Contribution of alpha- and beta-defensins to lung function decline and infection in smokers: an association study

Genetic Polymorphism and Gene Expression of β-Defensin-1 in Periodontitis Associated With Type 2 Diabetes Mellitus

Introduction Periodontitis is a multifactorial disease caused by periodontopathic bacteria and influenced by both genetic and environmental factors. Genetic predispositions are found to play a crucial part in the onset and progression of periodontal disease. There is a two-way relationship between diabetes and periodontitis with severe periodontal tissue destruction seen in diabetic patients. Antimicrobial peptide, β-defensin-1 (DEFB1 gene), plays an important role in the innate immune responses and forms the first line of host defense against periodontal pathogens. Single nucleotide polymorphisms (SNPs) in the specific genetic loci of the DEFB1 gene and its expression level could confer a degree of risk or protection from periodontitis associated with diabetes. The present study determined the association between SNPs at the 5' untranslated region (UTR) in the DEFB1 gene and susceptibility to periodontitis associated with type 2 diabetes mellitus (T2DM) and analyzed the effect of 5' UTR polymorphisms on DEFB1 gene expression. Methods SNPs in the 5' UTR of the DEFB1 gene (-20G>A (rs11362), -44C>G (rs1800972), and -52G>A (rs1799946)) were genotyped by polymerase chain reaction (PCR) followed by Sanger sequencing. The study group included periodontitis (n = 40), periodontitis with T2DM (n = 20), and periodontally and systemically healthy as controls (n = 40). DEFB1 gene expression was determined by real-time PCR in the study group comprising periodontitis (n = 20), periodontitis with T2DM (n = 15), and healthy controls (n = 20). The effect of 5' UTR polymorphisms on the expression was analyzed by statistical tools. Results Statistically significant higher prevalence of the variant AA genotype of rs11362 was observed in periodontitis (odds ratio (OR) = 3.64, 95% confidence Interval (CI) = 1.16-11.43, p = 0.04) and periodontitis with T2DM (OR = 5.14, 95% CI = 1.29-20.5, p = 0.03) in comparison with healthy controls. Moreover, there was a significant increase of the variant AA genotype of rs1799946 in periodontitis (OR = 3.88, 95% CI = 1.19-12.68, p = 0.04) compared to healthy controls. DEFB1 gene expression was downregulated in periodontitis and upregulated in periodontitis with T2DM patients when compared to healthy controls but was not statistically significant. No significant association was found for the effect of SNPs of the DEFB1 gene on its expression. Conclusion From the SNP analysis, it can be inferred that the presence of SNPs at the 5' UTR (rs11362 and rs1799946) in the DEFB1 gene may be an important predictive factor for periodontitis.

Airway microbiome-immune crosstalk in chronic obstructive pulmonary disease

Chronic Obstructive Pulmonary Disease (COPD) has significantly contributed to global mortality, with three million deaths reported annually. This impact is expected to increase over the next 40 years, with approximately 5 million people predicted to succumb to COPD-related deaths annually. Immune mechanisms driving disease progression have not been fully elucidated. Airway microbiota have been implicated. However, it is still unclear how changes in the airway microbiome drive persistent immune activation and consequent lung damage. Mechanisms mediating microbiome-immune crosstalk in the airways remain unclear. In this review, we examine how dysbiosis mediates airway inflammation in COPD. We give a detailed account of how airway commensal bacteria interact with the mucosal innate and adaptive immune system to regulate immune responses in healthy or diseased airways. Immune-phenotyping airway microbiota could advance COPD immunotherapeutics and identify key open questions that future research must address to further such translation.

Role of Atypical Chemokines and Chemokine Receptors Pathways in the Pathogenesis of COPD

Chronic obstructive pulmonary disease (COPD) represents a heightened inflammatory response in the lung generally resulting from tobacco smoking-induced recruitment and activation of inflammatory cells and/or activation of lower airway structural cells. Several mediators can modulate activation and recruitment of these cells, particularly those belonging to the chemokines (conventional and atypical) family. There is emerging evidence for complex roles of atypical chemokines and their receptors (such as high mobility group box 1 (HMGB1), antimicrobial peptides, receptor for advanced glycosylation end products (RAGE) or toll-like receptors (TLRs)) in the pathogenesis of COPD, both in the stable disease and during exacerbations. Modulators of these pathways represent potential novel therapies for COPD and many are now in preclinical development. Inhibition of only a single atypical chemokine or receptor may not block inflammatory processes because there is redundancy in this network. However, there are many animal studies that encourage studies for modulating the atypical chemokine network in COPD. Thus, few pharmaceutical companies maintain a significant interest in developing agents that target these molecules as potential antiinflammatory drugs. Antibody-based (biological) and small molecule drug (SMD)-based therapies targeting atypical chemokines and/or their receptors are mostly at the preclinical stage and their progression to clinical trials is eagerly awaited. These agents will most likely enhance our knowledge about the role of atypical chemokines in COPD pathophysiology and thereby improve COPD management.

