Are infections protecting from atopy?:

Cross-sectional comparison of the characteristics of respiratory allergy in immigrants and Italian children

BACKGROUND

Immigrants represent a good epidemiological model to evaluate the relative influence of environmental and inherited factors on the development of allergy. Several studies on allergy in adults have been published, but few data in children are available. We aimed to investigate the differences, between Italian and immigrant children, in clinical characteristics of respiratory allergy.

METHODS

This was a multicentre cross-sectional study involving children born in Italy from Italian parents and children born either in Italy or abroad from immigrants. Children referred firstly for allergic respiratory disease (rhinitis/asthma), with an ascertained clinical diagnosis and IgE sensitization to inhalants, were included. Demographic features, comorbidities, severity of disease, and sensitization profile were compared between Italians and immigrants, separating also those born in Italy from immigrant parents and those born abroad.

RESULTS

One hundred and sixty-five immigrant allergic children were enrolled (100 male, mean age 8.3 yr), 128 of whose had both parents immigrated. Italian children were 237 (156 male, mean age 8.4 yr). The Italian and immigrant children were similar, apart from pet's ownership and family size. There was no difference in the severity of rhinitis/asthma between the groups, whereas significant differences were found in the pattern of sensitization: immigrant children were more frequently sensitized to house dust mites (73.3% vs. 51%, respectively; p = 0.002) and less to grass (41.8% vs. 57.8%; p = 0.002); this was retained also in monosensitized children. Immigrant children born in Italy (n = 105) had a lower prevalence of rhinitis vs. Italians (68.3% vs. 87.6%, respectively, p = 0.003) and of sensitization to grass (28.3% vs. 49.5%, respectively, p = 0.008). No difference was found among macro-regions of origin and demographic or clinical features.

CONCLUSIONS

Immigrant children born either in Italy or abroad did not show significant differences in the clinical pattern of the respiratory allergic disease when compared to children born from Italian parents.

High levels of both n-3 and n-6 long-chain polyunsaturated fatty acids in cord serum phospholipids predict allergy development

BACKGROUND

Long-chain polyunsaturated fatty acids (LCPUFAs) reduce T-cell activation and dampen inflammation. They might thereby counteract the neonatal immune activation and hamper normal tolerance development to harmless environmental antigens. We investigated whether fatty acid composition of cord serum phospholipids affects allergy development up to age 13 years.

METHODS

From a population-based birth-cohort born in 1996/7 and followed until 13 years of age (n = 794), we selected cases with atopic eczema (n = 37) or respiratory allergy (n = 44), as well as non-allergic non-sensitized controls (n = 48) based on diagnosis at 13 years of age. Cord and maternal sera obtained at delivery from cases and controls were analysed for proportions of saturated, monounsaturated and polyunsaturated fatty acids among serum phospholipids.

RESULTS

The cord serum phospholipids from subject who later developed either respiratory allergy or atopic eczema had significantly higher proportions of 5/8 LCPUFA species, as well as total n-3 LCPUFA, total n-6 LCPUFA and total LCPUFA compared to cord serum phospholipids from controls who did not develop allergy (P<0.001 for all comparisons). Conversely, individuals later developing allergy had lower proportion of the monounsaturated fatty acid 18∶1n-9 as well as total MUFA (p<0.001) among cord serum phospholipids. The risk of respiratory allergy at age 13 increased linearly with the proportion of n-3 LCPUFA (Ptrend<0.001), n-6 LCPUFA (Ptrend = 0.001), and total LCPUFA (Ptrend<0.001) and decreased linearly with the proportions of total MUFA (Ptrend = 0.025) in cord serum phospholipids. Furthermore, Kaplan-Meier estimates of allergy development demonstrated that total LCPUFA proportion in cord serum phospholipids was significantly associated with respiratory allergy (P = 0.008) and sensitization (P = 0.002), after control for sex and parental allergy.

