Effect of phorbol myristate acetate on T cell colony formation, interleukin-2 (IL-2) receptor expression and IL-2 production by cells from patients at all stages of HIV infection

Abstract

We and others have shown that several T cell responses induced by the mitogen phytohaemagglutinin (PHA), including T cell colony formation, IL-2 receptor (IL-2R) expression, and IL-2 production are impaired in patients with AIDS and lymphadenopathy syndrome (LAS). We investigated whether phorbol myristate acetate (PMA) could act in synergy with PHA (as it does in healthy subjects) to enhance in vitro T cell responses of patients at all stages of infection by HIV. In AIDS patients with opportunistic infections (AIDS/OI), PHA + IL-2 + PMA led to a total disappearance of T cell colonies in 10/11 patients, among whom six already displayed very low numbers of colonies induced by PHA + IL-2 (less than 50 colonies/5 x 10(4) cells). In contrast, T cell colony formation induced by PHA + IL-2 + PMA was maintained or increased, compared with that induced by PHA + IL-2, in five out of six AIDS patients with Kaposi's sarcoma (AIDS/KS), 10/14 LAS and six out of seven HIV-seropositive asymptomatic (HIV+/AS) homosexuals. In these three groups of patients, a low percentage of colony cells induced by PHA + IL-2 + PMA expressed CD3 and CD4 molecules, but 50-89% of cells were IL-2R (Tac) positive, as in healthy controls. Studies on T cell activation and IL-2 production were performed on a selected group of 12 HIV-infected patients for whom sufficient numbers of lymphocytes could be obtained. PMA induced CD4 down-modulation in controls and in HIV-infected patients. However, CD3 down-modulation and induction of the Tac chain of IL-2R by PMA were significantly impaired in patients, compared with controls, and these two parameters were correlated. Although PHA alone induced virtually normal levels of Tac antigen on patients' cells, Tac induction by PHA + PMA was significantly decreased in patients versus controls. Cells from five out of 10 patients tested failed to produce detectable amounts of IL-2 after PHA stimulation, whereas IL-2 production increased significantly in all patients tested (n = 9) after PHA + PMA, with a level of IL-2 activity significantly higher than in controls. No correlation was found in this group of patients between the effects of PMA + PHA on T cell colony formation, Tac expression, or IL-2 production, as compared with PHA alone. Taken together, our results indicate that in vitro T cell functional studies with PMA may be useful to evaluate better the defects of T cell activation in HIV-infected patients.