Early life cytokines, viral infections and IgE-mediated allergic disease

Abstract: Background: The reasons why some individuals become IgE-sensitised and allergic are largely unknown, though genetic- and early life environmental factors seem to be of importance.Objective: The overall aim of this thesis was to investigate the relationship between IgE-sensitisation and allergic disease, viral infections, genetic markers and early life cytokines.Results: IgE-sensitised children were found to have reduced numbers of IL-12 producing cord blood mononuclear cells (CBMC), whereas children diagnosed with eczema were found to have reduced numbers of IFN-? producing CBMC. When dividing the children into early onset of IgE-sensitisation and late onset of IgE-sensitisation we found that the children with an early onset had low numbers of PHA-induced IL-4, IL-12 and IFN-? secreting CBMC. At the age of two there was a general exacerbation of cytokine responses in the IgE-sensitised children, and the results were similar for the children with early onset IgE-sensitisation. Children with a late onset IgE-sensitisation were more similar to the non-sensitised children, but with a specific increase in the response to cat allergen (IL-4 and IFN-?). The mothers of IgE-sensitised children, were just as their children, found to have an exaggerated cytokine response as compared to mothers of non-sensitised children. Maternal responses correlated well to the responses seen in the child, though the samples were taken two years after delivery.Cytomegalovirus (CMV) infection in early life was associated to reduced numbers of IL-4, and increased numbers of IFN-? producing cells at the age of two. No association between CMV seropositivity and IgE-sensitisation was seen. Epstein-Barr virus (EBV) infection, on the other hand, was inversely correlated with IgE –sensitisation, whereas no statistically significant association to cytokine production could be seen.We also showed that the IL12B 1188 C-allele was associated to having a positive skin prick test at the age of two. The rare alleles of the three SNPs investigated (IL12B 1188C, IL12RB1132C and IRF1 1688A) were all associated to low IL-12 production at birth.Conclusions: Our results indicate that allergic diseases are complex traits, and that both the genetic and the cytokine background differ between the different allergic diseases. We can also conclude that the time of onset seem to play a role when investigating IgE-sensitisation, and that perhaps early and late onset IgE-sensitisation have partly different causes. CMV and EBV infection early in life are associated to a protective cytokine profile and to protection from IgE-sensitisation, respectively, again indicating the heterogeneity and the complexity of allergic diseases.