Butyrophilin subfamily 3 member A1–phosphoantigen complex (BTN3A1/pAg complex)

Butyrophilin subfamily 3 member A1 (BTN3A1) is a type I transmembrane receptor in the immunoglobulin superfamily, closely related to the B7 family. It contains extracellular Ig-like domains and a unique intracellular B30.2 (PRYSPRY) domain, which binds small pyrophosphate-containing phosphoantigens (such as HMBPP and IPP). In complex with these phosphoantigens, BTN3A1 undergoes a conformational change, enabling the formation of a heterodimer with BTN2A1. This complex is recognized by the Vγ9Vδ2 T cell receptor, fundamentally activating this major subset of human γδ T cells, which execute immune responses against tumor cells and pathogens through cytotoxicity and cytokine secretion[1][2][3][4][5][9]. BTN3A1 is essential for the sensing of metabolic changes unique to transformed or infected cells and is a promising immunotherapeutic target[2][9]. No direct small-molecule antagonists or inhibitors of BTN3A1 are in routine clinical use, but therapeutics may act by modulating phosphoantigen levels or antibody-based agonism.

Other names

BTN3A1CD277Butyrophilin subfamily 3 member A1Butyrophilin 3A1BTN3.1

Agonistic antibodies: trigger conformational changes in BTN3A1, mimicking phosphoantigen binding and activating Vγ9Vδ2 T cells; Phosphoantigen accumulation: increases activation of Vγ9Vδ2 T cells by engaging BTN3A1; Small molecule modulation: altering endogenous levels of phosphoantigens (IPP, HMBPP)