Plasma levels of alarmin HNPs 1-3 associate with lung dysfunction after cardiac surgery in children

Background

Early onset of lung injury is considerable common after cardiac surgery and is associated with increasing in morbidity and mortality, but current clinical predictors for the occurrence of this complication always have limited positive warning value. This study aimed to evaluate whether elevated plasma levels of human neutrophil peptides (HNPs) 1–3 herald impaired lung function in infants and young children after cardiac surgery necessitating cardiopulmonary bypass (CPB).

Methods

Consecutive children younger than 3 years old who underwent cardiac surgery were prospectively enrolled. Plasma concentrations of HNPs 1–3 and inflammatory cytokines were measured before, and immediately after CPB, as well as at 1 h, 12 h, and 24 h after CPB.

Results

Thirty patients were enrolled, 18 (60%) of whom were infants. Plasma levels of HNPs 1–3 and the pro-inflammatory cytokine interleukin-6 (IL-6) significantly increased immediately after CPB (P < 0.001), while IL-8 increased 1 h after the CPB operation (P = 0.002). The anti-inflammatory cytokine IL-10 levels were also significantly elevated immediately after CPB compared with the baseline (P < 0.001). The stepwise multiple linear regression analysis showed that the plasma HNPs 1–3 levels immediately after CPB was independent correlated with the declined lung function, as reflected by the PaO₂/FiO₂ ratio on the first 2 days after operation (for the first day: OR, −1.067, 95% CI, −0.548 to −1.574; P < 0.001; for the second day: OR, −0.667, 95% CI, −0.183 to −1.148; P = 0.009) and prolonged mechanical ventilation time (OR, 0.039, 95% CI, 0.005 to 0.056; P = 0.011). Plasma levels of HNPs 1–3 and IL-10 returned to the baseline values, while IL-6 and IL-8 levels remained significantly higher than baseline 24 h after CPB (P ≤ 0.01).

Conclusions

Elevated HNPs 1–3 levels immediately after CPB correlate with impaired lung function, and HNPs 1–3 could serve as a quantifiable early alarmin biomarker for onset of lung injury in infants and young children undergoing cardiac surgery with CPB.

Electronic supplementary material

The online version of this article (10.1186/s12890-017-0558-4) contains supplementary material, which is available to authorized users.

DEFB1 gene polymorphisms and tuberculosis in a Northeastern Brazilian population

β-Defensin-1, an antimicrobial peptide encoded by the DEFB1 gene, is known to play an important role in lung mucosal immunity. In our association study we analyzed three DEFB1 functional polymorphisms −52G>A (rs1799946), −44C>G (rs1800972) and −20G>A (rs11362) in 92 tuberculosis patients and 286 healthy controls, both from Northeast Brazil: no association was found between the studied DEFB1 polymorphisms and the disease. However we cannot exclude that this lack of association could be due to the low number of subjects analyzed, as suggested by the low statistical power achieved for the three analyzed SNPs (values between 0.16 and 0.50).

