Figure 2.

IL-12 promotes early Th1 differentiation, but not T cell proliferation, in antigen-specific T cells exposed to tolerogenic antigen. BALB/c recipients of DO.11 T cells were left untreated (A); immunized with OVA^323–339 peptide in IFA in the footpad on day 0 (B); tolerized with OVA^323–339 peptide intravenously on day 0 (C); or tolerized and treated daily (days −1, 0, +1) with 1 μg of IL-12 (D). The submandibular, axillary, brachial, popliteal, and inguinal lymph nodes (only popliteal and inguinal lymph nodes in B) were harvested 3 d later. Lymph node cells were restimulated in vitro with OVA^323–339 peptide. Proliferative responses were assessed after 72 h by measuring [³H]-thymidine incorporation, and are corrected for the numbers of KJ-126⁺ CD4⁺ cells per well. Cytokine secretion was assayed daily by ELISA. Results are from one representative experiment of three. The error bars represent standard deviations calculated from duplicate wells.