BATF KO T cells are defective in up-regulation of CCR9 and α4β7 but not in becoming FoxP3⁺ T cells in response to RA. (A) CD4⁺ naive T cells were activated in the presence of RA, and expression of CCR9 and α4β7 was examined by flow cytometry. (B) Expression of the trafficking receptor genes at the mRNA by cultured CD4⁺ naive T cells was examined by quantitative RT-PCR. Normalized values to β-actin levels are shown. (C) Expression of other chemokine receptors was examined by flow cytometry. (D) RA-dependent induction of FoxP3⁺ T cells in vitro from naive CD4⁺ T cells was examined by flow cytometry. Naive CD4⁺ T cells were in vitro activated with concanavalin A and IL-2 in the presence or absence of 10 nM RA for 5 d. 1 ng/ml TGFβ1 was added to culture. (E) Expression of CCR9 and α4β7 by WT and BATF KO FoxP3⁺ cells induced by RA and TGFβ1. All graphs show pooled data obtained from four experiments (*, P < 0.05). All error bars are SEM obtained from pooled data.