus pan-delta bearing T cells ratio disclosed a predominance of non-V(delta)2 T cells in these patients whose average values were ident ical in both groups. It is therefore concluded that the difference seen bet ween these two types of mycobacterial infections concerning the DN T cells only involved the gamma delta T cells although the mechanism of their prefe rential expansion in disseminated M. avium infections remains a matter of s peculation.