Fig. 2.

Proliferation and cytokine production by distinct subsets of CD4SP thymocytes at discrete time points during ontogeny. Different subsets of CD4SP thymocytes (SP1–SP4) and splenic CD4⁺ T cells were obtained at each time point as indicated and stimulated with Con A. (A) Cell proliferation was measured by [³H]TdR incorporation assay at day 3. For cytokine production assays, culture supernatant was harvested at day 2 of culture. (B) IL-2 was measured by [³H]TdR incorporation assay by using IL-2-dependent cell line HT-2. (C and D) IL-4 (C) and IFN-γ (D) were measured by ELISA. Data shown are the mean ± SD of two to three repeated experiments. Filled diamond, SP1; ×, SP2; filled triangle, SP3; filled square, SP4; filled circle, splenic CD4 T cell.