Surprisingly, the blockade of PD-L2 in the infected mice reversed the infection-induced Th2 responses back to Th1 immune responses, with significantly increased IFN-γ-expressing T cells in the splenocytes and IFN-γ transcriptional level in the infected liver tissue, as well as decreased levels of IL-4 and IL-10, in parallel with increased M1-produced iNOS and decreased Arginase-1 expression on the M2. This evidence concerns the gene IL4 and infection.