Non-classical-MHC genetics of immunological disease in man and mouse. The key role of pro-inflammatory cytokine genes

Cis-regulatory evolution in a wild primate: Infection-associated genetic variation drives differential expression of MHC-DQA1 in vitro

Few studies have combined genetic association analyses with functional characterization of infection-associated SNPs in natural populations of nonhuman primates. Here, we investigate the relationship between host genetic variation, parasitism and natural selection in a population of red colobus (Procolobus rufomitratus tephrosceles) in Kibale National Park, Uganda. We collected parasitological, cellular and genomic data to test the following hypotheses: (i) MHC-DQA1 regulatory genetic variation is associated with control of whipworm (Trichuris) infection in a natural population of red colobus; (ii) infection-associated SNPs are functional in driving differential gene expression in vitro; and (iii) balancing selection has shaped patterns of variation in the MHC-DQA1 promoter. We identified two SNPs in the MHC-DQA1 promoter, both in transcription factor binding sites, and both of which are associated with decreased control of Trichuris infection. We characterized the function of both SNPs by testing differences in gene expression between the two alleles of each SNP in two mammalian cell lines. Alleles of one of the SNPs drove differential gene expression in both cell lines, while the other SNP drove differences in expression in one of the cell lines. Additionally, we found evidence of balancing selection acting on the MHC-DQA1 promoter, including extensive trans-species polymorphisms between red colobus and other primates, and an excess of intermediate-frequency alleles relative to genome-wide, coding and noncoding RADseq data. Our data suggest that balancing selection provides adaptive regulatory flexibility that outweighs the consequences of increased parasite infection intensity in heterozygotes.

The biological response to nanometre-sized polymer particles

Recently, nanometre-sized UHMWPE particles generated from hip and knee replacements have been identified in vitro and in vivo. UHMWPE particles in the 0.1-1.0μm size range have been shown to be more biologically active than larger particles, provoking an inflammatory response implicated in late aseptic loosening of total joint replacements. The biological activity of nanometre-sized particles has not previously been studied. The biological response to clinically-relevant UHMWPE wear particles including nanometre-sized and micrometre-sized, along with polystyrene particles (FluoSpheres 20nm, 60nm, 200nm and 1.0μm), and nanometre-sized model polyethylene particles (Ceridust 3615®), was determined in terms of osteolytic cytokine release from primary human peripheral blood mononuclear cells (PBMNCs). Nanometre-sized UHMWPE wear particles, nanometre-sized Ceridust 3615® and 20nm FluoSpheres had no significant effect on TNF-α, IL-1β, IL-6 and IL-8 release from PBMNCs at a concentration of 100μm(3) particles per cell after 12 and 24h. The micrometre-size UHMWPE wear particles (0.1-1.0μm) and 60nm, 200nm and 1.0μm FluoSpheres caused significantly elevated osteolytic cytokine release from PBMNCs. These results indicated that particles below circa 50nm fail to activate PBMNCs and that particle size, composition and morphology played a crucial role in cytokine release by particle stimulated macrophages.

Cytokine Genotype Polymorphisms in Breast Carcinoma: Associations of TGF-β1 with Relapse

