gp120 is present on the plasma membrane of apoptotic CD4 cells prepared from lymph nodes of HIV-1-infected individuals: an immunoelectron microscopic study

OBJECTIVE: To study whether free gp120 can be detected on the plasma membranes of apoptotic CD4+ T lymphocytes in lymph nodes from HIV-positive patients. METHODS: Lymph-node cell suspensions prepared from three HIV-positive patients were studied by pre-embedding, double-immunogold-labeling to identify cell type, determine cell morphology, and detect the presence of bound gp120 molecules. Cells were classified by their surface antigens as helper/inducer T lymphocytes (CD4+), cytotoxic/suppressor T lymphocytes (CD8+), B cells (CD20+), and total lymphocytes [CD45+, leukocyte common antigen (LCA)+]. RESULTS: gp120 colabelled with both apoptotic and normal CD4+ T lymphocytes and LCA+ cells, but not with either apoptotic or normal CD8+ T lymphocytes or B cells. gp120 was more often identified on apoptotic than on normal CD4+ T lymphocytes. The gp120 and CD45 label were often colocalized. HIV particles were not identified to be associated with or budding from either normal or apoptotic lymphocytes. CONCLUSIONS: Free gp120 is found bound to CD4+ T cells in lymph nodes of HIV-infected individuals and potentially mark them for premature death by apoptosis.