Oral immunization with GK-1 induced the activation of CD4 and CD19 cells in mucosal and peripheral lymphoid tissues. Groups of nine mice were orally primed with GK-1 (), BLS-GK-1 (), or BLS plus GK-1 (▪) and boosted with GK-1 (prime/boost). At 15 days after the third immunization, mice were primed in vivo, and 24 h later lymphocytes were recovered from PP, MLN, and spleen. The lymphocytes from groups of three mice were pooled and analyzed by fluorescence-activated cell sorter analysis. *, significant differences compared with mice treated only with saline (□) (P < 0.05, Tukey-Kramer multiple-comparisons test). Data are representative of three independent experiments.