Differential Priming to Programmed Cell Death of Superantigen-Reactive Lymphocytes of HIV Patients

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Abstract
Programmed cell death or apoptosis has been shown to play a central role in CD4+ T cell depletion following HIV infection. Because most apoptotic signals are delivered through T cell receptor stimulation, we investigated whether T cell depletion in AIDS is a stochastic phenomenon or if it preferentially affects T cell subsets defined by their interaction with superantigens. To address this problem we have taken advantage of the exclusive property of superantigens to trigger T cells expressing selective sets of T cell receptor V beta elements. Here we report that CD4+ T cells from HIV-infected patients can proliferate in vitro to T cell receptor mobilization by some superantigens, but not others. Furthermore, the failure of T cells to respond to some superantigens was shown to be due to an active cell death process that differentially affected T cells capable of interacting with different superantigens. The selective programmed cell death priming of T cells responsive to particular superantigens, observed in this study, suggests that T cell depletion in HIV infection is not simply due to the cytopathic effect of the virus. The possible link between programmed cell death and T cell receptor variable regions suggested by the present experiments may help to better define current models of AIDS pathogenesis.