Markers of angiogenesis, cell proliferation, and cytokine regulation are associated with the development and course of autoimmune and malignant diseases. We investigated associations between cytokine production genotypes in breast cancer patients compared with controls and explored associations with known prognostic indices and relapse status. Eighty-eight females with breast carcinoma (BC) were studied in this case-control study comparing the cytokine genotypes of TNF-alpha TGF-beta1, IL-10, IL-6, and IFN-gamma with controls. Cytokine polymorphisms were identified by sequence-specific primers for codons, introns, or promoters regulating cytokine production. Patient characteristics, such as estrogen and progesterone receptor status, DNA ploidy, Her-2 neu expression, lymph node involvement, tumor size, and relapse status were evaluated. Cytokine genotypes were not associated with breast cancer compared with controls. Correlations between TGF-beta1 high-production genotypes and greater than four positive lymph nodes (OR=2.3; p=ns) and TNF-alpha high-production genotype and the mean level of estrogen receptor expression (66 +/- 24 vs. 34 +/- 36, p=0.016) were identified. The median patient follow-up interval from diagnosis to evaluation was 50.1 months (range 13-387 months). Relapse status was known for 84 of the patients. The odds of relapse in TGF-beta1 codon 10 CC genotypes was 2.81 times that in TGF-beta1 high-production genotypes (OR=2.81; 95% CI for OR: 1.0, 7.8; p=0.04). Mean progesterone receptor expression was decreased in relapsed patients (40.9 +/- 29.9% vs. 23.1 +/- 24.5, p=0.05). The other cytokine genotypes studied (IL-10, IL-6, IFN-gamma, and TNF-alpha production were not associated with breast cancer overall or relapse status. In this study, TGF-beta1 low-production genotypes (TGF-beta1 10 CC) were associated with an increased odds of disease relapse. This finding should be confirmed in a longitudinal study to further investigate the regulatory function of cytokine production as a prognostic indicator of relapse.

Cytokine gene polymorphisms in recurrent spontaneous abortions: a comprehensive review

PROBLEM

Cytokine gene polymorphism studies in women with recurrent spontaneous abortion (RSA) are reviewed to provide comprehensive understanding and a direction for the future investigation.

METHOD OF STUDY

A search of PubMed was made to identify the published data between 2001 and 2007 regarding RSA and cytokine gene polymorphisms.

RESULTS

Either allele and/or genotype frequencies of the following polymorphisms were reported to be significantly different between women with RSA and controls: IFN-gamma +874A-->T, TA (P = 0.01), AA (P = 0.04); IL-6, -634C-->G CG/GG (P = 0.026); IL-10, -592C-->A CC (P = 0.016); IL-1B -511C (P = 0.035), -31T (P = 0.029); IL-1RA, IL1RN*2 (P = 0.002), and IL1RN*3 (P = 0.002). None of these studies was repeatedly reported by others to be significantly different. Among these, four cytokine polymorphisms (IFN-gamma, +874A-->T; IL-1B -511C; IL-1RA, IL1RN*2, IL1RN*3) were refuted by others and rest of them were studied once.

CONCLUSION

Multiple cytokine polymorphisms were reported to be associated with RSA. However, a majority of studies were not confirmed by other investigators or refuted by others. Inconsistent study results might be related to: (i) the production of these cytokines is partly under genetic controls and other factors affect cytokine levels; (ii) ethnic background, environmental factors, and selection criteria for study populations are different and (iii) the possibilities exist that multiple cytokine gene polymorphisms or other genes in linkage disequilibrium may play a role in RSA.

Genetic aspects of immune-mediated adverse drug effects

Adverse drug effects (ADEs) are of great importance in medicine and account for up to 5% of all hospital admissions. ADEs can arise from several mechanisms and a wide range of drugs can cause immune-mediated ADEs (IMADEs). For a drug to elicit an IMADE, it must be both immunogenic (that is, able to sensitize the immune system) and antigenic (that is, able to evoke a response from a sensitized immune system). Unlike protein therapeutics, small-molecule drugs (or xenobiotics) are usually neither immunogenic nor antigenic. IMADEs are therefore the result of complex interactions between drug-metabolizing enzymes, immune sensitization and immune effectors. The genetic aspects of this interplay are discussed in this review.

Enteroaggregative Escherichia coli: an emerging enteric pathogen

Enteroaggregative Escherichia coli (EAEC) represents an emerging pathogen that causes enteric and food-borne infectious diseases. Subgroups in many populations throughout the world are susceptible to EAEC infection. EAEC pathogenesis involves adherence to the intestinal mucosa; increased production and deposition of a mucus biofilm; and mucosal toxicity due to inflammation and cytokine release. Due to the heterogeneity of EAEC strains and differing host immune responses, not all EAEC infections are symptomatic. Recent data suggest that individuals with a homozygous genotype -251 AA single nucleotide polymorphism (SNP), in the IL-8 promoter region, are more susceptible to EAEC diarrhea. The HEp-2 cell adherent assay allows identification of EAEC's characteristic aggregative or "stacked brick" adherence pattern. Antimicrobial treatment of individuals who develop EAEC diarrhea should be individually based. Ciprofloxacin and rifaximin, compared to placebo, have been shown to significantly shorten the course of diarrhea in patients who developed EAEC infection. The objective of this review is to increase awareness of this important emerging pathogen and to discuss the epidemiology, pathogenesis, and host-pathogen factors associated with EAEC infection.

