Perturbed cytokine production by primed CD4⁺ T cells in the absence of B7-H2 costimulation. CD4⁺ T cells from the draining lymph nodes of KLH/CFA-immunized wild-type (•) and B7-H2^–/– (○) mice were isolated and cultured in vitro in the presence of soluble KLH for 2 to 5 days. The production of various cytokines was quantified via ELISA using known standards. IL-2 (A), IFN-γ (B), IL-4 (C), and IL-10 (D) were measured from day 2 to day 5 after restimulation. Data shown are representative of 2 independent experiments, each performed with 3 mice per group.