CCR9 and inflammatory bowel disease: Blockade of α4β7 integrin has shown clinical efficacy for treating IBD, whereas CCR9 blockade yielded mixed results.28, 29 To identify homing receptors expressed by bacteria-reactive CD4+ T cells, we enriched CD4+CD154+ T cells using magnetic beads to visualize rare enteric-bacteria-reactive T cells, and analyzed them by flow cytometry (Figure 2A).