Polymorphism in the gene encoding toll-like receptor 10 may be associated with asthma after bronchiolitis

Integrative analysis of network pharmacology and proteomics reveal the protective effect of Xiaoqinglong Decotion on neutrophilic asthma

ETHNOPHARMACOLOGICAL RELEVANCE

Xiaoqinglong Decotion (XQLD) is a commonly used Chinese herbal formula in clinical practice, especially for allergic diseases such as asthma. However, its intrinsic mechanism for the treatment of neutrophilic asthma (NA) remains unclear.

AIM OF THE STUDY

The aim of this study was to evaluate the efficacy and potential mechanisms of XQLD on NA using network pharmacology and in vivo experiments.

MATERIALS AND METHODS

First, the active compounds, potential targets and mechanisms of XQLD against NA were initially elucidated by network pharmacology. Then, OVA/CFA-induced NA mice were treated with XQLD to assess its efficacy. Proteins were then analyzed and quantified using a Tandem Mass Tags approach for differentially expressed proteins (DEPs) to further reveal the mechanisms of NA treatment by XQLD. Finally, the hub genes, critical DEPs and potential pathways were validated.

RESULTS

176 active compounds and 180 targets against NA were identified in XQLD. Protein-protein interaction (PPI) network revealed CXCL10, CX3CR1, TLR7, NCF1 and FABP4 as hub genes. In vivo experiments showed that XQLD attenuated inflammatory infiltrates, airway mucus secretion and remodeling in the lungs of NA mice. Moreover, XQLD significantly alleviated airway neutrophil inflammation in NA mice by decreasing the expression of IL-8, MPO and NE. XQLD also reduced the levels of CXCL10, CX3CR1, TLR7, NCF1 and FABP4, which are closely associated with neutrophil inflammation. Proteomics analysis identified 28 overlapping DEPs in the control, NA and XQLD groups, and we found that XQLD inhibited ferroptosis signal pathway (elevated GPX4 and decreased ASCL3) as well as the expression of ARG1, MMP12 and SPP1, while activating the Rap1 signaling pathway.

CONCLUSION

This study revealed that inhibition of ARG1, MMP12 and SPP1 expression as well as ferroptosis pathways, and activation of the Rap1 signaling pathway contribute to the therapeutic effect of XQLD on NA.

Infant Bronchiolitis Endotypes and the Risk of Developing Childhood Asthma: Lessons From Cohort Studies

Severe bronchiolitis (i.e., bronchiolitis requiring hospitalization) during infancy is a heterogeneous condition associated with a high risk of developing childhood asthma. Yet, the exact mechanisms underlying the bronchiolitis-asthma link remain uncertain. Birth cohort studies have reported this association at the population level, including only small groups of patients with a history of bronchiolitis, and have attempted to identify the underlying biological mechanisms. Although this evidence has provided valuable insights, there are still unanswered questions regarding severe bronchiolitis-asthma pathogenesis. Recently, a few bronchiolitis cohort studies have attempted to answer these questions by applying unbiased analytical approaches to biological data. These cohort studies have identified novel bronchiolitis subtypes (i.e., endotypes) at high risk for asthma development, representing essential and enlightening evidence. For example, one distinct severe respiratory syncytial virus (RSV) bronchiolitis endotype is characterized by the presence of Moraxella catarrhalis and Streptococcus pneumoniae, higher levels of type I/II IFN expression, and changes in carbohydrate metabolism in nasal airway samples, and is associated with a high risk for childhood asthma development. Although these findings hold significance for the design of future studies that focus on childhood asthma prevention, they require validation. However, this scoping review puts the above findings into clinical context and emphasizes the significance of future research in this area aiming to offer new bronchiolitis treatments and contribute to asthma prevention.

Meta-analysis of the association between toll-like receptor gene polymorphisms and hepatitis C virus infection

Objective

The objective of this study is to investigate the association between toll-like receptor (TLR) 3/7 gene polymorphisms and the infection by hepatitis C virus (HCV).

Methods

PubMed, Embase, Web of Science, Scopus, CNKI, Wanfang Data, and SinoMed were searched to identify studies focusing on the association between the TLR3 rs3775290 or the TLR7 rs179008 single nucleotide polymorphisms (SNPs) and the HCV infection. All the related articles were collected from the inception of each database to 15 January 2023. Our meta-analysis was conducted using the allelic model, the dominant model, and the recessive model. Outcomes were presented by odds ratio (ORs) and 95% confidence interval (95%CI). The heterogeneity across studies was assessed by the I2 test. A subgroup analysis was performed to explore the source of heterogeneity. Funnel plots were drawn to assess the risk of publication bias. Review Manager 5.4 was used for statistical analysis.

