HHLA2/B7-H7 (E1U6X) Rabbit mAb #52200

HERV-H LTR-associating protein 2 (HHLA2, with alternative names of B7-H5 and B7-H7) is a member of the B7 immunoglobulin superfamily (1). HHLA2 protein is constitutively expressed on the surface of human monocytes and is induced on B cells after stimulation with LPS and IFN-γ (1,2). Through interaction with TMIGD2, which is constitutively expressed on all naïve T cells and the majority of natural killer cells, but not on T regulatory cells or B cells, HHLA2 co-stimulates T cells in the context of TCR-mediated activation, enhancing T cell proliferation and cytokine production via an AKT-dependent signaling cascade (2). Contrary to this, HHLA2 has also been shown to inhibit T cell proliferation and cytokine production, suggesting a secondary receptor for HHLA2 that is expressed on activated T cells with co-inhibitory functions (3). Moreover, HHLA2 has been shown to be highly expressed in various types of cancer, and is associated with a poor prognosis (4-10). Further understanding the immunologic functions of the HHLA2 pathway will guide the selection of agents used for cancer immunotherapy, autoimmune disorders, infection, and transplant rejection.