Clone FR3-16A11 recognizes CD203c, a glycosylated type II transmembrane molecule that belongs to the family of ecto-nucleotide pyrophosphatase/ phosphodiesterase (E-NPP3) enzymes. Among hematopoietic cells, expression of CD203c is restricted to basophils, mast cells and their precursors, and has been described as specific for this lineage. Protein and/or mRNA expression of CD203c has also been found in solid tissues such as uterus or prostate. Basophils and mast cells are key producers of mediators that drive the onset of inflammatory responses, e.g. in allergy. Allergen challenge leads to a rapid up-regulation of activation markers such as CD203c or CD63. Due to its restricted expression pattern, CD203c is discussed as a specific marker to monitor the allergen-induced activation of basophils, e.g. in flow cytometric basophil activation tests of the peripheral blood.
Human peripheral blood mononuclear cells (PBMCs) were stained with CD203c antibodies as well as with CD123 antibodies and analyzed by flow cytometry. The Tandem Signal Enhancer has been used to increase binding specificity of tandem-dye–conjugated antibodies. For all other conjugates the FcR Blocking Reagent has been used to avoid Fc receptor–mediated antibody labeling. Cell debris and dead cells were excluded from the analysis based on scatter signals and propidium iodide fluorescence or 4',6-diamidino-2-phenylindole (DAPI) fluorescence, as in the case of tandems.