Eosinophil IgE receptor and CD23

The association between eosinophils (CD16+ eosinophils), basophils (CD203+ basophils), and CD23 B lymphocytes in patients with atopic dermatitis on dupilumab therapy: pilot study

BACKGROUND

Eosinophils, basophils, and the molecule CD23 on B cells are involved in the pathophysiology of atopic dermatitis (AD). The molecule CD23 is involved in the regulation of IgE synthesis and is expressed by activated B cells. The molecule CD16 is used to assess the activation of eosinophils and CD203 of basophils. The association between the count of eosinophils, basophils, CD16⁺ eosinophils, CD203⁺ basophils and the expression of the activation marker CD23 on B cells in patients with AD (with and without dupilumab therapy) is not described.

OBJECTIVE

The aim of this pilot study is to evaluate the association between the blood count of eosinophils, basophils, relative CD16⁺ eosinophils, relative CD203⁺ basophils, and the expression of molecule CD23 on B cells and on their subsets (total, memory, naive, switched, non-switched) in patients suffering from AD (with and without dupilumab therapy) and in control group.

METHODS

A total of 45 patients suffering from AD were examined; 32 patients without dupilumab treatment (10 men, 22 women, average age 35 years), 13 patients with dupilumab treatment (7 men, 6 women, average age 43.4 years), and 30 subjects as a control group (10 men, 20 women, average age 44.7 years). Immunophenotype was examined by flow cytometry in which monoclonal antibodies with fluorescent molecules were used. For statistical analysis we used non-parametric Kruskal-Wallis one-factor analysis of variance with post hoc by Dunn's test with Bonferroni modification and the Spearman's rank correlation coefficient; for coefficients higher than 0.41, we report R² (percent of variation explained).

RESULTS

The absolute count of eosinophils was significantly higher in patients with AD (with and without dupilumab) in comparison to healthy subjects. The difference in the relative count of CD16⁺ eosinophils in patients with AD (with and without dupilumab therapy) compared with control is not statistically significant. In patients with dupilumab therapy the significantly lower count of relative CD203⁺ basophils was confirmed compared with control. The higher association between the count of eosinophils (absolute and relative) and the expression of CD23 marker on B cells was confirmed in patients with dupilumab therapy; in contrast, this association was low in patients with AD without dupilumab therapy and in healthy subjects.

CONCLUSION

The higher association between the count of eosinophils (absolute and relative) and the expression of CD23 marker on B cells was confirmed in patients with AD under dupilumab therapy. It suggests that IL-4 production by eosinophils may play a role in B lymphocyte activation. The significantly lower count of CD203⁺ basophils has been demonstrated in patients with dupilumab therapy. This reduction of CD203⁺ basophil count may contribute to the therapeutic effects of dupilumab by reducing the inflammatory response and allergic reactions in patients with AD.

CAR-T Cells Shoot for New Targets: Novel Approaches to Boost Adoptive Cell Therapy for B Cell-Derived Malignancies

Chimeric antigen receptor (CAR)-T cell therapy is undeniably a promising tool in combating various types of hematological malignancies. However, it is not yet optimal and a significant number of patients experience a lack of response or relapse after the treatment. Therapy improvement requires careful analysis of the occurring problems and a deeper understanding of the reasons that stand behind them. In this review, we summarize the recent knowledge about CAR-T products' clinical performance and discuss diversified approaches taken to improve the major shortcomings of this therapy. Especially, we prioritize the challenges faced by CD19 CAR-T cell-based treatment of B cell-derived malignancies and revise the latest insights about mechanisms mediating therapy resistance. Since the loss of CD19 is one of the major obstacles to the success of CAR-T cell therapy, we present antigens that could be alternatively used for the treatment of various types of B cell-derived cancers.

Impact of Plasma Membrane Domains on IgG Fc Receptor Function

Lipid cell membranes not only represent the physical boundaries of cells. They also actively participate in many cellular processes. This contribution is facilitated by highly complex mixtures of different lipids and incorporation of various membrane proteins. One group of membrane-associated receptors are Fc receptors (FcRs). These cell-surface receptors are crucial for the activity of most immune cells as they bind immunoglobulins such as immunoglobulin G (IgG). Based on distinct mechanisms of IgG binding, two classes of Fc receptors are now recognized: the canonical type I FcγRs and select C-type lectin receptors newly referred to as type II FcRs. Upon IgG immune complex induced cross-linking, these receptors are known to induce a multitude of cellular effector responses in a cell-type dependent manner, including internalization, antigen processing, and presentation as well as production of cytokines. The response is also determined by specific intracellular signaling domains, allowing FcRs to either positively or negatively modulate immune cell activity. Expression of cell-type specific combinations and numbers of receptors therefore ultimately sets a threshold for induction of effector responses. Mechanistically, receptor cross-linking and localization to lipid rafts, i.e., organized membrane microdomains enriched in intracellular signaling proteins, were proposed as major determinants of initial FcR activation. Given that immune cell membranes might also vary in their lipid compositions, it is reasonable to speculate, that the cell membrane and especially lipid rafts serve as an additional regulator of FcR activity. In this article, we aim to summarize the current knowledge on the interplay of lipid rafts and IgG binding FcRs with a focus on the plasma membrane composition and receptor localization in immune cells, the proposed mechanisms underlying this localization and consequences for FcR function with respect to their immunoregulatory capacity.

