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

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Abstract
The aim of the present study was to better oinvokedcharacterize the expansion of double-negative (DN) T cells in vivo in AIDS patients and to ascertain the discrepant 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 (3), we have recently reported on an expansion of DN T cells which was observed only in patients with disseminated Mycobacterium avium infection, toxoplasmosis and Kaposi sarcoma, but not in patients with tuberculosis. The potential differential γδ T cells response observed in vivo in AIDS patients with tuberculosis or disseminated M. avium complex infection was investigated by collecting the concomitant or the closest T lymphocyte counts performed within 2 weeks of bacterial diagnosis of 112 disseminated M. avium infection and 41 tuberculosis patients. The DN and γδ T cell percentages were different between the two groups (P < 10–4) and the expansion of this compartment was found only with disseminated M. avium infections. An analysis of the variable δ2 segment versus pan-δ bearing T cells ratio disclosed a predominance of non-Vδ2 T cells in these patients whose average values were identical in both groups. It is therefore concluded that the difference seen between these two types of mycobacterial infections concerning the DN T cells only involved the γδ T cells although the mechanism of their preferential expansion in disseminated M. avium infections remains a matter of speculation.

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