Antibody-mediated neutralization of RANKL prevents differentiation of M cells in the follicle-associated epithelium of Peyer’s patches (39.4)

Abstract

Abstract Mucosal surfaces are bombarded with commensal bacteria and foreign antigens. Intestinal Peyer's patches (PP) are inductive sites where secretory IgA production and T cell tolerance are initiated. The follicle-associated epithelium (FAE) over PP includes M cells that transcytose particulate antigens. We have shown that RANKL, a TNF-related cytokine expressed by PP stromal cells, is required for M cell development. UEA-I+ M cells were reduced by >98% in RANKL-/- mice, a defect corrected by s.c. injection of RANKL. We investigated whether acute depletion of RANKL by neutralizing monoclonal antibody (mAb) in BALB/c mice also led to M cell loss. Loss of 70% of UEA-I+ M cells was detected 4 days after every other day injections of 250 μg of rat anti-mouse RANKL mAb (IK22-5). Further loss of M cells occurred after longer treatment, with loss of 92% of M cells after 8 days. Anti-RANKL treatment also led to functional loss of M cell antigen sampling as measured by uptake of 200 nm diameter fluorescent beads. We conclude that continuous RANKL expression on PP stromal cells is essential for the normal differentiation of M cells from epithelial stem cells in crypts adjacent to PP domes.