Effect on cell surface markers following allergen-induced desensitization of human whole-blood basophils.

Allergen-specific immunotherapy (SIT) leads to reduced symptoms upon allergen exposure through as yet unresolved mechanisms. Desensitization of basophils to specific allergens during the updosing phase of injection immunotherapy may contribute to the clinical effect of SIT. Here we report a protocol for efficient in vitro allergen-mediated desensitization of basophils in whole blood and the effect of desensitization on the expression of basophil activation markers (CD203c and CD63) as well as histamine release in response to allergen challenge. Whole blood from grass pollen-allergic subjects was incubated with Phleum pratense extract by stepwise increase of the allergen concentration in the culture from well below to well above the allergen threshold concentration for activation of basophils. Desensitization was determined by measuring the expression of the basophil activation markers CD63 and CD203c by FACS following challenge with high allergen concentrations. The basophil desensitization protocol reported here affected both the expression of the cell-surface markers and the levels of histamine release. Following the stepwise desensitization procedure the whole-blood basophils were not activated when challenged with more than 10-fold increased allergen concentration. We have established a protocol for basophil desensitization. By mimicking the updosing phase of immunotherapy we raised the allergen threshold for basophil activation and obtained efficient desensitization for all donors. We showed that conditions leading to desensitization affect histamine release and expression of different basophil markers alike.