Binding of Anti-CD23 Monoclonal Antibody to the Leucine Zipper Motif of FcεRII/CD23 on B Cell Membrane Promotes Its Proteolytic Cleavage

Here we describe the production of a rabbit polyclonal Ab (RAS1) raised against the stalk of murine CD23. RAS1 inhibits release of CD23 from the surface of both M12 and B cells resulting in an increase of CD23 on the cell surface. Despite this increase, these cells are unable to bind IgE as determined by FACS. CD23 has previously been shown to bind IgE with both a high (4–10 × 107 M−1) and low (4–10 × 106 M−1) affinity. Closer examination by direct binding of 125I-IgE revealed that RAS1 blocks high affinity binding while having no effect on low affinity binding. These data support the model proposing that oligomers of CD23 mediate high affinity IgE binding. These experiments suggest that RAS1 binding to cell surface CD23 results in a shift from oligomers to monomers, which, according to the model, only bind IgE with low affinity. These experiments also suggest that high affinity binding of IgE is required for IgE regulation by CD23 and is demonstrated by the fact that treatment of Ag/Alum-immunized mice treated with RAS1 results in a significant increase in IgE production similar to the levels seen in CD23-deficient mice. These mice also had significantly decreased levels of serum soluble CD23 and Ag-specific IgG1. RAS1 had no effect on IgE or Ag-specific IgG1 production in CD23-deficient mice.

Section: Figuresupporting

confidence: 82%

“…This same Ab was later shown to enhance cleavage of CD23. The enhancement of proteolysis by EBVCS-1 could be decreased by the addition of IgE (41).…”

Section: Figurementioning

confidence: 95%

Regulation of IgE Production Requires Oligomerization of CD23

Kilmon

Ghirlando

Strub

et al. 2001

“…The PCR products were sequenced to verify CD23b isoform-specific transcripts. To verify CD23 expression at the protein level, we blotted the cell lysates from Detroit 562, Calu-3, and A549 cells with EBVCS1 mAb, a specific IgG1 Ab for human CD23 (38,39). These airway epithelial cells expressed protein bands identical to 293T and intestinal T84 cells transfected with vectors expressing human CD23b cDNA in a Western blot (Fig.…”

Section: Human Respiratory Epithelial Cells Express Cd23mentioning

confidence: 99%

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

Palaniyandi

Tomei

et al. 2011

IgE-mediated allergic inflammation occurs when allergens cross-link IgE on the surface of immune cells, thereby triggering the release of inflammatory mediators as well as enhancing Ag presentations. IgE is frequently present in airway secretions, and its level can be enhanced in human patients with allergic rhinitis and bronchial asthma. However, it remains completely unknown how IgE appears in the airway secretions. In this study, we show that CD23 (FcεRII) is constitutively expressed in established or primary human airway epithelial cells, and its expression is significantly upregulated when airway epithelial cells were subjected to IL-4 stimulation. In a transcytosis assay, human IgE or IgE-derived immune complex (IC) was transported across a polarized Calu-3 monolayer. Exposure of the Calu-3 monolayer to IL-4 stimulation also enhanced the transcytosis of either human IgE or the IC. A CD23-specific Ab or soluble CD23 significantly reduced the efficiency of IgE or IC transcytosis, suggesting a specific receptor-mediated transport by CD23. Transcytosis of both IgE and the IC was further verified in primary human airway epithelial cell monolayers. Furthermore, the transcytosed Ag–IgE complexes were competent in inducing degranulation of the cultured human mast cells. Because airway epithelial cells are the first cell layer to come into contact with inhaled allergens, our study implies CD23-mediated IgE transcytosis in human airway epithelial cells may play a critical role in initiating and contributing to the perpetuation of airway allergic inflammation.

“…Therefore, it is important to better define the identities of the CD8 ϩ CD60 ϩ T cell subset (CD23 ϩ/Ϫ ) that help and/or suppress memory IgE responses in order that cells/ cytokine pathways might be accurately determined. Because CD23 is shed from cell surfaces (11)(12)(13) ϩ T cells; other cytokines were not studied). Interestingly, in the present studies, IL-13 was not required for induction of memory IgE responses.…”

Section: Discussionmentioning

confidence: 99%

Two Distinct T Cell Subsets, CD4+ and CD8+CD60+, and Their Cytokines Are Required for In Vitro Induction of Human Ragweed-Specific Memory IgE Responses

Smith‐Norowitz

Silverberg

Norowitz

et al. 2008

CD8+CD60+ T cells (80–98% CD45RO+; 20% CD23+) are significantly increased in the blood of serum IgE+ ragweed-sensitized (RS) compared with serum IgE-nonatopic humans (p = 0.001). CD8+CD60+ T cells of the RS patients produced IL-2, IL-4, IL-10, IL-12, IFN-α. and IFN-γ, but not IL-6 or IL-13. When their PBMC were cultured with ragweed Ag (RA), peak IgE responses occurred on day 10; none was induced with non-cross-reacting or without Ag; nonatopic PBMC did not respond to any stimulant. When either CD4+ or CD8+CD60+ T cells were depleted from RS PBMC before culture with RA, no IgE responses were induced. If purified CD4+ T cells or low numbers of CD8+CD60+ T cells were added back to the depleted PBMC, IgE responses were restored. However, higher numbers of CD8+CD60+ T cells totally suppressed IgE responses. Total suppression also was obtained when RS PBMC were cultured with RA and either anti-IL-2, IL-4, IL-10, IL-12, IFN-γ (all concentrations), or IFN-α (low concentrations), but not anti-IL-6 or IL-13. Higher concentrations of anti-IFN-α potentiated IgE responses.