Basophil activation markers (BAT markers)

Basophil activation markers are a group of cell surface proteins, most notably CD63 and CD203c, that are upregulated on the surface of basophils following activation by allergens or other stimuli (Hoffmann et al., 2015). CD63, also known as LAMP-3, is a tetraspanin protein that resides on the inner membrane of granules and is translocated to the cell surface during degranulation (UniProt P08962). CD203c, or ENPP3, is an ectoenzyme constitutively expressed at low levels on basophils and is rapidly upregulated upon activation via the FcεRI pathway (UniProt P22748). These markers are primarily utilized in the Basophil Activation Test (BAT), a flow cytometry-based assay used to diagnose IgE-mediated allergies and monitor the efficacy of allergen-specific immunotherapy (Hemmings et al., 2018). While these markers are not typically therapeutic targets themselves, they serve as critical biomarkers for assessing the pharmacodynamics of drugs like Omalizumab, which inhibits IgE-mediated basophil activation (MacGlashan, 2010). Their expression provides a functional readout of the allergic response, offering a more precise diagnostic tool than traditional skin tests or serum IgE measurements.

Other names

CD63CD203cENPP3LAMP-3Basophil activation test markersBAT markersCD107aLAMP-1CD164

These markers are not therapeutic targets; however, drugs like Omalizumab and BTK inhibitors (e.g., Ibrutinib) reduce their expression by blocking the signaling pathways (IgE/FcεRI or BTK) that lead to basophil activation and degranulation (MacGlashan, 2010; Hemmings et al., 2018).