CONCLUSION

A high proportion of long-chain PUFAs among cord serum phospholipids may predispose to allergy development. The mechanism is unknown, but may involve dampening of the physiologic immune activation in infancy needed for proper maturation of the infant's immune system.

The possible influence of the environment on respiratory allergy: a survey on immigrants to Italy

BACKGROUND

Respiratory allergy is influenced and determined by genetic and environmental factors. Migration is a good model to indirectly evaluate the possible influence of environment.

OBJECTIVE

To assess the clinical characteristics of respiratory allergy in immigrants to Italy, in comparison with the Italian population.

METHODS

The clinical/demographic data of those immigrants stably living in Italy and referred for the first time to allergy services for respiratory allergy were collected in a multicenter survey. All the patients underwent a standard diagnostic workup. A matched Italian population was also examined.

RESULTS

Six hundred ninety-eight immigrants and 859 Italians had at least one positive skin test and were analyzed. Most of the patients were referred to the allergy units by their general practitioners. In those patients, the demographic characteristics were not different, except for family size. Immigrants had less family history of atopy. Only 16% had a clinical history of allergy before migration. The time elapsed between migration and onset of symptoms was 5.3 ± 3.1 years, with a minimum of 0.5 and a maximum of 7 years. A higher rate of monosensitization was seen among immigrants, and the severity of their asthma/rhinitis was greater than in Italians. No difference was seen in the pattern of sensitizations.

CONCLUSION

In this population of immigrants, environmental factors play a relevant role in the onset of respiratory allergies.

Association of allergic sensitization with infectious diseases burden in Roma and non-Roma children

The hypothesis whether exposure to certain infections protects from atopy remains equivocal. To further investigate this, we compared serologic markers of infection and allergic sensitization prevalence in Roma children, who live under unfavorable hygienic conditions that facilitate the spread of infections, and non-Roma children who live in the same area. Analyses included 98 Roma and 118 non-Roma children. Serum IgG antibodies for 13 foodborne- airborne- and bloodborne infectious agents were determined, and a cumulative index of exposure was calculated by adding one point for each positive infection. Specific serum IgE to certain common food- and aero-allergens was also tested. and positivity to any of them was defined as indication of atopy. Roma children were found significantly more seropositive for T. gondii, Hepatitis A, H. pylori, HSV-1, CMV, and Hepatitis B (p < 0.0001). Non-Roma children were found more seropositive for RSV and M. pneumonia (p < 0.0001). Regarding the overall prevalence of atopy or the specific IgE responses to the allergens tested, no statistically significant differences were found between Roma and non-Roma children. A positive association of the cumulative index of exposure to infections with atopy was found in the non-Roma children (OR: 1.38, 95% CI: 1.08-1.75, p = 0.01) and in the total population (OR: 1.42, 95% CI: 1.11-1.83, p = 0.01). Regarding the specific infectious agents tested, a statistically significant positive association of atopy with seropositivity was found for M. pneumoniae in the non-Roma children (OR: 3.93, 95% CI: 1.39) as well as in the total population studied (OR: 2.83, 95% CI: 1.32-6.07, p = 0.01). Despite the higher burden of exposure to the battery of the infectious agents tested among Roma children, no protective effect for allergic disease development was evident. On the contrary, a positive association of exposure to infections with evidence of atopy was found, especially evident in the non-Roma children.

Exposure to animals and risk of oligoarticular juvenile idiopathic arthritis: a multicenter case-control study

Background

An inverse association between early contact with microbial compounds and respiratory allergies is well established. The protective effect of infant contact with animals was also shown for inflammatory bowel disease (IBD) and systemic lupus erythematosus (SLE). We aimed to test the association between animal contact in infancy and oligoarticular juvenile idiopathic arthritis (OA JIA).