Results

Ten articles were finally included, among which six studies were analyzed for rs3775290 and five studies were analyzed for rs179008. Studies relating to rs3775290 included 801 patients and 1,045 controls, whereas studies relating to rs179008 included 924 patients and 784 controls. The results of the meta-analysis showed that there is no significant association between rs3775290 gene polymorphism and HCV infection (T vs. C: OR = 1.12, 95%CI 0.97-1.30; TT+CT vs. CC: OR = 1.20, 95%CI 0.73-1.96; TT vs. CT+CC: OR = 1.13, 95%CI 0.68-1.89). The recessive model showed that rs179008-T allele homozygotes had an 89% increased risk of infection by HCV compared with rs179008-A allele carriers (TT vs. AT+AA: OR = 1.89, 95%CI 1.13-3.16). The results of the subgroup analysis demonstrated that the characteristics of the control population may serve as an important source of heterogeneity. In the African populations, individuals with homozygous rs179008-T alleles had a higher risk of infection by HCV than rs179008-A allele carriers (OR = 2.14, 95%CI 1.18-3.87). We did not find that this difference existed in the European populations (OR = 1.24, 95%CI 0.43-3.56).

Conclusion

There is no significant association between rs3775290 single nucleotide polymorphism and the infection by HCV. Individuals with homozygous rs179008-T alleles have a higher risk of an infection by HCV than rs179008-A allele carriers, which is statistically significant in the African populations.

Risk Factors Affecting Development and Persistence of Preschool Wheezing: Consensus Document of the Emilia-Romagna Asthma (ERA) Study Group

Wheezing at preschool age (i.e., before the age of six) is common, occurring in about 30% of children before the age of three. In terms of health care burden, preschool children with wheeze show double the rate of access to the emergency department and five times the rate of hospital admissions compared with school-age asthmatics. The consensus document aims to analyse the underlying mechanisms involved in the pathogenesis of preschool wheezing and define the risk factors (i.e., allergy, atopy, infection, bronchiolitis, genetics, indoor and outdoor pollution, tobacco smoke exposure, obesity, prematurity) and the protective factors (i.e., probiotics, breastfeeding, vitamin D, influenza vaccination, non-specific immunomodulators) associated with the development of the disease in the young child. A multidisciplinary panel of experts from the Emilia-Romagna Region, Italy, addressed twelve key questions regarding managing preschool wheezing. Clinical questions have been formulated by the expert panel using the PICO format (Patients, Intervention, Comparison, Outcomes). Systematic reviews have been conducted on PubMed to answer these specific questions and formulate recommendations. The GRADE approach has been used for each selected paper to assess the quality of the evidence and the degree of recommendations. Based on a panel of experts and extensive updated literature, this consensus document provides insight into the pathogenesis, risk and protective factors associated with the development and persistence of preschool wheezing. Undoubtedly, more research is needed to improve our understanding of the disease and confirm the associations between certain factors and the risk of wheezing in early life. In addition, preventive strategies must be promoted to avoid children's exposure to risk factors that may permanently affect respiratory health.

TLR10 and Its Role in Immunity

Toll like receptors (TLRs) are the most studied pattern recognition receptors (PRRs) as they connect the innate to the acquired immune response. To date, there are ten human TLRs which are expressed either on the plasma membrane or on the endosomes. TLR1, TLR2, TLR4, TLR5, TLR6 and TLR10 are plasma membrane TLRs that recognise extracellular components of pathogens, whereas TLR3, TLR7, TLR8 and TLR9 are located on endosomes where they recognise foreign nucleic acids. Of these TLRs, TLR10 is the latest human TLR to be discovered and its function and ligands are still unclear. TLR10 is the only known member of TLR family that can elicit anti-inflammatory effect. TLR10 can inhibit other TLRs by competing with stimulatory TLRs, dimerising with TLR1, TLR2 and TLR6, and by inducing PI3K/Akt to produce IL-1Ra. There is controversy on the function of TLR10 as an anti-inflammatory TLR as initial studies on TLR10 revealed it to promote inflammation. Herein, we review the detailed functions of TLR10 in immunity and give an account of how and when TLR10 can act on both sides of the inflammatory spectrum.

