FIG. 2.

T cells are not essential for E. muris-induced immunity following IOE challenge. a. CD4-deficient mice were immunized with E. muris and then challenged with IOE (2× LD₅₀) approximately 30 days later. Similar studies were performed with CD8-deficient (b) and class II MHC-deficient (c) mice. Unimmunized (unimm) and immunized (imm) mice were used as controls. Data in panel b were statistically significant (P = 0.043). d. Wild-type and CD4-deficient mice were immunized with E. muris and then challenged with IOE. One group of wild-type mice was administered anti-CD4 1 day prior to IOE challenge (GK1.5; 200 μg/injection). e. Naive mice were administered 2 × 10⁶ splenocytes (imm. SPCs) or flow cytometry-purified CD4 T cells (imm. CD4⁺; 99.2% purity) that had been obtained from E. muris-immunized mice at least 30 days after immunization. All experiments utilized three to five mice per group.