Synergistic effect of interleukin 1 and soluble CD23 on the growth of human CD4+ bone marrow-derived T cells.

Low-affinity Fc epsilon receptor (Fc epsilon RII/CD23) is expressed by various human cells and known to be cleaved into soluble fragments (sCD23). Several biological activities were ascribed to these molecules. In this study, we have assessed the effect of recombinant 25-kDa sCD23 (rsCD23) on human bone marrow-derived T cells. Our results show that rsCD23 in synergy with recombinant interleukin 1 enhances mitogenic responsiveness of CD4+ T cells but does not affect CD8+ cell growth. Furthermore, rsCD23 synergizes autologous marrow cells in enhancement of CD4+ cell growth while CD23 monoclonal antibodies decrease accessory cell effect. Together, these data confirm cytokine-like activity of sCD23 on human T cell lineage.     

Induction of Fc epsilon RII/CD23 on PHA-activated human peripheral blood T lymphocytes and association of fyn tyrosine kinase with Fc epsilon RII/CD23.

Despite the evidence for the expression of Fc epsilon RII/CD23, a glycoprotein that is a low-affinity Fc receptor for IgE, obtained on T cell lines and some pathological T cells, that of Fc epsilon RII/CD23 on normal human T cells is still unclear. We studied the emergence of T cells bearing Fc epsilon RII/CD23 in short-term culture of normal human peripheral blood mononuclear cells stimulated with 15 microliters/ml phytohemagglutinin (PHA). Using two-dimension flow cytometry, more than 10% of Fc epsilon RII/CD23(+) cells were shown to co-express CD3 antigen. Both CD4(+) and CD8(+) T cells expressed Fc epsilon RII/CD23. The expression of mRNA for Fc epsilon RII/CD23 on PHA and IL-4 stimulated PBMC was demonstrated by northern blotting and in-situ hybridization. The mechanism of signal transduction through Fc epsilon RII/CD23 was dissected by transfection of cDNA coding for Fc epsilon RII to the human natural killer-like cell line YT, activation of which was easily detected by the induction of interleukin-2 receptor/p55 (Tac). Cross-linking of Fc epsilon RII/CD23 with H107 anti-Fc epsilon RII monoclonal antibody enhanced IL-2R/p55 expression on YT cells transfected with Fc epsilon RII cDNA (YTSER). A possible involvement of protein-tyrosine kinase in the Fc epsilon RII-mediated signal transduction was studied using YTSER. Fc epsilon RII was physically associated with an src-family tyrosine kinase p59fyn and not with p56lck, which was also found in YT cells. Recently it was reported that p59fyn was associated with T-cell antigen receptor. Our results collectively suggest the multiple function of p59fyn which may be implicated in the Fc epsilon RII-mediated activation signal in YT cells.     

Effect of anti-IgE antibodies on IgE binding to CD23

Human sera contain anti-IgE autoantibodies. Using a human B lymphoblastoid cell line (Wil-2WT cells) and monoclonal murine anti-IgE antibodies (BSW17 and Le27) we investigated a possible role of such anti-IgE antibodies. A 100-fold excess of monoclonal anti-IgE antibodies inhibited binding of 125I labeled IgE to Fc epsilon RII on Wil-2WT cells. Further, both monoclonal anti-IgE antibodies dissociated surface bound IgE from Fc epsilon RII on Wil-2WT cells. However, BSW17 which does not trigger histamine release from human leucocytes, was much more effective in dissociating Fc epsilon RII bound IgE than Le27 which triggers histamine release. These results may suggest that naturally occurring IgG anti-IgE antibodies are able to inhibit binding of IgE to its receptor.     

Affinity-purified soluble Fc epsilon RII/CD23 derived from RPMI-8866 cells induces histamine release from human nasal polyp mast cells through a non-IgE-mediated mechanism.

Soluble Fc epsilon RII/CD23 (IgE-binding factor) is released spontaneously from activated B cells and most EBV-immortalised B cell lines. We have purified soluble Fc epsilon RII/CD23 from culture supernatants of RPMI-8866 cells on an IgE Sepharose column, and studied its ability to release histamine from human nasal polyp mast cells. Soluble Fc epsilon RII/CD23 induces release of a significant amount of histamine from nasal polyp mast cells in a dose-dependent manner. IgE, and a monoclonal antibody specific for the soluble form of this receptor, were shown to neutralise this effect. It was found that soluble Fc epsilon RII/CD23 was still capable of triggering histamine release from nasal polyp mast cells from which IgE had been eluted by incubation in a low pH buffer, suggesting that a non-IgE mediated mechanism was responsible for this effect.     