Immune response to parasitic attack: evolution of a pulsed character

Pulsed characters are temporary biochemical, cellular, or structural changes produced in response to environmental or biotic challenge. For example, response to parasitic attack develops as a pulse of defensive chemicals or cells that typically decay after the parasite has been controlled. Almost all theories for the genetic variability of characters assume measurements on static characters. This paper presents theoretical tools to examine optimal control variables for pulsed characters and the expected level of genetic variability in those control variables. The example of host immune response to parasitic attack is used to develop the theory.

Asthma genetics

Asthma is the most common chronic childhood disease in developed nations and is a complex disease that has high social and economic costs. Asthma and its associated intermediate phenotypes are under a substantial degree of genetic control. Identifying the genes underlying asthma offers a means of better understanding its pathogenesis, with the promise of improving preventive strategies, diagnostic tools, and therapies. A number of chromosomal regions containing genes influencing asthma and atopy have been identified consistently by different groups, and a role for several candidate genes has been established.

Current concepts on the genetics of asthma

Asthma is a complex genetic disorder with variable phenotype, largely attributed to the interactions of the environment and multiple genes, each potentially having small effects. Numerous asthma and atopy loci have been reported in studies demonstrating associations and/or linkage of the asthma-associated phenotypes, atopy, elevated IgE levels, and bronchial hyperresponsiveness to alleles of microsatellite markers and single nucleotide polymorphisms within specific cytokine/chemokine and IgE regulating genes. Although the studies reporting these observations are compelling, most of them lack statistical power. This review compiles the evidence that supports linkage and associations to the various genetic loci and candidate genes. Whereas significant progress has been made in the field of asthma genetics in the past decade, the roles of the genes and genetic variations within the numerous candidate asthma genes that have been found to associate with the expression of the asthmatic phenotype remain to be determined.

The levels of TNF alpha, IL4 and IL10 production by T-cells in B-cell chronic lymphocytic leukaemia (B-CLL)

Tumour necrosis factor alpha (TNF alpha), interleukin (IL) 4 and IL10 are important for the growth and survival of the leukaemic cells in B-cell chronic lymphocytic leukaemia (B-CLL). The present study investigates the production of TNF alpha, IL4 and IL10 in patients with B-CLL. Significant increases in the TNF alpha and IL4 mean levels compared to normal control CD2(+)-cells were observed for B-CLL lymphocytes (TNF alpha: P=0.0004 and IL4: P=0.0026). By contrast, the mean level of IL10 produced by purified B-CLL CD2(+)-cells was significantly lower than that seen with normal control T-cells (P=0.0136). No significant difference in the percentage (%) of T-cells that expressed cytoplasmic TNF alpha, IL4 and IL10 was observed between B-CLL and normal T-cells. However, a significant increase in the mean level of intracellular TNF alpha and IL4 expression was observed in B-CLL compared with normal control T-cells (TNF alpha: P=0.031; IL4: P=0.0027). The increased expression of cytoplasmic TNF alpha and IL4 appeared to be associated with increased cytokine production in the tested samples. The differences observed with some B-CLL cases in the production of TNF alpha, IL4 and IL10 by peripheral blood T-cells may suggest survival mechanisms for the leukaemic cells in these patients.

