N-terminal ectodomain of BTNL2 inhibits T cell activation via a non-canonical interaction with its putative receptor that results in a delayed progression of DSS-induced ulcerative colitis

Abstract

Butyrophilin-like 2 (BTNL2) is a T cell inhibitory molecule that interacts with unknown binding partners to modulate the immune response in a number of inflammatory and autoimmune diseases. In this study, we found that the inhibitory effects of BTNL2 on T cell activation and effector functions can be executed by its N-terminal IgV domain (BTNL2 IgV1) alone. Structure-guided mutation of key residues on BTNL2 IgV1 based on known receptor-ligand interfaces involving immunoglobulin superfamily members revealed that BTNL2 uses a non-canonical binding interface with its putative receptor. A high avidity BTNL2 IgV1 probe revealed that in an inducible model of ulcerative colitis, severe colitis was accompanied by a selective enrichment of BTNL2-receptor expressing effector-memory CD4+ and CD8+ T cells in the Peyer’s patches. Intraperitoneal administration of BTNL2 IgV1 resulted in a significant delay in the progression of DSS-induced colitis and also showed reduced activation of the BTNL2-receptor-expressing T cells in the Peyer’s patches. Thus, this study demonstrates that the BTNL2-receptor-expressing T cells in the Peyer’s patches participate in the disease pathogenesis and can serve as a novel therapeutic target in ulcerative colitis, which can be modulated by BTNL2 IgV1.