I-45 ISLET-CELL ANTIGEN IS A 68KD NEUROENDOCRINE PROTEIN

A monoclonal antibody approach was used to characterize islet cell dif ferentiation antigens involved in autoimmunity related diabetes mellit us. This procedure yielded islet cell monoclonal antibodies (ICMAbs)th at demonstrated varying tissue/cellular distribution. The ICMAb I-45 s howed a pan-islet reactivity similar to the reactivity of islet cell a utoantibodies. The target antigen of the ICMAb I-45 demonstrated a neu roendocrine distribution. Single step immunoaffinity purification of I -45 antigen using I-45 monoclonal antibody immunoaffinity matrix yield ed a 68kD protein. The specificity of the immunoaffinity purified 68kD protein was further demonstrated by the lack of binding of this prote in to immunoaffinity columns of irrelevant monoclonal antibodies. The neuroendocrine distribution of the I-45 antigen, like that of other di fferentiation molecules like HISL-19, neuron specific enolase and chro mogranin A strengthens the hypothesis of neuroectodermal origin of the islets of Langerhans.