Genetic and familial considerations of primary biliary cirrhosis

The genetic basis of human autoimmune diseases is receiving increasing attention. Primary biliary cirrhosis (PBC) is a model autoimmune disease reflective of other organ-specific autoimmune pathology. PBC is an enigmatic autoimmune disease that predominantly affects women and leads to destruction of intrahepatic bile ducts. The serological hallmark of this disease is characterized by antimitochondrial antibodies that specifically react with the E2 components of 2-oxodehydrogenase enzymes, including PDC-E2. There are no clear major histocompatibility complex associations with the development of PBC, despite the observation that first-degree relations of index patients with PBC have a 4-6% prevalence of development of PBC. This risk factor is comparable or higher than any other human autoimmune disease and suggests that a genome-wide approach towards dissection of genetic associations would lead to valuable new insights. In this review, we place these concepts in perspective and highlight in particular the genetic associations in PBC and the importance of studying siblings with PBC who are concordant for disease.

Evaluation of the response of primary human peripheral blood mononuclear phagocytes to challenge with in vitro generated clinically relevant UHMWPE particles of known size and dose

The response of primary human peripheral blood mononuclear phagocytes to challenge with clinically relevant ultra-high molecular weight polyethylene (UHMWPE) wear debris of known particle size and dose was evaluated. Particles with a mean size of 0.24, 0. 45, 1.7, 7.6, and 88 microm were cocultured with cells for 24 h before assessment of cell viability and production of the osteolytic cytokines interleukin (IL)-1 beta, IL-6, tumor necrosis factor-alpha, and granulocyte macrophage colony-stimulating factor, and prostaglandin E(2). All particle fractions were evaluated at particle volume (microm(3)) to cell number ratios of 10:1 and 100:1, which had been previously identified as being the most stimulatory and clinically relevant. None of the test fractions had an effect on cell viability. Whereas the heterogeneity of human individuals was clearly evident in the responses of the donors evaluated in this study (the response of donor 3 was between 5 and 20 times greater than the other donors), the most biologically active particles were found to be submicrometer in size. Stimulation with phagocytosable particles (0.24, 0.45, and 1.7 microm) resulted in enhanced levels of cytokine secretion. Macrophages stimulated with particles outside this size range produced considerably less cytokines at the volumes tested. These results confirm earlier findings and suggest that the size and volume of UHMWPE particles are critical factors in macrophage activation. Furthermore, they suggest that the heterogeneity of human individuals may be another important factor in determining implant life.

Comparison of the response of primary human peripheral blood mononuclear phagocytes from different donors to challenge with model polyethylene particles of known size and dose

The response of primary human peripheral blood mononuclear phagocytes to challenge with polyethylene particles of known size and dose was evaluated. Particles with mean sizes of 0.21, 0.49, 4.3, 7.2, and 88 microm were co-cultured with cells for 24 h prior to the assessment of cell viability and production of the osteolytic mediators IL-1beta, IL-6, TNFalpha, GM-CSF and PGE2. All particle fractions were evaluated at particle volume (microm3) to cell number ratios of 10:1 and 100:1 which were previously identified as being the most biologically active and clinically relevant. The heterogeneity of human individuals was clearly evident both in the profile and the magnitude of the response of the donors evaluated in this study (the response of donor 5 being 2- to 15-fold lower than that of the other donors). Only the sub-micrometre particles stimulated significantly enhanced cytokine secretion at the ratios tested: mean particle sizes of 0.49 and 0.21 microm being the most biologically active. Macrophages stimulated with particles outside this size range produced considerably lower levels of mediator. These results compared favourably with the results of earlier studies, which demonstrated that particles within the phagocytosable size range (0.1-10 microm) were the most biologically active. These results, therefore, confirm earlier findings and suggest that the size and volume of polyethylene particles are critical factors in macrophage activation. Furthermore, they suggest that the heterogeneity of human individuals may be another important factor in determining implant life and could provide the basis for a valuable diagnostic tool to identify those patients most at risk of implant loosening.

The role of immune responses in bone loss during periodontal disease

A network of cytokines and other soluble mediators unites the immune system and bone; bacterial infections induce immune responses which may perturb this network. Periodontal diseases are Gram-negative infections resulting in bone loss in the jaw. Evidence is presented that immune responses to these infections produces net resorption of bone.

