Impaired interferon‐γ production in response to live bacteria and Toll‐like receptor agonists in patients with ataxia telangiectasia

Summary Ataxia telangiectasia (AT) is a pleiotropic autosomal recessive neurodegenerative disorder with associated immunodeficiency and cancer predisposition, caused by mutational inactivation of the ATM gene. Early death usually results from lymphoreticular malignancy or recurrent, chronic respiratory infections. Immune deficiency of AT patients is heterogeneous and involves both humoral and cellular responses. Reports on the number and integrity of immunocompetent cells in AT are conflicting. In the early phase of infection, the interleukin (IL)‐12/interferon (IFN)‐γ axis plays a crucial role in first‐line defence against pathogens. In a whole blood assay we studied the IL‐12/IFN‐γ axis in the immune response of AT cells to the Toll‐like receptor agonists lipopolysaccharide and heat‐killed Staphylococcus aureus , as well as whole live M. bovis bacille Calmette–Guérin (BCG). The function of AT antigen‐presenting cells was normal in terms of IL‐12 production, while IFN‐γ production by T and natural killer (NK) cells was severely impaired, even in the presence of adequate co‐stimulation by exogenous IL‐12.