Kwang-Myong Kim

Soluble Low Affinity Fc Receptors for IgE in the Serum of Allergic and Nonallergic Children

ABSTRACT: IgE-binding factors are thought to have regulatory activity in in vitro IgE synthesis. To obtain evidence of the participation of IgE-binding factors in in vivo IgE synthesis, the serum level of low affinity Fc receptors for IgE (sFceRII) (IgE-BFs) was examined in 41 nonallergic children and in 37 allergic children whose serum IgE levels were significantly higher than those of nonallergic children. The serum level of sFceRII showed a marked age-dependent variation. It was highest in infants and then decreased gradually with age. The serum level of sFceRII in allergic children was significantly higher than that of nonallergic children in early childhood (1128.0 ± 323.8 vs 777.3 ± 227.0 pg/ml, p<0.01 in infants (<1 y) and 851.8 ± 270.0 vs 579.4 ± 197.1 pg/ml, p<0.05 in children aged 1-2 y) but not in older children (3-15 y). Three allergic infants (<1 y) with serum sFceRII levels higher than the mean + 1 SD (1451.8 pg/ml) of all allergic infants (<1 y) had serum IgE levels (geometric mean 125.9 IU/ml) significantly higher than the other seven allergic infants (<1 y) (geometric mean 5.6 IU/ml, p<0.05). A close positive correlation between the serum level of sFceRII and the absolute number of FceRII(+) peripheral blood lymphocytes was observed (Spearmans rank correlation coefficient = 0.79, p<0.001 in 27 allergic and Spearmans rank correlation coefficient = 0.72, p<0.001 in 19 nonallergic children). In conclusion, serum sFceRII may be derived mainly from FceRII(+) lymphocytes, and may have relationship to the increased production of IgE in early childhood (0-2 y).

Regulation of Fcϵ receptor 2 (CD23) expression on a human eosinophilic cell line EoL3 and a human monocytic cell line U937 by transforming growth factor β

Abstract Regulation of low-affinity receptors for IgE (Fc ϵ R 2 /CD23) on a human eosinophilic cell line EoL3 and a human monocytic cell line U937 was studied using an anti-Fc ϵ R 2 /CD23 monoclonal antibody H107 by flow cytometry. While platelet-activating factor, interleukin 4, and interferon γ significantly augmented Fc ϵ R 2 /CD23 expression on both cell lines, transforming growth factor β (TGFβ) inhibited both the basal level of Fc ϵ R 2 /CD23 expression and the enhanced Fc ϵ R 2 / CD23 expression induced by these reagents in dose- and time-dependent manners. However, TGFβ did not significantly suppress the high basal level of Fc ϵ R 2 /CD23 expression on RPMI 8866 cells. These results suggest that Fc ϵ R 2 /CD23 expression on EoL3 and U937 cells is regulated by various cytokines and growth factors, and that TGFβ plays an important regulatory role in IgE-mediated immune responses.

Mechanisms involved in the inhibition of growth of a human B lymphoma cell line, B104, by anti-MHC class II antibodies

The mechanisms involved in the inhibition of growth of a human B lymphoma cell line, B104, by anti‐MHC class II antibodies (Ab) were compared with those in anti‐IgM Ab‐induced B104 growth inhibition. Two anti‐MHC class II Ab, L227 and 2.06, inhibited the growth of B104 cells, although 2.06, but not L227, needed to be further cross‐linked with a goat anti‐mouse IgG Ab (GAM) to show the effect. L227 induced an increase in intracellular free Ca2+ concentration ([Ca2+]i) from the intracellular pool and little or no protein tyrosine phosphorylation. phosphatidyl inositol turnover, or expression of Egr‐1 mRNA, whereas 2.06 plus GAM induced an increase in [Ca2+]i from both the intracellular and, in particular, the extracellular pools. The inhibition of B104 cell growth induced by anti‐MHC class II Ab was Ca2+ ‐independent and not inhibited by actinomycin D or cyclosporin A, and cell cycle arrest at the G2/M interphase was not observed. These features are very different from those observed in B104 cell death induced by anti‐IgM Ab. Neither DNA fragmentation nor the morphology of apoptosis was observed. These findings demonstrate that cross‐linking of MHC class II molecules transduced the negative signals through intracellular mechanisms different from those present in the cross‐linking of surface IgM.

Cyclosporin A and FK506 block the negative signaling mediated by surface IgM cross-linking in normal human mature B cells.