IgE-dependent antigen focusing by human B lymphocytes is mediated by the low-affinity receptor for IgE

In this study we investigated the role of the low-affinity receptor for IgE (Fc epsilon RII, CD23) on Epstein-Barr virus (EBV)-transformed human B cells in the uptake and presentation to T cells of antigen after complexing with IgE. Cloned EBV-transformed B cells were incubated for 5 h with (4-hydroxy-3-iodo-5-nitrophenyl)acetyl (NIP)-haptenized tetanus toxoid (NIP-TT) or NIP-TT complexed with a chimeric human IgE/mouse anti-NIP monoclonal antibody (IgE x NIP-TT) and then contacted for 2 min with autologous cloned TT-specific T cells. Intracellular Ca2+ mobilization in T cells was determined as an early indicator of T cell activation. The antigen-presenting capacity of B cells was significantly increased by complexing the antigen with IgE. This effect could be selectively reversed in a dose-dependent manner by blocking the Fc epsilon RII with an anti-CD23 monoclonal antibody. The IgE-mediated increased capacity for presenting antigen became particularly evident when B cells were incubated with NIP-TT or IgE x NIP-TT for only 1 h at 4 degrees C, washed and then cultivated for 6 h at 37 degrees C allowing uptake and processing of the antigen. These results indicate a new role of the Fc epsilon RII/CD23 molecules in the uptake of antigen by APC which might be of importance in the maintenance of an ongoing immune response against allergens.     

Allergen-directed expression of Fc receptors for IgE (CD23) on human T lymphocytes is modulated by interleukin 4 and interferon-gamma

T lymphocytes bearing Fc receptors (FcR) for immunoglobulins are known to have immunoglobulin class-specific regulatory functions. Here we report that expression on T cells of the low-affinity FcR for IgE (Fc epsilon RII/CD23) is preferentially induced by stimulation with antigens that cause an IgE response. T cells from eight patients allergic to the hemoglobin of Chironomus thummi thummi mosquito larvae (CHIT I) were analyzed for reactivity with the anti-FcERII/CD23 monoclonal antibody (mAb) M-L25 under various conditions. No Fc epsilon RII/CD23+ T cells were observed among freshly isolated, resting peripheral blood mononuclear cells (PBMC). Stimulation of PBMC with CHIT I, however, induced a marked although transient Fc epsilon RII/CD23 expression on a large portion of the allergen-activated T lymphocytes. It reached a maximum of 37.2 +/- 4.6% Fc epsilon RII/CD23+ T cell blasts on day 5 of culture. The selectivity of this expression became evident when compared to non-allergenic control antigens: after stimulation of PBMC with tetanus toxoid or purified protein derivative from tuberculin a maximum of 4.6% +/- 1.4% and 4.2% +/- 1.1% T cell blasts was found to express Fc epsilon RII/CD23, respectively. Activation by an anti-CD3 mAb was insufficient to induce Fc epsilon RII/CD23 on T cells. The allergen-stimulated Fc epsilon RII/CD23+ T cells exclusively belonged to the CD4+CD29+ helper inducer T cell subset. Using a cDNA probe coding for the B cell Fc epsilon RII/CD23, Northern blot analysis revealed a 1.7-kb Fc epsilon RII/CD23 mRNA in extracts of highly purified allergen-stimulated T cells. It was of the same size as Fc epsilon RII/CD23 mRNA of the lymphoblastoid B cell line WI-L2. Of several cytokines tested [interleukin (IL) 1 to IL 6, interferon-gamma (IFN-gamma), tumor necrosis factor-alpha] only IL 4 and IFN-gamma significantly modified allergen-induced Fc epsilon RII/CD23 expression on T cells. The latter was enhanced nearly twofold in the presence of IL 4, and was almost completely abrogated by IFN-gamma. IL 4, however, could not increase the number of Fc epsilon RII/CD23+ T lymphocytes either alone or in combination with an anti-CD3 mAb. Taken together, the selective induction of Fc epsilon RII/CD23 on T cells by allergen and its inclusion in the regulatory network of cytokines point to an important role of Fc epsilon RII/CD23+ T lymphocytes in the human IgE response.     

