CD4 and infection: Of the 14 Th1 response genes tested, the expression levels of 8 genes (IL2, IFNG, CSF2, TLR4, CD4, IRF1, SOCS5 and STAT4) were significantly elevated at 2 weeks and several of these (IL2, IFNG, TLR4, CD4 and STAT4) had similar expression levels at 4 and 8 weeks post-infection (Figure 4A).