Oligoclonal T cell expansion in blood but not in the thymus from a patient with thymoma-associated pure red cell aplasia.

Despite the well-known association between thymoma and PRCA, the role of thymoma remains uncertain. There is accumulating evidence that clonal T cells are involved in acquired PRCA. We examined T cell receptor repertoires in blood and thymus from a patient with PRCA associated with thymoma and myasthenia gravis. Oligoclonal expansions of Vdelta1- and Vbeta1-expressing T cells were found in peripheral blood, whereas the repertoires of Vdelta1+ and Vbeta1+ T cells in thymoma were not skewed. Oligoclonal expansion of Vdelta1-expressing T cells remained unchanged after thymectomy. Thymus may not be the site of clonal T cell expansion in thymoma-associated PRCA.