Expression of CD69 after in vitro stimulation: A rapid method for quantitating impaired lymphocyte responses in HIV-infected individuals

A flow cytometric assay based on expression of the activation antigen CD69 was developed to analyze immunological responses of T cells from human immunodeficiency virus (HIV)-infected (HIV+) or HIV-seronegative (HIV-) donors after in vitro simulation by antigens and polyclonal activators. The levels of CD69 on freshly-isolated or unstimulated, cultured CD3(+), CD4(+), or CD8(+) peripheral blood lymphocyte (PBL) subsets were low and did not differ greatly between HIV+ and HIV- donors. The frequencies of CD3(+), CD4(+), and CD8(+) lymphocytes from HIV+ donors that expressed CD69 after culture with antigenic or mitogenic stimuli were significantly lower than in HIV- donors. Comparison of CD69 expression with [H-3]thymidine incorporation revealed that both assays could detect lymphocyte responses to antigenic or mitogenic stimuli. The CD3(+) PBL from HIV+ or HIV- donors did not show increased CD69 expression after culture with soluble or cross-linked recombinant envelope glycoprotein, gp120, The gp120, however, significantly inhibited CD69 expression in phytohemagglutinin-stimulated T cells in vitro and may also affect T-cell activation in vivo. These studies demonstrate the usefulness of this CD69 expression assay for the rapid assessment of defects in immune responses of phenotypically defined lymphocyte subsets in HIV+ patients and for testing the effects of agents that modulate immune activation.