Predicted to be involved in T cell receptor signaling pathway. Predicted to act upstream of or within regulation of T cell proliferation. Predicted to be located in plasma membrane. Predicted to be active in external side of plasma membrane. Is expressed in head kidney; kidney; spleen; and testis. Human ortholog(s) of this gene implicated in several diseases, including carcinoma (multiple); graft-versus-host disease; hematologic cancer (multiple); kidney disease (multiple); and primary immunodeficiency disease (multiple). Orthologous to several human genes including CTLA4 (cytotoxic T-lymphocyte associated protein 4).