ATRA inhibits in vitro Th2 cell differentiation. Naïve CD4 T cells were isolated by MACS and differentiated under Th2 culture conditions in the presence of 1nM ATRA or DMSO vehicle control. (A, B) After 2 and 3 rounds of differentiation (2xTh2 and 3xTh2, respectively) cells were restimulated with PMA and ionomycin and analyzed by ICCS. (C, D) Percentages and (E, F) mean fluorescence intensity (MFI) of cytokine positive 2xTh2 (C, E) and 3xTh2 (D, F) cells are plotted from 3 experiments. Data is presented as mean +/- SEM. 2-way ANOVA was performed and Bonferroni multiple comparisons p values are displayed.