title: S-phase entry leads to cell death in circulating T cells from HIV-infected persons.
abstract: Central memory T cells are thought to play a critical role in memory T cell homoestasis by undergoing self-renewal and by maturating into effector T cells that mediate immunity at tissue sites. Circulating T cells in S phase of the cell cycle are found at increased frequencies during HIV infection and are predominantly composed of cells with a central memory phenotype. Here, we tested the hypothesis that CD4 and CD8 S-phase T cells have different capacities to complete cell cycle and survive. S-phase T cells in peripheral blood from HIV-infected donors were identified by incubating whole blood with BrdU ex vivo. Upon in vitro cultivation, S-phase T cells were more likely to die than to complete mitotic division. Intrinsic differences were observed between CD4 and CD8 S-phase T cells during incubation. Higher frequencies of CD4+ S-phase T cell underwent apoptosis after incubation in medium alone or after TCR stimulation, and CD4+ S-phase T cells were less readily induced to proliferate after incubation with IL-2 than were CD8+ S-phase T cells. CD4+ and CD8+ S-phase T cells expressed low levels of Bcl-2, which could contribute to their heightened susceptibility to cell death. Intrinsic differences in the proliferation and survival of CD4+ and CD8+ S-phase T cells could influence the homeostatic maintenance of these T cell subsets in HIV disease.
authors: Case Western Reserve University and University Hospitals of Cleveland, Center for AIDS Research, Cleveland, OH 44106, USA. sfs2@case.edu
authors: Scott F
authors: SF
authors: Sieg
authors: Douglas A
authors: DA
authors: Bazdar
authors: Michael M
authors: MM
authors: Lederman
mesh_terms: D017209:Apoptosis; D002478:Cells, Cultured; D015658:HIV Infections / Q000276:immunology*; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D016196:S Phase; D013601:T-Lymphocytes / Q000166:cytology*
chemical_list: D007376:Interleukin-2; D019253:Proto-Oncogene Proteins c-bcl-2; D011948:Receptors, Antigen, T-Cell