Tumour necrosis factor gene polymorphisms in lymphoproliferative disease

Tumour necrosis factor (TNF) alpha is involved in the pathogenesis of established lymphoproliferative disease. Serum levels of TNFalpha and its soluble receptors are above normal values in B-cell chronic lymphocytic leukaemia (B-CLL) and they are valuable prognostic markers in lymphoma patients. The production of TNFalpha is genetically controlled. Altered synthesis of TNFalpha has been associated with polymorphisms at the TNF gene cluster (i.e. TNFA, TNFB and LTB). In the present study, we evaluated the prevalence of the known high TNFalpha- and TNFbeta- producing alleles TNF1, TNF2 of the TNFA gene, TNFB1, TNFB2 alleles of the TNFB gene and of the polymorphic alleles TNFd1, d2, d3, d4 and d5 of the microsatellite TNFd in patients with B-CLL, non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD). This study demonstrates that there is no difference in the frequency of the tested TNF alleles between normal controls and cohorts of patients with lymphoproliferative disease. These results indicate that TNF alleles are not genetic predisposing factors in the development of these diseases.

Familial autoimmunity and the idiopathic inflammatory myopathies

Many lines of evidence suggest that autoimmune diseases result from chronic immune activation following environmental exposures in genetically susceptible individuals. A genetic basis for autoimmunity is supported by twin and family studies, candidate gene investigations, animal models, and whole genome microsatellite scans. These findings predict, and clinical observations support, familial clustering of a number of individual autoimmune diseases, notably lupus, multiple sclerosis, type-1 diabetes mellitus, rheumatoid arthritis, and recently the idiopathic inflammatory myopathies. Yet, not only is the same autoimmune disease increased in prevalence in pedigrees of persons affected with a given disorder, but other autoimmune diseases are as well. We review these data and propose a hypothesis consistent with these findings. This model posits that a rheumatic disease, as currently classified, is actually composed of a number of elemental disorders. Each of these is defined by the minimal necessary and sufficient environmental exposures and genes that result in a pathology leading to a given sign-symptom complex.

Association of a vitamin D receptor gene polymorphism with localized early-onset periodontal diseases

BACKGROUND

Early-onset periodontal diseases (EOP) are caused by interactions between host factors, specific microbial pathogens, and environmental factors. It is, therefore, of interest to investigate the nature of host factors as they may provide useful risk markers and reveal important information regarding the disease pathogenesis. Genetic polymorphisms in the vitamin D receptor (VDR) gene are associated with parameters of bone homeostasis and with diseases in which bone loss is a cardinal sign, in particular osteoporosis. Rapidly progressive bone loss is one feature of EOP. We, therefore, sought to determine whether EOP is associated with a polymorphism in the VDR gene.

METHODS

A restriction fragment length polymorphism (RFLP) for Taq I in exon nine of the VDR gene was analyzed by PCR, followed by restriction digestion with Taq I and gel electrophoresis. We analyzed the genotypes of 69 EOP patients, including 20 patients with unequivocal evidence of localized disease (L-EOP), and 72 controls with no history of EOP.

RESULTS

The genotype distribution in the L-EOP patient group was 7 (35%), 5 (25%) and 8 (40%) and in the control group 31 (43.1%), 36 (50.0%) and 5 (6.9%) for TT, Tt and tt respectively (where t and T represent the alleles with and without the Taq I RFLP respectively). Chi2 analysis indicated that the distribution of the genotypes between these two groups was highly significantly different (P = 0.001). Allele frequencies were 47.5% and 52.5% for T and t in the L-EOP group; 68.1% and 31.9% in the control group, showing a significant association between the prevalence of the less frequent allele (t) and L-EOP (P = 0.017). There was no significant difference in the genotype distribution or the allele frequencies between the control samples and the larger EOP patient group (n = 69) which included patients with generalized and localized disease.

CONCLUSIONS

These data indicate that carriage of the less frequent allele of the Taq I RFLP (t) in the VDR gene significantly increases the risk of developing L-EOP. However, VDR genotype may not affect the incidence of all cases of EOP. These findings contribute to our understanding of the genetic basis for periodontal disease and may help define sub-groups of this disease which share common pathogenic factors.

