immunodeficiency in ataxia-telangiectasia.

Ataxia-telangiectasia is characterized by endocrine, neurologic, hematologic, hepatic, cutaneous and immunologic abnormalities. The immunologic deficiencies vary considerably from patient to patient, and in each patient with respect to time. The most frequent deficiencies of humoral immunity are diminished or absent serum and salivary IgA, diminished or absent serum IgE and impaired antibody responses to a variety of bacterial and viral antigens. Deficiencies of cellular immunity are commonly found by both in vivo and in vitro analyses. Histologic confirmation of these immunodeficiencies is readily observed in the lymphoid tissue. The thymus, which may be the seat of the primary abnormality in the immunodeficiency syndrome, regularly shows morphologic characteristics of an embryonic thymus.