Both innate and adaptive immune responses are dependent on activation of nuclear factor κB (NF-κB), induced upon binding of pathogen-associated molecular patterns to Toll-like receptors (TLRs). In murine models, defects in NF-κB pathway are often lethal and viable knockout mice have severe immune defects. Similarly, defects in the human NF-κB pathway described to date lead to severe clinical disease. Here, we describe a patient with a hyper immunoglobulin M–like immunodeficiency syndrome and ectodermal dysplasia. Monocytes did not produce interleukin 12p40 upon stimulation with various TLR stimuli and nuclear translocation of NF-κB was impaired. T cell receptor–mediated proliferation was also impaired. A heterozygous mutation was found at serine 32 in IκBα. Interestingly, his father has the same mutation but displays complex mosaicism. He does not display features of ectodermal dysplasia and did not suffer from serious infections with the exception of a relapsing Salmonella typhimurium infection. His monocyte function was impaired, whereas T cell function was relatively normal. Consistent with this, his T cells almost exclusively displayed the wild-type allele, whereas both alleles were present in his monocytes. We propose that the T and B cell compartment of the mosaic father arose as a result of selection of wild-type cells and that this underlies the widely different clinical phenotype.

Patients with defects in IFN-γ- or IL-12-mediated immunity are susceptible to infections with Salmonella and non-tuberculous mycobacteria, but rarely suffer from infections with other intracellular pathogens such as Toxoplasma gondii. Here we describe macrophage and T cell function in eight individuals with partial IFN-γ receptor 1 (IFN-γR1) deficiency due to a mutation that results in elevated cell surface expression of a truncated IFN-γR1 receptor that lacks the intracellular domain. We show that various effector mechanisms dependent on IFN-γR signaling are affected to different extents. Whereas TNF-α production was normally up-regulated in response to IFN-γ, IL-12 production and CD64 up-regulation were strongly reduced, and IFN-γ-mediated killing of the intracellular pathogens Salmonella typhimurium and T. gondii was completely abrogated in patient’s macrophages. Since these patients suffer selectively from infections with non-tuberculous mycobacteria and Salmonella, but not T. gondii, despite sero-immunity in six of eight patients, which indicates previous contact with this pathogen, we next studied the role of TNF-α as a possible immune compensatory mechanism. IFN-γ-induced killing of T. gondii appeared to be partially mediated by TNF-α, and addition of TNF-α could compensate for the abrogated killing of T. gondii in the patient’s macrophages. In contrast, IFN-γ-mediated killing of S. typhimurium appeared to be independent of TNF-α. We propose that the divergent role of TNF-α in IFN-γ-induced killing of T. gondii and S. typhimurium may at least partially explain the highly selective susceptibility of patients.

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Case presentationWe analysed a 38-year-old woman with disseminated histoplasmosis for primary immunodeficiency. Her blood showed no IFN-γ response while her peripheral blood mononuclear cells (PBMCs) did. We identified IFN-γ autoantibodies of the IgG class in her serum.Conclusion IFN-γ autoantibodies leading to infections were so far mainly detected in people from Asian descent, where it was found to be associated with certain HLA types. This may be the first patient of African descent, and without the typical HLA types that predispose to this problem, that produces IFN-γ autoantibodies.