Induction of cytokines in CD4+ T cells by different costimulatory receptors. Human CD4+ T cells were stimulated with various stimuli. (A) Cytokine mRNA level were determined after eight hours stimulation using real-time RT-PCR. mRNA level were normalized to β-actin and CD3 stimulated cells were set to 1. Each column represents mean ± s.e.mean of three different donors. (B) Cytokine protein level was determined in the supernatant by ELISA after twenty-four hours of stimulation. Each column represents mean ± s.e.mean of three different volunteers. *P < 0.05 (versus CD3 stimulated samples).