Identification of B Regulatory Cells by Flow Cytometry

Overview

The goal of this laboratory and observational study is to develop a test to quantify B-regulatory cells in blood. This will be used to detect changes in B-regulatory cell populations in pollen and insect venom allergic patients who are receiving routine allergen immunotherapy treatment. The primary question this study aims to answer is; 1). Are changes in blood B-regulatory cells associated with successful allergen immunotherapy treatment, and therefore do these changes suggest patients have developed a suitable level of allergen tolerance and reduction in their allergic symptoms upon re-exposure to the causal allergen. Patients will also be asked to complete quality of life questionnaire periodically throughout the study to determine if there are associations between variation in B-regulatory cell populations in blood and allergic symptoms experienced.

Allergen immunotherapy (AIT) is a disease-modifying treatment for allergic disease which promotes immune system tolerance, i.e. reduces clinical manifestations of allergy and is the only known effective treatment to prevent anaphylaxis in patients who have previously had serious reactions to insect venoms. AIT induces a variety of immune system changes to facilitate this process, one mechanism of which is the production of a population of white blood cells called B-regulatory cells (BREGs). These cells release a chemical called interleukin-10 (IL-10) which inhibits (controls) the allergic immune response. The success of AIT is difficult to establish/monitor during treatment. Often treatment success can only be established at the end of a long treatment period (typically 3 years) and currently clinicians rely on patient symptoms upon re-exposure to further allergen post-treatment. Therefore there is a requirement to identify a marker (biomarker) which can be tested for during treatment to help clinicians establish at an earlier time, if the AIT is showing success or if a change to treatment is required. This research will measure the BREG and IL-10 production in patients before and at multiple points during AIT, to establish if there is a relationship between the BREG/IL-10 concentration and the success or failure of AIT in controlling patient symptoms of allergy. The hope is that BREG measurement could be used in the future as a biomarker for AIT efficacy, and therefore provide evidence of AIT success sooner than current protocols, or establishing failure of AIT and therefore expediting a change in treatment. The latter will likely result in saving time in pursuing a treatment which is not working, but also for understanding when the treatment has already reached optimal effectiveness and can be stopped. Overall Aim: To develop a flow cytometry assay for the identification and quantitation of human B regulatory cells to allow evaluation of their potential role as a treatment efficacy biomarker in allergen-specific immunotherapy. Primary Objectives: 1. Identification of a biomarker that defines success of allergen immunotherapy 2. Development of a novel flow cytometry assay to detect and quantify B-regulatory cells in whole blood/peripheral blood mononuclear cell (PBMC) isolate 3. Determine the reference intervals for BREG cell quantitation in the test and control groups using conventional parametric or non-parametric measures, depending on the characteristics of the data obtained Secondary Objectives: 1. Evaluation of the performance of the flow cytometry methods as per usual laboratory protocol 2. Comparison of BREG cell quantitation in the control group verses the test group, and the test group at baseline verses on AIT 3. Comparison of BREG cell quantitation in patients receiving subcutaneous and sublingual AIT 4. Comparison of allergen-specific blocking antibodies (allergen-specific IgG4) in the test group at baseline and in those on AIT 5. Assess correlation of allergen-specific blocking antibody quantitation with changes in whole blood B regulatory cell concentrations