Methods

Parents of children with OA JIA registered at the Hospital for Pediatric Rheumatology in Garmisch-Partenkirchen were asked to complete a questionnaire. Children who underwent strabismus surgery at six referral centers for ophthalmology served as controls. Children age 6 to 18 years born in Germany without malformations were included (238 cases; response 89% and 832 controls; response 86%). Data were analyzed using logistic regression models after adjusting for potential confounders.

Results

Neither place of living (urban vs. rural area), living on a farm, nor regular farm animal (adjusted odds ratio 0.79; 95% confidence interval 0.42-1.47) or pet contact (0.79; 0.55-1.14) during infancy were clearly related to case status. Allergic rhinitis was inversely related to OA JIA (0.57; 0.34-0.95).

Neither place of living (urban vs. rural area), living on a farm, nor regular farm animal (adjusted odds ratio 0.79; 95% confidence interval 0.42-1.47) or pet contact (0.79; 0.55-1.14) during infancy were related to case status. Allergic rhinitis was inversely related to OA JIA (0.57; 0.34-0.95).

Conclusions

Contact with farm environments in infancy might not be associated with OA JIA. This finding is consistent with previous findings for diabetes mellitus type 1 but contradicts results for IBD and SLE.

Diversity of the gut microbiota and eczema in early life

BACKGROUND

A modest number of prospective studies of the composition of the intestinal microbiota and eczema in early life have yielded conflicting results.

OBJECTIVE

To examine the relationship between the bacterial diversity of the gut and the development of eczema in early life by methods other than stool culture.

METHODS

Fecal samples were collected from 21 infants at 1 and 4 months of life. Nine infants were diagnosed with eczema by the age of 6 months (cases) and 12 infants were not (controls). After conducting denaturating gradient gel electrophoresis (DGGE) of stool samples, we compared the microbial diversity of cases and controls using the number of electrophoretic bands and the Shannon index of diversity (H') as indicators.

RESULTS

Control subjects had significantly greater fecal microbial diversity than children with eczema at ages 1 (mean H' for controls = 0.75 vs. 0.53 for cases, P = 0.01) and 4 months (mean H' for controls = 0.92 vs. 0.59 for cases, P = 0.02). The increase in diversity from 1 to 4 months of age was significant in controls (P = 0.04) but not in children who developed eczema by 6 months of age (P = 0.32).

CONCLUSION

Our findings suggest that reduced microbial diversity is associated with the development of eczema in early life.

Soluble CD14: role in atopic disease and recurrent infections, including otitis media

Soluble CD14 (sCD14) is a part of innate immunity that has been implicated in many diseases, including allergic diseases. However, many influencing factors and confounders, including gender-gene-environment interactions, may complicate interpretations of the observed associations to allergic diseases. In this paper, we review current literature describing the functions of sCD14 and its associations with common (recurrent) infections and with allergic diseases. Because sCD14 is involved with immunologic responses to infections, and exposure to microbial compounds is debated as a protective or a trigger factor for allergy development, these factors-which include genotypes, gender, age, microbial agents (from the environment and infection), and tobacco smoke-cannot be assessed independently. We conclude that confounding effects are important and must be considered to understand the role of sCD14 in allergic development.

Allergic sensitization and microbial load--a comparison between Finland and Russian Karelia

Epidemiological data have indicated that some infections are associated with a low risk of allergic diseases, thus supporting the idea (hygiene hypothesis) that the microbial load is an important environmental factor conferring protection against the development of allergies. We set out to test the hygiene hypothesis in a unique epidemiological setting in two socio-economically and culturally markedly different, although genetically related, populations living in geographically adjacent areas. The study cohorts included 266 schoolchildren from the Karelian Republic in Russia and 266 schoolchildren from Finland. The levels of total IgE and allergen-specific IgE for birch, cat and egg albumen were measured. Microbial antibodies were analysed against enteroviruses (coxsackievirus B4), hepatitis A virus, Helicobacter pylori and Toxoplasma gondii. Although total IgE level was higher in Russian Karelian children compared to their Finnish peers, the prevalence of allergen-specific IgE was lower among Russian Karelian children. The prevalence of microbial antibodies was, in turn, significantly more frequent in the Karelian children, reflecting the conspicuous difference in socio-economic background factors. Microbial infections were associated with lower risk of allergic sensitization in Russian Karelian children, enterovirus showing the strongest protective effect in a multivariate model. The present findings support the idea that exposure to certain infections, particularly in childhood, may protect from the development of atopy. Enterovirus infections represent a new candidate to the list of markers of such a protective environment. However, possible causal relationship needs to be confirmed in further studies.

