Immunodeficiency, radiosensitivity, and the XCIND syndrome.

Through the analysis of a rare disorder called ataxia-telangiectasia (A-T), many important biological lessons have been gleaned. Today, it is clear that the underlying defect of A-T lies in the nucleus, as an inability to repair or process double strand breaks. More important, by the A-T phenotype now allows us to appreciate a much more general distinction between immunodeficiencies that are radiosensitive and those that are not.