REACTIVITY AND INTRACELLULAR LOCATION OF THE ACTH CELL AUTOANTIGEN INHUMAN FETAL AND ADULT ANTERIOR-PITUITARY TISSUE

Autoantibodies to anterior pituitary ACTH cells have been described in the sera from patients with Cushing's disease. We were here able to s how that true ACTH cell autoantibodies do not react with the hormone i tself or with Fc receptors in ACTH cells. They rather recognize a dist inct pituitary cell-specific cytoplasmatic autoantigen located in a ju xtanuclear position. ACTH cells from human adult pituitaries express F c receptors producing a non-specific broad and diffuse cytoplasmic bin ding of normal immunoglobulins. After preparation of Fc-free F(ab)2 fr actions from human immunoglobulins it could be demonstrated by immunoh istochemical methods that human adult pituitary ACTH cells also contai n the fetal ACTH cell autoantigen. However, Fc receptors, ACTH hormone or other proopiomelanocortin- (POMC-) derived fragments and the ACTH cell autoantigen are all located at distinct intracellular sites. ACTH cells in human fetal pituitaries were shown to lack Fc receptors. Thu s, with this source of antigen the characteristic autoantibody pattern can be detected with undigested sera.