CD4 and infection: In addition, the expression of IFN-γ, TNF-α, CD69, and IFN-γ mRNA in the lung CD4+ T cells and IFN-γ in spleen CD4+ T cells significantly elevated after infection in WT mice (p = 0.00012, 0.0172, 0.0038, 0.00562, and 0.0117, respectively) (Figure 2).