Biology and chemistry of low affinity IgE receptor (Fc epsilon RII/CD23).

Recent studies have established that the low affinity Fc receptor for IgE (Fc epsilon RII/CD23) is a structurally and functionally unique immunoglobulin receptor. DNA sequence analysis predicts that, in contrast to other FcR, Fc epsilon RII is not a member of the immunoglobulin gene superfamily and, indeed, is inserted into the membrane in opposite orientation from most other membrane proteins. While the Fc epsilon RII of macrophages, eosinophils, and platelets mediate IgE-dependent cytotoxicity and promote phagocytosis of IgE-antigen complexes, the function of Fc epsilon RII on B lymphocytes remains unclear. Much effort has been directed toward establishment of its role in IgE regulation, but the plurality of B cell Fc epsilon RII expression, i.e. greater than 90% of the mu + /delta + B lymphocytes, is incongruous with simply a role in regulating only IgE responses. Hence, the discovery that Fc epsilon RII is identical to the B-cell activation antigen, CD23, together with its novel structural features, suggests an additional more important role for this interesting protein and would explain the disparity between a commonly expressed receptor with apparently limited functions.     

Direct demonstration of binding of aggregated mouse IgG1 to the 40-kDa Fc receptor for IgG (Fc gamma RII) in both high and low responders.

Several directly fluorochrome-conjugated murine monoclonal antibodies (mAb) of the IgG1 subclass and directed against B or T cell antigens were found to bind to monocytes via the 40-kDa Fc receptor for IgG (Fc gamma RII). As expected from the established polymorphism of Fc gamma RII, strong staining was observed in about 75% of individuals. In the remaining 25% staining was clearly weaker, but could be definitely demonstrated with a mAb against the B cell-specific CD19 differentiation antigen. Specificity of binding to Fc gamma RII was confirmed by the ability to block the binding of the CD19 mAb by pre-incubation with aggregated IgG1 or with mAb against Fc gamma RII. The extent of T cell proliferation induced with a CD3 mAb of the IgG1 isotype (a-Leu 4), which is dependent on the interaction of monocyte Fc gamma RII with the Fc portion of the CD3 mAb, exactly correlated with the amount of binding to Fc gamma RII in all individuals. Proliferation was dose-dependent for both high and low responders; cells of low responders did not proliferate at concentrations below 16 ng/ml of mAb, whereas there was a small but unequivocal proliferation at higher concentrations. These results confirm that monocytes from previously characterized "non-responders" are able to bind aggregated murine IgG1 via Fc gamma RII. They also demonstrate that directly labeled mAb can cause extensive nonspecific staining which may not be excluded by the use of control antibodies of the same isotype.     

Development and characterization of a human monoclonal antibody probably detecting the leukocyte differentiation antigen CD39

A human monoclonal IgM antibody, referred to as TU223, has been produced. The reactivity of TU223 was tested in various cells and cell lines by complement-dependent microcytotoxicity test and fluorescence-activated cell sorter analysis. The antigen defined by TU223 was expressed on Epstein-Barr virus-transformed B-cell lines and on some Burkitt's lymphoma cell lines, but was not expressed on normal T cells, B cells or erythrocytes. In addition, expression of the antigen defined by TU223 was also induced on B cells activated by Epstein-Barr virus or pokeweed mitogen, and on T cells activated by phytohemagglutinin, concanavalin A, pokeweed mitogen or recombinant interleukin-2. However, no expression of the antigen detected by TU223 was induced at all on recombinant interleukin-4-treated B cells or macrophage-like cell line U937. When the ability of TU223 and various mouse monoclonal antibodies to bind to human differentiation antigens was compared, interestingly, the reactivity of TU223 was found to be very similar to that of mouse monoclonal antibody CD23 (H107), which reacts with Fc epsilon receptor II. Two-color analysis revealed that the antigen defined by TU223 is expressed on the cell surface of certain lymphoid cells expressing CD23 antigen. However, it can be concluded that the antigen defined by TU223 is clearly distinct from Fc epsilon receptor II, based on assay of cross-blocking between H107 and TU223. The surface antigen on B85 cells recognized by TU2232 had the molecular size of 80-82 kiloDaltons as determined by immunoblotting analysis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Production and characterization of two murine monoclonal antibodies directed against epitopes exclusive to soluble fragments of FcεRII/CD23