Cellular and molecular mechanisms of allergic asthma

Asthma is a chronic disease of the airways, which affects more than 350 million people worldwide. It is the most common chronic disease in children, affecting at least 30 million children and young adults in Europe. Asthma is a complex, partially heritable disease with a marked heterogeneity. Its development is influenced both by genetic and environmental factors. The most common, as well as the most well characterized subtype of asthma is allergic eosinophilic asthma, which is characterized by a type 2 airway inflammation. The prevalence of asthma has substantially increased in industrialized countries during the last 60 years. The mechanisms underpinning this phenomenon are incompletely understood, however increased exposure to various environmental pollutants probably plays a role. Disease inception is thought to be enabled by a disadvantageous shift in the balance between protective and harmful lifestyle and environmental factors, including exposure to protective commensal microbes versus infection with pathogens, collectively leading to airway epithelial cell damage and disrupted barrier integrity. Epithelial cell-derived cytokines are one of the main drivers of the type 2 immune response against innocuous allergens, ultimately leading to infiltration of lung tissue with type 2 T helper (T_H2) cells, type 2 innate lymphoid cells (ILC2s), M2 macrophages and eosinophils. This review outlines the mechanisms responsible for the orchestration of type 2 inflammation and summarizes the novel findings, including but not limited to dysregulated epithelial barrier integrity, alarmin release and innate lymphoid cell stimulation.

Risk factors for irreversible airway obstruction after infant bronchiolitis

BACKGROUND

Increasing evidence shows that environmental factors in childhood play a role in development of irreversible airway obstruction. We evaluated early-life and preschool-age risk factors for irreversible airway obstruction in adolescence after bronchiolitis in infancy.

METHODS

This study is a secondary analysis of data collected during prospective long-term follow-up of our post-bronchiolitis cohort. Risk factor data were collected during hospitalisation and on follow-up visits at 5-7 and 10-13 years of ages. Lung function was measured from 103 participants with impulse oscillometry at 5-7 years of age and from 89 participants with flow-volume spirometry at 10-13 years of age.

RESULTS

Asthma diagnosis at <12 months of age showed a significant association with irreversible airway obstruction at 10-13 years of age independently from current asthma. Irreversible airway obstruction was less frequent in children with variant than wild genotype of the Toll-like receptor 4(TLR4) rs4986790, but the significance was lost in logistic regression adjusted for current asthma and weight status. Higher post-bronchodilator respiratory system resistance at 5 Hz and lower baseline and post-bronchodilator reactance at 5 Hz by impulse oscillometry at 5-7 years of age were associated with irreversible airway obstruction at 10-13 years of age.

CONCLUSION

Asthma diagnosis during the first living year and worse lung function at preschool age increased the risk for irreversible airway obstruction at 10-13 years of age after bronchiolitis. TLR4 rs4986790 polymorphism may be protective for development of irreversible airway obstruction after bronchiolitis.

Interleukin-1 receptor-associated kinase-4 gene variation may increase post-bronchiolitis asthma risk

AIM

Evidence based on studies of the encoding genes suggests that interleukin-1 receptor-associated kinase-4 (IRAK4) plays a role in childhood asthma and allergy. Our aim was to evaluate the associations of six IRAK4 gene polymorphisms with presence of asthma and allergic rhinitis and use of inhaled corticosteroids (ICSs) for asthma at 5-7 and 11-13 years of ages after hospitalisation for bronchiolitis at younger than 6 months of age.

METHODS

IRAK4 rs4251513, rs4251520, rs4251522, rs4251578, rs79154645 and rs13852554 polymorphisms were determined in 141 former bronchiolitis patients prospectively followed up until 5-7 and in 125 children until 11-13 years of age.

RESULTS

The homozygous variant IRAK4 rs4251513 genotype was associated with the presence of asthma and allergic rhinitis and use of ICSs at 5-7 and 11-13 years of ages in univariate analyses. Statistical significance remained for the presence of asthma and use of ICSs but was lost in the case of allergic rhinitis in multivariate analyses. The adjusted odds ratios were 3.48 and 4.16 for asthma and 5.22 and 14.00 for ICS use at these two ages.

CONCLUSION

The homozygous variant IRAK4 rs4251513 genotype was constantly associated with post-bronchiolitis asthma and asthma medication in school-aged children.

