Long-Lived Colitogenic CD4+ Memory T Cells Residing Outside the Intestine Participate in the Perpetuation of Chronic Colitis

Abstract

To understand the perpetuation of inflammatory bowel disease (IBD), it is important to clarify whether the colitogenic CD4+ T cells are self-limited effector or long-lived memory T cells. We here investigate the latency of colitogenic CD4+ T cells in the remission stage of colitis under germfree (GF) conditions. We isolated splenic (SP) CD4+ T cells from colitic CD4+CD45RBhigh T cell-injected SCID mice maintained under specific pathogen-free (SPF) conditions and transferred them into SPF or GF SCID mice. Donor colitic SP CD4+ T cells have a characteristic CD44highCD62L−IL-7Rαhigh effector-memory T-type phenotype. Six weeks after transfer of cells to GF SCID mice, one group of mice was continued in GF conditions (GF→GF), and the other was transferred into SPF conditions (GF→SPF). GF→SPF but not GF→GF SCID mice developed colitis with elevated production of Th1 and Th17 cytokines at 4 wk after transfer. Surprisingly, a large number of CD4+ effector-memory T cells and a small but substantial number of central-memory T cells remained resident in SP and bone marrow, but not in lamina propria, of the GF→GF SCID recipients. Consistent with this, GF→SPF but not GF→GF SCID mice rapidly developed colitis. Taken together, these findings suggest that long-lived colitogenic memory CD4+ cells can be established even in the presence of commensal Ags, reside outside the intestine in the absence of commensal bacteria, and participate in the perpetuation of colitis. Thus, blocking a stimulus of colitogenic memory CD4+ cells such as IL-7 may have therapeutic benefit for treatment of inflammatory bowel disease.