Imbalances of t-cells in thymoma-associated hypogammaglobulinemia

The case is described of a 74-year-old man with severe diarrhoea and late-onset hypogammaglobulinaemia associated with spindle-cell thymoma. Plasma cells and B-lymphocytes were absent in the peripheral blood, bone marrow and lymphoid tissue with the exception of the gut. Functional studies revealed impaired in-vitro cellular immunity with a reversed ratio of T4 T8-reactive cells. After depletion of T8-reactive cells, the mitogen-induced lymphocyte proliferative response increased to median normal values. Infiltration of T8 positive cells was also noted in the thymus. Normal thymocytes (T4-, T6-, T8-reactive) were hardly present, whereas clustering of T8-reactive cells was associated with expression of class II MHC antigens on epithelial thymoma cells. Thymectomy and gamma-globulin substitution resulted in the disappearance of diarrhoea and respiratory infections, but did not influence the reversed T4 T8 ratio. The possible implications of these findings are discussed.