Gene-environment Interactions in the Etiology of Dental Caries

Dental caries is a multifactorial disease that can be conceptualized as an interaction between genetic and environmental risk factors. The aim of this study is to examine the effects of AMELX, CA6, DEFB1, and TAS2R38 gene polymorphism and gene-environment interactions on caries etiology and susceptibility in adults. Genomic DNA was extracted from the buccal mucosa, and adults aged 20 to 60 y were placed into 1 of 2 groups: low caries risk (DMFT ≤ 5; n = 77) and high caries risk (DMFT ≥ 14; n = 77). The frequency of AMELX (+522), CA6 (T55M), DEFB1 (G-20A), and TAS2R38 (A49P) single-nucleotide polymorphisms was genotyped with the polymerase chain reaction-restriction fragment length polymorphism method. Environmental risk factors examined in the study included plaque amount, toothbrushing frequency, dietary intake between meals, saliva secretion rate, saliva buffer capacity, mutans streptococci counts, and lactobacilli counts. There was no difference between the caries risk groups in relation to AMELX (+522) polymorphism (χ(2) test, P > 0.05). The distribution of CA6 genotype and allele frequencies in the low caries risk group did not differ from the high caries risk group (χ(2) test, P > 0.05). Polymorphism of DEFB1 (G-20A) was positively associated, and TAS2R38 (A49P) negatively associated, with caries risk (χ(2) test, P = 0.000). There were significant differences between caries susceptibility and each environmental risk factor, except for the saliva secretion rate (Mann-Whitney U test, P = 0.000). Based on stepwise multiple linear regression analyses, dental plaque amount, lactobacilli count, age, and saliva buffer capacity, as well as DEFB1 (G-20A), TAS2R38 (A49P), and CA6 (T55M) gene polymorphism, explained a total of 87.8% of the variations in DMFT scores. It can be concluded that variation in CA6 (T55M), DEFB1 (G-20A), and TAS2R38 (A49P) may be associated with caries experience in Turkish adults with a high level of dental plaque, lactobacilli count, and age and when saliva buffer capacity is low.

The therapeutic impact of HNP-1 in condyloma acuminatum

BACKGROUND

Condyloma acuminatum is one of the most commonly occurring sexually transmitted diseases. HNP1 is a small antimicrobial peptide that has been reported to have antiviral activities.

AIM

Using the condyloma acuminatum tissue culture to resemble the situation more closely in vivo, we investigate the therapeutic effect of a recombinant plasmid encoding HNP1 gene in condyloma acuminatum tissue.

METHODS

Recombinant plasmid DNA carrying HNP1 cDNA was constructed and identified. Then the recombinant plasmid was transfected into a condyloma acuminatum tissue fragment, and the HNP1 expression was determined on these tissue fragments by immunohistochemistry. TUNEL staining and flow cytometry techniques were used to examine cell apoptosis of condyloma acuminatum tissue. Relative real-time polymerase chain reaction was used to validate antihuman papillomavirus therapeutics of the treatment groups.

RESULTS

Transfected HNP1 gene was expressed mainly in the cytoplasmic granules of the condyloma acuminatum tissues. Positive apoptotic cells were observed in condyloma acuminatum tissues transfected with the HNP1 gene. In addition, the HPV expression was lower in the HNP1 treatment tissues as compared to their corresponding control tissues.

CONCLUSION

The results indicate that HNP1 can directly promote condyloma acuminatum cell apoptosis and play an antivirus role in the condyloma acuminatum tissue by limiting viral replication. These observations suggest a possible application for human HNP1 on condyloma acuminatum therapy.

Differential DNA methylation profiles of infants exposed to maternal asthma during pregnancy

BACKGROUND

Asthma is a complex disease that involves both genetic factors and environmental exposures. Aberrant epigenetic modifications, such as DNA methylation, may be important in asthma development. Fetal exposure to maternal asthma during critical periods of in utero development may lead to epigenetic alterations that predispose infants to a greater risk of developing asthma themselves. We investigated alterations in the DNA methylation profile of peripheral blood from infants exposed to maternal asthma during pregnancy.

METHODS

Peripheral blood was collected from 12-month-old infants born to women with (n = 25) and without (n = 15) doctor diagnosed asthma during pregnancy. Genomic DNA was extracted, bisulfite converted, and hybridized to Infinium Methylation 27 arrays (Illumina), containing over27,000 CpGs from 14,495 genes. CpG loci in only autosomal genes were classified as differentially methylated at the 99% level (P < 0.01, |DiffScore| > 22 and delta beta >0.06).

RESULTS

There were 70 CpG loci, corresponding to 67 genes that were significantly differentially methylated. Twelve CpG loci (11 genes) showed greater than 10% comparative difference in DNA methylation, including hyper-methylated loci of FAM181A, MRI1, PIWIL1, CHFR, DEFA1, MRPL28, AURKA, and hypo-methylated loci of NALP1L5, MAP8KIP3, ACAT2, and PM20D1 in maternal asthma. Methylation of MAPK8IP3 was significantly negatively correlated with maternal blood eosinophils (r = -0.38; P = 0.022), maternal eNO (r = -0.44; P = 0.005), and maternal serum total IgE (r = -0.39, P = 0.015). Methylation of AURKA negatively correlated with maternal hemoglobin (r = -0.43; P = 0.008), infants height (r = -0.51; P < 0.001) and weight (r = -0.36; P = 0.021). Methylation of PM20D1 was lower in infants born to mothers with asthma on inhaled corticosteroid treatment. Methylation of PM20D1 was lower and MRI1 was higher in infants born to atopic mothers without asthma.

