Allergic disease: the diagnosis of peanut allergy and the role of heat shock proteins in chronic allergic inflammation

Introduction

In this thesis we have discussed two main questions. First we have examined the role of heat shock proteins in allergic inflammation, as we had seen in previous research that immune responses to heat shock proteins play a role in various chronic inflammatory disorders. Secondly we have examined the difficulties of the diagnosis of peanut allergy. We examined both the role of the current extracts used for diagnosis as the role of IL-25, a cytokine that possibly plays both a role at the start of the allergic inflammation as in the chronic state of peanut allergy.

Methods

We have tested T cell responses to HSP both in cord blood from healthy newborns, as in blood from patients with atopic dermatitis. For the analysis of the blood samples we used a combination of proliferation assays, multiplex particle based immunoassay, flow cytometry and functional assays. We used immunochemistry to examine the presence of HSP in the skin of atopic patients.

For our study related to peanut allergy we collected samples of patients with a suspected peanut allergy, that underwent a double blind placebo controlled food challenge in the hospital. We determined plasma cytokine levels via Xmap technology (Luminex Austin). We also examined the IgE responses to extracts and various peanut proteins and compared the peanut positive samples with samples of patients of which the food challenge was negative.

Results

In chapter 2 we have reviewed the literature on HSP and allergic diseases, which shows that only scarce data is available. In chapter 3 we have shown that immune response to HSP are present in cord blood, a disease free environment. In chapter 4 it was seen that immune responses are also present in patients with atopic dermatitis.

In chapter 5 we have shown that IL-25 is elevated only in a subgroup of patients with a positive outcome of the food challenge. Our data shows in chapter 6 that many conventional extracts are deficient in some significant

IgE binding components, which can result in a low sensitivity of the test. Also some components are clinically irrelevant, causing a low specificity of the test.

Conclusion

From the first part it can be concluded that the role of endogenous alarmins in the initiation and maintenance of tissue inflammation in allergic disease and their role as potential therapeutic targets is an interesting and important avenue for future research. Responses to HSP are not only present in patients with chronic inflammation but also in a disease free environment. This supports the hypothesis that responses to HSP can be a healthy immunogenic response.

From the second part it can be concluded that IL-25 is elevated in a subgroup of patients, possibly indicating that IL-25 contributes to the chronic inflammation in peanut allergy. Further it can be concluded that that there is need for improvements in the management of food allergy by better sensitization tests. Improved diagnosis is likely to result in more targeted therapy including appropriate diets.