In this study, at the 5th week after infection, the parasite load of undernutrition 65% + infection group in the spleen was the lowest, the expression of PD-1, PD-L1 and Bax in the spleen of this group was downregulated, and TCR, Bcl-2 and TLR4 were upregulated. The gene discussed is BAX; the disease is infection.