Butyrophilin subfamily 2 member A1–Butyrophilin subfamily 3 member A1 complex (BTN2A1–BTN3A1 complex) (BTN2A1–BTN3A1 complex)

The Butyrophilin subfamily 2 member A1–Butyrophilin subfamily 3 member A1 (BTN2A1–BTN3A1) complex is a heteromeric protein assembly that serves as a critical molecular sensor for metabolic stress and infection in humans [2, 12]. It is the primary mediator for the activation of Vγ9Vδ2 T cells, a major subset of gamma-delta T cells that provide rapid, MHC-unrestricted immune responses against malignant and infected cells [3, 16]. The complex functions through an "inside-out" signaling mechanism: intracellular phosphoantigens (pAgs), such as isopentenyl pyrophosphate (IPP) or microbial HMBPP, bind to the B30.2 domain of BTN3A1, acting as a molecular glue that promotes its association with BTN2A1 [2, 14]. This intracellular interaction induces a conformational change in the extracellular domains, allowing BTN2A1 to bind directly to the Vγ9 chain of the T cell receptor (TCR) [4, 18]. In oncology, this complex is a high-priority therapeutic target; agonistic monoclonal antibodies like ICT01 are designed to stabilize the complex and bypass the requirement for high pAg levels, thereby potently activating gamma-delta T cells to eliminate a wide range of solid and hematologic tumors [9, 11].

Other names

Butyrophilin 2A1/3A1 complexBTN2A1-BTN3A1 heterodimerHMBPP receptor complexCD277 complex

Agonistic activation of Vγ9Vδ2 T cells by stabilizing the heteromeric association between BTN2A1 and BTN3A1, which facilitates the engagement of the gamma-delta T cell receptor (TCR) and subsequent cytotoxic activity against target cells [2, 9].