T cells were collected from age- and gender-matched WT, EGR1KO and EGR4KO mice. (A) CD4+ T cells were isolated from the spleen by negative selection before incubating with anti-CD3/CD28 antibodies for the indicated time periods. Levels of expression of EGR1, EGR2, EGR3 and EGR4 were measured by qPCR. 