Mouse genetic model for antigen-induced airway manifestations of asthma

Identification of the Mhc region as an asthma susceptibility locus in recombinant congenic mice

Mouse models of allergic asthma are characterized by airway hyperreactivity (AHR), Th2-driven eosinophilic airway inflammation, high allergen-specific IgE (anti-OVA IgE) levels in serum, and airway remodeling. Because asthma susceptibility has a strong genetic component, we aimed to identify new asthma susceptibility genes in the mouse by analyzing the asthma phenotypes of the Leishmania major resistant (lmr) recombinant congenic (RC) strains. The lmr RC strains are derived from C57BL/6 and BALB/c intercrosses and carry congenic loci on chromosome 17 (lmr1) and 9 (lmr2) in both backgrounds. Whereas the lmr2 locus on chromosome 9 contributes to a small background-specific effect on anti-OVA IgE and AHR, the lmr1 locus on chromosome 17 mediates a strong effect on Th2-driven eosinophilic airway inflammation and background-specific effects on anti-OVA IgE and AHR. The lmr1 locus contains almost 600 polymorphic genes. To narrow down this number of candidate genes, we performed genome-wide transcriptional profiling on lung tissue from C.lmr1 RC mice and BALB/c control mice. We identified a small number of differentially expressed genes located within the congenic fragment, including a number of Mhc genes, polymorphic between BALB/c and C57Bl/6. The analysis of asthma phenotypes in the C.B10-H2b RC strain, carrying the C57Bl/6 haplotype of the Mhc locus in a BALB/c genetic background, reveals a strikingly similar asthma phenotype compared with C.lmr1, indicating that the differentially expressed genes located within the C.B10-H2b congenic fragment are the most likely candidate genes to contribute to the reduced asthma phenotypes associated with the C57Bl/6 allele of lmr1.

GITR signaling potentiates airway hyperresponsiveness by enhancing Th2 cell activity in a mouse model of asthma

Background

Allergic asthma is characterized by airway hyperresponsiveness (AHR) and allergic inflammation of the airways, driven by allergen-specific Th2 cells. The asthma phenotypes and especially AHR are sensitive to the presence and activity of regulatory T (Treg) cells in the lung. Glucocorticoid-induced tumor necrosis factor receptor (GITR) is known to have a co-stimulatory function on effector CD4⁺ T cells, rendering these cells insensitive to Treg suppression. However, the effects of GITR signaling on polarized Th1 and Th2 cell effector functions are not well-established. We sought to evaluate the effect of GITR signaling on fully differentiated Th1 and Th2 cells and to determine the effects of GITR activation at the time of allergen provocation on AHR and airway inflammation in a Th2-driven mouse model of asthma.

Methods

CD4⁺CD25^- cells were polarized in vitro into Th1 and Th2 effector cells, and re-stimulated in the presence of GITR agonistic antibodies to assess the effect on IFNγ and IL-4 production. To evaluate the effects of GITR stimulation on AHR and allergic inflammation in a mouse asthma model, BALB/c mice were sensitized to OVA followed by airway challenges in the presence or absence of GITR agonist antibodies.

Results

GITR engagement potentiated cytokine release from CD3/CD28-stimulated Th2 but not Th1 cells in vitro. In the mouse asthma model, GITR triggering at the time of challenge induced enhanced airway hyperresponsiveness, serum IgE and ex vivo Th2 cytokine release, but did not increase BAL eosinophilia.

Conclusion

GITR exerts a differential effect on cytokine release of fully differentiated Th1 and Th2 cells in vitro, potentiating Th2 but not Th1 cytokine production. This effect on Th2 effector functions was also observed in vivo in our mouse model of asthma, resulting in enhanced AHR, serum IgE responses and Th2 cytokine production. This is the first report showing the effects of GITR activation on cytokine production by polarized primary Th1 and Th2 populations and the relevance of this pathway for AHR in mouse models for asthma. Our data provides crucial information on the mode of action of the GITR signaling, a pathway which is currently being considered for therapeutic intervention.

