Immunological defects in healthy twin siblings to patients with Hodgkin's disease.

We studied the immunocompetence of 6 healthy twins, whose monozygotic or dizygotic same-sexed twin partner had died from Hodgkin's disease. Lymphocyte DNA synthesis induced by concanavalin A was markedly reduced at 3 different concentrations in all twins compared to an age-matched group of healthy controls. The lymphocyte response to pokeweed mitogen and to phytohaemagglutinin was also impaired. PPD induced lymphocyte DNA synthesis was low in 3 twins and correlated well with their delayed skin hypersensitivity to the antigen. One twin was completely anergic to 3 different skin antigens. The mean total blood lymphocyte count did not differ from that of controls. There was no change in T or B-lymphocyte subpopulations. The presence of a functional lymphocyte deficiency in all twins strongly suggests that the immunodeficiency in Hodgkin's disease is partly caused by genetic and/or environmental factors.