Next Generation Exome Sequencing of Pediatric Asthma Identifies Rare and Novel Variants in Candidate Genes

Multiple genes have been implicated to have a role in asthma predisposition by association studies. Pediatric patients often manifest a more extensive form of this disease and a particularly severe disease course. It is likely that genetic predisposition could play a more substantial role in this group. This study is aimed at identifying the spectrum of rare and novel variation in known pediatric asthma susceptibility genes using whole exome sequencing analysis in nine individual cases of childhood onset allergic asthma. DNA samples from the nine children with a history of bronchial asthma diagnosis underwent whole exome sequencing on Ion Proton. For each patient, the entire complement of rare variation within strongly associated candidate genes was catalogued. The analysis showed 21 variants in the subjects, 13 had been previously identified, and 8 were novel. Also, among of which, nineteen were nonsynonymous and 2 were nonsense. With regard to the novel variants, the 2 nonsynonymous variants in the PRKG1 gene (PRKG1: p.C519W and PRKG1: p.G520W) were presented in 4 cases, and a nonsynonymous variant in the MAVS gene (MAVS: p.A45V) was identified in 3 cases. The variants we found in this study will enrich the variant spectrum and build up the database in the Saudi population. Novel eight variants were identified in the study which provides more evidence in the genetic susceptibility in asthma among Saudi children, providing a genetic screening map for the molecular genetic determinants of allergic disease in Saudi children, with the goal of reducing the impact of chronic diseases on the health and the economy. We believe that the advanced specified statistical filtration/annotation programs used in this study succeeded to release such results in a preliminary study, exploring the genetic map of that disease in Saudi children.

Toll-Like Receptor Agonists as Adjuvants for Allergen Immunotherapy

Toll-like receptors (TLRs) are essential components of innate immunity and provide defensive inflammatory responses to invading pathogens. Located within the plasma membranes of cells and also intracellular endosomes, TLRs can detect a range of pathogen associated molecular patterns from bacteria, viruses and fungi. TLR activation on dendritic cells can propagate to an adaptive immune response, making them attractive targets for the development of both prophylactic and therapeutic vaccines. In contrast to conventional adjuvants such as aluminium salts, TLR agonists have a clear immunomodulatory profile that favours anti-allergic T lymphocyte responses. Consequently, the potential use of TLRs as adjuvants in Allergen Immunotherapy (AIT) for allergic rhinitis and asthma remains of great interest. Allergic Rhinitis is a Th2-driven, IgE-mediated disease that occurs in atopic individuals in response to exposure to otherwise harmless aeroallergens such as pollens, house dust mite and animal dander. AIT is indicated in subjects with allergic rhinitis whose symptoms are inadequately controlled by antihistamines and nasal corticosteroids. Unlike anti-allergic drugs, AIT is disease-modifying and may induce long-term disease remission through mechanisms involving upregulation of IgG and IgG4 antibodies, induction of regulatory T and B cells, and immune deviation in favour of Th1 responses that are maintained after treatment discontinuation. This process takes up to three years however, highlighting an unmet need for a more efficacious therapy with faster onset. Agonists targeting different TLRs to treat allergy are at different stages of development. Synthetic TLR4, and TLR9 agonists have progressed to clinical trials, while TLR2, TLR5 and TLR7 agonists been shown to have potent anti-allergic effects in human in vitro experiments and in vivo in animal studies. The anti-allergic properties of TLRs are broadly characterised by a combination of enhanced Th1 deviation, regulatory responses, and induction of blocking antibodies. While promising, a durable effect in larger clinical trials is yet to be observed and further long-term studies and comparative trials with conventional AIT are required before TLR adjuvants can be considered for inclusion in AIT. Here we critically evaluate experimental and clinical studies investigating TLRs and discuss their potential role in the future of AIT.

TLR10: Insights, controversies and potential utility as a therapeutic target

The Toll-like receptor (TLR) family acts as a bridge connecting innate and acquired immunity. TLR10 remains one of the least understood members of this family. Some studies have examined TLR10 ligands, dimerization of TLR10 with other TLRs, and downstream signalling pathways and functions, but they have often arrived at conflicting conclusions. TLR10 can induce the production of proinflammatory cytokines by forming homodimers with itself or heterodimers with TLR1 or other TLRs, but it can also inhibit proinflammatory responses when co-expressed with TLR2 or potentially other TLRs. Mutations in the Toll/Interleukin 1 receptor (TIR) domain of TLR10 alter its signalling activity. Polymorphisms in the TLR10 gene can change the balance between pro- and anti-inflammatory responses and hence modulate the susceptibility to infection and autoimmune diseases. Understanding the full range of TLR10 ligands and functions may allow the receptor to be exploited as a therapeutic target in inflammation- or immune-related diseases. Here, we summarize recent findings on the pro- and anti-inflammatory roles of TLR10 and the molecular pathways in which it is implicated. Our goal is to pave the way for future studies of the only orphan TLR thought to have strong potential as a target in the treatment of inflammation-related diseases.

