873:
Development of a Biomarker of Pre-existing IgE Crosslinking on Human Basophils
Monday, March 5, 2018
South Hall A2 (Convention Center)
Santiago Alvarez Arango, MD, Donald W. MacGlashan, MD PhD
RATIONALE:

Clinically, the effect of IgE-mediated drug allergy desensitization is considered transient. In vitro, basophils and mast desensitization of an IgE-mediated reaction may also be transient. Details on desensitization signaling and its kinetics are lacking. Aggregation leading to desensitization induces an alteration in the basophil response to PMA (a non-physiological phorbol ester secretagogue). Based on early results obtained with non-releasing basophils, this alteration in the PMA-response was not expected to be sensitive to syk activity. We tested this expectation using selective inhibitors of syk, btk, PI3K.

METHODS:

Releasers and non-releasers basophils were desensitized with anti-IgE antibody for 90 min in the absence of extracellular calcium. After desensitization, basophils were challenged with a PMA at different concentrations; ±syk, ±btk, or ±PI3K inhibitors were included in the desensitization and re-challenge phases.

RESULTS:

In the absence of the inhibitors, the EC50 for PMA-induced release shifted leftward by 10.7-fold after desensitization. In the presence of the inhibitors, the EC50 shifted only by 1.4-, 1.3-, 1.3-fold (syk, btk, PI3K inhibitors, respectively). An inspection of results from different basophil phenotypes showed that the amount of curve shift was correlated with the maximum response of basophils to anti-IgE Ab.

CONCLUSIONS:

These results suggest that the EC50 for PMA-induced histamine release shift characteristic is dependent on syk activity and related to syk expression in different basophil phenotypes. The signals that shift the response to PMA persist longer than what would be expected from the kinetics of histamine release. This effect may be used to detect cell exposure to allergen during clinical desensitization.