Evidence for autoantibody-induced CD4 depletion mediated by apoptotic and non-apoptotic mechanisms in HIV-positive long-term surviving haemophilia patients

Abstract

SUMMARY It is believed that autoimmune phenomena and apoptosis contribute to CD4 depletion. We investigated 11 long-term (>20 years) HIV-infected haemophilia patients and 10 healthy controls. Using four-colour-fluorescence flow cytometry, we studied the proportions of CD3+CD4+ and CD3+CD4– blood lymphocytes that were CD95+, CD95L+, immune complex+ (IC+, consisting of IgM, IgG, C3d and/or gp120), and were viable or non-viable (propidium iodide+ = PI+). In addition, we studied viability of CD4+IgG+ patient lymphocytes using the apoptosis marker annexin and the permeability indicator 7-amino actinomycin D (7-AAD). HIV+ patients had a higher proportion of CD3+CD4+IgG+PI+ lymphocytes than healthy controls (median: 3·7%versus 0·3%; P = 0·00001). These non-viable IgG-coated lymphocytes might have been killed in vivo by ADCC or complement lysis; 9·1% of the circulating CD3+CD4+ blood lymphocytes were IgG+PI– (controls: 2·5%; P = 0·001). These viable IgG-coated lymphocytes might be targets for phagocytosis or anti-CD95 autoantibody-mediated apoptosis. Because HIV+ patients and healthy controls had similar proportions of PI+ or PI– CD3+CD4+ lymphocytes that carried CD95L on the surface, and because CD3+CD4+CD95L+ cells that were IgG+, C3d+ and/or gp120– were increased in HIV+ patients, the role of CD95L-induced apoptosis in long-term HIV-infected haemophilia patients remains unclear. The findings that HIV+ patients had higher proportions of CD3+CD4+CD95+ (PI+: 6·5%versus 1·4%; P = 0·00002; PI–: 55·8%versus 44·4%; P = 0·04) blood lymphocytes and that the proportion of CD4+IgG+Annexin+7-AAD– blood lymphocytes was associated inversely with peripheral CD4 counts (r = −0·636; P < 0·05) suggest that attachment of IgG to CD4+ blood lymphocytes (anti-CD95?) induces in some lymphocytes apoptosis with subsequent depletion of these IgG-coated apoptotic CD4+ lymphocytes from the circulation. We found supporting evidence for the contention that autoantibody-induced apoptotic and non-apoptotic mechanisms contribute to CD4 depletion in long-term HIV-infected haemophilia patients.