CD28 EXPRESSION IN PEDIATRIC HUMAN-IMMUNODEFICIENCY-VIRUS INFECTION

Increased apoptosis of lymphocytes represents a key event of immune de struction 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 dec reased CD28 expression. In 26 HIV-infected and 20 healthy children, as well as 10 infants exposed to HIV, expression of CD28 and the apoptos is-related marker CD95 was studied by fluorescence-activated cell sort ing 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 show ed a markedly decreased mean CD28 (36.2% +/- 16.1 SD) and increased CD 95 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 CD2 8 and CD95 expression was not altered in category 1 patients. Of the e xposed children, the child with the lowest CD28 expression on CD8 cell s was determined later to be infected with HIV. Significant immunophen otypical alterations are observed in early stage pediatric HIV infecti on, which may indicate an early loss of protection against apoptosis i n the CD8(+) T cell population.