New insight into the causes of immunodeficiency disorders.

The ability to define subpopulations of immunologically competent lymphocytes has permitted an enhanced understanding of the interaction between functionally distinct components of the immune system. T cells can provide help in antibody formation or they may suppress antibody production. Abnormal immunoregulatory mechanisms have been demonstrated in the hyperimmunoglobulin E-recurrent infection syndrome. This disorder is associated with a marked elevation of IgE and specific elevations of IgE antibodies directed toward staphylococcal antigens. Abnormal T cell regulation of immune responses has been demonstrated. Graft-versus-host disease (GVHD) occurs in an immunodeficient patient who has received an infusion of immunocompetent cells. The diagnosis of graft-versus-host (GVH) reaction may be complicated by the protean manifestations of the disorder. The acute form, consisting of a maculopapular rash, fever, and diarrhea, may be confused with acute infection or drug reaction. Chronic GVHD has been incorrectly diagnosed as histiocytosis X, acrodermatitis enteropathica, or scleroderma. Utilizing chromosome markers and/or identification of histocompatibility antigens, the presence of circulating lymphocytes from donor immunocompetent cells (blood transfusion, maternal source) can be documented. The development of sensitive technics for identifying cells can establish a precise diagnosis. Certain immunodeficiency disorders can be identified by biochemical means. Biotin-dependent multiple carboxylase enzyme deficiency is associated with a chronic dermatitis, alopecia, ataxia, and secondary infection of the skin with Candida. The disorder responds promptly to the administration of biotin with correction of dermatologic, neurologic, and immunologic abnormalities.