Central Immune Tolerance of T and B Cells in Patients With Idiopathic Hypoparathyroidism, T1D, and Autoimmune Thyroiditis

CONTEXT: Pathogenesis of idiopathic hypoparathyroidism (IH) is under investigation. Abnormalities in central immune tolerance have yet not been investigated in this condition. T-cell receptor excision circles (TRECs) and kappa-deleting recombination excision circles (KRECs), formed during receptor gene rearrangements, are tools to assess central T- and B-cell output. OBJECTIVE: We assessed the number of circulating TRECs and KRECs in patients with IH, autoimmune type 1 diabetes (T1D), and autoimmune thyroiditis (ATs) and healthy controls (HCs). DESIGN: Comparative case-control at tertiary care center. SUBJECTS AND METHODS: Absolute and relative TRECs and KRECs were measured in DNA extracted from whole blood of patients with IH (n = 181, 22 of whom were reassessed after a decade of follow-up) and T1D (n = 133), AT (n = 53), and HC (n = 135) using a quantitative real-time PCR/TaqMan(®) probe technique. RESULTS: Absolute and relative means of TRECs and KRECs in IH were comparable to HCs, and no differences were found between IH with and without calcium-sensing receptor antibodies or class I HLA-A*26:01 association. TRECs and KRECs did not change after a decade of follow-up. T1D had significantly higher absolute TRECs than IH, AT, and HCs, whereas AT patients showed lower TRECs and the highest KRECs; these levels showed no noteworthy correlation with thyroid dysfunctions. CONCLUSION: Patients with IH showed TRECs and KRECs comparable to HCs, indicating an intact mechanism of T- and B-cell central immune tolerance. Interestingly, absolute TRECs were significantly higher in T1D than HCs, suggesting impaired central immune tolerance in T1D.