Cross-linking of surface IgM (sIgM) or sIgD by anti-IgM Ab or anti-IgD Ab, respectively, induced DNA synthesis in peripheral blood B cells (PBL-B). Cell division, determined by the increase in the number of M phase cells, was also induced when PBL-B were stimulated with anti-IgD Ab plus IL-4 or Staphylococcus aureus Cowan I (SAC), but far less by stimulation with anti-IgM Ab plus IL-4. Anti-IgM Ab did not suppress the DNA synthesis induced by SAC or anti-IgD Ab plus IL-4, but it did suppress the cell division induced by them. Thus, sIgM cross-linking generates both positive and negative signaling to B-cell proliferation. Cyclosporin A (CSA) and FK506 suppressed DNA synthesis and cell division at relatively high concentrations. On the other hand, CSA and FK506 at lower concentrations blocked the anti-IgM Ab-generated inhibition of cell division without affecting DNA synthesis. Low concentrations of CSA did not affect the cell division induced by anti-IgD Ab plus IL-4 but did increase the cell division induced by SAC or anti-IgM Ab plus IL-4, suggesting that stimulation with SAC, as well as with anti-IgM Ab plus IL-4, generates both positive and negative signals to cell division, whereas sIgD lacks the ability to transduce negative signaling.

Prediction of the development of atopic symptoms in early childhood by cord IgE-binding factors (soluble FcϵR2)

The relationship of cord serum sFcϵR2 levels to the development of atopic symptoms in early childhood was studied. Cord sFcϵR2 was 444.2±235.1 pg/ml (n = 77), which was not significantly different from maternal serum sFcϵR2 (541.7±346.9 pg/ml, n = 42). However,there was no correlation between cord and maternal serum sFcϵR2, suggesting that most, if not all, of cord serum sFcϵR2 was produced by the fetus itself. Cord serum sFcϵR2 in infants who developed atopic symptoms later was significantly higher than that in infants who were free of atopic symptoms (P<0.01 at 7 and 13 months of age). The incidence of the development of atopic symptoms increased with the increase of cord serum sFcϵR2. These results suggest that sFcϵR2 is related to the development of atopic disorders and that the measurement of cord serum sFcϵR2 may be of value in predicting the development of atopic disorders in early childhood.

Negative signaling in B cells by surface immunoglobulins

Cross-linking of surface immunoglobulins generates negative signals that cause B-cell death unless appropriate rescue signals are provided. Surface IgM is the main transducer of the negative signaling, but surface IgD and IgG may also transduce negative signaling when cross-linked intensively. In the surface IgM+, IgD+ human malignant B lymphoma cell lines B104 and DND-39, cross-linking of surface IgM by anti-IgM antibodies induced cell death. Anti-IgM antibody-induced B104 cell death was inhibited by stimulation with alpha- and beta-interferons but not stimulation with anti-CD40 antibody or IL-4, whereas anti-IgM antibody-induced DND-39 cell death was inhibited by stimulation with anti-CD40 antibody but not stimulation with alpha- and beta-interferons. Anti-IgM antibody-stimulated B104 cells had morphologic features compatible with necrosis, whereas anti-IgM antibody-stimulated DND-39 cells showed morphologic features of apoptosis. CD11a/CD54-dependent cell adhesion induced by stimulation with anti-CD40 antibody was involved in anti-CD40 antibody-mediated inhibition of anti-IgM antibody-induced DND-39 cells. In normal human mature B cells, cross-linking of surface IgM induced different signaling consequences, including DNA synthesis or cell division (positive signaling) or cell cycle arrest or death (negative signaling). In this system, too, CD40-transduced signal inhibited anti-IgM antibody-induced negative signaling, and CD11a/CD54-dependent cell adhesion played a role in the rescue process. It is suggested that quantitatively different intensities of surface IgM cross-linking induce qualitatively different signaling consequences; relatively weak cross-linking may induce DNA synthesis; moderate cross-linking may induce DNA synthesis with cell cycle arrest at the G2/M interphase; and intense cross-linking may induce apoptotic cell death. The reasons for this difference are not yet known. Further elucidation of the molecular mechanisms responsible for surface IgM-mediated negative signaling and its rescue signaling may contribute toward development of therapy for allergic disorders by artificial modulation of specific immunoglobulin production.

IgE receptor-bearing lymphocytes in allergic and nonallergic children.

