HLA‐DMB expression by thyrocytes: indication of the antigen‐processing and possible presenting capability of thyroid cells
Expression of HLA class II molecules on thyrocytes is a characteristic feature of autoimmune thyroid disease and may lead the thyroid cells to present autoantigens to CD4+ T lymphocytes. Since HLA‐DM is a critical molecule in class II‐restricted antigen processing and presentation, we assessed the expression of HLA‐DMB, ‐invariant chain (Ii), class II transactivator (CIITA) and DRA in an untransformed, pure thyrocyte strain HTV‐59A. Here we report that both HLA‐DMB mRNA and the protein are expressed in thyrocytes and that CIITA expression is enhanced by interferon‐gamma (IFN‐γ) treatment and occurs before DMB, Ii and DRA up‐regulation, suggesting CIITA expression is a requirement for antigen processing in thyrocytes. These results indicate that thyrocytes are capable of antigen processing and possibly antigen presentation to T cells.