Approaches to target IgE antibodies in allergic diseases

IgE is the antibody isotype found at the lowest concentration in the circulation. However IgE can undeniably play an important role in mediating allergic reactions; best exemplified by the clinical benefits of anti-IgE monoclonal antibody (omalizumab) therapy for some allergic diseases. This review will describe our current understanding of the interactions between IgE and its main receptors FcεRI and CD23 (FcεRII). We will review the known and potential functions of IgE in health and disease: in particular, its detrimental roles in allergic diseases and chronic spontaneous urticaria, and its protective functions in host defense against parasites and venoms. Finally, we will present an overview of the drugs that are in clinical development or have therapeutic potential for IgE-mediated allergic diseases.

CD23/FcεRII: molecular multi-tasking

CD23 is the low-affinity receptor for immunoglobulin (Ig)E and plays important roles in the regulation of IgE responses. CD23 can be cleaved from cell surfaces to yield a range of soluble CD23 (sCD23) proteins that have pleiotropic cytokine-like activities. The regions of CD23 responsible for interaction with many of its known ligands, including IgE, CD21, major histocompatibility complex (MHC) class II and integrins, have been identified and help to explain the structure-function relationships within the CD23 protein. Translational studies of CD23 underline its credibility as a target for therapeutic intervention strategies and illustrate its involvement in mediating therapeutic effects of antibodies directed at other targets.

Immunoglobulin E-mediated hypersensitivity in food-producing animals

Type I hypersensitivity has been described as a cause of allergic reactivity to inhalants, injectables, endoparasites, and ectoparasites in food animal species. In addition, IgE is credited with showing some host-sparing effect when produced in response to certain gastrointestinal and other parasites. Recently, the sophistication of diagnostic procedures has increased with the elucidation of epsilon heavy chain sequences, expressed protein, development of chimeric IgE antibodies, and production of species-specific anti-IgE reagents. Application of ELISA and Western blotting has replaced the passive cutaneous anaphylaxis test for demonstration of antigen-specific IgE in serum. Regulation of the IgE response is complex, and its dependence on induction of T helper cell type 2 cytokines is now established. The next frontier in IgE research, as for many inherited diseases, lies in understanding the genetic make-up of the animal and which genes are important in controlling the IgE response.

Human eosinophil-lymphocyte interactions

While the eosinophil's effector functions clearly can contribute to the pathogenesis of allergic diseases, the evolutionary benefit to having eosinophils as a distinct class of leukocyte is not clear, especially if one must reconsider the nominally beneficial role of eosinophils in parasite host defense, Eosinophils are equipped to respond to lymphocytes and their cytokines (and not solely the eosinophil growth factor cytokines), but the functional consequences of such eosinophil responses need to be defined. Conversely, eosinophils, as antigen-presenting cells (APCs) or sources of lymphocyte-active cytokines, may stimulate and affect lymphocyte functioning. Eosinophils share with CD4+ lymphocytes expression of a number of receptors, including CD4 and IL-2R, and specific alpha-4 integrins that may help in their common recruitment and activation. Further, elucidation of the interactions between lymphocytes and eosinophils will contribute to a broader understanding of the functioning of eosinophils in "normal" ongoing immune responses and in allergic disorders.

CD23 deficient mice develop allergic airway hyperresponsiveness following sensitization with ovalbumin

The low affinity receptor for IgE (CD23) is reported to regulate immune and inflammatory events and as a result, it may have a role in the development of allergic airway inflammation and hyperresponsiveness (AHR). To test this hypothesis CD23-deficient mice were studied following different modes of allergic sensitization. Mice were actively sensitized either intraperitoneally with ovalbumin (OA)/alum or via the airways (10 days exposure to OA aerosol with no adjuvant). Passive sensitization was performed by intravenous injections of OA-specific IgE. Airway responsiveness, serum IgE and IgG levels were assessed together with airway inflammation. Passive sensitization followed by airway challenges resulted in increased OA-specific lgG and IgE in the serum of wild-type mice only, while both the CD23+/+ and CD23-/- groups developed tracheal smooth muscle hyperresponsiveness to electrical field stimulation, indicating that IgE/CD23-mediated immune functions may not be necessary for the development of allergic changes. Active sensitization of both CD23-/- and CD23+/+ mice resulted in increased serum levels of OA-specific IgE and lgG, airway eosinophilia and significant AHR when compared with nonsensitized mice. The genetic deficiency of CD23-/- mice not only failed to prevent but was associated with a significant increase of these responses. These results indicate that CD23 may not be essential for the development of allergen-induced AHR and further, that its presence may have some inhibitory effects on the allergic response.