Thymic dysfunction in histiocytosis-X.

In some patients with histiocytosis-X there is a deficiency of suppressor T cells, which is corrected in vitro by incubation with either crude calf thymic extract or thymostimulin. This finding suggests that a thymus deficiency could be involved in this disease. Low levels of serum thymic factor (FTS) are found in patients with histiocytosis-X. Their plasma contain factors capable of inhibiting biological activity of FTS in vitro. Elucidation of the mechanism by which FTS is inhibited would be helpful in understanding the immunological defect in histiocytosis-X. The presence of evidence of thymic dysfunction and the fact that patients respond to thymic hormone therapy suggest that histiocytosis-X could be due to a primary immunodeficiency syndrome. Thymulin, which stimulates the generation of suppressor T cells, could be of benefit in therapy.