Chromosome 12q24.3 controls sensitization to cat allergen in patients with asthma from Siberia, Russia

In Russian population of Siberia asthma is usually concomitant with high sensitization to indoor allergens (cat, dog and house dust mites), overproduction of total immunoglobulin E (IgE) and airway hyperreactivity. Definition of genes that predispose to development of various sub-components of the asthma phenotype is important for understanding of etiology of this disease. To map genes predisposing to asthma, we tested 21 microsatellite markers from candidate chromosomal regions in 136 Russian nuclear families with asthma from Siberia. We performed non-parametric analysis for linkage with asthma, total IgE, specific IgE to cat, dog, and dust mites, and spirometric indices (FEV1 (%) - percentage of predicted forced expiratory volume in 1s, FVC (%) - percentage of predicted forced vital capacity, and FEV1/FVC (%) - Tiffenau index). The most significant linkage was to the candidate region on chromosome 12. Locus controlling cat-specific IgE, which is the most abundant in asthma patients from Siberian population, mapped within the interval between 136 and 140 cM on chromosome 12q24.3, with the suggestive linkage at the marker D12S1611 (LOD=2.23, P=0.0007). Total IgE was also linked to this region (D12S1611 - LOD=1.12, P=0.012). FEV1 (%) exceeded LOD>1 threshold for significance with the same locus 12q24.3, but with the peak at a more proximal region at 111.87 cM (D12S338 - LOD=1.21, P=0.009). Some evidence of linkage (LOD>1.0) was also detected for asthma at 6p21.31 (D6S291) and total IgE at 13q14.2 (D13S165). These data indicate that the locus 12q24.3 is the most promising candidate for identification of asthma genes in Russian population of Siberia.

IFN-lambda1 (IL-29) inhibits GATA3 expression and suppresses Th2 responses in human naive and memory T cells

IFN-lambda1 (IL-29) plays a novel, emerging role in the inhibition of human Th2 responses. Here, we demonstrate that both naive and memory human CD4(+) T cells express mRNA for the IFN-lambda1-specific receptor, IL-28Ralpha, and are responsive to IFN-lambda1. Expression of Th2 cytokines (IL-4 and IL-13) was suppressed in naive and memory CD4(+) T cells by IFN-lambda1, without affecting their proliferation. Further, acquisition of IL-4Ralpha expression after stimulation was inhibited by IFN-lambda1, as was GATA3 expression. Finally, IFN-lambda1 diminished the change in cell-surface phenotype that accompanies differentiation of "central memory" T cells into "effector memory" T cells. Taken together, our data describe unique immunomodulatory effects of IFN-lambda1 and identify novel mechanisms for the reduction of existing Th2 responses and the regulation of new ones, in circulating naive and memory CD4(+) T cells.

Interferon-lambda1 (interleukin-29) preferentially down-regulates interleukin-13 over other T helper type 2 cytokine responses in vitro

Interferon (IFN)-lambda1 [interleukin (IL)-29] is a member of the interferon lambda family (also known as type III interferons), whose members are distantly related to both the type I interferons and members of the IL-10 family. While IFN-lambda1 has significant antiviral activity, it is also becoming apparent that it has important immunoregulatory properties, especially with regard to the T helper type 2 (Th2) response. Previously, we have shown that IFN-lambda1 is capable of down-regulating IL-13 production in an IFN-gamma-independent manner and that this is mediated in part via monocyte-derived dendritic cells. Here, we have extended our knowledge of IFN-lambda1 regulation of the human in vitro Th2 response by examining the regulation of three major Th2 cytokines, IL-4, IL-5 and IL-13, by IFN-lambda1. Our results reveal that IFN-lambda1 preferentially inhibits IL-13 production, compared with IL-4 or IL-5. Levels of IL-13 mRNA, the amount of secreted IL-13 protein and numbers of IL-13-positive CD3(+) CD4(+) cells were all significantly diminished by IFN-lambda1. IFN-lambda1 significantly decreased some aspects of IL-4 and IL-5 production, but its effects were not as consistent as those seen on IL-13. IFN-lambda1 was also effective at decreasing IL-13 secretion under conditions designed to support the generation of Th2 cells. Irrespective of whether Concanavalin-A or T-cell-stimulatory microbeads were used, IFN-lambda1 markedly diminished IL-13 secretion in cultures where IL-4 had been added. Thus, IFN-lambda1 appears to be an inhibitor of human Th2 responses whose action is primarily directed towards IL-13 but which may also affect Th2 responses generally and does not invoke a complementary elevation of IFN-gamma secretion.

