Characteristics of experimental autoimmune hypophysitis in rats: Major antigens are growth hormone, thyrotropin, and luteinizing hormone in this model

We produced experimental autoimmune hypophysitis (EAH) in rats and investig ated its characteristics. Female Lewis rats were immunized by two injection s with homologous pituitary homogenate and complete Freund's adjuvant. Bloo d was collected serially from the rats, and serum antibodies to pituitary a ntigens were examined. The rats were sacrificed 2 or 4 weeks after the fina l immunization, and histological examinations of the endocrine organs were carried out. Histological examination revealed slight, focal infiltration o f mononuclear cells in the pituitary gland only in the rats immunized with the pituitary homogenate. Infiltration of mononuclear cells was not observe d in the thyroid gland, pancreas, adrenal gland, or ovary. In the serologic al examination, antibodies to both cytosolic antigens and cytoplasmic parti cle antigens from the pituitary gland were detected by enzyme-linked immuno sorbent assay (ELISA), and these antibody levels increased with time. Weste rn blotting using the serum antibodies identified an immunoreactive protein of similar to 21.5 kDa among these antigens, and we confirmed that this pr otein was rat growth hormone (GH). Furthermore, antibodies to GH, thyrotrop in (TSH), and luteinizing hormone (LH) were detected by ELISA. Antibodies t o follicule stimulating hormone, prolactin, or adrenocorticotropin were not detected. These data suggest that several antigens from the pituitary glan d are involved in EAH in rats, and that GH, TSH, and LH are major antigens among the pituitary antigens in this model.