Prevalence of T and B lymphocytes in the small intestine of wild-type and F/A-2^+/+ mice. The relative percentage of intestinal lymphocytes, including those from PPs, that express the T cell markers CD3 (a), CD8 (b),CD4 (c), integrin α^IEL (d), the B cell markers CD19 (e), and MHC-II (f), was determined in wild-type (squares) and F/A-2^+/+ small intestine (diamonds) by flow cytometry. The percentage of cells that expresses T cell markers is similar in both groups, but the percentage that expresses B cell markers is significantly reduced in F/A-2^+/+ small intestine. Data shown are mean ± SEM of six mice of each genotype. Significant differences (P < 0.05), determined by one-way ANOVA followed by Dunnett’s multiple comparison test, are indicated by asterisks.