IMMUNOPHENOTYPIC ANALYSIS OF PERIPHERAL-BLOOD MONONUCLEAR-CELLS UNDERGOING IN-VITRO APOPTOSIS AFTER ISOLATION FROM HUMAN IMMUNODEFICIENCY VIRUS-INFECTED CHILDREN

Lymphocytes of human immunodeficiency virus (HIV)infected individuals undergo accelerated apoptosis in vitro, but the subsets of cells affec ted have not been clearly defined. This study examined the relationshi p between lymphocyte phenotype and apoptotic cell death in HIV-infecte d children by flow cytometry, Direct examination of the phenotype of a poptotic lymphocytes was accomplished using a combination of surface a ntigen labeling performed simultaneously with the Tdt mediated Utp nic k end-labeling (TUNEL) assay. In comparison to live cells, apoptotic l ymphocytes displayed an overrepresentation of CD45RO and HLA-DR expres sing cells, while CD28 and CD95 expressing cells were underrepresented . Lymphocytes expressing CD4, CD8, and CD38 were equally represented i n apoptotic and live populations. When percent lymphocyte apoptosis fo llowing culture was examined independently with lymphocyte subsets in fresh blood, apoptosis was negatively correlated with the percentage o f CD4 cells, but not with specific CD4 T-cell subsets. Although not co rrelated with the percentage of total CD8 cells, apoptosis was positiv ely correlated with specific CD8 T-cell subsets expressing CD45RO and CD95 and negatively correlated for CD8 T cells expressing CD45RA. Thes e results provide direct evidence that a population of activated lymph ocytes with the memory phenotype lacking the costimulatory molecule CD 28 are especially prone to undergo apoptosis. The findings related to CD95 expression in fresh and apoptotic cells implicate Fas-dependent a nd Fas-independent pathways of apoptosis in HIV disease in children. ( C) 1998 by The American Society of Hematology.