Enhanced inhibition of lymphocyte activation by Mycobacterium avium complex in human T lymphotrophic virus type I carriers

Background-We have previously reported that disseminated pulmonary Mycobact erium avium complex (MAC) infection is more common in human T lymphotrophic virus type I (HTLV-I) carriers than in non-carriers. However, the reason f or this remains unclear. It has been shown that glycopeptidelipid (GPL), on e of the lipid components of the cell envelope of MAC, is able to reduce th e lymphocyte blastogenic response to mitogens. The purpose of this study wa s to clarify whether or not the inhibitory effect of GPL differs between HT LV-I carriers and non-carriers. Methods-Peripheral blood lymphocytes were obtained from 29 patients who had recovered from pulmonary MAC infection (10 of whom also had HTLV-I infecti on) and the lymphocyte counts and T cell subpopulations of the peripheral b lood lymphocytes in HTLV-I carriers and noncarriers were compared. The inhi bitory effect of GPL on the lymphocyte blastogenic response to phytohaemagg lutinin (PHA) was tested in these 29 cases and in 15 healthy controls who h ad never suffered from MAC (seven of whom also had HTLV-I infection). All H TLV-I positive cases were carriers. Results-There was no significant difference in the numbers or subset propor tions of T cells between HTLV-I carriers and non-carriers. Lymphocyte activ ation by PHA was significantly inhibited by GPL in MAC positive and negativ e HTLV-I carriers compared with MAC negative noncarriers and MAC negative h ealthy controls (p <0.001). Conclusions-We suggest that MAC infection leads to strong inhibition of lym phocyte activation in HTLV-I carriers. This may account, in part, for the s everity of pulmonary MAC infection in HTLV-I carriers.