Fc epsilon receptor II/CD23 positive lymphocytes in atopic dermatitis: II. Infiltration of Fc epsilon R II(+) T cells in the skin lesion

Expression of CD23/CD21 and CD40/CD40 ligand in vernal keratoconjunctivitis

PURPOSE

The overproduction of immunoglobulin E (IgE) antibodies is associated with vernal keratoconjunctivitis (VKC). CD23/CD21 and CD40/CD40 ligand (CD40L) interactions have been proposed to be involved in the regulation of IgE synthesis. The purpose of the present study was to investigate the presence and distribution of CD23, CD21, CD40 and CD40L in the conjunctiva from patients with active VKC.

METHODS

Conjunctival biopsy specimens from 8 subjects with active VKC and 6 control subjects were studied. We used immunohistochemical techniques and a panel of monoclonal antibodies (mAbs) directed against CD23, CD21, CD40 and CD40L. In addition, a panel of mAbs were used to characterise the composition of the inflammatory infiltrate.

RESULTS

In the normal conjunctiva, basal epithelial cells and vascular endothelial cells in the upper substantia propria showed a constitutive very weak immunoreactivity for CD40. The immunoreactivity for CD23, CD21 and CD40L was absent. In VKC specimens, the stromal inflammatory infiltrate was orgnanised as a diffuse infiltrate and as small lymphoid follicles consisting of CD20+ B lymphocytes intermingled with smaller numbers of CD3+ T lymphocytes, and CD68+ monocytes/macrophages. Lymphocytes in the centre of the lymphoid follicles showed CD23 and CD21 immunoreactivity. CD40 immunoreactivity in epithelial cells and vascular endothelial cells was stronger in VKC specimens than in control eyes. Furthermore, the majority of mononuclear cells, including T and B lymphocytes, showed immunoreactivity for CD40. CD40L immunoreactivity was not detected.

CONCLUSION

B lymphocytes in the lymphoid follicles expressing CD23, CD21 and CD40 are activated and might be precursors of IgE-producing B cells. These results suggest that the conjunctiva might contribute to IgE synthesis.

The high-affinity receptor for IgE is the predominant IgE-binding structure in lesional skin of atopic dermatitis patients

While the skin of most patients with atopic dermatitis (AD) is known to contain IgE-bearing cells, the contribution of the various IgE-binding structures to this phenomenon is not fully understood. To address this issue, we eluted cell-bound IgE from cryostat sections of lesional AD skin by acid treatment and performed reconstitution experiments with IgE in the absence or presence of reagents directed against the currently known IgE-binding structures. We found that incubation of acid-treated sections, with either chimeric or serum IgE, resulted in the appearance of sizable numbers of anti-IgE-reactive cells. This cellular IgE loading could be entirely prevented by preincubation of the sections with the anti-Fc epsilonRI alpha MoAb 15-1 but not with either antibodies against Fc epsilonRII/CD23 and Fc gammaRII/CD32 or with alpha-lactose. To exclude the possibility that acid treatment of tissue sections may have adversely influenced the IgE-binding capacity of IgE receptors other than Fc epsilonRI, we performed an identical series of experiments on AD skin samples that, as an exception, were essentially devoid of anti-IgE-reactive cells. Again, no IgE loading was detected when these sections were preincubated with anti-Fc epsilonRI alpha MoAbs. In contrast, preincubation of the sections with alpha-lactose and/or MoAbs against Fc epsilonRII/CD23 or Fc gammaRII/CD32 did not affect IgE loading. Together with the observations that anti-Fc epsilonRI alpha-reactive and IgE-binding cells are largely overlapping populations and include cells of the Langerhans cell/dendritic cell lineage, mast cells, and a few dermal dendrocytes and eosinophils, our results demonstrate that Fc epsilonRI is the predominant and, perhaps, the only biologically relevant IgE-binding structure on histogenetically and functionally diverse cell populations of AD skin.

Serum soluble CD23 levels in giant cell arteritis

Lymphocytes and monocytes express various levels of membrane-bound CD23, the low affinity receptor for IgE (Fc epsilon RII), and in some cases release it as a soluble form. Soluble CD23 (sCD23) has been implicated in the regulation of many immunological functions of T and B lymphocytes, macrophages and myeloid cells in humans. To study serum sCD23 levels in inflammatory conditions, we selected a systemic disease sensitive to corticotherapy, the giant cell arteritis, which is characterized by an inflammation of the temporal artery. Serum sCD23 levels, as measured by a radioimmunoassay, were increased in these patients, and returned to normal values within the 24 h following initiation of corticotherapy. The data suggest that the increase in sCD23 levels in giant cell arteritis results from an overproduction.

