Immunoreactivities of gastrin (G-) cells. I. dilution-dependent staining of G-cells by antisera and non-immune sera.

Results of immunocytochemical studies reported by several laboratories suggest that gastrin (G-) cells of the stomach show immunoreactivities for various pituitary hormones (ACTH, met-enkephalin, beta-endorphin and growth hormone) in addition to gastrin. By reinvestigating the immunocytochemistry of G-cells we found that these cells exhibited reactivities towards a variety of antisera against enteric, pancreatic and hypophyseal hormones. Gastrin cells can also be "immunostained" by antisera towards proteins unrelated to any peptide hormones (e.g. alpha-fetoprotein antiserum) and by nonimmune sera. Thus the specificity of immunocytochemical findings in G-cells seems to be uncertain. According to our findings the polyvalent immunoreactivities of G-cells may be caused by a distinct binding capacity for IgG molecules. This binding of IgG to G-cells seems to be mediated by the Fab fragments of the IgG molecules which may behave like a basic dye and therefore "immunostain" anionic components within G-cells. Thus the significance of the immunocytochemical proof of peptide hormones within G-cells is limited unless extended specificity controls have been performed. The results of specificity controls performed in this study (adsorption controls, use of ascending dilutions of the primary and secondary antisera, comparison of crude antisera and affinity chromatographically purified antibodies) suggest that corticotropin-lipotropin related peptides are not contained in G-cells.