IgE Mediated Allergy

Allergic hypersensitivity – a challenge to modern diagnostics

A rapid increase of patients with allergic hypersensitivity over the last decades has become a serious social and economical burden. According to WHO, e.g. the current numbers of asthmatic patients and of patients with food allergy are around 300 million and 250 million, respectively. Not only the worldwide increase of allergic patients, but also the increase of particular allergens occurs. To face this problem the reliable diagnostics is crucial.

Advantages of the Basophil Activation Test (BAT) in diagnosing allergies

When diagnosing allergies, the crucial task is determining the causal allergen(s). The commonly used method of skin prick tests (SPT) is not optimal due to its low specificity and the risk of further aggravating the condition. More suitable are in vitro approaches, such as the determination of specific IgE in the serum (sIgE) or the analysis of basophil activation markers. In most cases, the specificity of sIgE detection is sufficient, but the sensitivity is usually only about 75%, and in cases of some allergens (mainly food and drug) both sensitivity and specificity of sIgE detection are substantially lower. Basophil Activation Test (BAT), however, is known not only for very high specificity, but also for high sensitivity, even in cases of many problematic antigens. This test is based on the detection of basophil activation markers using flow cytometry. The BasoFlowEx® Kit is based on the principles of the BAT. Its use is simple and suitable for every laboratory with basic equipment and with a flow cytometer, which uses blue laser excitation (488 nm) and detection channels for FITC and PE.

Allergens and their use in BAT

The measure of basophil response to a particular allergen exposure is usually expressed as % of CD63+ basophils. The response is triggered by antigen‑dependent cross‑linking of specific IgE bond to the high‑affinity IgE receptor (FcεRI) on the surface of basophils. Amount of IgE‑FcεRI receptor complexes on the basophil surface directly depends on the free IgE concentration in the blood. Hence the signal obtained out of the basophil activation test (BAT) reflects functional activation of basophil in relation to the sensitivity to particular activating allergen and its concentration in the test tube. Whereas CD63 externalization after challenge with one high allergen dose gives an information about cell reactivity, allergen titration reveals allergen threshold, which is a measure of allergen sensitivity.
Allergens representing different areas of allergy like inhalant allergy, food allergy, hymenoptera venom allergy, drug allergy or chronic urticaria can be used in BAT for diagnostic evaluation of a patient allergy profile together with typically performed tests such as skin prick testing and determination of specific IgEs. Whole allergen extracts as well as recombinant molecules of dominant allergens are commercially available from different sources and regions. Thus it can happen that the values of basophil reactivity reached in BAT with different compounds of the same allergen type may even vary based on geographical origin of the reagent. Therefore it is very important to standardize the use of allergen compounds of particular origin with BAT diagnostic products like BasoFlowEx® Kit.
Various allergens differ in the optimal concentration which provokes the maximum basophil activation, and also in individual variations of the dose‑response curves. If the activation by allergen takes place over a broad concentration range and with low number of individual variations, it is much easier to chose the allergen concentration to be used in BAT, than in case that the effective concentration range is narrow and shows great individual variations.
The set of titration experiments has been conducted in order to evaluate the basophil activation profile of donors with known allergy history by using all allergens in EXBIO offer (both allergen extracts and recombinant allerhgens) and BasoFlowEx® Kit as analytical tool. The extracts of Betula verruccosa, Dermatophagoides pteronyssinus titration experiments are shown in Fig. 1a,b.

Fig. 1a,b Data demonstrate that patients reactive to the same antigen can differ substantially in the course of antigen dose-dependent activation curve. Percentage of activated basophils (% CD63+) is plotteed against log concentration of allergen extract. Both allergic and healthy donors were taken into ananlysis. A supression of basophil response appeared for some samples at very high concentration of allergen. 
Fig1-2.jpg

IgE Mediated Allergy products: 

BasoFlowEx® Kit
Allergens

Other related products:

anti-CD203c antibody
anti-CD63/LAMP3 antibody
anti-CD193 / CCR3 antibody
anti-IgE antibody
 

IgE Mediated Allergy literature: 

Examination of Allergic Hypersensitivity by Flow Cytometry using BasoFlowEx kit
Minicatalog Allergy
 
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