Defective allosuppression in patients with ataxia-telangiectasia.

We describe a novel in vitro assay system that detects the generation of suppressor T cells after exposure of human lymphocytes to class I alloantigens. We have used this system to study immune functions in a group of seven patients with ataxia-telangiectasia (AT). Normal T lymphocytes exposed to cells differing at the A and B locus histocompatibility locus antigens (HLA) become activated for suppression of Epstein-Barr virus (EBV)-induced immunoglobulin (Ig) production. In contrast to the normal, T cells from patients with AT demonstrate no inhibitory effect after allostimulation. These data indicate that patients with AT have a profound defect involving responses to class I antigens of the major histocompatibility complex (MHC).