Fc gamma and CD11/CD18 receptor expression on normal density and low density human eosinophils

We have studied the expression of Fc gamma receptors and leucocyte integrins (CD11/CD18 family) on human eosinophils using specific monoclonal antibodies (mAb) and flow cytometric analysis. Peripheral blood eosinophils of normal density and low density were compared with neutrophils and monocytes. Several properties of the human eosinophil were established. These were (i) that the eosinophil expressed Fc gamma RII (CDw32) only (unlike monocytes which bear Fc gamma RI and Fc gamma RII and neutrophils which bear Fc gamma RII and Fc gamma RIII); (ii) that the absence of Fc gamma RIII (CD16) on eosinophils served as a basis for distinguishing eosinophil and neutrophil populations by immunofluorescence; (iii) that the leucocyte adhesion glycoproteins, LFA-1 alpha (CD11a), CR3-alpha (CD11b), p150, 95-alpha (CD11c) and the common beta-chain (CD18), were expressed on the eosinophil as well as the neutrophil; (iv) that CD18 expression was significantly reduced on low-density eosinophils from the hypereosinophilic syndrome. Thus, our findings emphasize the unique phenotype of the human eosinophil in terms of Fc gamma receptor expression, the similarity of the eosinophil and neutrophil with regard to the leucocyte integrins and that eosinophils of low density do not differ greatly from those of normal density in terms of receptor expression.