Background: Hypohidrotic ectodermal dysplasia (HED) is a group of disorders of ectodermal tissues, resulting from mutations in the ectodysplasin-A (EDA) pathway. Hypomorphic mutations in the NF-?B essential modulator (NEMO) result in HED with immunodeficiency (HED-ID, OMIM 300291), characterized by susceptibility to encapsulated bacteria, mycobacteria, and herpes virus infections. Objective: To analyze B-cell compartment and TLR9 signaling in HED-ID patients. Methods: Two HED-ID patients and a patient with HED caused by EDA gene mutation (XLHED) to confirm the implication of NFkB in this pathway were studied. Results: In HED-ID, differently from XLHED, only few B cells acquired the phenotype of IgM memory and differentiated into plasma cells upon TLR9 stimulation. Memory B cells did not produce IgG and IgA, and only small amounts of IgM in vitro. Conclusion: In HED-ID patients, TLR9 signaling is abnormal, in keeping with the lack of IgM memory B cells and natural antibodies. In individuals at a high risk of developing pneumococcal diseases, increased susceptibility to Streptococcus pneumonia infections and poor response to polysaccharide antigens have been associated with the lack of IgM memory B cells, required for the T-independent response toward encapsulated bacteria, whose differentiation from transitional B cells is under TLR9 control. This finding helps explain the susceptibility to infections by encapsulated bacteria.

TLR9 signaling in patients with ectodermal dysplasia and immunodeficiency associated with Nuclear Factor Essential Modulator (NEMO) mutations

GIARDINO, GIULIANA;NADDEI, ROBERTA;CIRILLO, EMILIA;GALLO, VERA;PIGNATA, CLAUDIO
2014

Abstract

Background: Hypohidrotic ectodermal dysplasia (HED) is a group of disorders of ectodermal tissues, resulting from mutations in the ectodysplasin-A (EDA) pathway. Hypomorphic mutations in the NF-?B essential modulator (NEMO) result in HED with immunodeficiency (HED-ID, OMIM 300291), characterized by susceptibility to encapsulated bacteria, mycobacteria, and herpes virus infections. Objective: To analyze B-cell compartment and TLR9 signaling in HED-ID patients. Methods: Two HED-ID patients and a patient with HED caused by EDA gene mutation (XLHED) to confirm the implication of NFkB in this pathway were studied. Results: In HED-ID, differently from XLHED, only few B cells acquired the phenotype of IgM memory and differentiated into plasma cells upon TLR9 stimulation. Memory B cells did not produce IgG and IgA, and only small amounts of IgM in vitro. Conclusion: In HED-ID patients, TLR9 signaling is abnormal, in keeping with the lack of IgM memory B cells and natural antibodies. In individuals at a high risk of developing pneumococcal diseases, increased susceptibility to Streptococcus pneumonia infections and poor response to polysaccharide antigens have been associated with the lack of IgM memory B cells, required for the T-independent response toward encapsulated bacteria, whose differentiation from transitional B cells is under TLR9 control. This finding helps explain the susceptibility to infections by encapsulated bacteria.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11588/602204
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