Serum levels of soluble CD23 in patients with bullous pemphigoid

In this study, we tested the serum levels of soluble CD23 (sCD23) in 27 bullous pemphigoid (BP) patients and compared them with the disease activity. Soluble CD23 is the cleaved portion of the low affinity Fc receptor for IgE (Fc epsilon RII/CD23) which has an affinity for IgE and regulates IgE synthesis. Although bullous pemphigoid (BP) is a subepidermal blistering disease characterized by IgG class autoantibodies against the basement membrane of stratified squamous epithelia, several IgE-related phenomena have been reported. Recently, we have shown that Fc epsilon RII-expressing and IgE-bearing cells are detectable in the lesional skin and concluded that an IgE-Fc epsilon RII/CD23 system may be involved in the pathogenesis of this disease. The serum level of sCD23 in BP patients was significantly higher than healthy controls (p < 0.01). In 11 out of 12 patients, the alteration of serum sCD23 levels correlated well with the disease activity. Thus the serum level of sCD23 is useful as a new parameter for assessing the level of disease activity in BP. High levels of sCD23 may represent part of an IgE-mediated immune reaction which may play a role in the pathogenesis of BP.

Functional significance of CD23- on CD23-transfected Th2 clone

CD23, a low-affinity IgE Fc receptor, is not displayed on most resting T cells but its expression has been shown to be transiently induced in vivo and in vitro on some CD4+ T cells [1-4] and in vivo on CD8+ T cells by IgE-secreting hybridoma tumors [5]. To investigate the functional role of CD23 on T cells, we inserted a CD23 construct into an expression vector driven by a CD2 promoter and transfected it into a murine Th2 clone D10.G4.1 (D10). We stimulated the transfected D10 cells (D10.3M.24) with anti-TCR antibody in the presence or absence of IgE, and measured IL-4, IL-5 and IL-6 production in the culture supernatants. Activation of D10.3M.24 cells by anti-TCR antibody induced greater levels of IL-4, IL-5 and IL-6 production, when the TCR and CD23 were co-crosslinked by TNP anti-TCR and IgE anti-TNP antibodies. IgG anti-TNP antibody did not enhance lymphokine production by D10.3M.24 cells. The enhanced lymphokine production by IgE was blocked by monoclonal anti-CD23 antibody. IgE anti-TNP antibody did not enhance lymphokine production by the wild-type D10 cells induced by TNP anti-TCR antibody. These studies show that when co-crosslinked with the TCR, CD23 can modulate the lymphokine production in activated Th2 cells. Since CD23 binds to IgE and also binds to CD21 [6], a complement receptor commonly expressed on B cells, T-cell CD23 could play an immunoregulatory role during cognate T-B cell interaction and during IgE antibody responses.

Atopic dermatitis--immunological abnormality and its background

The production of IgE is mainly regulated by cognate and/or non-cognate interaction between B cells and T cells. Two types of helper T cells are recognized in the murine system, Th1 and Th2, by the type of cytokine they produce. Several lines of evidence disclosed that unbalanced generation of Th2/Th1-like cells occurs in atopic disorders, such as atopic dermatitis, in which a high level of serum IgE is found in the majority of patients. Analysis of skin-derived immunocompetent cells, such as Langerhans cells and T cells, has provided us with a new understanding of the pathophysiology of atopic dermatitis. The recent progress in immunological aspects of atopic dermatitis is reviewed.

E-selectin and vascular cell adhesion molecule-1 as critical adhesion molecules for infiltration of T lymphocytes and eosinophils in atopic dermatitis

To study the temporal and spatial relationship between infiltrating T-cell subsets or eosinophils and cell adhesion molecules on endothelial cells in skin lesions of atopic dermatitis (AD), we undertook immunohistochemical analysis using monoclonal antibodies against surface markers of T cells, eosinophil granule proteins and cell adhesion molecules. Predominant mononuclear cells in acute and chronic skin lesions were CD3, CD4 and CD45RO positive helper-inducer/memory T cells. Their number was significantly and strongly correlated with the intensity of E-selectin expression. Eosinophils and deposition of eosinophil-derived granule proteins such as eosinophil cationic protein (ECP), major basic protein (MBP) and eosinophil peroxidase (EPO) were found constantly in acute lesions and only occasionally in chronic lesions. The total number of immunoreactive eosinophils and deposits of MBP, EPO and ECP were significantly and strongly correlated with the staining intensity of VCAM-1. In chronic lesions significant reduction of VCAM-1 expression paralleled occasional infiltration of eosinophils. Our results demonstrate the possibility that E-selectin and VCAM-1 are the critical adhesion molecules for trafficking of memory T cells and eosinophils, respectively, into skin lesion of AD. Persistent expression of the adhesion molecules may be related to prolongation of the skin lesion in AD.

