Butyrophilin-like protein 9 (BTNL9)

Butyrophilin-like protein 9 (BTNL9) is a type I transmembrane glycoprotein, belonging to the butyrophilin/microtubule-associated oligodendrocyte glycoprotein (BTN/MOG) immunoglobulin superfamily[1][2]. It is predominantly expressed in immune cells—especially B cells—with lower transcript levels found in adipose tissue, lung, thymus, spleen, colon, and cardiac tissue[1]. BTNL9 acts as a negative regulator of immune cell activation, with recombinant BTNL9 shown to inhibit IFN-gamma secretion by peripheral blood mononuclear cells upon stimulation[1]. It binds to various immune cell types, including T cells, B cells, macrophages, and dendritic cells[1]. BTNL9 is emerging as both a tumor suppressor and a prognostic biomarker: expression is downregulated in multiple cancers (breast cancer, uveal melanoma, lung adenocarcinoma), which correlates with poor prognosis, increased cellular proliferation, metastasis, and lower immune infiltration[2]. Restoration of BTNL9 is associated with cell cycle arrest via p53-dependent pathways[2]. Besides cancer, altered BTNL9 expression has been observed in vascular pathologies such as intrauterine growth restriction and is differentially expressed in osteosarcoma versus normal bone[2]. No drugs directly targeting BTNL9 or clinical mechanisms of action have been reported to date[3]. Its safety profile, druggability, and utility as a therapeutic target remain under active investigation.

Other names

Butyrophilin-like protein 9BTNL9BTN8BTN3VDLS1900FLJ32535UNQ1900/PRO4346butyrophilin 3