DOWN-REGULATION OF CD28 SURFACE-ANTIGEN ON CD4(-LYMPHOCYTES DURING HIV-1 INFECTION() AND CD8(+) T)

A progressive significant decrease of CD28 surface antigen expression on CD4(+) (mean, 90, 86, 79, 68% in stages I, II, III, and IV, respect ively, versus 96% in normals), as well as on CD8(+) T lymphocytes (mea n, 38, 32, 31, and 29% in stages I, II, III, and IV, respectively, ver sus 47% in normals) was observed during HIV-1 infection. The increase of cytotoxic/suppressor T cells, in both percentage and absolute numbe rs, that was observed in almost all HIV-1 patients, was associated wit h an increase of the CD8(+) cells lacking the CD28 surface antigen. Th e loss of CD28 antigen expression was parallel to the increase of CD38 , human leukocyte antigen (HLA)-DR, and CD45RO antigen expression on T lymphocytes throughout the disease. Furthermore, a positive significa nt correlation within the CD4(+) but not the CD8(+) subset was observe d between the percentage of cells lacking the CD28 antigen and the per centage of cells expressing the HLA-DR and CD38 antigens, a finding su ggesting that the loss of CD28 antigen expression on CD4(+) lymphocyte s may be associated with T-lymphocyte activation. Patients treated wit h zidovudine showed no significant differences in the percentages of e ither CD4(+)CD28(+) or CD8(+)CD28(+) T-cell subsets when compared to u ntreated patients. These phenotypic changes may be associated with the functional defects of T lymphocytes in HIV-1 infected individuals.