Circulating integrin alpha4/beta7+ lymphocytes targeted by vedolizumab have a pro-inflammatory phenotype.

Integrin alpha4/beta7 on circulating lymphocytes identifies them as gut-tropic, and can be targeted by the humanized antibody vedolizumab to treat inflammatory bowel disease (IBD). We found lymphocytes expressing alpha4/beta7 were significantly more responsive to the pro-inflammatory cytokines IL-6, IL-7, and IL-21, and less responsive to the regulatory T cell (Treg)-supporting cytokine IL-2. Alpha4/beta7 was expressed by a smaller percent of FOXP3 + Helios+ thymically-derived Tregs (tTregs) than FOXP3 + Helios- peripherally-derived Tregs (pTregs) or FOXP3- effector T cells. Integrin alpha4/beta7+ CD4 T cells were also rare among cells expressing the Th2 marker CRTh2, but enriched in cells bearing the circulating T follicular helper cell marker CXCR5. Thus the effect of this anti-integrin therapy on the mucosal immune system may be more qualitative than quantitative, and selectively replace pro-inflammatory effector cells with Tregs and Th2 cells to facilitate immune tolerance in the mucosa without globally depleting lymphocytes from the intestinal mucosa.