CD28 expression in pediatric human immunodeficiency virus infection.

Increased apoptosis of lymphocytes represents a key event of immune destruction in HIV infection. In this study it was investigated at which stage of the disease and in which T lymphocyte subpopulation (CD4+ or CD8+) protection against apoptosis may be lost as measured by decreased CD28 expression. In 26 HIV-infected and 20 healthy children, as well as 10 infants exposed to HIV, expression of CD28 and the apoptosis-related marker CD95 was studied by fluorescence-activated cell sorting analysis. According to established Centers for Disease Control and Prevention definitions, children were divided into three immunologic categories. In the CD8 population, patients in category 1 already showed a markedly decreased mean CD28 (36.2%+/-16.1 SD) and increased CD95 expression (48.8+/-24.1%), compared with the age-matched control group (67.7+/-14.4%, 15.8+/-8.9%). In the CD4 population, mean CD28 and CD95 expression was not altered in category 1 patients. Of the exposed children, the child with the lowest CD28 expression on CD8 cells was determined later to be infected with HIV. Significant immunophenotypical alterations are observed in early stage pediatric HIV infection, which may indicate an early loss of protection against apoptosis in the CD8+ T cell population.