Experimental study of possible involvement of some apoptosis mechanisms in pathogenesis of the HIV infection: 2. The CD4+ T lymphocytes depletion in the HIV infection occurs through activation-induced apoptosis.

The present work is a part of a complex experimental study aimed at the demonstration of the two previously published hypotheses regarding the involvement of apoptosis in general in the viral infection and especially in HIV infection (1). Our researches have shown that the significant lowering of the number of peripheral CD4+ T lymphocytes in HIV-infected children is associated with a marked increase of the soluble interleukin 2-receptor (sIL2-R)# concentration, in comparison with HIV-negative, healthy or acute infections exhibiting controls. As sIL-2R is a circulating marker of cell activation, we investigated the role of monocytes (antigen-presenting cells) in the viability of peripheral lymphocytes isolated from HIV-infected children in comparison with the controls. Lymphocytes cultivation in the absence and in the presence of autologous monocytes led to the following conclusions: 1) freshly isolated lymphocytes from HIV-positive individuals undergo an accelerated spontaneous apoptosis in comparison with that of lymphocytes isolated from HIV-negative individuals: 2) the normal antiapoptotic effect of monocytes on lymphocytes diminishes gradually in the HIV infection, changing into a proapoptotic effect, corresponding to the sIL-2R augmentation to increasingly higher values. Our results show that peripheral CD4+ T-lymphocyte depletion in HIV infection occurs through apoptosis and the activation-induced cell death is one of the possible apoptosis mechanisms.