Antibodies cytotoxic to bovine parathyroid cells in autoimmune hypoparathyroidism

We utilized a recently developed long-term serum-free culture system for bovine parathyroid cells to detect antibodies in seven patients with autoimmune hypoparathyroidism (AHP). Antibodies were tested by indirect immunofluorescence methods and by cytotoxicity utilizing the chromium (51Cr) release technique. Seven AHP sera caused specific lysis [57 +/- 6% release of 51Cr vs. 5 +/- 1% for 56 controls (15 normal subjects and 41 patients with diverse other conditions associated with immune dysfunction)]. The least effect of any of the AHP sera on cell lysis exceeded the greatest effect of any of the control sera. Absorption of AHP sera (two cases) with bovine pituitary, thyroid, liver, or kidney cells did not affect lysis, but absorption with adrenal or parathyroid cells caused a marked decrease in specific lysis. Cytotoxicity determined by 51Cr release increased with antiserum concentration and time of incubation. Cytotoxicity was dependent on complement. Replicating parathyroid cells provide a uniform reproducible detection method for anti-parathyroid antibodies in AHP. The autoantibodies in AHP appear to be specific for tissue (parathyroid and adrenal cortex) but not for species.