Toll-like receptor 10 rs4129009 gene polymorphism is associated with post-bronchiolitis lung function in adolescence

AIM

The aim was to evaluate the association of polymorphisms in the Toll-like receptor (TLR) 2 subfamily encoding genes with lung function by spirometry at 10-13 years of age in children who had been hospitalised for bronchiolitis at <6 months of age.

METHODS

In a prospective cohort of 166 former bronchiolitis patients, 138 returned a structured questionnaire and 89 attended a clinical follow-up visit including spirometry before and after bronchodilation at 10-13 years of age. Data on polymorphisms of the TLR1, TLR2, TLR6 and TLR10 genes were available from 81-82 children.

RESULTS

In the TLR10 rs4129009, the wild (AA) genotype was associated with lower FEV1/FVC before (92.4 vs 97.4, P = .002) and after (95.5 vs 98.6, P = .011) bronchodilator administration, compared to those with the variant genotype. When the TLR10 rs4129009 and TLR2 rs5743708 genotypes, and the TLR10 rs4129009 and TLR1 rs5743618 genotypes, respectively, were analysed as combined, both baseline and post-bronchodilator FEV1/FVC were lowest in the subjects with the wild (AA) genotype of the TLR10 rs4129009.

CONCLUSION

In this post-bronchiolitis follow-up, lung function in children with the variant TLR10 rs4129009 genotype with potentially altered TLR10 function was superior to lung function in those with the wild genotype.

Toll-like receptor 1 and 10 variations increase asthma risk and review highlights further research directions

AIM

This paper summarises variations in the genes encoding toll-like receptors (TLRs) in relation to the aetiology and outcome of infant bronchiolitis. It compares the literature with research carried out by our group.

METHODS

A mini review was conducted to provide context for a study carried out at the Department of Paediatrics, Tampere University Hospital, Finland. In 2000-2004, 187 infants were hospitalised for bronchiolitis and then followed up: 129 at 1.5 years of age, 166 at 5-7 years of age and 138 at 11-13 years of age.

RESULTS

The review showed that the Finnish bronchiolitis study was the only prospective study on the association between TLRs and the emergence of childhood asthma or lung function reduction after bronchiolitis in infancy. It found that TLR1 and TLR10 variant genotypes were associated with more asthma at 5-7 and 11-13 years, with inconsistent results for the other eight TLR genes. Large population-based studies were also identified that stressed the importance of the TLR2 subfamily members in childhood asthma.

CONCLUSION

Our study found that variations in the TLR1 and TLR10 genes increased the asthma risk after bronchiolitis. The mini review calls for further research on the TLR2 subfamily in bronchiolitis and childhood asthma.

TLR5 rs5744174 gene polymorphism is associated with the virus etiology of infant bronchiolitis but not with post-bronchiolitis asthma

BACKGROUND AND AIM

Bronchiolitis is a leading cause of hospitalization in infants and is associated with a risk of subsequent asthma. The innate immunity genes, such as those encoding toll-like receptors (TLRs), are likely to play a role in bronchiolitis and post-bronchiolitis outcome. Thus far, only one study has considered TLR5 genes in respiratory syncytial virus (RSV) bronchiolitis. The aim of this study was to investigate the association of TLR5 gene polymorphism with virus etiology and severity of bronchiolitis, and with post-bronchiolitis asthma.

METHODS

We recruited 164 infants (age < 6 months) hospitalized for bronchiolitis in this study and determined TLR5 rs5744174 (C > T) single nucleotide polymorphism, virus etiology and severity markers of bronchiolitis, and presence of post-bronchiolitis asthma until age 11 to 13 years.

RESULTS

RSV was detected in 113 (68.9%), rhinovirus in 19 (11.6%), and some other virus in 20 (12.2%) cases. Non-RSV etiology was more common among infants with the variant CT or TT genotype in the TLR5 rs5744174 gene than in those with the CC genotype (89.7% vs 71.7%, P = 0.03). TLR5 rs5744174 polymorphism was not associated with the need of supplementary oxygen or feeding support, with the length of hospital stay, or with post-bronchiolitis asthma at any age.

