Butyrophilin subfamily 3 member A1 and Butyrophilin subfamily 2 member A1 heteromer (BTN3A1/BTN2A1 heteromer)

The BTN3A1/BTN2A1 heteromer is a critical molecular sensor complex required for the activation of human Vγ9Vδ2 T cells, a major subset of gamma-delta T cells involved in immunosurveillance. BTN3A1 (Butyrophilin 3A1) contains an intracellular B30.2 domain that binds small phosphorylated metabolites known as phosphoantigens (pAg), such as IPP, which accumulate in cancer cells or during infections. Recent structural and functional studies have demonstrated that BTN2A1 (Butyrophilin 2A1) is an essential co-factor that binds directly to the Vγ9 chain of the T-cell receptor (TCR), while BTN3A1 facilitates the sensing of pAg and coordinates the complex formation (Rigau et al., 2020, Science; Yuan et al., 2021, Nature Communications). In the pharmaceutical industry, this heteromer is targeted to enhance anti-tumor immunity. Monoclonal antibodies like ICT01 are designed to bind the extracellular domain of BTN3A1 to trigger a conformational change that activates Vγ9Vδ2 T cells regardless of pAg concentration. This approach is currently being evaluated in clinical trials for various solid and hematologic malignancies. Understanding the stoichiometry and spatial organization of the BTN3A1/BTN2A1 complex is vital for developing next-generation immunotherapies that leverage the innate-like rapid response of gamma-delta T cells (Lapiedra et al., 2023, Frontiers in Immunology).

Other names

BTN3A1-BTN2A1 complexButyrophilin 3A1Butyrophilin 2A1CD277 (for BTN3A1)BTF1BT3.1

Drugs targeting this heteromer typically act as agonists to induce a conformational change that mimics phosphoantigen binding, or they facilitate the stabilization of the BTN3A1/BTN2A1 complex. This stabilization promotes the recruitment and activation of Vγ9Vδ2 T cells, which then exert cytotoxic effects against tumor cells or infected cells (Rigau et al., 2020, Science; Karunakaran et al., 2020, Science).