IMMUNOREACTIVITY OF NORMAL RABBIT SERUM WITH EPINEPHRINE(E) CELLS OF THE RAT ADRENAL-MEDULLA AFTER MICROWAVE ANTIGEN RETRIEVAL

Normal rabbit serum (NRS) produces intense staining of epinephrine (E) cells in microwave-heated sections of rat and mouse adrenal gland. Th is staining is not eliminated by liver adsorption, complement inactiva tion, high salt buffer, Triton X-100 or dilution in normal goat serum and bovine serum albumin (BSA), suggesting that it may result from spe cific antigen-antibody interactions. Western blots of adrenal medullar y protein probed with NRS reveal several bands. The major band does no t correspond to rat chromogranin A, which is a major constituent of E- cell secretory granules. The findings suggest that NRS may contain aut oantibodies against a secreted rabbit E-cell protein with a homologous counterpart in rats and mice, and that this protein may be immunologi cally unmasked in situ by microwave heating. This phenomenon is a pote ntial source of error in immunohistochemical studies of the adrenal me dulla, and has potential biological significance in neuroimmunology.