In vitro effect of interleukin-12 on antigen-specific lymphocyte proliferative responses from persons infected with human immunodeficiency virus type 1.

The relationship between CD4 lymphocyte count and the in vitro effect of interleukin (IL)-12 on lymphocyte proliferative responses to Candida, tetanus toxoid, and streptokinase antigens was studied in peripheral blood mononuclear cells (PBMC from 30 human immunodeficiency virus (HIV)-infected persons and 10 seronegative controls. IL-12 significantly increased proliferative responses to microbial recall antigens of PBMC from HIV-infected persons with >200 CD4 lymphocytes/mm3 but had little effect on PBMC from patients with more advanced disease. The greatest increase was seen in patients with 200-500 CD4 cells/mm3. Results of limiting dilution analysis suggested that the increase in antigen-specific lymphocyte proliferation in the presence of IL-12 was due to an increase in the number of responding cells rather than an increase in the extent of proliferation of a fixed number of responder cells.