[Activation of cell death in lymphocytes from individuals infected with HIV]

In HIV infection, T cells depletion cannot only be explained by direct viral infection. Programmed cell death (PCD), also know as apoptosis or activation-induced cell death, may be responsible for the deletion of reactive T cells that contributes to HIV induced immunodeficiency. We studied the response of lymphocytes in vitro to different polyclonal and oligoclonal (superantigen) activators, and tested whether the stimulation of T cells from individual with HIV infection lead to cell death.

Peripheral blood mononuclear cells, total T lymphocytes, TCD4+ and TCD8+ cells from 10 positive patients, 2 patients with AIDS and 10 negative individual for the virus were cultured in RPMI medium and subjected to stimulation with PHA, PWM and SEB (staphylococcus B enterotoxin). Trypan blue was used to distinguish viable from dead cells.

TCD4+ cells from HIV-infected patients die after SEB or PWM activation (almost 40% from asymptomatic and 80% from AIDS), and do not die TCD8+ from the same individuals (around 10-15%), or T cells from seronegative controls.

Lymphocytes from patients with HIV-infection showed as abnormal proliferative response to self-MHC class II restricted recall antigens and PWM whereas the response to PHA was conserved. Probably, apoptosis is triggered by an aberrant form of T cell activation in the mature TCD4+ cell population in HIV-infected individuals.