I-J and mechanism of immunosuppression

I-J has been found to be an inducible isomorphic molecule expressed on class II-restricted T cells. It undergoes a systematic adaptive change in radiation bone marrow chimeras according to the environmental major histocompatibility complex (MHC). Recent biochemical studies demonstrated that I-J is a homodimer of MW 84,000-90,000 composed of 42,000-46,000 MW glycopeptide subunits. The molecule is different from class II-restricted T-cell receptor, class II antigens or putative mouse CD28. The ligation of I-J molecules with anti-I-J results in the suppression of T-cell responses by the inhibition of early signal transduction through antigen recognition.