[Ataxia telangiectasia and characterization of its immunological disorders].

Ataxia telangiectasia (AT) is a primary immunodeficiency syndrome characterized by cerebellar ataxia, extrapyramidal signs, oculocutaneous telangiectasia, recurrent respiratory infections and development of malignancies. AT is a complex autosomal recessive disorder involving several systems other than lymphoid cells or the central nervous system. Such a diversity of abnormalities includes hypersensitivity of fibroblasts and lymphocytes to ionizing radiation (anomaly of DNA repair), non-random chromosomal rearrangements in lymphocytes, elevated serum level of alpha-fetoprotein, premature aging and endocrine disorders. A DNA processing or repair protein is the suspected common denominator in this pathology. Whatever the putative common underlying mechanism, AT patients have profound alterations of the humoral and cellular immune system whose mechanisms should be discussed in terms similar to those for other immunodeficiency diseases. The usual immunological abnormalities in this disease include decreased levels of CD 3 and CD 4 positive T lymphocytes, impaired delayed hypersensitivity, hypoplasia of thymus, decreased blast transformation in vitro in response to mitogen or antigenic stimulation, and decreased levels of serum IgA, IgE, and IgG 2 subclass. In this paper, the results of our recent studies on the defects of B cells in patients with AT were presented. (1) We found that the geometric means of IgA production in the supernatants of the lymphoblastoid cell lines established by EB virus, from all patients with AT, were significantly lower than those from healthy controls (P less than 0.01). (2) IgG subclasses of the patients' sera were also measured by ELISA, and IgG 4 was defective in four cases among six patients with AT.(ABSTRACT TRUNCATED AT 250 WORDS)