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Expression of toll-like receptors and immune-regulatory markers during early infancy and allergy development in Estonian and Swedish infants
Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Pediatrics .
Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Pediatrics .
Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Pediatrics .
(English)Manuscript (Other academic)
Abstract [en]

Background: Allergies have increased during the last decades with the highest prevalences in countries with a Westernised lifestyle. As microbial activation might be required for an accurate maturation of the immune system, a reduced or altered microbial exposure during infancy has been suggested as a possible cause for the increase of allergic diseases in affluent countries.

Aim: The aim of this study was to investigate the gene expression of TLR2, TLR4, Foxp3, Ebi3 and SOCS3 involved in LPS signaling pathways and immune regulation in two prospectively followed birth cohorts, one from Estonia and one from Sweden, in relation to domestic endotoxin levels and allergy development.

Material and methods: Twenty-three children from Estonia and 52 from Sweden were followed from birth to five years of age regarding allergy development using questionnaires, clinical examinations and skin prick tests. RNA was isolated from unstimulated peripheral blood mononuclear cells (PBMC) in samples collected at birth, 3, 6, 12 and 24 months of age. mRNA expression of TLR2, TLR4, SOCS3, Ebi3 and Foxp3 was analysed with real-time RTPCR. The mRNA expression of the genes were compared to previously obtained data of LPS/IFN-γ induced cytokine and chemokine PBMC secretion at the corresponding time-points and also to domestic endotoxin levels.

Results: The Estonian infants had higher mRNA expression of the two regulatory T cell (Treg) associated markers Foxp3 and Ebi3 at birth than the Swedish infants. The Foxp3 and Ebi3 expression correlated at all time-points. The mRNA expression of TLR2, TLR4 and SOCS3 was similar in Estonian and Swedish infants at all ages. None of the genes were associated with endotoxin levels.TLR4 mRNA expression correlated positively with cytokines that were upregulated by LPS/IFN- γ stimulation, but was negatively correlated to CCL2 secretion which was downregulated by the stimulation. Low expression of TLR2 mRNA at birth was found in Swedish children who were allergic at 5 years of age. Sensitisation up to 5 years of age was associated with low Ebi3 expression at birth.

Conclusion: Estonian children are born with enhanced Ebi3 and Foxp3 expression compared to Swedish children, suggesting an increased capacity for early immune regulation among infants from a country with a low prevalence of allergic disease. An increased early capacity to respond to TLR2 ligands, i.e. Gram positive bacteria, may protect against allergy development.

Keyword [en]
Regulatory T cells, TLR2, TLR4, SOCS3, foxp3, Ebi3, allergy, LPS, endotoxin
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-16782OAI: oai:DiVA.org:liu-16782DiVA: diva2:173888
Available from: 2009-02-18 Created: 2009-02-18 Last updated: 2010-01-14Bibliographically approved
In thesis
1. Immune responses to lipopolysaccharide in relation to allergic disease: a TLR4 gene polymorphism and endotoxin exposure
Open this publication in new window or tab >>Immune responses to lipopolysaccharide in relation to allergic disease: a TLR4 gene polymorphism and endotoxin exposure
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Allergic diseases have increased during the last decades, particularly in affluent countries, possibly due to a reduced and/or altered microbial exposure during infancy. Activation of the immune system by microbes early in life is probably required for accurate maturation of the immune system and tolerance development. It is not fully understood how microbial exposure is associated with the development of allergic diseases, however. Genetic factors may influence microbial induced immune responses. A certain polymorphism, in the gene coding for the Toll-like receptor 4, i.e. (TLR4 Asp299Gly), has been suggested to alter the immunological responsiveness to bacterial lipopolysaccharide (LPS).

Aim: The aim of this thesis was to study the interplay between LPS induced immune responses, LPS signalling related genetic polymorphisms, allergic disease and endotoxin exposure.

Subjects: The thesis is based on the results obtained from individuals in three different study groups, i.e. Estonian and Swedish children followed prospectively from birth up to five years of age, Swedish school-children eight and 14 years of age and young adults.

Methods: The study subjects were clinically evaluated regarding allergic diseases with skin prick tests, circulating IgE levels, validated questionnaires and clinical examinations by paediatricians or research nurses. The gene polymorphisms TLR4 Asp299Gly and CD14/-159 were analysed. Peripheral blood mononuclear cells were isolated from blood and cultured with LPS from two Gram negative bacterial strains, i.e. Salmonella enterica serotype Typhimurium (Serotype Typhimurium) and Escherichia coli (E. coli). Cytokine and chemokine secretions were analysed with Luminex or ELISA technique. Receptor expression of circulating peripheral blood monocytes was analysed with flow cytometry. The phosphorylation of intracellular proteins involved in LPS signalling pathways was analysed with Luminex technique. mRNA expression of proteins involved in LPS signalling pathways and of markers for T regulatory cells were analysed with realtime-PCR.

Results: In school-children and young adults, the TLR4 Asp299Gly gene polymorphism was associated with reduced LPS induced IκBα phosphorylation, IL-10 and IL-12 cytokine secretion. Interestingly, these findings were observed only when the cells were cultured with LPS from Serotype Typhimurium but not with LPS from E. coli. The polymorphism was positively associated with asthma, especially atopic asthma.

