Elucidation of the Mechanism of Immune Tolerance in Beekeepers

Beekeepers experience multiple stings each year many of whom (25-60%) become sensitised to bee (apis mellifera) venom through the production of IgE antibodies. However only a small proportion of the sensitised group go on to have anaphylaxis to bee venom. This study will investigate differences in T cell tolerance to bee venom in 3 groups by exploring factors that "protect" sensitised individuals from having anaphylactic reactions - meaning that despite being sensitised they are tolerant and do not react to subsequent stings.

T regulatory cell (Tregs) play a critical role in promoting immune tolerance to allergens and Treg generation has been shown to occur in bee venom allergic individuals following venom desensitisation therapy. Observations in sensitised tolerant (non-allergic) beekeepers (TB) suggest that exposure to venom through bee stings results in a similar increase in the frequencies of induced Tregs (iTregs). Helios negative induced Treg cells have also been suggested to contribute significantly to the establishment of immune tolerance in beekeepers. We will analyse the differences in Treg and Teffector (Teff) populations comparing sensitised beekeepers who are able to tolerate venom exposure (sensitised, tolerant beekeepers TB) with those beekeepers who do develop symptoms of systemic allergic reactions following bee sting (AB). A group of non-sensitised (NS) individuals will be recruited as a control population. We will perform RNA-seq to analyse the gene expression in Treg cells and Teff cells from all three groups. This will help to identify molecular targets that are involved in inducing the allergic reaction and also the genes that are involved in suppressing this reaction.

Considering the outcome of tolerance or anaphylaxis following bee stings, and the role of Treg and Teff cells in these processes, we will investigate the epigenetic regulations involved, which determine these cell's function. RNA-seq analysis will provide critical information about the genes involved in allergic reaction or in its suppression. DNA and histone modification analyses in the regulatory regions of these genes will help to better understand the underlying mechanism.

This project will investigate why some beekeepers who are sensitised to bee venom are able to tolerate bee stings, while in other sensitised individuals a bee sting can lead to life threatening anaphylaxis. This is not only of significance to beekeepers, but also has potential implications for the understanding of allergen tolerance in other allergic disease.