Immunoreactivity of cultured pancreatic islet cells with monoclonal antibody ICA-1

The aim of the present study was to characterize the expression of the pancreatic beta cell antigen family with molecular masses of 64 to 69 kDa [p(64-69)]. This antigen family was detected by immunoreactivity with biotinylated monoclonal antibody (Mab) ICA-1, and Mab against insulin. The molecular masses of the antigens affinity-purified from islet cell lysates by ICA-1 were 64, 67, and 69 kDa. Detailed analysis of p(64-69) expression was carried out on cultured islet cells reassociated into clusters of islet-like structures. Cell-fluorescence image processing by computerized image analysis, combined with transmission and scanning electron microscopy, of cells labelled with Mab ICA-1 and immunogold revealed the localization of the 64-65 kDa antigen family on the beta cell surface and its grouping on microvilli and near areas of fusion of the insulin-containing beta granules with the plasma membrane. In view of the effect of ICA-1 on insulin release and its localization on the beta cell surface in immunoreactions it is proposed that the p(64-69) antigen family is involved in insulin secretion.