IgE antibody concentration, specific activity, clonality, and affinity measures from future diagnostic confirmatory tests

摘要

For years, allergy researchers have been investigating the constellation of parameters that modulate effector cell mediator release. Their goal has been to devise new strategies for reducing IgE-mediated responses in sensitized individuals after allergen exposure. The article by Christensen et al in this issue of the Journal provides clarity to the humoral immune response component of the allergic response through empiric data that show that concentration, specific activity (specific to total IgE ratio), affinity, and clonality (epitope specificity) of the IgE antibody response all work together to affect effector cell activation. In this study the authors use an impressive combination of molecular biology, immunochemistry, cellular biology, and chip-based surface plasmon resonance techniques to prepare and characterize a unique a panel of IgE anti-Der p 2 antibodies. Surface plasmon resonance technology allowed the authors an effective means of characterizing the interaction of Der p 2 with IgE anti-Der p 2 in real time. Surface plasmon resonance permits this by attaching one interacting partner (Der p 2) to the surface of a sensor chip and passing a sample containing the other interacting partner (IgE anti-Der p 2) over the surface. In the case of the study by Christensen et al, binding of IgE anti-Der p 2 to insolubilized Der p 2 generated a measured response that is proportional to the bound mass. This analysis allowed the authors to accurately characterize the specificity, concentration, affinity, and clonality of their unique panel of Der p 2-specific IgE antibodies. The authors prepared a panel of 10 mouse/human chimeric IgE antibodies and 9 fully human Der p 2-specific recombinant IgE antibodies that had been cloned from the B cells of a patient with dust mite allergy by using a phage display technique. This unique antibody panel allowed the authors to perform a flow cytometry-based basophil activation test using combinations of IgE antibody affinities ranging from 0.0358 to 291 nmol/L with up to 9 distinct Derp 2-binding epitopes. The authors used basophils from nonatopic donors. All the antibodies of the different affinities or clonalities were studied by using a common basophil preparation to minimize potential variability associated with the basophil source (nonatopic vs atopic donor). The authors also adjusted the Der p 2-specific IgE/total IgE ratio by adding varying amounts of non-Der p 2-specific IgE. For possibly the first time, the authors were able to simultaneously control the IgE antibody concentration, affinity, clonality, and specific activity added to the basophil activation effector cell model. With this unique flexibility, they were able to control for the actual IgE antibody characteristics and empirically show that higher levels of basophil activation occurred with (1) higher total IgE levels, (2) higher specific activity or Der p 2-specific/total IgE ratios, (3) broader clonality, and (4) a higher-affinity IgE antibody.