CONCLUSIONS

In an Australian study population, exposure to maternal asthma during pregnancy is associated with differential methylation profiles of infants' peripheral blood DNA, which may act as risk factors for future asthma development.

Defensins and sepsis

Sepsis is a leading cause of mortality and morbidity in the critical illness. Multiple immune inflammatory processes take part in the pathogenesis of sepsis. Defensins are endogenous antimicrobial peptides with three disulphide bonds created by six cysteine residues. Besides the intrinsic microbicidal properties, defensins are active players which modulate both innate and adaptive immunity against various infections. Defensins can recruit neutrophils, enhance phagocytosis, chemoattract T cells and dendritic cells, promote complement activation, and induce IL-1β production and pyrotosis. Previous publications have documented that defensins play important roles in a series of immune inflammatory diseases including sepsis. This review aims to briefly summarize in vitro, in vivo, and genetic studies on defensins' effects as well as corresponding mechanisms within sepsis and highlights their promising findings which may be potential targets in future therapies of sepsis.

Critical COPD respiratory illness is linked to increased transcriptomic activity of neutrophil proteases genes

BACKGROUND

Gene expression profiling (GEP) in cells obtained from peripheral blood has shown that this is a very useful approach for biomarker discovery and for studying molecular pathogenesis of prevalent diseases. While there is limited literature available on gene expression markers associated with Chronic Obstructive Pulmonary Disease (COPD), the transcriptomic picture associated with critical respiratory illness in this disease is not known at the present moment.

FINDINGS

By using Agilent microarray chips, we have profiled gene expression signatures in the whole blood of 28 COPD patients hospitalized with different degrees of respiratory compromise.12 of them needed of admission to the ICU, whilst 16 were admitted to the Respiratory Medicine Service. GeneSpring GX 11.0 software was used for performing statistical comparisons of transcript levels between ICU and non-ICU patients. Ingenuity pathway analysis 8.5 (IPA) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to select, annotate and visualize genes by function and pathway (gene ontology). T-test showed evidence of 1501 genes differentially expressed between ICU and non-ICU patients. IPA and KEGG analysis of the most representative biological functions revealed that ICU patients had increased levels of neutrophil gene transcripts, being [cathepsin G (CTSG)], [elastase, neutrophil expressed (ELANE)], [proteinase 3 (PRTN3)], [myeloperoxidase (MPO)], [cathepsin D (CTSD)], [defensin, alpha 3, neutrophil-specific (DEFA3)], azurocidin 1 (AZU1)], and [bactericidal/permeability-increasing protein (BPI)] the most representative ones. Proteins codified by these genes form part of the azurophilic granules of neutrophils and are involved in both antimicrobial defence and tissue damage. This "neutrophil signature" was paralleled by the necessity of advanced respiratory and vital support, and the presence of bacterial infection.

CONCLUSION

Study of transcriptomic signatures in blood suggests an essential role of neutrophil proteases in COPD patients with critical respiratory illness. Measurement and modulation of the expression of these genes could present an option for clinical monitoring and treatment of severe COPD exacerbations.

Polymorphisms of beta defensins are associated with the risk of severe acute pancreatitis

AIMS

Bacterial translocation from the intestinal tract plays an important role in severe acute pancreatitis (AP). Human β-defensins are a family of antimicrobial peptides present at the mucosal surface. The aim of this study was to investigate the relevance of single nucleotide polymorphisms (SNPs) in the DEFB1 gene and copy number polymorphisms of the DEFB4 genes in AP.

METHODS

124 AP patients (30 with mild and 94 with severe disease) and 100 healthy controls were enrolled in the study. Three SNPs of the DEFB1 gene [G-20A (c.-20G→A), C-44G (c.-44C→G) and G-52A (c.-52G→A)] were genotyped by Custom TaqMan assay. The DEFB4 gene copy number was determined by means of a TaqMan real-time PCR assay.

