BTNL2 (butyrophilin-like protein 2), also known as BTL-II, is a 455 amino acid single-pass type II membrane protein that acts as a negative regulator of T cell proliferation. BTNL2 exists as at least six alternatively spliced isoforms, which are encoded by a gene located on human chromosome 6. Expression of BTNL2 isoform 3 is associated with susceptibility to sarcoidosis type 2 (SS2), an immune disorder that causes chronic inflammatory granulomatous lesions.