At this late stage of infection it was up-regulated in activated CD4+ T cells of both wt (mean = 67.9-fold) and Tnf-/- (mean = 48.6-fold) mice to a similar extent (Figure 3A), although expression of IL-17A was generally low and barely detectable either by real-time PCR (Figure 3B) or by intracellular cytokine staining (Figure 2A). Here, CD4 is linked to infection.