RESULTS

Significantly higher frequencies of the AA genotype of G-20A (c.-20G→A) and the AA genotype of G-52A (c.-52G→A) were observed among the patients with severe AP (SAP) compared with the healthy controls (38 vs. 20 and 41 vs. 18%, respectively). The GG protective genotype of C-44G (c.-44C→G) SNP was much less frequent (1%) among the patients than among the controls (9%). A higher frequency of a lower (<4) copy number of the DEFB4 gene was observed in the patients with SAP compared with the healthy controls (62 vs. 24%, respectively).

CONCLUSIONS

The variations in the genes encoding human β-defensin-1 and -2 may be associated with the risk of SAP. and IAP.

Genomic copy number determines functional expression of {beta}-defensin 2 in airway epithelial cells and associates with chronic obstructive pulmonary disease

RATIONALE

Copy number variations of the cluster of beta-defensin genes have been associated with psoriasis and inflammatory bowel disease. Controversy still exists on whether the beta-defensins genes determine susceptibility for chronic obstructive pulmonary disease (COPD).

OBJECTIVES

We investigated whether genomic copy number variations of the beta-defensin gene cluster have a functional role in airway epithelial cells and associate with the presence of COPD.

METHODS

Baseline and inflammatory induced transcript expression of DEFB4 was studied in nasal epithelial cell cultures and its effect on Pseudomonas aeruginosa inhibition was assessed. Subsequently, relevant functional cut-offs for copy numbers were used to explore associations with COPD in two independent case-control studies.

MEASUREMENTS AND MAIN RESULTS

Copy number variation in the beta-defensin encoding genes correlated with baseline mRNA DEFB4 expression levels (R(2) = 0.96; P = 0.02), with a plateau effect from five copies or more. Only when higher copy numbers of beta-defensin genes were present, transcription was significantly up-regulated by tumor necrosis factor-alpha (P < 0.0001), which resulted in better antimicrobial activity in vitro. When comparing healthy smokers with COPD patients, a copy number greater than or equal to 5 was associated with increased risk for COPD with an adjusted odds ratio of 1.8 (confidence interval, 1.1-2.8; P = 0.02), which was confirmed by a second independent case-control study.

CONCLUSIONS

Genomic copy number variation of beta-defensin encoding genes has a functional role in airway epithelial cells, which may contribute to the pathogenesis of COPD.

Potential role of human beta-defensin 1 in Helicobacter pylori-induced gastritis

OBJECTIVE

Helicobacter pylori-induced gastric inflammation is dependent on the persistence of the microorganism in the gastric epithelium. Modulation of the host epithelial antimicrobial responses may be a critical determinant in H. pylori-induced gastritis. Human beta-defensins (hBDs) are important components of the host defence at mucosal surfaces. The aim of the present study was to investigate the relevance of three single nucleotide polymorphisms (SNPs) of the human beta defensin-1 (hBD-1) gene in H. pylori-induced gastritis and to assess the mRNA expression of hBD-1 in H. pylori-infected AGS cells.

MATERIAL AND METHODS

Three SNPs of the beta defensin DEFB1 gene, DEFB1 G-20A (rs11362), DEFB1 C-44G (rs1800972) and DEFB1 G-52A (rs1799946), were genotyped either by Custom TaqMan SNP genotyping assays or by restriction fragment length polymorphism (RFLP) in 150 patients with chronic active gastritis; 100 serologically H. pylori-positive subjects without gastric or duodenal symptoms served as controls. hBD-1 mRNA expression in AGS cells was measured by quantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Significant differences in frequencies of the GA and AA genotypes of G-52A SNPs were observed between patients with chronic active gastritis and healthy controls. The maximum level of hBD-1 mRNA expression in AGS cells was observed at 24 h after infection with H. pylori, this not being dependent on the presence of the cag pathogenicity island (PAI).

CONCLUSIONS

The results of these genetic and in vitro experiments suggest that not only the inducible, but also the constitutive form of hBD may be important in the pathogenesis of H. pylori-induced gastritis.