Viral infections and allergies

Respiratory viral infections have been implicated in the origin of, protection from and exacerbation of allergy-related symptoms in a variety of ways. Viral infections are closely linked to infantile wheezing. Severe bronchiolitis in early infancy may predispose to chronic childhood asthma as well as allergic sensitization; alternatively it could represent a marker of susceptible individuals. In contrast, repeated mild infections in early life may have a protective role in the development of asthma or atopy by driving the immune system towards Th1 responses. However, evidence on this hypothesis is not consistent as far as respiratory viruses are concerned. Several factors, including the presence of an atopic environment, timing of exposure and severity of the infection, interactively contribute to the allergy-infection relationship. In the present report, recent data on the role of viral infections in the development and progression of allergy and asthma are reviewed.

Chronic helminth infections modulate allergen-specific immune responses: Protection against development of allergic disorders?

Inflammatory diseases are on the rise in westernized countries, but also in urbanized areas of developing countries. A number of studies have now demonstrated a negative association between helminth infections and inflammatory diseases, such as allergy, suggesting a potential role for helminth-induced immune responses. However, this is not the case for all studies. In this review both supporting and opposing literature on the role of helminth infections, particularly in allergy, are discussed. Furthermore, the concept is put forward that chronic helminth infections, but not acute infections, may be associated with the expression of regulatory networks necessary for downmodulating allergic immune responses to harmless antigens. Lastly, different components of helminth-induced regulatory networks are detailed, such as the role of regulatory T and B cells, modulation of dendritic cells, the presence of suppressory alternatively activated macrophages, and their individual contributions to protection against allergic diseases. Advantage should be taken from this knowledge to identify and select individual helminth-derived molecules that may harbor therapeutic potential against inflammatory diseases.

Glomerulonephritis, Th1 and Th2: what's new?

Glomerulonephritis (GN), the major worldwide cause of chronic renal disease and renal failure, shows a wide spectrum of histological patterns, severity of injury and clinical outcomes that may be related to the nature of the nephritogenic immune response. In the majority of cases, there is evidence of a central role for cognate immunity in the initiation of human GN and contributions of both humoral and cellular effector mechanisms have been demonstrated in both humans and in animal models. T helper cell subsets are known to activate different immune effector mechanisms which influence disease outcomes in infectious and autoimmune diseases and evidence is now accumulating that Th1 and Th2 subsets direct diverging effector pathways that lead to different patterns and severity of glomerular injury in GN. Th1-predominant responses appear to be associated strongly with proliferative and crescentic forms of GN that result in severe renal injury, while Th2 responses are associated with membranous patterns of injury. The challenge remains to understand fully the relevance of T helper cell subset responses to the spectrum of human GN and to apply this new knowledge to the development of more potent and selective therapeutic strategies.

Exposure to farming environments in early life and type 1 diabetes: a case-control study

It has been hypothesized that a stimulation of regulatory cytokines by microbial compounds reduces autoimmune as well as atopic diseases. Farm-related contact to microbial compounds protects from allergies, but no data on the association between farm contact and type 1 diabetes is available. The aim of this study was to test this association. A case-control study was conducted in five children's hospitals. Regular contact to farm animals and potential confounders were assessed using a postal questionnaire. Eligible subjects were all prevalent cases with type 1 diabetes registered in the hospitals and hospital-based control subjects (response rate 91%). Included were children aged 6-16 years living in rural areas with German nationality (242 case and 224 control subjects). Regular contact to stables (adjusted odds ratio 1.2 [95% CI 0.5-2.7]) was not associated with type 1 diabetes. In addition, regular contact to specific farm animals was not associated with case status. There was a tendency for an inverse relationship between allergic rhinitis and type 1 diabetes (0.6 [0.3-1.1]; P = 0.11). There was no evidence that early exposure to farm animals largely decreases the risk in children for developing type 1 diabetes.

