Fig 2. Transfer of S. aureus antigen-specific peritoneal Th1 cells protects against subsequent S. aureus infection via enhanced macrophage responses.

Groups of mice received transfers of 5x10⁶ S. aureus specific Th1 cells originating from the peritoneal cavity of previously exposed mice via i.p. injection. Another group of mice received a transfer of 5x10⁶ naive splenic CD3⁺ cells as a control. At 3 h post transfer both groups of mice were challenged with S. aureus (5x10⁸ CFU) via i.p. injection. At 72 h post-bacterial challenge the bacterial burden was assessed in the peritoneal cavity, kidneys and spleen (A). Results expressed as log₁₀ CFU/ml with mean indicated by bars. At indicated time points post-bacterial challenge, the peritoneal cavity was lavaged with PBS to assess CXCL1 and CCL5 secretion by ELISA (B,C). Results expressed as mean ± SEM. At indicated time points post-challenge, the absolute numbers of macrophages (F4/80⁺Ly6G^-) were assessed in the peritoneal cavity by flow cytometry (D). MHCII expression by infiltrating macrophages was determined 24 h post infection (E). Absolute numbers of neutrophils (Ly6G⁺CD11b⁺) in the peritoneal cavity were assessed at the indicated time points post-challenge (F). Results expressed as mean ± SEM. n = 5–8 mice per group. Data pooled from 3 independent experiments. *p<0.05, **p<0.005.