Enhancement of Fc epsilon RII/CD23 expression on U937 cells with opsonized zymosan: the requirement of a Fc gamma RI/CD64 mediated signal associated phagocytosis

The kinetics of surface Fc epsilon RII/CD23 was tested on monocytic cell line U937 stimulated with opsonized zymosan. Zymosan opsonized with human serum enhanced not only the expression of surface Fc epsilon RII/CD23 but also Fc epsilon RII/CD23 mRNA detected by Northern blot and in situ hybridization techniques. This stimulation showed a marked synergism with IL-4 in the induction of Fc epsilon RII/CD23. Heat-inactivation of serum did not affect the inducibility of Fc epsilon RII/CD23 by opsonized zymosan, suggesting the involvement of serum substances other than complement. Zymosan treated with human gamma-globulin also induced Fc epsilon RII/CD23, indicating the possible involvement of Fc gamma receptors. The Fc epsilon RII/CD23 inducing effect of opsonized zymosan was partially blocked by pretreatment with heat-aggregated human gamma-globulin or an anti-Fc gamma RI monoclonal antibody but not by the anti-Fc gamma RII or Fc gamma RIII antibody. Our results showed the involvement of signals from Fc gamma receptor associated phagocytosis in the induction of Fc epsilon RII/CD23.

CD23/Fc epsilon R11 expression in contact sensitivity reactions: a comparison between aeroallergen patch test reactions in atopic dermatitis and the nickel patch test reaction in non-atopic individuals

The immunopathology of patch test reactions to aeroallergens in patients with atopic dermatitis (AD) has been compared to that of contact sensitivity reactions to nickel in non-atopic individuals. Both reactions were found to exhibit equivalent erythema and induration on gross examination at 48 h. Four millimetre punch biopsies were obtained at 48 h frozen, and cryostat sections stained with a panel of MoAbs. The distribution of macrophages, dermal dendritic cells, Langerhans cells, T lymphocytes and the expression of CD23 antigen was recorded. Increased numbers of dermal dendritic cells, macrophages, T lymphocytes and Langerhans cells were found in the dermal infiltrates of both the nickel patch test reactions and the aeroallergen patch test reactions compared with their respective controls. There were no significant differences between atopic patch test reaction and nickel patch test reaction samples in the tissue distribution of these cell types. There was a significant increase in CD23 expression on Langerhans cells and dermal dendritic cells in the atopic patch test reactions, whereas an increase was only observed on dendritic cells in nickel patch test reactions. No significant difference in CD23 expression was observed in the control skin samples taken from patients with AD, nickel-sensitive patients and normal controls. This study supports the hypothesis that the aeroallergen patch test reaction in atopic dermatitis is a delayed hypersensitivity reaction, yet is distinct from the contact sensitivity reaction to nickel in terms of raised expression of CD23.

Fc epsilon receptor II/CD23+ lymphocytes in atopic dermatitis. III. Aberrant control in the in vitro expression of Fc epsilon RII/CD23 on peripheral blood T cells in atopic dermatitis

In vitro Fc epsilon RII expression was examined in patients with atopic dermatitis, those with non-atopic eczematous dermatitis and normal individuals following stimulation of peripheral blood cells with recombinant IL-4 (rIL-4), phytohaemagglutinin (PHA), or PHA plus rIL-2. At various days cells were stained with MoAbs to human lymphocyte Fc epsilon RII and to lymphoid cell-surface antigens and analysed by flow cytometry. rIL-4, but not rIL-2, specifically induced Fc epsilon RII on T cells as well as B cells in atopic dermatitis, eczematous dermatitis and normal individual groups. Both atopics and non-atopics generated comparable proportions of Fc epsilon RII+ T cells (T epsilon cells), whereas the frequency of B cells bearing Fc epsilon RII(B epsilon cells) was significantly higher in patients with extensive atopic dermatitis than in those with mild atopic dermatitis and other subjects. Comparable levels of T epsilon cells were detected in both atopic and non-atopic donors following stimulation of peripheral blood cells with PHA or pre-activation of the cells with PHA plus subsequent incubation with rIL-2. Whereas both CD8+ and CD4+ subsets were present in T epsilon cell populations induced specifically by rIL-4, PHA and PHA plus rIL-2, patients with atopic dermatitis had a greater tendency for Fc epsilon RII expression on CD8+ T cells compared with patients with eczematous dermatitis and normal individuals. Recombinant interferon-gamma (rIFN-gamma), but not rIFN-alpha or prostaglandin E2 (PGE2), suppressed the generation of T epsilon cells by rIL-4 in atopics and non-atopics to the same degree. These results suggest the aberrant control of Fc epsilon RII expression on T cells, especially those bearing CD8, in atopic dermatitis.