Hygiene hypothesis and prevalence of glomerulonephritis

The hygiene hypothesis was proposed to explain the marked increase in allergies that has been observed in industrialized (Westernized) societies. This hypothesis proposes that early and frequent exposure to bacterial and other antigens, such as is common in developing nations, leads to a normal Th1 response, but that better public hygiene and less infections observed in industrialized nations may lead to persistence of the Th2 phenotype and thereby increase our risk for developing allergies. Infection early in life with measles or hepatitis A virus, immunization with bacille Calmette-Guérin, certain gastrointestinal bacteria (lactobacillus), and environmental endotoxin exposure may protect individuals from developing allergy in adulthood. Paradoxically, infestation by parasites stimulates a Th2-cell response; however, the incidence of allergic disease is very low, perhaps due to the stimulation of T-regulatory lymphocytes that can downregulate Th1 and Th2 responses. Some types of human glomerulonephritis (GN) have Th1-predominant immune responses, including crescentic and membranoproliferative GN, whereas other types of GN have a predominant Th2 immune response, including membranous nephropathy, minimal change disease, and immunoglobulin A nephropathy. A review of the prevalence of specific GN shows that the higher prevalence of membranoproliferative GN in developing countries and the higher frequency of immunoglobulin A nephropathy and minimal change disease in industrialized countries could be explained by the hygiene hypothesis. We suggest that studies examining Th1/Th2 balance, particularly as it develops in childhood, should be performed to determine if early polarization of the immune response is responsible for the later development of specific forms of GN.

Helminth infections: protection from atopic disorders

Westernized countries are suffering from an epidemic rise in immunologic disorders, such as childhood allergy. A popular explanation is that the increased prevalence in allergy is due to a diminished or altered exposure to gut-dwelling microbes, resulting in a disordered immunoregulation. Various population studies have provided a strong case for the involvement of helminth infections in this respect. Detailed analysis of helminth-induced immune responses showed that helminths not only prime for polarized Th2 responses but also potently induce T-cell hyporesponsiveness. Recently, it has been demonstrated that helminths induce suppressed host immune responses by the priming for regulatory T cells. It is proposed that this regulatory T cell-inducing activity accounts for the protection observed in the development of allergic disorders. It would be interesting to define and characterize particular helminth molecules that have profound immunomodulatory capacities as a target for therapeutic application in the treatment or prophylaxis of allergic manifestations.

Occupational allergy as a challenge to developing countries

A steady increase in the incidence of allergic diseases can be observed since 1950s. For such atopic diseases as bronchial asthma, pollinosis or atopic dermatitis, a significantly increased morbidity rate in the general population has been found. Strikingly enough, the highest prevalence of asthma and allergy was recorded in highly developed countries. It can thus be assumed that the high rate of asthma may be an attribute of the post-industrial societies. The prevalence of occupational allergies is thought to be in direct proportion to the rate with which allergies occur in the general population. In view of the changing environment and lifestyles in the developing countries, their communities are expected to be faced with similar negative epidemiological effects concerning allergies. To counteract the spreading of negative health effects, the following measures need to be undertaken: 1. Limitation of exposure to strong allergens. 2. Modification of the training curriculum for medical personnel and of health service infrastructure, according to new tasks and challenges. 3. Considering a possibility of introducing a system of surveillance over occupational allergies and asthma, like the Surveillance of Work-related and Occupational Respiratory Disease (SWORD) system implemented in UK. This system ensures effective cooperation between specialists in preventive medicine, occupational hygiene services and research workers dealing with occupational health that enables prompt response to emerging hazards.

