Liver immunity,autoimmunity,and inborn errors of immunity

The liver is the front line organ of the immune system.The liver contains the largest collection of phagocytic cells in the body that detect both pathogens that enter through the gut and endogenously produced antigens.This is possible by the highly developed differentiation capacity of the liver immune system between self-antigens or non-self-antigens,such as food antigens or pathogens.As an immune active organ,the liver functions as a gatekeeping barrier from the outside world,and it can create a rapid and strong immune response,under unfavorable conditions.However,the liver's assumed immune status is anti-inflammatory or immuno-tolerant.Dynamic interactions between the numerous populations of immune cells in the liver are key for maintaining the delicate balance between immune screening and immune tolerance.The anatomical structure of the liver can facilitate the preparation of lymphocytes,modulate the immune response against hepatotropic pathogens,and contribute to some of its unique immunological properties,particularly its capacity to induce antigen-specific tolerance.Since liver sinusoidal endothelial cell is fenestrated and lacks a basement membrane,circulating lymphocytes can closely contact with antigens,displayed by endothelial cells,Kupffer cells,and dendritic cells while passing through the sinusoids.Loss of immune tolerance,leading to an autoaggressive immune response in the liver,if not controlled,can lead to the induction of autoimmune or autoinflammatory diseases.This review mentions the unique features of liver immunity,and dysregulated immune responses in patients with autoimmune liver diseases who have a close association with inborn errors of immunity have also been the emphases.

Cellular and molecular mechanisms breaking immune tolerance in inborn errors of immunity

In addition to susceptibility to infections,conventional primary immunodeficiency disorders(PIDs)and inborn errors of immunity(IEI)can cause immune dysregulation,manifesting as lymphoproliferative and/or autoimmune disease.Autoimmunity can be the prominent phenotype of PIDs and commonly includes cytopenias and rheumatological diseases,such as arthritis,systemic lupus erythematosus(SLE),and Sjogren’s syndrome(SjS).Recent advances in understanding the genetic basis of systemic autoimmune diseases and PIDs suggest an at least partially shared genetic background and therefore common pathogenic mechanisms.Here,we explore the interconnected pathogenic pathways of autoimmunity and primary immunodeficiency,highlighting the mechanisms breaking the different layers of immune tolerance to self-antigens in selected IEI.

Current understanding of ELF4 deficiency:a novel inborn error of immunity

Background ELF4 deficiency has been recently recognized as a novel disorder within the spectrum of inborn errors of immunity(IEIs),specifically categorized as a“disease of immune dysregulation.”Cases of this condition,reported by our team and others,are very limited worldwide.As such,our current knowledge of this new disease remains preliminary.This review aims to provide a brief overview of the clinical manifestations,pathogenesis,and treatment strategies for this novel IEI.Data sources A comprehensive review was conducted after an extensive literature search in the PubMed/Medline database and websites concerning transcriptional factor ELF4 and reports concerning patients with ELF4 deficiency.Our search strategy was“ELF4 OR ETS-related transcription factor Elf-4 OR EL4-like factor 4 OR myeloid Elf-1-like factor”as of the time of manuscript submission.Results The current signature manifestations of ELF4 deficiency disorder are recurrent and prolonged oral ulcer,abdominal pain,and diarrhea in pediatric males.In some cases,immunodeficiency and autoimmunity can also be prominent.Targeted Sanger sequencing or whole exome sequencing can be used to detect variation in ELF4 gene.Western blotting for ELF4 expression of the patient’s cells can confirm the pathogenic effect of the variant.To fully confirm the pathogenicity of the variant,further functional test is strongly advised.Glucocorticoid and biologics are the mainstream management of ELF4 deficiency disorder.Conclusions Pediatric males presenting with recurring ulcerations in digestive tract epithelium with or without recurrent fever should be suspected of DEX.When atypical presentations are prominent,variations in ELF4 gene should be carefully evaluated functionally due to the complex nature of ELF4 function.Experience of treating DEX includes use of glucocorticoid and biologics and more precise treatment needs more patients to identify and further mechanistic study.

Druggable monogenic immune defects hidden in diverse medical specialties:Focus on overlap syndromes

In the last two decades two new paradigms changed our way of perceiving primary immunodeficiencies:An increasing number of immune defects are more associated with inflammatory or autoimmune features rather than with infections.Some primary immune defects are due to hyperactive pathways that can be targeted by specific inhibitors,providing innovative precision treatments that can change the natural history of diseases.In this article we review some of these“druggable”inborn errors of immunity and describe how they can be suspected and diagnosed in diverse pediatric and adult medicine specialties.Since the availability of precision treatments can dramatically impact the course of these diseases,preventing the development of organ damage,it is crucial to widen the awareness of these conditions and to provide practical hints for a prompt detection and cure.