CD63 and Allergy: Additionally, further parameters such as the determination of the half-maximal allergen concentration (EC50, CD-sens, basophil sensitivity), the calculation of a ratio (CD63 ratio) of allergen-induced CD63 activation in comparison to an IgE-dependent positive control (anti-IgE or anti-FcεRI) or of the area under the curve (AUC) in dose-response curves turned out to be of value for the assessment of clinically relevant allergies and therapy outcomes [2].