Cytokine Gene Polymorphisms Associating With Severe Acute Graft-Versus-Host Disease in HLA-Identical Sibling Transplants

It is now well known that the initial phase of graft-versus-host disease (GVHD) involves cytokine release during preconditioning of the recipient of an allogeneic bone marrow transplant (BMT). Tumor necrosis factor  (TNF), in particular, has been implicated in pathological damage and is released pretransplant due to irradiation and cytotoxic preconditioning regimens. Interleukin-10 (IL-10), a natural immunosuppressant of TNF , may be involved in downregulation of these responses, which may be an individual patient-specific effect. In this study, we determined the genotype for polymorphisms associated with TNF and IL-10 in 80 potential allo-BMT recipients and correlated the genotype with the severity of GVHD in 49 patients for whom clinical data relating to GVHD was available. The widely studied TNF −308 polymorphism does not show any significant associations, but the d3 homozygous allele of the TNFd microsatellite is preferentially associated with grade III/IV GVHD (7 of 11 patients) compared with its occurrence in 8 of 38 patients with grade 0/II GVHD (P = .006). Alleles of the IL-10 −1064 promoter region microsatellite polymorphism that possess greater numbers of dinucleotide (CA) repeats also significantly associate with more severe GVHD. This region has been demonstrated to be important in the regulation of the IL-10 promoter. Eighteen of 38 patients with grade 0-II GVHD possessed alleles with greater numbers (12 or more) of dinucleotide repeats, compared with 9 of 11 cases with grade III-IV GVHD (P < .02). Of the 38 patients with grade 0-II GVHD, 3 of 38 had a both TNFd3/d3 and IL-10 (12-15) genotype, compared with 6 of 11 patients with grade III-IV GVHD (P < .001). There was no association of either the TNFd or IL-10 microsatellite polymorphisms with mortality (P = .43 and .51, respectively). Our results suggest that patient cytokine gene polymorphism genotypes may influence GVHD outcome by affecting cytokine activation during the pretransplant conditioning regimens, and these results are the first to suggest a genetic predisposition to this important transplant-related complication.

Cytokine Gene Polymorphisms Associating With Severe Acute Graft-Versus-Host Disease in HLA-Identical Sibling Transplants

It is now well known that the initial phase of graft-versus-host disease (GVHD) involves cytokine release during preconditioning of the recipient of an allogeneic bone marrow transplant (BMT). Tumor necrosis factor  (TNF), in particular, has been implicated in pathological damage and is released pretransplant due to irradiation and cytotoxic preconditioning regimens. Interleukin-10 (IL-10), a natural immunosuppressant of TNF , may be involved in downregulation of these responses, which may be an individual patient-specific effect. In this study, we determined the genotype for polymorphisms associated with TNF and IL-10 in 80 potential allo-BMT recipients and correlated the genotype with the severity of GVHD in 49 patients for whom clinical data relating to GVHD was available. The widely studied TNF −308 polymorphism does not show any significant associations, but the d3 homozygous allele of the TNFd microsatellite is preferentially associated with grade III/IV GVHD (7 of 11 patients) compared with its occurrence in 8 of 38 patients with grade 0/II GVHD (P = .006). Alleles of the IL-10 −1064 promoter region microsatellite polymorphism that possess greater numbers of dinucleotide (CA) repeats also significantly associate with more severe GVHD. This region has been demonstrated to be important in the regulation of the IL-10 promoter. Eighteen of 38 patients with grade 0-II GVHD possessed alleles with greater numbers (12 or more) of dinucleotide repeats, compared with 9 of 11 cases with grade III-IV GVHD (P &lt; .02). Of the 38 patients with grade 0-II GVHD, 3 of 38 had a both TNFd3/d3 and IL-10 (12-15) genotype, compared with 6 of 11 patients with grade III-IV GVHD (P &lt; .001). There was no association of either the TNFd or IL-10 microsatellite polymorphisms with mortality (P = .43 and .51, respectively). Our results suggest that patient cytokine gene polymorphism genotypes may influence GVHD outcome by affecting cytokine activation during the pretransplant conditioning regimens, and these results are the first to suggest a genetic predisposition to this important transplant-related complication.

