Immunohistochemical demonstration of alpha 1 -antichymotrypsin and alpha 1 -antitrypsin in the normal pituitary gland and its tumors.

The immunohistochemical distribution of the protease inhibitors alpha ₁ -antichymotrypsin (alpha ₁ -ACT) and alpha ₁ -antitrypsin (alpha ₁ -AT) has been documented in the normal human pituitary gland and in a series of pituitary tumors. In normal gland, alpha ₁ -ACT was localized mainly in the dendritic folliculostellate cells, identified by immunopositivity for S 100 protein. A minority of endocrine cells also stained in 3 of 10 autopsy glands. Folliculostellate cells were identified in 11 of 28 tumors, and again, the distribution of alpha ₁ -ACT positivity corresponded to these cells. In 4 cases, there was staining of a small minority of tumor cells. Alpha ₁ -AT was localized to colloid in the microfollicles of the anterior lobe. In I normal gland, there was granular staining of endocrine cells. Alpha ₁ -AT was present in 5 tumors, in microfollicles and in scattered endocrine cells in 2 adenomas. These data would support a physiological role for alpha ₁ -ACT and alpha ₁ -AT in the pituitary gland. Their differing distribution might reflect different functions.