title: T helper type 1/T helper type 2 cytokines and T cell death: preventive effect of interleukin 12 on activation-induced and CD95 (FAS/APO-1)-mediated apoptosis of CD4+ T cells from human immunodeficiency virus-infected persons.
abstract: Human immunodeficiency virus (HIV) infection leads to a progressive loss of CD4+ T helper (Th) type 1 cell-mediated immunity that is associated with defective in vitro CD4+ T cell proliferation and abnormal T cell death by apoptosis in response to T cell receptor (TCR) stimulation. Quantification of interleukin (IL)-2, interferon gamma, IL-4, IL-5, and IL-10 secretion by immunoassays, and of interferon gamma, IL-4 and IL-10 messenger RNA expression by competitive reverse transcriptase polymerase chain reaction after in vitro stimulation of the TCR revealed a similar Th1 cytokine profile in T cells from HIV-infected persons and from controls. These data indicated that the loss of CD4+ Th1 cell function in HIV-infected persons is not related to a Th1 to Th2 cytokine switch as previously proposed, but to a process of activation-induced death of CD4+ Th1 cells. Despite the absence of elevated levels of Th2 cytokines, apoptosis of CD4+ T cells, but not of CD8+ T cells, was prevented in vitro by antibodies to IL-10 or IL-4, two Th2 cytokines that downregulate Th1 cell responses, or by the addition of recombinant IL-12, a cytokine that upregulates Th1 functions. TCR-induced apoptosis of T cell hybridomas and preactivated T cells has been shown to involve the CD95 (Fas/Apo-1) molecule. CD4+ and CD8+ T cells from HIV-infected persons expressed high levels of the CD95 molecule, and, in contrast to T cells from controls, were highly sensitive to antibody-mediated CD95 ligation, which induced apoptosis in a percentage of T cells similar to that induced by TCR stimulation. As TCR-induced apoptosis, CD95-mediated apoptosis of CD4+ T cells, but not of CD8+ T cells, was prevented by the addition of recombinant IL-12. Together, these findings suggest that apoptosis of CD4+ T cells from HIV-infected persons involves an abnormal sensitivity to CD95 ligation, and to TCR stimulation in the presence of normal levels of Th2 cytokines. The preventive effect of IL-12 on both mechanisms has potential implications for the design of immunotherapy strategies aimed at the upregulation of CD4+ Th1 cell functions in AIDS.
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001483:Base Sequence; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D017931:DNA Primers / Q000737:chemistry; D015870:Gene Expression; D015658:HIV Infections / Q000276:immunology*; D006801:Humans; D016753:Interleukin-10 / Q000502:physiology; D018664:Interleukin-12 / Q000494:pharmacology*; D015847:Interleukin-4 / Q000502:physiology; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D018417:Th1 Cells / Q000276:immunology*; D018418:Th2 Cells / Q000276:immunology*; D019014:fas Receptor / Q000502:physiology*
chemical_list: D016207:Cytokines; D017931:DNA Primers; D012333:RNA, Messenger; D019014:fas Receptor; D016753:Interleukin-10; D018664:Interleukin-12; D015847:Interleukin-4