PRODUCTION OF MONOCLONAL-ANTIBODIES AGAINST A NOVEL GLYCOPROTEIN SYNTHESIZED AND SECRETED BY DOG THYROID C-CELLS

A monoclonal antibody (MAb) that reacted only with thyroid C-cells was raised against cell suspensions from dog thyroid glands, to examine a glycoprotein secreted by C-cells. After chronically-induced hypercalc emia and administration of an anti-thyroid drug, reaction products for the antibody markedly decreased in C-cells, coinciding with alteratio ns in calcitonin immunoreactivity. The antigen recognized by the MAb a ppears to be a secretory protein. The MAb reacted with C-cells from a wide variety of mammalian species, including rats, mice, hamsters, cat tle, cats, rabbits, and monkeys. Furthermore, tumor cells of human med ullary thyroid carcinoma, which is derived from C-cells, were immunore active to the MAb. Exceptionally, C-cells from guinea pigs and pigs we re not stained with the MAb. No crossreactivity was observed in any of the dog tissues examined. Immunoblot analysis demonstrated that the M Ab recognized a single prominent band at a molecular weight of approxi mately 79,000. The 79 KD band reacted with various digoxigenin-labeled lectins, including GNA, DSA, SNA, and MAA; it is a glycoprotein conta ining mannose, N-acetylglucosamine, and sialic acid. Dog thyroid C-cel ls were also densely stained with these lectins. The results indicate that thyroid C-cells synthesize and secrete a specific glycoprotein in addition to peptide hormones.