TRIM is a 30 kD disulfide-linked protein also known as T cell receptor interacting molecule. TRIM is a type III membrane protein containing a very short extracellular domain (8 amino acids). TRIM is highly expressed in T cells with some expression also observed in NK cells. TRIM is a signaling adaptor molecule that links extracellular and intracellular signaling. The TRIM protein is phosphorylated by Src kinases and associates with the PI3K regulatory subunit alpha after phosphorylation. TRIM has also been shown to associate with TCRalpha,beta, and ?. The TRIM-4 monoclonal antibody recognizes human TRIM and has been shown to be useful for Western blotting, intracellular staining by flow cytometry, and immunofluorescence staining.