At the 8th week post-infection in the liver, PD-1, PD-L1, CTLA-4, Tim-3, Caspase-3 and TCR were all upregulated in two undernutrition infected groups, but more upregulated in undernutrition 75% + infection group, which might explain why the parasite load of undernutrition 75% + infection group was also the highest in the liver. The gene discussed is PDCD1; the disease is infection.