In the peritonitis model, depletion of CD4+ T cells significantly decreased the survival of mice vaccinated with 4C-Staph/T7-alum (58% survival vs. 79% of mice treated with isotype control antibody, p = 0.034), but not of mice vaccinated with 4C-Staph/alum (13% survival vs. 31% of mice treated with isotype control antibody, p = 0.207, Fig 5B). This evidence concerns the gene CD4 and peritonitis.