Induction Of Antigen-specific, Isotype-selective Suppression Of Immunoglobulin-e Responses With Glutaraldehyde - Polymerized Ovalbumin

Polymerization of protein allergens with glutaraldehyde (GA) has been shown to lead to decreased local or systemic adverse reactions when used in human hyposensitization therapy. At the same time, clinical trials have revealed that their immunotherapeutic value was at least as good, and in many cases significantly better than that of the corresponding conventional native allergen extracts. Despite these advantages their mechanism of action remains unclear.;The purpose of this study was to determine the characteristics and classification of immunosuoppressive activity established as a consequence of treatment with GA-proteins.;Treatment of mice, a widely accepted animal prototype for human allergy, with GA-polymerized ovalbumin (OA-POL) led to highly efficient antigen-specific suppression of primary and secondary IgE responses. On the other hand, IgG antibody and delayed hypersensitivity responses were not suppressed. Decreased binding to antibodies against the native OA molecule occurred with all GA-modified OA preparations regardless of whether they were polymerized or not. On the other hand, the ability to suppress IgE responses appeared to correlate directly with the size of the polymers used. Suppression was transferable to syngeneic recipients and depended upon the presence in the donor spleens of live Thy 1.2+ and Lyt 1+ lymphocytes.;OA-POL treatment of mice previously immunized with OA (alum) abrogated ongoing IgE responses. Not only were IgE anti-OA responses 8-10 fold lower in the treated group, but anamnestic IgE responses were prevented. Abrogation persisted for over 300 days despite multiple OA (alum) boosters. These results, taken in combination with experiments demonstrating undiminished antigen- and IgE isotype-specific suppression more than seven months after a single course of OA-POL pretreatment, suggested the existence of memory suppressor T cells. Direct evidence for such cells was obtained in adoptive transfer experiments where memory Ts cells were shown to be long-lived ((GREATERTHEQ) 200 d), rapidly recallable and displaying greater suppressive activity than conventional primary suppressor cells.;The study suggests that homeostasis of IgE responses may be maintained, at least in part, by long-lived and boosterable antigen-specific, isotype-selective suppressor T cells. The experimental manipulation of such cells indicates that increasing their activity may provide a useful approach for the selective regulation of IgE- mediated hypersensitivity

Regulation of the High Affinity IgE Receptor (FcεRI) in Human Neutrophils: Role of Seasonal Allergen Exposure and Th-2 Cytokines

The high affinity IgE receptor, FcεRI, plays a key role in the immunological pathways involved in allergic asthma. Previously we have demonstrated that human neutrophils isolated from allergic asthmatics express a functional FcεRI, and therefore it was of importance to examine the factors regulating its expression. In this study, we found that neutrophils from allergic asthmatics showed increased expression of FcεRI-α chain surface protein, total protein and mRNA compared with those from allergic non asthmatics and healthy donors (p<0.001). Interestingly, in neutrophils isolated from allergic asthmatics, FcεRI-α chain surface protein and mRNA expression were significantly greater during the pollen season than outside the pollen season (n = 9, P = 0.001), an effect which was not observed either in the allergic non asthmatic group or the healthy donors (p>0.05). Allergen exposure did not affect other surface markers of neutrophils such as CD16/FcγRIII or IL-17R. In contrast to stimulation with IgE, neutrophils incubated with TH2 cytokines IL-9, GM-CSF, and IL-4, showed enhanced FcεRI-α chain surface expression. In conclusion, these results suggest that enhanced FcεRI expression in human neutrophils from allergic asthmatics during the pollen season can make them more susceptible to the biological effects of IgE, providing a possible new mechanism by which neutrophils contribute to allergic asthma

TLR4 Asp299Gly and Thr399Ile Polymorphisms: No Impact on Human Immune Responsiveness to LPS or Respiratory Syncytial Virus

A broad variety of natural environmental stimuli, genotypic influences and timing all contribute to expression of protective versus maladaptive immune responses and the resulting clinical outcomes in humans. The role of commonly co-segregating Toll-like receptor 4 (TLR4) non-synonymous single nucleotide polymorphisms Asp299Gly and Thr399Ile in this process remains highly controversial. Moreover, what differential impact these polymorphisms might have in at risk populations with respiratory dysfunction, such as current asthma or a history of infantile bronchiolitis, has never been examined. Here we determine the importance of these polymorphisms in modulating LPS and respiratory syncytial virus (RSV)--driven cytokine responses. We focus on both healthy children and those with clinically relevant respiratory dysfunction.To elucidate the impact of TLR4 Asp299Gly and Thr399Ile on cytokine production, we assessed multiple immune parameters in over 200 pediatric subjects aged 7-9. Genotyping was followed by quantification of pro- and anti-inflammatory cytokine responses by fresh peripheral blood mononuclear cells upon acute exposure to LPS or RSV.In contrast to early reports, neither SNP influenced immune responses evoked by LPS exposure or RSV infection, as measured by the intermediate phenotype of pro- and anti-inflammatory cytokine responses to these ubiquitous agents. There is no evidence of altered sensitivity in populations with "at risk" clinical phenotypes.Genomic medicine seeks to inform clinical practice. Determination of the TLR4 Asp299Gly/Thr399Ile haplotype is of no clinical benefit in predicting the nature or intensity of cytokine production in children whether currently healthy or among specific at-risk groups characterized by prior infantile broncholitis or current asthma

Influence of Socioeconomic Status Trajectories on Innate Immune Responsiveness in Children

Lower socioeconomic status (SES) is consistently associated with poor health, yet little is known about the biological mechanisms underlying this inequality. In children, we examined the impact of early-life SES trajectories on the intensity of global innate immune activation, recognizing that excessive activation can be a precursor to inflammation and chronic disease.Stimulated interleukin-6 production, a measure of immune responsiveness, was analyzed ex vivo for 267 Canadian schoolchildren from a 1995 birth cohort in Manitoba, Canada. Childhood SES trajectories were determined from parent-reported housing data using a longitudinal latent-class modeling technique. Multivariate regression was conducted with adjustment for potential confounders.SES was inversely associated with innate immune responsiveness (p=0.003), with persistently low-SES children exhibiting responses more than twice as intense as their high-SES counterparts. Despite initially lower SES, responses from children experiencing increasing SES trajectories throughout childhood were indistinguishable from high-SES children. Low-SES effects were strongest among overweight children (p<0.01). Independent of SES trajectories, immune responsiveness was increased in First Nations children (p<0.05) and urban children with atopic asthma (p<0.01).These results implicate differential immune activation in the association between SES and clinical outcomes, and broadly imply that SES interventions during childhood could limit or reverse the damaging biological effects of exposure to poverty during the preschool years