Proliferation and frequency of cytokine-producing CD4⁺ T cells.

Groups of young (6–8 weeks) and older (12 months) BALB/c mice were infected with 2×106L. major promastigotes in one hind footpad. Four weeks post infection, the popiteal lymph nodes were harvested and restimulated with L. major parasites. The frequency of cytokine-expressing CD4+ T cells was determined by intracellular cytokine staining and the frequency of proliferating CD4+ T cells was determined by BrdU incorporation. Data show the results of one representative experiment out of three independent experiments.