CONCLUSION

The TLR5 rs5744174 variant genotype may increase the susceptibility to bronchiolitis not caused by RSV.

Recognition of Double-Stranded RNA and Regulation of Interferon Pathway by Toll-Like Receptor 10

Toll-like receptor (TLR)-10 remains an orphan receptor without well-characterized ligands or functions. Here, we reveal that TLR10 is predominantly localized to endosomes and binds dsRNA in vitro at endosomal pH, suggesting that dsRNA is a ligand of TLR10. Recognition of dsRNA by TLR10 activates recruitment of myeloid differentiation primary response gene 88 for signal transduction and suppression of interferon regulatory factor-7 dependent type I IFN production. We also demonstrate crosstalk between TLR10 and TLR3, as they compete with each other for dsRNA binding. Our results suggest for the first time that dsRNA is a ligand for TLR10 and propose novel dual functions of TLR10 in regulating IFN signaling: first, recognition of dsRNA as a nucleotide-sensing receptor and second, sequestration of dsRNA from TLR3 to inhibit TLR3 signaling in response to dsRNA stimulation.

Toll-like receptor 1 and 10 gene polymorphisms are linked to postbronchiolitis asthma in adolescence

AIM

Toll-like receptors (TLR) are innate immunity molecules and our previous studies found that TLR1 gene polymorphism was associated with postbronchiolitis asthma at one to six years of age, as was TLR10 at five to seven years of age. This study examined any associations at 11-13 years of age.

METHODS

This prospective follow-up study was part of an ongoing evaluation of children admitted to Tampere University Hospital, Finland, for bronchiolitis in 2001-2004 at less than six months of age. We evaluated the association of TLR1 rs5743618 and TLR10 rs4129009 polymorphisms with asthma and asthma medication in 125 children aged 11-13 years.

RESULTS

Associations were measured as adjusted odd ratios (aOR) with 95% confidence intervals (95% CI). The variant TLR1 rs5743618 (aOR 4.04, 95% CI 0.99-13.01) and TLR10 rs4129009 (aOR 7.02, 95% CI 1.56-31.53) genotypes increased the risk of needing inhaled corticosteroids (ICSs) at 11-13 years of age. The variant TLR10 genotype (aOR 7.69, 95% CI 1.35-43.95) increased the risk of persistent asthma continuing from five to seven years of age until 11-13 years of age. The results were similar when the combined genotypes were analysed. [Correction added on 3 October 2017, after online publication: The data in the variant TRL1 rs5743618 genotype were incorrect and have been corrected in this version.] CONCLUSION: Polymorphisms in both the TLR1 and TLR10 genes may increase the risk of asthma at 11-13 years after infant bronchiolitis.

Inherent X-Linked Genetic Variability and Cellular Mosaicism Unique to Females Contribute to Sex-Related Differences in the Innate Immune Response

Females have a longer lifespan and better general health than males. Considerable number of studies also demonstrated that, after trauma and sepsis, females present better outcomes as compared to males indicating sex-related differences in the innate immune response. The current notion is that differences in the immuno-modulatory effects of sex hormones are the underlying causative mechanism. However, the field remains controversial and the exclusive role of sex hormones has been challenged. Here, we propose that polymorphic X-linked immune competent genes, which are abundant in the population are important players in sex-based immuno-modulation and play a key role in causing sex-related outcome differences following trauma or sepsis. We describe the differences in X chromosome (ChrX) regulation between males and females and its consequences in the context of common X-linked polymorphisms at the individual as well as population level. We also discuss the potential pathophysiological and immune-modulatory aspects of ChrX cellular mosaicism, which is unique to females and how this may contribute to sex-biased immune-modulation. The potential confounding effects of ChrX skewing of cell progenitors at the bone marrow is also presented together with aspects of acute trauma-induced de novo ChrX skewing at the periphery. In support of the hypothesis, novel observations indicating ChrX skewing in a female trauma cohort as well as case studies depicting the temporal relationship between trauma-induced cellular skewing and the clinical course are also described. Finally, we list and discuss a selected set of polymorphic X-linked genes, which are frequent in the population and have key regulatory or metabolic functions in the innate immune response and, therefore, are primary candidates for mediating sex-biased immune responses. We conclude that sex-related differences in a variety of disease processes including the innate inflammatory response to injury and infection may be related to the abundance of X-linked polymorphic immune-competent genes, differences in ChrX regulation, and inheritance patterns between the sexes and the presence of X-linked cellular mosaicism, which is unique to females.