Two murine monoclonal antibodies (mAb) designated as SU1 and SU3 directed against soluble FcεRII/CD23 have been generated by fusing X.63.AG.8653 (a mouse myeloma cell line) with spleen cells from mice immunized with an Epstein Barr virus (EBV)-transformed B cell line (RPMI-8866). The antibodies have been shown to be capable of detecting affinity purified soluble FcεRII/CD23 in an enzyme-linked immunosorbent assay. Indirect immunofluorescence has shown that the SU1 and SU3 mAb do not stain RPMI-8866, a FcεRII/CD23⁺ B cell line. By studying the migration profiles of affinity purified SU1- and SU3-reactive molecules on sodium dodecylsulfate-polyacrylamide gel electrophoresis it has been shown that SU1 mAb immunoprecipitates 33- and 12-kDa components, while the SU3 mAb recognized 25- and 45-kDa proteins from culture supernatants of RPMI-8866 cells. Moreover, affinity purified SU1- and SU3-reactive proteins have been shown to be recognized by human IgE but not by the human IgG molecule. These results provide evidence that SU1 and SU3 mAb may recognize some putative post-cleavage epitopes on the N-terminal end of the low affinity receptor which appear, perhaps, following the process of fragmentation. In addition, the effect of these antibodies on continuous growth of a panel of lymphoblastoid cell lines indicates that SU1 mAb was found incapable of influencing the spontaneous proliferation of EBV-immortalized B cell lines; whereas SU3 mAb completely blocked the spontaneous growth and proliferation of all B cell lines tested. The results are discussed in relation to the appearance of a functional post-cleavage epitope on soluble FcεRII/CD23.     

Pharmacological modulation of the antigen-induced expression of the low-affinity IgE receptor (Fc epsilon RII/CD23) on rat alveolar macrophages.

Brown-Norway (BN) rats were sensitized by 3 aerosol exposures to ovalbumin (OA; 10 mg/ml) at days 1, 3 and 14. At day 21, the rats were challenged with the antigen or vehicle by aerosol. Alveolar macrophages (AM) were obtained by bronchoalveolar lavage and the expression of Fc epsilon RII/CD23 was assessed by flow cytometry after staining with the BB10 monoclonal antibody. A maximum of 74% of the AM from sensitized and challenged BN rats expressed FC epsilon RII/CD23 24 h after OA exposure, compared to 12% of the cells from rats exposed to vehicle. Sprague-Dawley rats were passively sensitized by intravenous injection of 0.1 or 0.05 ml/kg mouse ascitic fluid containing dinitrophenyl (DNP)-specific monoclonal IgE (2682-1) and after 24 h exposed to an aerosol of 5 mg/ml of DNP-bovine serum albumin for 30 min. In this case also, antigen exposure induced the expression of Fc epsilon RII/CD23 on 75% AM, compared to 17% AM from saline-challenged rats. Such an induction of Fc epsilon RII/CD23 on AM was, however, not observed when the animals were challenged with either histamine, serotonin or acetylcholine by aerosol. The antigen-induced expression of Fc epsilon RII/CD23 on AM was inhibited upon treatment of the rats with ketotifen or beclomethasone. In addition, oral or aerosol administration of respectively BN 50730 or BN 52021 (two structurally unrelated platelet-activating factor antagonists), inhibited the antigen-induced Fc epsilon RII/CD23 expression on AM, indicating the participation of this lipid mediator in this process.     

Synovial T lymphocyte recognition of organisms that trigger reactive arthritis.

To clarify the differential state of B cell activation in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), we investigated the expression of low-affinity receptor for IgE (Fc epsilon RII; CD23) on their peripheral B cells by a cytofluorometry using H107 (CD23) and Leu-16 (CD20) monoclonal antibodies. The percentage of CD23-negative B cells in total lymphocytes was significantly greater in both groups of patients than in normal subjects, suggesting the hyperactivity of late-phase B cells in both diseases. However, the increase of CD23-negative B cells in RA was brought about by the increased number of total B cells, although that in SLE was mainly based on the relative decrease of CD23-positive B cells. The number of IgD-positive B cells was decreased, and the number of colony-forming B cells was markedly increased in SLE patients. These observations indicate that a B cell abnormality is mainly qualitative in SLE but quantitative in RA.     

