HLA Class I Expression Changes in Different Types of Cultured Parathyroid Cells

Tissue-specific immunogenicity can be characterized by the determination of human leukocyte antigens (HLA). Parathyroid hyperplasia tissue cells are presumed to have the ability to lose HLA class I expression profile during cultivation, whereas healthy parathyroid cells are presumed to already express HLA class I molecules at low levels. However, there are conflicting results about the expression of HLA class I antigens. In this study, our aim was to evaluate different patterns of HLA class I expression in different parathyroid tissue cells.

Parathyroid tissue cells were isolated enzymatically and cultured in vitro. Expression of HLA class I (HLA-A, HLA-B, HLA-C) mRNA and protein levels were studied in 7 parathyroid adenomas and 9 parathyroid hyperplasia tissue samples by reverse transcriptase-polymerase chain reaction and Western blot analyses.

HLA-A protein expression remained stable in parathyroid adenoma and hyperplasia tissue, but HLA-A mRNA expression decreased in adenoma tissue. In parathyroid hyperplasia tissue, HLA-B protein expression remained stable, although mRNA expres-sion levels decreased during cultivation. HLA-C mRNA expression was steady in parathyroid adenoma yet significantly decreased in hyperplasia tissue samples. HLA-C protein expression levels were below 30 pg for both types of parathyroid tissue during cultivation.

HLA class I expression levels of para-thyroid hyperplasia and adenoma tissue were not found to be similar. Parathyroid hyperplasia tissue is the donor tissue for the treatment of permanent hypoparathyroidism. Therefore, expression patterns of HLA class I are directly relevant to the transplant process. In particular, the HLA region is highly polymorphic, and, as a consequence of this, heterogeneous correlations among HLA-A, HLA-B, and HLA-C expression patterns of parathyroid tissue should be evaluated in detail before transplant for future studies.