The present study was performed with the purposes to: (1) investigate the potential role of APS in regulating Tregs and the influence of APS on CD4+ T cell-mediated immunity after burns with Pseudomonas aeruginosa (P. aeruginosa) infection in vivo; and (2) elucidate the underlying mechanism of APS on the Tregs, which might regulate CD4+ T lymphocyte immune function via down-regulating Toll-like receptor (TLR) 4 expression on Tregs followed by shifting of Th2 to Th1 ex vivo. Here, CD4 is linked to infection.