CD4⁺ T cell deficiency leads to impaired control of primary and secondary infection.

Wild-type C57BL/6 or I-A-/-I-Enull mice were i.v. injected with 200cfu TAS2010. A) Infection-induced weight variation overtime is calculated as the percentage of initial body weight. Shown are mean ± SEM, n = 9–14, data pooled from 3 independent experiments. B) The bacterial load in the spleen and liver from individual mice is shown with geometric mean for each group at the indicated time points post-infection. C) C57BL/6 mice were intraperitoneally (i.p.) injected with αCD4 GK1.5 mAb or PBS at Wk 12 post-vaccination, a day prior to challenge with 107cfu wild-type S. Typhimurium SL1344 by oral gavage. The depletion was maintained by i.p. injection with GK1.5 mAb twice weekly thereafter. Shown is the percentage of mice remaining protected at the indicated time points post-challenge. Data are pooled from 2 independent experiments. Log-rank Mantel-Cox test was used for statistical analysis between PBS-treated and CD4-depleted groups.