Commensal communism and the oral cavity

The world we live in contains unimaginable numbers of bacteria, and these and other single-celled creatures represent the major diversity of life on our planet. During the last decade or so, the complexity and intimacy of the interactions which occur between bacteria and host eukaryotic cells during the process of infection have begun to emerge. The study of such interactions is the subject of the new discipline of cellular microbiology. This intimacy of bacteria/host interactions creates a major paradox. The average human being is 90% bacteria in terms of cell numbers. These bacteria constitute the commensal or normal microflora and populate the mucosal surfaces of the oral cavity, gastrointestinal tract, urogenital tract, and the surface of the skin. In bacterial infections, much of the pathology is due to the release of a range of bacterial components (e.g., modulins such as lipopolysaccharide, peptidoglycan, DNA, molecular chaperones), which induce the synthesis of the local hormone-like molecules known as pro-inflammatory cytokines. However, such components must also be constantly released by the vast numbers of bacteria constituting the normal microflora and, as a consequence, our mucosae should constantly be in a state of inflammation. This is patently not the case, and a hypothesis is forwarded to account for this "commensal paradox", namely, that our commensal bacteria and mucosal surfaces exist in a state of bio-communism, forming a unified "tissue" in which interactions between bacteria and epithelia are finely balanced to ensure bacterial survival and prevent the induction of damaging inflammation. Evidence is emerging that bacteria can produce a variety of proteins which can inhibit the synthesis/release of inflammatory cytokines. The authors predict that such proteins are simply one part of an extensive signaling system which occurs between bacteria and epithelial cells at mucosal surfaces such as those found in the oral cavity.

Interleukin 10 secretion in relation to human IL-10 locus haplotypes

Stimulation of human blood cultures with bacterial lipopolysaccharide (LPS) shows large inter-individual variation in interleukin 10 (IL-10) secretion, which has been shown to have a genetic component of over 70%. Alleles at two microsatellite loci in the 4 kb immediately upstream of the human IL-10 transcription initiation site in 132 individuals from 56 Dutch families were defined and assigned as haplotypes. LPS-induced IL-10 secretion was measured by ELISA and related to the IL-10 promoter haplotypes present in 78 unrelated individuals obtained from these families. Analysis showed that LPS-induced IL-10 secretion from unrelated individuals varied with IL-10 promoter haplotypes (P = 0.024; Kruskal-Wallis test). Two observations were made in relation to secreted IL-10 levels and promoter haplotypes; first, those haplotypes containing the allele IL10.R3 were associated with lower IL-10 secretion than haplotypes containing any other IL10.R allele. Second, the haplotype IL10.R2/IL10.G14 was associated with highest IL-10 secretion overall, whereas the haplotype IL10.R3/IL10.G7 was associated with lowest IL-10 secretion. These data demonstrate that the ability to secrete IL-10 can vary in man according to the genetic composition of the IL-10 locus.

The distribution of variation in regulatory gene segments, as present in MHC class II promoters

Diversity in the antigen-binding receptors of the immune system has long been a primary interest of biologists. Recently it has been suggested that polymorphism in regulatory (noncoding) gene segments is of substantial importance as well. Here, we survey the level of variation in MHC class II gene promoters in man and mouse using extensive collections of published sequences together with unpublished sequences recently deposited by us in the EMBL gene bank using the Shannon entropy to quantify diversity. For comparison, we also apply our analysis to distantly related MHC class II promoters, as well as to class I promoters and to class II coding regions. We observe a high level of intraspecies variability, which in mouse but not in man is localized to a significant extent near the binding sites of transcription factors-sites that are conserved over longer evolutionary distances. This localization may both indicate and enhance heterozygote advantage, as the presence of two functionally different promoters would be expected to confer flexibility in the immune response.