Fcγ receptor II dependency of enhanced presentation of major histocompatibility complex class II peptides by a B cell lymphoma

Here we show that the B cell lymphoma A20.292 is capable of enhanced antigen presentation to CD4⁺ T cells in the presence of specific antibodies. This enhancement was inhibited by anti-Fcγ receptor (R) antibodies, suggesting that it might be due to preferential uptake of the antigen/antibody complex through the FcγRII receptor. However, immunoprecipitation studies revealed that the FcR of A20.292 cells was of the B cell type, FcγRIIb1, which is not thought to be able to internalize antigen/antibody complexes via clathrin-coated pits. It was considered unlikely that A20.292 had an altered form of the B cell FcγR (RIIb1) receptor that enabled internalization, since similar enhancing effects were also observed using an FcγRII^? cell line that had been transfected with FcγRIIb1. To reconcile these findings with the expression of FcγRIIb1, it is postulated that immune complexes are concentrated on the cell surface by the FcγRIIb1 and are thus available for preferential uptake by random fluid-phase endocytosis. This results in more efficient generation of the epitopes recognized by these T cell hybridomas.     

Induction and function of Fc epsilon RII on YT cells; possible role of ADF/thioredoxin in Fc epsilon RII expression.

The regulation of low-affinity Fc receptor for IgE (Fc epsilon RII) and the characteristics of both membrane and soluble forms of Fc epsilon RII were studied using YT cell line. We found that YT cells, a human NK like cell line, expressed Fc epsilon RII after IL-1 stimulation. Cross-linking of Fc epsilon RII on IL-1-stimulated YT cells as well as the transfectant of Fc epsilon RII-cDNA (YTSER) resulted in the up-regulation of IL-2R alpha (p55/Tac). A 59 kDa protein phosphorylated at tyrosine residues was co-immunoprecipitated with Fc epsilon RII from YTSER lysate using H107 anti-Fc epsilon RII mAb. YTSER not only expressed Fc epsilon RII on their surface but also secreted soluble form of Fc epsilon RII (sFc epsilon RII/sCD23; IgE binding factor). Affinity purification revealed that sFc epsilon RII released from YTSER is heterogeneous and consisted of several proteins differing in molecular weight. Both EBV+ B cells and HTLV-1+ T cells are high producers of ATL derived factor (ADF)/thioredoxin (TRX) and express Fc epsilon RII and IL-2R alpha respectively. To clarify the mechanism of Fc epsilon RII and IL-2R alpha induction by ADF/TRX, we examined the effect of ADF/TRX on the bindability of nuclear factor kappa B (NF-kappa B), which is known to regulate IL-2R alpha gene expression. In the gel shift assay, ADF/TRX was shown to enhance the bindability of NF-kappa B to its responsive element.     

Isolation and characterization of IgE receptors from rat intestinal mucosal mast cells

High-(Fc epsilon RI) and low-(Fc epsilon RII) affinity IgE receptors were isolated from surface radioiodinated, Nonidet-P40-solubilized rat intestinal mucosal mast cells (IMMC) and compared with those on rat peritoneal mast cells (PMC) and rat basophilic leukemia (RBL) cells. Fc epsilon RII were isolated by affinity chromatography using IgE-Sepharose or by anti-Fc epsilon RII antisera and protein A-Sepharose. The surface-exposed, IgE-binding alpha subunits of Fc epsilon RI [Fc epsilon RI alpha] were isolated by affinity chromatography using IgE and anti-IgE-Sepharose. Fc epsilon RI alpha on IMMC had an apparent molecular mass of 59 kDa, somewhat larger than that of PMC (51 kDa), RBL-2H3 cells (51 kDa) or RBL-CA10.7 cells (46 kDa). Brief (45 s) incubation of IMMC or PMC in glycine-HCl, pH 3, prior to iodination removed much of the surface-bound IgE. This permitted more thorough labeling of the receptors, but had no affect on the estimate of receptor size. Surprisingly and in contrast to acid-treated PMC, upon anti-IgE-Sepharose isolation acid-treated IMMC yielded an intensely radioactive Fc epsilon RI alpha band in the absence of added IgE. Such a finding suggests that IMMC, more so than PMC, may have an intracellular store of IgE, as has been suggested by many others. IMMC also differed from PMC in the number of forms of Fc epsilon RII isolated; 50-kDa and 58-kDa forms of Fc epsilon RII were obtained from IMMC, whereas PMC yielded most often a single 56-kDa Fc epsilon RII band. These results were mimicked by the two RBL cell sublines: RBL-2H3 cells yielded two Fc epsilon RII (46 kDa and 55 kDa), but only one form of Fc epsilon RII (54-kDa) was obtained from RBL-CA10.7 cells. Thus, the two subtypes of rat mast cells, which have previously been shown to differ in mediator profile and responsiveness to secretagogues and antiallergic drugs, are also distinguished by differences in IgER profile.     