Mouse to human comparative genetics reveals a novel immunoglobulin E-controlling locus on Hsa8q12

Atopy is a predisposition to hyperproduction of immunoglobulin E (IgE) against common environmental allergens. It is often associated with development of allergic diseases such as asthma, rhinitis, and dermatitis. Production of IgE is influenced by genetic and environmental factors. In spite of progress in the study of heredity of atopy, the genetic mechanisms of IgE regulation have not yet been completely elucidated. The analysis of complex traits can benefit considerably from integration of human and mouse genetics. Previously, we mapped a mouse IgE-controlling locus Lmr9 on chromosome 4 to a segment of <9 Mb. In this study, we tested levels of total IgE and 25 specific IgEs against inhalant and food allergens in 67 Czech atopic families. In the position homologous to Lmr9 on chromosome 8q12 marked by D8S285, we demonstrated a novel human IgE-controlling locus exhibiting suggestive linkage to composite inhalant allergic sensitization (limit of detection, LOD = 2.11, P = 0.0009) and to nine specific IgEs, with maximum LOD (LOD = 2.42, P = 0.0004) to plantain. We also tested 16 markers at previously reported chromosomal regions of atopy. Linkage to plant allergens exceeding the LOD > 2.0 was detected at 5q33 (D5S1507, LOD = 2.11, P = 0.0009) and 13q14 (D13S165, LOD = 2.74, P = 0.0002). The significant association with plant allergens (quantitative and discrete traits) was found at 7p14 (D7S2250, corrected P = 0.026) and 12q13 (D12S1298, corrected P = 0.043). Thus, the finding of linkage on chromosome 8q12 shows precision and predictive power of mouse models in the investigation of complex traits in humans. Our results also confirm the role of loci at 5q33, 7p14, 12q14, and 13q13 in control of IgE.

Radiation-induced lung response of AcB/BcA recombinant congenic mice

The genetic factors that influence the development of radiotherapy-induced lung disease are largely unknown. Herein we identified a strain difference in lung response to radiation wherein A/J mice developed alveolitis with increased levels of pulmonary mast cells and cells in bronchoalveolar lavage while the phenotype in C57BL/6J mice was fibrosis with fewer inflammatory cells. To identify genomic loci that may influence these phenotypes, we assessed recombinant congenic (RC) mice derived from the A/J and C57BL/6J strains for their propensity to develop alveolitis or fibrosis after 18 Gy whole-thorax irradiation. Mouse survival, lung histopathology and bronchoalveolar lavage cell types were recorded. Informative strains for each of mast cell influx, bronchoalveolar cell numbers, alveolitis and fibrosis were identified. In mice with the A/J strain background, the severity of alveolitis correlated with increased mast cell numbers while in C57BL/6J background strain mice fibrosis was correlated with the percentage of neutrophils in lavage. The data for RC mice support the association of specific inflammatory cells with the development of radiation-induced lung disease and provide informative strains with which to dissect the genetic basis of these complex traits.

Positional cloning of the Igl genes controlling rheumatoid factor production and allergic bronchitis in rats

Rheumatoid factors (RF), autoantibodies that bind the Fc region of IgG, are one of the major diagnostic marker in rheumatoid arthritis (RA) but occur with lower frequency also in other infectious and inflammatory conditions. Through positional cloning of the previously described quantitative trait locus (QTL) Rf1 in congenic and advanced intercrossed rats, we identified the Ig lambda light chain locus as a locus that regulates the production of RF in rats. The congenic rats produce RF-Ig lambda and have significant higher levels of RF-IgG and RF-IgM in serum, while the DA rat has an impaired RF production and does not produces RF-Ig lambda. Thus, we could investigate the role of RF in pristane-induced arthritis (PIA) as well as ovalbumin-induced airway inflammation. We show that there was no difference in the development and severity of PIA between congenic and parental DA rats, suggesting that RF using lambda light chains have no impact on PIA. However, the RF producing congenic rats developed a more severe airway inflammation as indicated in the significantly increased number of eosinophils in bronchoalveolar lavage fluid as well as total IgE in serum. In addition, RF congenic rats had a significantly enhanced immune response toward OVA due to increased OVA-Igk but not OVA-Igl antibodies, suggesting a possible involvement of RF in the regulation of the humoral immune response.

Immunoinformatics: an overview of computational tools and techniques for understanding immune function

In recent years, there has been a rapid expansion in the application of information technology to biological data. Although the use of information science techniques is less common for the discipline of immunology, this field has seen great strides in recent years. This review addresses why in silico modeling is needed in immunology research, highlights some of the major areas of research and suggests what may be important for the future of immunoinformatics.