[Immune defect following thymoma. Case description and review].

The clinical and immunologic findings in a 57-year-old woman with hypogammaglobulinemia are described. The immunodeficiency occurred 11 years after surgical removal of an invasive lymphocytic thymoma. The typical findings of hypogammaglobulinemia as a thymoma-associated clinical syndrome are absence of peripheral blood B-lymphocytes and deficiency of plasma cells in bone marrow. However, in our patient peripheral blood B-lymphocytes and plasma cells in bone marrow were within normal limits, while the total number of peripheral blood mononuclear cells was subnormal. This subnormality was found to be a diminution of peripheral blood T-helper cells. Our patient was anergic to a battery of skin test antigens and her lymphocytes showed a decreased in vitro response to mitogen stimulation. In particular, the response to phytohemagglutinin (PHA) was low, but could be improved by the addition of interleukin-2 to the culture medium. Cocultures between patient B-cells and normal T-cells revealed normal function of patient B-cells. However, cocultures between patient T-cells and normal B-cells showed a significant depression of mitogen-induced immunoglobulin synthesis. These results are suggestive of T-helper cell dysfunction. Consequently, in our case the hypogammaglobulinemia was assumed to be secondary to deficient T-helper cell function.