National Emphysema Treatment Trial state of the art: genetics of emphysema

Although a hereditary contribution to emphysema has been long suspected, severe alpha1-antitrypsin deficiency remains the only conclusively proven genetic risk factor for chronic obstructive pulmonary disease (COPD). Recently, genome-wide linkage analysis has led to the identification of two promising candidate genes for COPD: TGFB1 and SERPINE2. Like multiple other COPD candidate gene associations, even these positionally identified genes have not been universally replicated across all studies. Differences in phenotype definition may contribute to nonreplication in genetic studies of heterogeneous disorders such as COPD. The use of precisely measured phenotypes, including emphysema quantification on high-resolution chest computed tomography scans, has aided in the discovery of additional genes for clinically relevant COPD-related traits. The use of computed tomography scans to assess emphysema and airway disease as well as newer genetic technologies, including gene expression microarrays and genome-wide association studies, has great potential to detect novel genes affecting COPD susceptibility, severity, and response to treatment.

Association of beta-defensin 1 single nucleotide polymorphisms with Crohn's disease

OBJECTIVE

It has been suggested that deficient defensin expression is associated with the chronic inflammation of Crohn's disease. The regional localization of Crohn's disease, ileal or colonic disease can be linked to different defensin profiles. As constitutive beta-defensin 1 has a colonic expression, we considered it of interest to investigate single nucleotide polymorphisms (SNPs) of the beta-defensin 1 gene (DEFB1) in Crohn's disease.

MATERIAL AND METHODS

Three SNPs of the DEFB1 gene, DEFB1 G-20A (rs11362), DEFB1 C-44G (rs1800972) and DEFB1 G-52A (rs1799946), were genotyped either by Custom TaqMan SNP genotyping assays or by restriction fragment length polymorphisms (RFLP) in 190 patients with Crohn's disease and 95 Hungarian controls.

RESULTS

It was found that the G-20A and C-44G SNPs had a strong association with the colonic and ileocolonic localizations of the disease, respectively, but no association was detected for the ileal localization. A significantly higher frequency of the GA genotype of G-20A was observed among patients with colonic localization (60%) as compared with healthy controls (39%), with an odds ratio (OR) of 2.39. The GG genotype of C-44G SNP, which is regarded as a protective genotype, was much less frequent (4%) among patients than among controls (12%), OR 3.367.

CONCLUSIONS

These results indicate that genetic variations in the DEFB1 gene encoding constitutive human beta-defensin 1 may be associated with the risk for Crohn's disease and may determine disease phenotype, e.g. colonic localization.

Airways disease: phenotyping heterogeneity using measures of airway inflammation

: Despite asthma and chronic obstructive pulmonary disease being widely regarded as heterogeneous diseases, a consensus for an accurate system of classification has not been agreed. Recent studies have suggested that the recognition of subphenotypes of airway disease based on the pattern of airway inflammation may be particularly useful in increasing our understanding of the disease. The use of non-invasive markers of airway inflammation has suggested the presence of four distinct phenotypes: eosinophilic, neutrophilic, mixed inflammatory and paucigranulocytic asthma. Recent studies suggest that these subgroups may differ in their etiology, immunopathology and response to treatment. Importantly, novel treatment approaches targeted at specific patterns of airway inflammation are emerging, making an appreciation of subphenotypes particularly relevant. New developments in phenotyping inflammation and other facets of airway disease mean that we are entering an era where careful phenotyping will lead to targeted therapy.

Multispecific myeloid defensins

PURPOSE OF REVIEW

This review describes recent progress in our understanding of defensins and their contributions to innate immunity. Defensins are small, cysteine-rich endogenous antibiotic peptides. Human neutrophils contain large amounts of three alpha-defensins (HNP-1-HNP-3), and smaller amounts of a fourth, HNP-4. Monocytes and macrophages generally lack defensins, but they release messengers that induce the synthesis of beta-defensins in epithelial cells.

RECENT FINDINGS

In addition to their antimicrobial and immunomodulatory effects, HNP-1-HNP-3 possess antiviral and toxin-neutralizing properties. Induction of beta-defensins in epithelial cells is mediated by cell-surface Toll-like receptors or cytoplasmic peptidoglycan receptors that can recognize pathogen-associated molecules. Mutations in Nod2, a cytoplasmic peptidoglycan receptor, are associated with reduced levels of intestinal alpha-defensins and ileal Crohn's disease. Human defensin genes show marked copy-number polymorphism. High level constitutive expression of defensins may afford protection against HIV-1 and other defensin-sensitive pathogens. Theta-defensins (cyclic octadecapeptides found in nonhuman primates) have impressive antiviral and antitoxic properties.

SUMMARY

The multiple properties of defensins contribute to human innate immunity against bacteria, bacterial toxins, and viruses.