HLA-DMB expression by thyrocytes: indication of the antigen-processing andpossible presenting capability of thyroid cells

Expression of HLA class II molecules on thyrocytes is a characteristic feat ure 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 (CII TA) and DRA in an untransformed, pure thyrocyte strain HTV-59A. Here we rep ort that both HLA-DMB mRNA and the protein are expressed in thyrocytes and that CIITA expression is enhanced by interferon-gamma (IFN-gamma) treatment and occurs before DMB, Ii and DRA up-regulation, suggesting CIITA expressi on is a requirement for antigen processing in thyrocytes. These results ind icate that thyrocytes are capable of antigen processing and possibly antige n presentation to T cells.