Comparative immunoreactivity of the eosinophil constituents MBP and ECP in different types of urticaria

In order to elucidate the role of eosinophil constituents in urticaria, we investigated major basic protein expression immunohistologically in comparison with that of eosinophilic cationic protein and the low-affinity IgE receptor in lesional and uninvolved skin of different types of urticaria. Eosinophil activation was studied with the markers EG1 and EG2. Different eosinophil constituents were found in all urticarial lesions except those of urticaria pigmentosa. MBP staining tended to be distributed diffusely throughout the tissue, whereas EG1 and EG2 antibodies were located at or close to individual cells. Staining with the low affinity IgE receptor antibody was rare. In uninvolved skin, major basic protein and particularly eosinophilic cationic protein reactivity was found in chronic recurrent urticaria, delayed pressure urticaria and, to a minor degree, in cholinergic urticaria. No correlation was found between antibody reactivity and eosinophil counts. Reactivity with either of the eosinophil constituents is thus a better marker for eosinophil involvement than routine H&E staining of the cells. The demonstration of eosinophil constituents in nonlesional skin of some urticaria patients suggests generalized eosinophil activation in certain subtypes of the disease.