Limiting dilution analysis of interleukin-2-producing T cells responsive to recall and alloantigens in human immunodeficiency virus-infected and uninfected individuals

Peripheral blood mononuclear cells (PBMC) from individuals who were seropositive for the human immunodeficiency virus type 1 (HIV), and most without symptoms (HIV⁺) were compared with PBMC from healthy HIV-seronegative (HIV^-) individuals for in vitro generated T helper cell (Th) responses. Th function in bulk culture and limiting dilution analysis was assessed by IL-2 production following stimulation with influenza A virus (FLU) or irradiated allogeneic PBMC (ALLO). We observed that the frequencies of FLU- and ALLO-stimulated Th cells were not appreciably different in the PBMC of HIV^- individuals, and that they were also not different in the PBMC of those HIV⁺ individuals who responded to both FLU and ALLO in bulk culture. However, there was a severe drop in the Th frequency to FLU in HIV⁺ individuals who were unresponsive to FLU but responsive to ALLO by bulk culture. The PBMC of HIV⁺ individuals who were unresponsive by bulk culture to both FLU and ALLO exhibited a drastic reduction in the Th frequencies for both stimuli. These results demonstrate a concordance between Th functional analysis performed by limiting dilution and bulk culture. The results also indicate that the early selective loss in Th function to recall antigens is not likely to be due simply to a difference in frequencies of FLU- and ALLO-stimulated Th cells present prior to the onset of Th dysfunction.