title: Contact of human immunodeficiency virus type 1-infected and uninfected CD4+ T lymphocytes is highly cytolytic for both cells.
abstract: Individuals infected with the human immunodeficiency virus (HIV) experience a marked loss of CD4+ T lymphocytes, leading to fatal immunodeficiency. The mechanisms causing the depletion of these cells are not yet understood. In this study, we observed that CD4+ T lymphocytes from HIV type 1 (HIV-1)-infected and uninfected individuals rapidly lysed B lymphoblasts expressing the HIV-1 envelope glycoprotein on the cell surface and Jurkat cells expressing the complete virus. Contact of uninfected CD4+ T cells with envelope glycoprotein-expressing cells also resulted in the lysis of the uninfected CD4+ T cells. Cytolysis did not require priming or in vitro stimulation of the CD4+ T cells and was not restricted by major histocompatibility complex molecules. Cytotoxicity was inhibited by soluble CD4 and anti-CD4 monoclonal antibodies that block binding of CD4 to gp120. In addition, neutralizing anti-CD4 and anti-gp120 monoclonal antibodies which block postbinding membrane fusion events and syncytium formation also inhibited cell lysis, suggesting that identical mechanisms in HIV-infected cultures underlie cell-cell fusion and the cytolysis observed. However, cytotoxicity was not always accompanied by the formation of visible syncytia. Rapid cell lysis after contact of uninfected and HIV-1-infected CD4+ T cells may explain CD4+ T-cell depletion in the absence of detectable syncytia in infected individuals. Moreover, because of its vigor, lysis of envelope-expressing targets by contact with unprimed CD4+ T lymphocytes may at first glance resemble antigen-specific immune responses and should be excluded when cytotoxic T-lymphocyte responses in infected individuals and vaccinees are evaluated.
mesh_terms: D019138:Antibodies, Blocking / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015703:Antigens, CD / Q000276:immunology; D015704:CD4 Antigens / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000821:virology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002450:Cell Communication; D002460:Cell Line; D003602:Cytotoxicity, Immunologic; D015726:Giant Cells; D015699:HIV Envelope Protein gp120 / Q000276:immunology; D015658:HIV Infections / Q000097:blood / Q000276:immunology*; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D016130:Immunophenotyping; D008285:Major Histocompatibility Complex; D012016:Reference Values; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D019138:Antibodies, Blocking; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D015704:CD4 Antigens; D015699:HIV Envelope Protein gp120