CD21 expressed on basophilic cells is involved in histamine release triggered by CD23 and anti‐CD21 antibodies

Abstract

Recombinant full-length human CD23 incorporated into fluorescent liposomes was used to detect a ligand for CD23 on the basophilic leukemia cell line, KU 812. Based on our recent finding that CD23 interacts with CD21 on subsets of B and T cells, we investigated if the same ligand was involved on KU 812 cells. An anti-CD21 monoclonal antibody (mAb) BU-33, was able to totally block CD23-liposome binding to KU 812 cells. Moreover, KU 812 cells express CD21 mRNA and have a cell surface molecule that reacts with anti-CD21 mAb. The CD23/CD21 interaction was not merely physical but was also associated with an increase in histamine release by KU 812 cells. Both recombinant soluble CD23 and an anti-CD21 mAb-mediated effect on histamine release was not restricted to and anti-CD21 mAb-mediated effect on histamine release was not restricted to the leukemic cell line, but was also observed with normal human blood basophils. These data demonstrate that CD21 is expressed on basophilic cells and that CD21 controls histamine production upon ligand-induced stimulation (CD23 or anti-CD21 mAb).

Critical role of CD23 in allergen-induced bronchoconstriction in a murine model of allergic asthma

“…Alternatively, either the lack or blockade of sCD23 could explain the absence of bronchoconstriction in response to OVA in both models. Indeed with human cells, sCD23 promotes IgE synthesis [25][26][27] and directly mediates the release of histamine by mast cells and basophils [8,9], but a similar activity of murine sCD23 needs to be formally demonstrated. This hypothesis is currently being tested using a purified recombinant form of sCD23.…”

“…For example, endocytosis of IgE bound to CD23 facilitates antigen uptake, processing and presentation by APC and thereby augments antigen-specific IgE synthesis [5,6]. CD23 interactions on cells expressing membrane CD21, a receptor for complement fragments and EBV, regulates IgE synthesis and activates effector cells such as basophils and mast cells [7][8][9]. CD23 binding to the § chains of the g 2 integrins CD11b and CD11c expressed on macrophages leads to a pro-inflammatory pattern of activation and cytokine secretion [10].…”

Silencing of CD21 expression in synovial lymphocytes is independent of methylation of the CD21 promoter CpG island

“…It is mainly expressed on B lymphocytes [2] and follicular dendritic cells [3], but to a lesser extent it is also found on thymocytes [4,5,6], a subpopulation of peripheral T lymphocytes [7,8], cervical and pharyngeal epithelial cells [9,10], basophils [11], natural killer cells [12], and astrocytes [13]. As a receptor, it binds the complement fragments iC3b, C3dg, and C3d [14] as well as Epstein-Barr and human immunode®ciency viruses (EBV and HIV) [15,16,17].…”

Redox regulation of CD21 shedding involves signaling via PKC and indicates the formation of a juxtamembrane stalk

“…CD21 is expressed in mature B lymphocytes and B cell lines, but not on early pre and pro B cells and late developmental stages (Schwab and Illges, 2001;Tedder et al, 1984). In addition it is expressed in low amounts on subsets of thymocytes, T cells, human follicular dendritic cells (Delibrias et al, 1994;Fischer et al, 1991;Reynes et al, 1985), epithelial cells such as the 293 cell line (Fingeroth et al, 1999), astrocytes (Gasque et al, 1996) and basophilic cells (Bacon et al, 1993). CD21 is necessary for B cell activation to T celldependent antigens (Ahearn et al, 1996) and for the survival of B cells in the germinal center reaction .…”