Fig. 5. BI induces significantly higher BCG-specific CD4 T cells in recipient gnotobiotic and SPF animals.

(A) Experimental approach: GF or SPF pups were orally gavaged with either 10⁸ CFUs of BI, BT, heat-killed BI, or PBS alone at day 7 of life. A second gavage of similar dosage was performed at day 10. All animals were immunized with 10⁶ CFUs of BCG subcutaneously at day 11 of life. Vaccine-specific responses were assessed 4-weeks after immunization. (B) Time course showing sequential colonization patterns of bacteria in gnotobiotic mice. CFUs were determined by plating serial dilutions of homogenized feces on agar plates. (C) Gating strategy to enumerate CD4⁺ TB10.4⁺ cells. (D) TB10.4-specific CD4 T cells in gnotobiotic mice. (E) TB10.4-specific CD4 T cells in SPF mice. Data are combined from at least two independent experiments. Means ± SEM are plotted (*P < 0.05 and **P < 0.01).