PRODUCTION OF A MONOCLONAL-ANTIBODY 14A20 THAT REACTS WITH A 220-KDA PROTEIN IN THE ISLET CELLS

To study the target antigens of the islet cell cytoplasmic antibodies (ICA), we tried to make a monoclonal islet cell antibody. We made a mo noclonal antibody 14A20 (IgM, kappa) that reacted strongly with Wistar and BB rat islet cells and weakly with pancreatic acinar cells. The i mmunoreactivity of the 14A20 was also found to react extensively in ne uroendocrine cells. Immunostaining showed a granular pattern in both n eurons and islet cells. Chemical and enzymic studies revealed that the antigen has the property of a protein. We compared immunoreactivity o f the monoclonal antibody 14A20 with anti-insulin, -glucagon or -somat ostatin antibodies. The antigen recognized by the monoclonal antibody 14A20 was equally present in the alpha, beta, and delta cells of islet , which mimicked the immunoreactivity of the ICA in the pancreas. The recognized protein had a relative molecular weight of 220 000, indicat ing that it is different from the previously identified target antigen of the ICA.