Microarray Technology Applied to Human Allergic Disease.

Robert Hamilton

doi:10.3390/microarrays6010003

Abstract

IgE antibodies serve as the gatekeeper for the release of mediators from sensitized (IgE positive) mast cells and basophils following a relevant allergen exposure which can lead to an immediate-type hypersensitivity (allergic) reaction. Purified recombinant and native allergens were combined in the 1990s with state of the art chip technology to establish the first microarray-based IgE antibody assay. Triplicate spots to over 100 allergenic molecules are immobilized on an amine-activated glass slide to form a single panel multi-allergosorbent assay. Human antibodies, typically of the IgE and IgG isotypes, specific for one or many allergens bind to their respective allergen(s) on the chip. Following removal of unbound serum proteins, bound IgE antibody is detected with a fluorophore-labeled anti-human IgE reagent. The fluorescent profile from the completed slide provides a sensitization profile of an allergic patient which can identify IgE antibodies that bind to structurally similar (cross-reactive) allergen families versus molecules that are unique to a single allergen specificity. Despite its ability to rapidly analyze many IgE antibody specificities in a single simple assay format, the chip-based microarray remains less analytically sensitive and quantitative than its singleplex assay counterpart (ImmunoCAP, Immulite). Microgram per mL quantities of allergen-specific IgG antibody can also complete with nanogram per mL quantities of specific IgE for limited allergen binding sites on the chip. Microarray assays, while not used in clinical immunology laboratories for routine patient IgE antibody testing, will remain an excellent research tool for defining sensitization profiles of populations in epidemiological studies.

Highlights

IgE antibodies serve as the gatekeeper for the release of mediators from sensitized (IgE positive) mast cells and basophils following a relevant allergen exposure which can lead to an immediate-type hypersensitivity reaction
The use of molecular allergens can enhance the limit of quantitation of an IgE antibody assay by supplementing allergens that are missing or in low abundance in extracts
They can enhance analytical specificity by detecting IgE antibodies to particular stable allergens that signal a high risk for a systemic allergic reaction

Summary

IgE and Allergic Disease

IgE antibody was identified in 1967 as the molecular gatekeeper which controls the elicitation of allergic symptoms in humans [1,2]. IgE antibodies circulate in the blood and bind onto high affinity epsilon specific receptors on mast cells in the skin and basophils in the blood. At this point, an individual can be considered sensitized (IgE antibody-positive) to the particular allergen specificity, they may not manifest any allergic symptoms [3]. At the point where a critical mass of IgE antibody binds to the surface of an individual’s mast cells and basophils, allergen that is inhaled, ingested or injected into the body produces cross-links of surface bound antibodies sufficient to cause mast cells and basophils to become activated and release stored histamine and produce new vasoactive leukotriene mediators. Systemic release of mediators can cause anaphylaxis, in some cases leading to death [4]

Detection of IgE Antibody in Serum

Technological Enhancements Leading to Microarrays

Concluding Thoughts