Characterization of new rat anti-mouse IgE monoclonals and their use along with chimeric IgE to further define the site that interacts with Fc epsilon RII and Fc epsilon RI.

Three rat monoclonal antibodies specific for mouse IgE (C12B9, 23G3, and B1E3) were established by using monoclonal anti-DNP mouse IgE (mIgE) as immunogen. These antibodies, as well as a fourth, (R1E4) were characterized. It was found that one antibody (C12B9) recognizes an allotypic determinant (Igh-7a) found on the C epsilon chain of mIgE. Antibody cross-blocking studies and epitope mapping studies using recombinant mIgE indicated that 3 antibodies (C12B9, R1E4 and 23G3) were directed against the C epsilon 3 domain while one (B1E3) was directed against the C epsilon 4 domain. A highly specific sandwich RIA for mIgE was developed using these antibodies. Use of these monoclonal anti-mIgE antibodies in conjunction with recombinant chimeric mIgE-human IgG1 molecules, demonstrated that the C epsilon 3 domain is important in the binding of mIgE to the murine B cell Fc epsilon RII as well as to the murine mast cell F epsilon RI. The presence of the C epsilon 4 domain influenced the binding of the recombinant IgE to the Fc epsilon RII; in contrast to the C epsilon 4 domain had no effect on binding to the Fc epsilon RI.     

Interferon and (2'-5')oligoadenylate enhance the expression of low affinity receptors for IgE (Fc epsilon R2/CD23) on the human monoblast cell line U937

The regulation of low affinity IgE receptor (Fc epsilon R2/CD23) expression on the human monoblast cell line U937 was examined by an anti-Fc epsilon R2/CD23 monoclonal antibody (H107) and the cDNA probe for Fc epsilon R2/CD23. Alpha interferon (IFN-alpha) and its intracellular mediator, (2'-5')oligoadenylate (2, 5-A), induced Fc epsilon R2/CD23 expression on U937 with no significant increase of the Fc epsilon R2/CD23 mRNA. PMA and IFN-gamma increased both surface Fc epsilon R2/CD23 expression and the Fc epsilon R2/CD23 mRNA levels. IFN-alpha effectively induced 2, 5-A synthetase activity in U937 cells, whereas IFN-gamma induced little. The results suggest that the mechanisms of enhancement of Fc epsilon R2/CD23 expression on U937 cells by IFN-alpha and IFN-gamma are different and that 2, 5-A may play an important role in the Fc epsilon R2/CD23 expression on U937 cells induced by IFN-alpha.     

Fc epsilon receptor II/CD23-positive lymphocytes in atopic dermatitis. I. The proportion of Fc epsilon RII+ lymphocytes correlates with the extent of skin lesion.

