**Author details**

However, the mechanism by which the host's immune system develops the tolerance (healthy reaction) or sensitization (allergy) against a food has been partially elucidated. A subtype of

system tune against the food allergens, leading the immune responses either toward a tuned (healthy) or a false response (allergy). DCs sample the food allergens thorough the epithelial cell barrier of the gut. Other antigen presenting cells such as macrophages help the DCs for antigen sampling. Then these antigen activated DCs migrate from the lamina propria toward a secondary lymphoid tissue and there prime the naïve T lymphocytes to differentiate into

T cell to polarize into FOXP3−

called type 1 regulatory T cells (Tr1 cells). Tr1 cells have also critical role in dampening the immune response against food antigens. The DC-mediated polarized T cells contribute in suppressing the immune reaction against food allergens and induce the IgA production by

toward a cascade of responses directed by TH2 cells. In sensitized patients, the food allergens trigger inflammatory responses mediated by gut epithelial cells via producing the thymic stromal lymphopoietin (TSLP), IL-25, and IL-33. These cytokines affect the DCs, empowering them to deviate the polarization of naïve T cells toward the TH2 cells rather than the TH1 cells. Then TH2 cells induce the class-switching of B cells to produce allergen-specific IgE followed by subsequent responses by effector cells (mast cells, basophils) which is end in the food

There have been a series of diagnostic methods, some of them developed decades ago but until recently have been remained reliable enough although in some cases they give false positive or false negative result. However, the medical history and physical examination are the first line approach for medical diagnosis of food allergy in which some disorders such as the history of an atopic disease can guide the physician toward a proper diagnosis. In addition, a method based on step-by-step removing the nonallergic food from the dietary regimen until reaching the food causing the allergic response is the only fully reliable method of identifying the original cause of the food allergy. An accurate and generally accepted variant of the method called oral food challenge (OFC) has been developed but it could not be used extensively thus far due to requirement of intensive laboratory resources, its time-consuming procedures and the risk of undergoing anaphylactic reactions. The serologic tests such as measuring the total IgE and allergen-specific IgE, skin tests such as skin prick test, intradermal skin test, and atopy patch test can also help for diagnosis, though these tests indicate only the sensitization not a clinical food allergy. There are also two novel highly accurate diagnostic tests including the component-resolved diagnosis and basophil activation test although yet

The management and treatment methods for food allergy are mostly based on avoidance or elimination of the allergenic food from the dietary regimen. Currently, the only method whose effect can last for long time is known as the allergen-specific immunotherapy (SIT). In the SIT method, the allergen food is usually administered orally to the patient in a controlled manner in order to relieve the food allergy, which is called antigen desensitization. However,

cells responsible for tolerance against food allergens. In addition, CD103<sup>+</sup>

B cells. In contrast, during the sensitization process, CD103<sup>+</sup>

are being in the developing process in research settings.

regulatory T (Treg) cells. These primed and antigen-specific Treg cells are main immune

DCs are the key cells concerting the immune

DCs also involved

, IL-10-secreting T cells which are

DCs shift the immune system

dendritic cells (DCs) classified as the CD103<sup>+</sup>

FOXP3<sup>+</sup>

4 Allergen

allergy.

in triggering the naïve CD4<sup>+</sup>

Seyyed Shamsadin Athari1 \*, Ghasem Vahedi2

\*Address all correspondence to: ss.athari@gmail.com and ss.athari@zums.ac.ir

1 Department of Immunology, Faculty of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran

2 Research Center for Food Hygiene and Safety, Shahid Sadoughi University of Medical Sciences, Yazd, Iran

**Provisional chapter**