Co-aggregation of FcgammaRII with FcepsilonRI on human mast cells inhibits antigen-induced secretion and involves SHIP-Grb2-Dok complexes

Signaling through the high affinity IgE receptor FcepsilonRI on human basophils and rodent mast cells is decreased by co-aggregating these receptors to the low affinity IgG receptor FcgammaRII. We used a recently described fusion protein, GE2, which is composed of key portions of the human gamma1 and the human epsilon heavy chains, to dissect the mechanisms that lead to human mast cell and basophil inhibition through co-aggregation of FcgammaRII and FcepsilonRI. Unstimulated human mast cells derived from umbilical cord blood express the immunoreceptor tyrosine-based inhibitory motif-containing receptor FcgammaRII but not FcgammaRI or FcgammaRIII. Interaction of the mast cells with GE2 alone did not cause degranulation. Co-aggregating FcepsilonRI and FcgammaRII with GE2 1) significantly inhibited IgE-mediated histamine release, cytokine production, and Ca(2+) mobilization, 2) reduced the antigen-induced morphological changes associated with mast cell degranulation, 3) reduced the tyrosine phosphorylation of several cellular substrates, and 4) increased the tyrosine phosphorylation of the adapter protein downstream of kinase 1 (p62(dok); Dok), growth factor receptor-bound protein 2 (Grb2), and SH2 domain containing inositol 5-phosphatase (SHIP). Tyrosine phosphorylation of Dok was associated with increased binding to Grb2. Surprisingly, in non-stimulated cells, there were complexes of phosphorylated SHIP-Grb2-Dok that were lost upon IgE receptor activation but retained under conditions of Fcepsilon-Fcgamma co-aggregation. Finally, studies using mast cells from Dok-1 knock-out mice showed that IgE alone triggers degranulation supporting an inhibitory role for Dok degranulation. Our results demonstrate how human FcepsilonRI-mediated responses can be inhibited by co-aggregation with FcgammaRIIB and implicate Dok, SHIP, and Grb2 as key intermediates in regulating antigen-induced mediator release.

Is there a causative role for tetanus toxoid vaccination in the development of allergy-like symptoms and in the increasing prevalence of atopic diseases?

Allergic diseases are a worldwide health problem. They mainly affect people living in developed countries where an increasing prevalence of allergy symptoms has been recorded in the last 20-30 years. The cause of this increase is still disputed, and, among others, the "hygiene hypothesis" supported the concept that relevant changes in lifestyle could have a relationship with the phenomenon. More recently the recorded parallel increase in autoimmune diseases has suggested to consider the "hygiene hypothesis" as a cause of a more general disregulation of the immune system leading to both allergy and to autoimmunity. Here are reported a series of observations, evidence, and data from the literature leading to a different hypothesis. The key points are: (1) the presence of two subsets of patients having allergy symptoms based on an IgE-mediated mechanism or not; (2) the positive results obtained with the autologous serum skin test in either cutaneous or respiratory affected subjects, mainly in children and adult females; (3) the presence of IgG autoantibodies against the alpha-chain of the high affinity IgE receptor (FcepsilonRIalpha) in non-IgE-mediated urticaria and even in respiratory subjects; (4) the cross-reactivity between epitopes of the tetanus toxoid molecule and the FcepsilonRIalpha detected by means of an alpha-chain affinity purified IgG fraction; (5) the positive skin reactivity obtained using IgG anti-tetanus toxoid preparations in allergic and non-allergic volunteers. The presence of IgG autoantibodies actively generated by the population-based vaccination with tetanus toxoid could induce both mediator release from activated mast cell and Th2 cytokine production early in life. There are epidemiological evidences that tetanus toxoid vaccination could be linked with an increased tendency to have allergy symptoms. The different epidemiological distribution of non-IgE-mediated symptoms, mainly affecting young infants would be in agreement with the present hypothesis. The prevalent mother-to-child relationship in terms of risk for allergy symptoms could be explained with the trans-placenta transfer of IgG. A similar transfer could also take place through the mother milk during breast feeding. It may thus be hypothesized that the increased prevalence of allergic diseases could be caused by the generalized tetanus toxoid immunization procedure, progressively extended to most of the countries worldwide in the last 30-40 years. Both the induction of non-IgE-mediated symptoms caused by the mast cell activation via the anti-FcepsilonRIalpha IgG and the long lasting Th2 inflammation of affected tissues would be the inducing mechanisms. This hypothesis would re-configure part of the allergic diseases as a Th2 phenotypic expression of an autoimmune disease.