Cells expressing Fc receptors for IgE (Fc epsilon RII) were identified in the peripheral blood from patients with atopic dermatitis and with eczematous dermatitis, and normal non-atopic subjects by using monoclonal antibodies to human lymphocyte Fc epsilon RII, and to lymphoid cell-surface antigens by immunofluorescence staining. Based on the extent of the dermatitis patients were classified as severe (greater than 50% skin surface involved), moderate (50-10%) and mild (less than 10%). Patients with severe and moderate atopic dermatitis had 5.9% and 5.7% Fc epsilon RII+ peripheral blood mononuclear cells (PBMC), respectively, that were significantly higher than percentages in mild atopic dermatitis patients (2.6%), severe to moderate eczematous dermatitis patients (2.3%), mild eczematous dermatitis patients (2.2%) and normal individuals (1.7%)(0.05 greater than P). In severe and moderate atopic dermatitis patients, 10% of Fc epsilon RII+ PBMC were T cells that preferentially expressed CD8, and the remainder B cells and monocytes. Fc epsilon RII+ T cells comprised 1% of peripheral T cells, while half or more of peripheral B cells expressed Fc epsilon RII. In mild atopic dermatitis patients, eczematous dermatitis patients and normal subjects. Fc epsilon RII were expressed exclusively on 25-35% of peripheral B cells. Short-term treatment and long-term follow-up of atopic dermatitis patients revealed that changes in the skin condition were related closely to fluctuations in the proportion of Fc epsilon RII+ PBMC. Total serum IgE levels and atopic respiratory allergy did not influence the percentage of Fc epsilon RII+ PBMC. These findings suggest that the percentage of Fc epsilon RII+ PBMC reflects the extent of atopic dermatitis.     

Soluble Fc gamma receptors II (Fc gamma RII) are generated by cleavage of membrane Fc gamma RII.

This study describes the production of soluble Fc gamma RII by a cell line, D1B1, obtained by transfection of mouse L cells with a murine beta 1 Fc gamma RII cDNA. Upon incubation at 37 degrees C, radioiodinated D1B1 cells release a 39-kDa soluble Fc gamma RII, reacting with the rat anti-mouse Fc gamma RII monoclonal antibody 2.4G2, and binding to mouse IgG2a, IgG2b and IgG1 but not IgG3. In contrast to the transmembrane 50- to 70-kDa receptor, this soluble Fc gamma RII does not react with antibodies directed against a peptide corresponding to the 15 carboxy-terminal intracytoplasmic amino acids of beta Fc gamma RIII. N-Glycosidase F treatment generates a 18-kDa polypeptide. A 32- to 40-kDa soluble Fc gamma RII, which resolves into 18.5- and 20-kDa polypeptides after deglycosylation, was also isolated from the culture medium of unlabeled D1B1 cells. Therefore, this study indicates that soluble Fc gamma RII corresponding to the two extracellular domains of Fc gamma RII are generated by cleavage of membrane Fc gamma RII. Proteolysis occurs most probably at the vicinity of the transmembrane region of the receptor, around amino acids 165 to 180.     

Tumour necrosis factor-alpha augments the expression of Fc IgE receptor (Fc epsilon RII/CD23) on human monocytic cell lines and down-regulates interleukin-4-driven Fc epsilon RII expression on monocytes.

We investigated the expression of the low affinity Fc IgE receptor (Fc epsilon RII/CD23) on the human monocytic cell lines U937, THP-1, Mono-Mac-6, and cultured human peripheral blood monocytes under stimulation with human tumour necrosis factor-alpha (TNF-alpha) and other cytokines. Fc epsilon RII was demonstrated by flow cytometry analysis employing the anti-Fc epsilon RII monoclonal antibody 3-5. TNF-alpha alone had a weak but significant stimulating effect on the Fc epsilon RII expression on the cell lines U937 and THP-1, and very modestly on Mono-Mac-6 cells. TNF-alpha strongly synergized with interferon-gamma (IFN-gamma) and interleukin-4 (IL-4). IFN-alpha per se was ineffectual, but was able to increase the TNF-alpha effect. Furthermore, the action of TNF-alpha was slightly augmented by human IL-6. Similar effects were noted with TNF-beta alone or in combination with other cytokines. Interestingly, on human monocytes TNF-alpha weakly reduced the basal level of Fc epsilon RII, and markedly diminished the IL-4-induced Fc epsilon RII expression. Our results indicate that several cytokines may interact in a cytokine network to modulate Fc epsilon RII expression on monocytic cell lines. On human blood monocytes, TNF-alpha, like IFN-gamma or IL-6, counteracts the IL-4-induced Fc epsilon RII expression. These data suggest different regulatory pathways of Fc epsilon RII expression on blood monocytes and myelomonocytic cell lines.