Correlates of apoptosis of CD4(+) and CD8(+) T cells in tonsillar tissue in HIV type 1 infection

The immunopathogenesis of human immunodeficiency virus type 1 (HIV-1) infec tion has been associated with increased death by apoptosis of T cell subset s, In the present study, we have examined correlates of apoptosis of CD4(+) , CD8(+)CD28(+), and CD8(+)CD28(-) T cells in tonsillar lymphoid tissue in persons with HIV-1, Single-cell suspensions of tonsillar lymphocytes were a nalyzed by flow cytometry to determine the fraction of cells showing typica l characteristics of apoptosis as well as the expression of activation mark ers within the live and the apoptotic cell populations, The proportion of c ells carrying infectious provirus was quantified by limiting dilution analy sis. Compared with uninfected controls, apoptosis of both CD4(+) and CD8(+) T cells was enhanced in HIV-1 infection and was higher among CD8(+) than a mong CD4(+) T cells, Apoptosis of CD28(-) cells was more prevalent than apo ptosis of CD28(+) cells for both CD4(+) and CD8(+) T cells. Occurrence of a poptosis of CD4(+) T cells correlated with provirus levels and proportional expression of the activation marker HLA-DR. Apoptosis of CD8(+)CD28(+) cel ls correlated with expression of the activation markers CD69 and HLA-DR whi le apoptosis within CD8(+)CD28(-) cells did not correlate with any of the s tudied parameters. Although apoptosis was much more prevalent among CD8(+) than CD4(+) T cells, CD8+ T cells still accumulated in tonsillar lymphoid t issue in persons with HIV-1. Our data may be interpreted to suggest that ap optosis of CD4(+), CD8(+)CD28(+), and CD8(+)CD28(-) cells in tonsillar tiss ue is regulated by different mechanisms and the results are of importance t o our understanding of the immunopathogenesis of HIV-1 infection.