Cohort studies of association between self-reported allergic conditions, immune-related diagnoses and glioma and meningioma risk

An inverse association between self-reported allergies and glioma and meningioma risk, has been previously observed in case-control studies. Approximately 27% (median) of the information on both glioma and meningioma in these studies, however, is collected from proxy respondents. In fact, the odds ratios (OR) among previous brain tumor studies are inversely related to the proportion of proxy respondents (Pearson correlation coefficient = -0.94; 95% CI = -1.00 to -0.65); this correlation suggests bias. We therefore constructed 3 cohorts based on the Swedish Twin, Hospital Discharge, and Cancer Registries. In Cohorts I (14,535 people developed 37 gliomas and 41 meningiomas) and II (29,573 people developed 42 gliomas and 26 meningiomas) median time from self-report of allergies to brain tumor diagnosis was 15.4 years. Cohort III, which overlaps with Cohorts I and II (52,067 people developed 68 gliomas and 63 meningiomas), was linked to the Swedish Hospital Discharge Registry where pre-brain tumor immune-related discharge diagnoses were recorded. Allergies are inversely associated with glioma risk in Cohort I (Hazard ratio [HR] = 0.45; 95% CI = 0.19-1.07) and among high grade (III and IV, HR = 0.45; 95% CI = 0.11-1.92) but not low grade (I and II, HR = 2.60; 95% CI = 0.86-7.81) gliomas in Cohort II. In Cohort III, immune-related discharge diagnoses are also inversely associated with glioma (HR = 0.46; 95% CI = 0.14-1.49). There is no strong evidence against (and some for) the hypothesis that allergies reduce glioma risk.

Hypothesis: dysregulation of immunologic balance resulting from hygiene and socioeconomic factors may influence the epidemiology and cause of glomerulonephritis worldwide

Glomerular diseases show diverse epidemiological characteristics throughout the world, which has been suggested to be caused by differences in genetics of the underlying populations or environmental exposure to the putative antigens or agents that either trigger or induce the disease. Recently, an alteration in immune balance of the T helper 1 (T(H)1) and T helper 2 (T(H)2) subsets has been implicated as a mechanism to explain the relative increase in allergic diseases in industrialized nations. According to the Hygiene Hypothesis, overcrowding and poor hygiene early in life may protect from atopic diseases because exposure to microbes predisposes in favor of a T(H)1-dominant response. Conversely, dominance of the T(H)2 subset would be responsible for the increasing incidence of allergies. We present the hypothesis that this imbalance may help explain the predilection for membranoproliferative glomerulonephritis (GN) and mesangial proliferative GN to be associated with developing and/or poor nations, whereas immunoglobulin A nephropathy and minimal change disease are observed more commonly in industrialized nations. The implication of the Hygiene Hypothesis is that clinical expression of immune-mediated renal disease would depend on the prevailing T(H)1/T(H)2 balance, rather than the etiologic agent, and it may help explain the epidemiological pattern of glomerular diseases worldwide.

Inner-city asthma and the hygiene hypothesis

OBJECTIVE

Our goals were to analyze some of the similarities and differences in the increase in asthma, hay fever, and atopic sensitization between Europe and the United States and attempt to explain "inner-city asthma" within the framework of the hygiene hypothesis.