Several differences in immunological responses to LPS were observed between allergic and non-allergic individuals. Asthma in school-children was associated with reduced LPS induced cytokine production of IL-10 and IL-12. The phosphorylation of IκBα was lower in adult allergic compared to non-allergic individuals. Swedish children who had developed allergic disease at five years of age had lower TLR2 mRNA expression at birth compared to children who remained healthy.

Estonian children displayed generally lower LPS induced cytokine and chemokine production as compared to Swedish children both at birth and at 3 and 6 months of age. The mRNA expression of the T regulatory associated markers Foxp3 and Ebi3 were higher in the Estonian compared to the Swedish children at birth.

Conclusion: Polymorphisms in genes coding for pattern recognition receptors can alter the immune responsiveness of the host to microbial components and may be of importance for the development of asthma. Lower LPS induced cytokine response and higher expression of T regulatory associated markers were seen in children from Estonia as compared to Sweden, suggesting an increased capacity for early immune regulation among infants from a country with a low prevalence of allergic disease.

Abstract [sv]

Bakgrund: Under de senaste decennierna har förekomsten av allergiska sjukdomar ökat i västvärlden. En av möjliga förklaringar kan vara en minskad eller förändrad mikrobiell exponering under uppväxttiden. Mikrobiella stimuli under de första levnadsåren tros vara viktiga för utmognaden av immunsystemet och utveckling av tolerans. Exakt hur mikroorganismers påverkan på immunförsvaret är kopplat till utvecklingen av allergiska sjukdomar är dock ännu okänt. Genetiska polymorfier kan påverka immunsvar mot mikrobiella komponenter. En sådan polymorfi, TLR4 Asp299Gly, har observerats i genen som kodar för receptorn TLR4 som känner igen lipopolysackarid (LPS) från Gramnegativa bakteriers cellvägg, och har föreslagits vara associerad med en förändrad förmåga att svara immunologiskt mot LPS.

Syfte: Syftet med studierna var att studera immunsvar mot LPS i relation till specifika genetiska polymorfier, allergisk sjukdom samt mikrobiellt tryck i form av endotoxinnivåer.

Studiepopulationer: Denna avhandling baseras på resultat från tre studiegrupper: estniska och svenska barn som är följda från födseln upp till fem års ålder, en grupp svenska skolbarn 8 och 14 år gamla samt en grupp unga vuxna.

Metoder: Två genetiska polymorfier, TLR4 Asp299Gly och CD14/-159, analyserades. Mononukleära celler isolerades från perifert blod och odlades tillsammans med LPS från två olika Gramnegativa bakteriestammar, Salmonella enterica serotype Typhimurium (Serotype Typhimurium) och Escherichia coli ( E. coli). Cytokin- och kemokinsekretion analyserades i cellsupernatanter med Luminex eller ELISA. Ytmarkörer på monocyter i helblod studerades med flödescytometri. Intracellulära signaleringsproteiner, som är inblandade i TLR4s signalvägar analyserades med Luminexteknik. mRNA uttryck av proteiner som är relaterade till LPS signalering och markörer för regulatoriska T celler analyserades med realtids-PCR.

Resultat: TLR4 Asp299Gly polymorfin var associerad med lägre fosforylering av det intracellulära signaleringsproteinet IκBα och lägre utsöndring av cytokinerna IL-12 och IL-10 efter cellstimulering med LPS hos skolbarn och unga vuxna. Skillnader i cellsvar mellan individer med och utan polymorfin kunde påvisas när cellerna odlats med LPS från Serotype Typhimurium men inte med LPS från E. coli. Polymorfin var också associerad med astma och särskilt atopisk astma.

Flera skillnader i immunsvar mot LPS observerades mellan allergiska och ickeallergiska individer. Skolbarn med astma hade lägre LPS inducerad IL-10 och IL-12 cytokinproduktion. Vuxna allergiker hade lägre LPS inducerad IκBα fosforylering. Svenska barn som vid fem års ålder hade utvecklat allergisk sjukdom hade lägre mRNA uttryck av TLR2 vid födseln.

Estniska barn hade generellt lägre LPS inducerade cytokinsvar än svenska barn vid födseln och vid 3 och 6 månaders ålder. mRNA uttrycket av de T-regulatoriskt associerade markörerna Foxp3 och Ebi3 var vid födseln högre hos de estniska jämfört med de svenska barnen.

Slutsats: Genetiska förutsättningar kan påverka immunsvar mot LPS och kan möjligen ha en betydelse för utveckling av astma. De generellt lägre LPS inducerade cytokinsvaren och högre uttryck av markörer för Treg celler hos estniska jämfört med svenska barn skulle kunna bero på att deras uppväxtmiljö med ett högre mikrobiellt tryck påverkar den tidiga utvecklingen av immunförsvaret och kan möjligen vara en bidragande förklaring till den lägre allergifrekvens som ses i Estland jämfört med Sverige.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 73 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1098
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-16783 (URN)978-91-7393-704-7 (ISBN)
Public defence
2009-03-05, Berzeliussalen, Campus US, Linköpings Universitet , Linköping, 09:00 (English)
Opponent
Supervisors
Available from: 2009-02-18 Created: 2009-02-18 Last updated: 2009-05-13Bibliographically approved

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Lundberg, AnnaJenmalm, Maria C:Jimenez, EnriqueFagerås Böttcher, Malin

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