The number of Ag-specific CD8 T cells specific for B8R, OVA257, HSV, GAP-50, and LCMV gp33 and CD4 T cells specific for 2W1S, Ag28m, LCMV gp66–77, and L. monocytogenes LLO190–201 was determined using tetramer enrichment. Representative flow plots showing gating strategy used in tetramer-enriched cell fractions to detect the frequency of Ag-specific (A) CD8 and (B) CD4 T cell populations. Shown are examples used to detect B8R- and GAP-50-specific CD8 T cells and Ag28- and 2W1S-specific CD4 T cells. Graphs show the number of Ag-specific T cell precursors across the 5 MHC I- and 4 MHC II-restricted epitopes in SPF and CoH mice. Data were combined from 3 individual experiments, using 4–7 mice/group. Statistical significance was determined using group-wise, one-way ANOVA with multiple-testing correction using the Holm-Sidak method, and α = 0.05. No significant difference was noted for any of the Ag-specific T cell populations.