DATA SOURCES

We reviewed historical descriptions of hay fever and asthma as well as the currently available related literature.

STUDY SELECTION

The authors' judgment was used in the selection of historical and epidemiologic evidence.

RESULTS

Analyses of patterns of risk factors for allergic rhinoconjunctivitis and asthma in Europe led to a causal theory of the epidemic: the hygiene hypothesis. This theory claims that hygiene removed a protective influence against atopy and asthma that was once provided by exposure to infections in early life. This hypothesis has been questioned in the United States, where allergic asthma since the 1970s has increased among minorities living in poverty and with suboptimal hygienic conditions (inner-city asthma). When seen from a historical perspective, the recent increasing trend in respiratory allergies among the less advantaged in the United States may be explained as the consequence of several epiphenomena linked to westernization (including declining exposure to foodborne and orofecal infections) that first affected the richest socioeconomic strata during the 19th century, expanded among the middle classes during the first half of the 20th century, and eventually cascaded down to affect the least-advantaged Americans.

CONCLUSION

Inner-city asthma may be the final stage of a class-driven urbanization and westernization that began 2 centuries ago in the United States and that is now coming full circle.

Is there scientific evidence that suppression of acute diseases in childhood induce chronic diseases in the future?

Seeking to understand the individual in his symptomatic totality has been an aim of homeopathy since its beginning. Throughout its history, homeopaths have been concerned that inadequate treatment of acute diseases in childhood may lead to future chronic diseases. Hahnemann cautioned that by treating acute diseases with allopathic medicine, with strong doses of drugs, or suppressing local symptoms of those diseases, would increase the risk of future chronic diseases. Burnett proposed the theory of vaccinosis and warned of chronic manifestations subsequent to smallpox vaccination. French homeopaths, seeking the physiopathological origin of chronic diseases, correlated it to the abnormal reaction of the reticuloendothelial system (RES). Through the study of experimental pathology, Maffei attributed symptomatic manifestations to the imbalance between the immunological phenomena of allergy and immunity. He termed the sensitizing and pathogenic effects of medications and vaccines, 'metallergy' and 'parallergy', respectively. The hygiene hypothesis is based on evidence that the imbalance of immunological response in childhood, specifically among the Th1 and Th2 lymphocyte subpopulations, is responsible for the development of some allergic and chronic diseases in the future. The deranging factor for the predisposition to future allergic response (Th2) is the obstruction of natural manifestations of infectious diseases (Th1 response) in young children. Homeopathic treatment aims to equilibrate vital reaction, corresponding to an integrative physiological response, it may regulate Th1/Th2 imbalance. However, clinical trials to support this hypothesis are lacking.

Dust mite allergens: mitigation and control

In recent years, greater attention has been given to the role of indoor allergens as a cause of sensitization and allergic respiratory diseases. Although indoor allergen control measures to reduce symptoms in individuals allergic to mites have produced controversial results, environmental allergen avoidance is today one of the four primary goals of asthma management recommended in several guidelines of asthma treatment. Exposure to high indoor aeroallergen levels, especially to house dust mite allergens, is an important environmental risk factor for allergic sensitization and the subsequent development and exacerbation of asthma. Therefore, effective aeroallergen avoidance is of use to prevent and treat allergic diseases. Although endotoxin exposure may be protective in early life, it has been demonstrated that the inhalation of endotoxin may exacerbate asthma in house dust mite sensitized patients. Mite-allergic asthmatic patients should be aware of the dangerous combination of mite allergen exposure associated with high endotoxin levels in house dust. These two immunologically active substances have been associated with severe asthma and seasonal exacerbation of symptoms. Effective house dust mite allergen avoidance will never be achieved using a single control measure; various methods are required to affect the multiple factors that facilitate high indoor allergen levels. Education of the patients and their families is also an important component of environmental control strategies.