Inhibition of interleukin-2-induced T-cell proliferation by sera from patients with the acquired immune deficiency syndrome.

Sera from 22 patients with either lymphadenopathy syndrome (LAS), acquired immune deficiency syndrome (AIDS)-related complex (ARC), or acquired immune deficiency syndrome were examined for their effect on the interleukin-2 (IL-2)-induced proliferative response of an IL-2-dependent cytotoxic T-cell line, CTL-20. All of the patient sera included in this study were positive for the presence of antibodies against human T-cell lymphotropic virus type III (HTLV-III) as determined by an HTLV-III-specific enzyme-linked immunosorbent assay (ELISA). Eighteen of the 22 patient sera examined (81.8%) exhibited at least a modest suppressive effect on the proliferative response of CTL-20 cells. The inhibitory effect was dose-dependent and varied in intensity for each individual serum. In many cases, the magnitude of suppression was absolute in that it totally abrogated IL-2-induced DNA synthesis. Normal human serum (NHS) exerted no suppressive influence on the IL-2-induced proliferative response of identical control cultures. This same panel of 22 patient sera exhibited no significant inhibitory effects on the levels of protein synthesis in cultures of a non-IL-2-dependent human T-cell line, CCRF-HSB-2, indicating that the suppressive effect was not mediated by nonspecific serum cytotoxicity. The inhibitory effect of patient sera in the IL-2-dependent target cell assay correlated with the ability of these same sera to suppress the mitogen-induced proliferative response of normal human peripheral blood lymphocytes (PBL). These observations are particularly striking in view of the recognized defects of IL-2-dependent effector T-cell functions in AIDS.