CD28 and infection: In the liver, CTLA-4 (P = 0.0473), TCR (P = 0.0470), ICOS (P = 0.0382), CD28 (P = 0.0072) and Bcl-2 (P = 0.0462) were upregulated in undernutrition 75% + infection group at the 5th week post-infection.