Fig. 1. Host microbiota play a key role in the development of intestinal IL-9-producing T cells.

Colonic lamina propria cells from conventional Swiss, germ-free or germ-free conventionalised (CNV) mice were extracted and stimulated with PMA (50 ng/ml), ionomycin (500 ng/ml) and Brefeldin A (5 μg/ml) for 4 h at 37 °C and 5% CO₂, and analysed by flow cytometry (a) to determine the frequency of IL-9-producing CD4 + (b) and CD8 + (c) T cells. Data are shown as mean ± SD. One-way ANOVA followed by Tukey’s multiple-comparison test was used for statistical analysis.