Upregulated Surface Expression of Intracellularly Sequestered Igɛ Receptors (FcɛRII/CD23) Following Activation in Human Peripheral Blood Eosinophils

Abstract

We investigated the regulation, secretion, and surface expression of the low-affinity FcepsilonRII receptor (CD23) in eosinophils isolated from human blood using multiple monoclonal antibodies (mAbs) directed at different epitopes of human CD23. Substantial surface expression of CD23 was not demonstrated in the resting state. Mean fluorescence intensity (MFI) measured by flow cytometry was 7. 1 +/- 0.8 for 9P25 mAb (p = NS) and 15.7 +/- 3.8 for BU38 mAb (p <. 04) versus 5.3 +/- 1.0 for IgG1 isotype control Ab. By contrast, MFI using BU38 mAb was 154 +/- 18 for JY-B lymphocytes (p <.0001 versus eosinophils). Despite weak surface expression, eosinophil permeabilization demonstrated substantial intracellular expression of CD23; MFI was 33.6 +/- 5.2 for 9P25 mAb versus 4.4 +/- 0.43 for IgG control (p <.001). Western blot analysis using both positive and negative controls demonstrated immunological identity with CD23 on JY-B lymphocytes. Activation of eosinophils caused rapid translocation of CD23 to the surface membrane (160 +/- 33 MFI; p <. 005), which was maximal within 30 sec. Secretory CD23 was detected within the perfusate also at 30 sec and was fully reinternalized at 10 min. This is the first demonstration of the presence of intracellular CD23 in human eosinophils. Our data indicate that eosinophils rarely express CD23 on their surface but are capable of transient high-level expression and secretion with rapid reuptake of intracellular stores of CD23.

Stimulation of eosinophil IgE low-affinity receptor leads to increased adhesion molecule expression and cell migration

“…In contrast with a recent paper showing, by flow cytometry, no CD23 expression on eosinophils isolated from atopic subjects [10], detectable CD23 was found on eosinophils from all atopic subjects and the majority of the controls in the present study. Patient selection and/or methodological differences may account for the discrepancy in results between the present results and those previously reported [24].…”

CD23-Dependent Transcytosis of IgE and Immune Complex across the Polarized Human Respiratory Epithelial Cells

“…The distinct cellular distribution of CD23 between airway epithelial and B lymphocytes has not been appreciated in previous studies. In addition, activation of human eosinophils leads to increased surface expression of CD23 (44). Our data showed that IL-4 stimulation also increased the surface expression of CD23 in A549 cells (data not shown).…”

“…CD23 is known to be expressed intracellularly and/or at the cell surface (44). To show the expression pattern of CD23 in airway epithelial cells, we stained lung epithelial cells A549 with EBVCS1 mAb for cell surface or intracellular expression by flow cytometry (Fig.…”

Anti-CD23 monoclonal antibody, lumiliximab, inhibited allergen-induced responses in antigen-presenting cells and T cells from atopic subjects

“…1,2 This 45-kd calcium-dependent C-type lectin 3 is expressed by eosinophils 4,5 and as a membrane receptor on several cell types including B and T cells, Langerhans cells, monocytes, dendritic cells, macrophages, platelets, and neutrophils. [6][7][8][9] The expression of CD23 is greatly increased on monocytes, lung alveolar macrophages, and circulating B lymphocytes of subjects with allergy.…”