ABSTRACT: Using a monoclonal anti-human IgE receptor (FceR) antibody, the percentage of FceR(+) cells among peripheral blood lymphocytes in children with or without allergic disorders was determined. The percentage of FctR(+) cells in 63 nonallergic children was 4.3 ± 1.5%, which did not vary with age and was equal to that of adults (4.2 ± 1.2%). Allergic younger children (0–2 yr) showed a significantly higher percentage of FceR(+) cells (7.7 ± 3.0%) than nonallergic younger children (0–2 yr) (4.0 ± 1.3%, p < 0.001). Similarly, in allergic younger children, serum IgE levels (geometric mean = 58.9 IU/ml) were also significantly higher than those of nonallergic younger children (geometric mean = 2.0 IU/ml) (p < 0.01). A positive correlation between the percentages of FccR(+) cells and serum IgE levels was observed (Spearman rank = 0.88, p < 0.01)) in eight allergic younger children (0–2 yr) with serum IgE levels higher than 100 IU/ml. The increase in the percentage of FctR(+) cells in allergic younger children (0–2 yr) was not a secondary phenomenon caused by serum IgE because serum IgE levels in these children were much lower than the concentration at which IgE enhance FceR expression on lymphocytes. In conclusion, FceR(+) lymphocytes may play a regulatory role in IgE synthesis in allergic younger children (0–2 yr).

Regulation of Fcγ receptor subtype expression on a human eosinophilic leukemia cell line EoL-3: Participation of cAMP and protein kinase C in the effects of interferon-γ and phorbol ester☆

Abstract We investigated the effects of interferon-γ (IFN-γ), phorbol myristate acetate (PMA), and dibutyryl cAMP (Bt2cAMP) on FcγR subtype expression on a human eosinophilic leukemia cell line, EoL-3. Unstimulated EoL-3 cells expressed FcγRII as determined by monoclonal antibody (mAb) IV-3, whereas there was little or no FcγRI and FcγRIII expression as determined by mAbs 32.2 and 3G8, respectively. IFN-γ induced FcγRI expression, and Bt2 cAMP, which did not induce FcγRI expression by itself, showed an additive effect on IFN-γ-induced FcγRI expression. FcγRII expression was augmented by IFN-γ, PMA, and Bt2 cAMP. Bt2 cAMP also showed an additive effect on IFN-γ-augmented FcγRII expression. FcγRIII expression could be induced only by IFN-γ plus Bt2 cAMP. H-7, a protein kinase C (PK-C) inhibitor, suppressed the enhancement of FcγR subtype expression induced by these reagents. These results show that FCγR subtype expression on EoL-3 cells is regulated differently in each subtype and that cAMP and PK-C play important roles in the regulation.

IgE, IL4, and soluble FcɛRII in the serum of atopic and nonatopic children

We correlated serum IgE, interleukin 4 (IL4) and soluble low affinity Fc receptor for IgE (sFcɛRII) in atopic and nonatopic children. Serum sFcɛRII was significantly higher in atopic than in nonatopic children (0‐2 yr). Serum sFcɛRII correlated closely with serum IgE in infants, but not in older children. To study further the characteristics of IgE synthesis in infants, we measured the serum level of IL4, which has been demonstrated to enhance the production of both IgE and sFcɛRIIin vitro. Serum IL4 was significantly higher in atopic than in nonatopic infants, but there was no significant difference between atopic and nonatopic older children. These results suggest that IL4 plays an important role in the regulation of IgE synthesis in infants and that IgE synthesis in older children might be modulated by other factors.

Positive and negative signals transduced through surface immunoglobulins in human B cells

Cross-linking of surface IgM and surface IgD by anti-IgM antibodies and anti-IgD antibodies, respectively, showed different effects on the growth of normal human peripheral blood B cells and the human B lymphoma cell line, B104. Only cross-linking of surface IgM transduced signals that inhibited cell division of peripheral blood B cells and B104 cells at the G2/M interphase. In B104 cells, the inhibition of cell division was followed by rapid B104 cell death. The negative signals were inhibited by cyclosporin A and FK-506 at lower concentrations than those that inhibited proliferation of the B cells. Anti-IgM antibody-induced B104 cell death was dependent on Ca2+ influx and macromolecular synthesis. B104 cells treated with anti-IgM antibodies showed neither DNA fragmentation or morphology of apoptosis but showed DNA single-strand breaks and morphology of necrosis. Nicotinamide inhibited anti-IgM antibody-induced B104 cell death and the involvement of poly(adenosine diphosphate-ribosyl)ation was suggested in the process of the B104 cell death. With regard to the intracellular mechanisms responsible for the different signals, however, no qualitative difference was detected in putative signal transducers, including tyrosine phosphorylated protein, phosphatidyl inositol turnover, Ca2+ influx, activation of protein kinase C, and messenger ribonucleic acid expression of c-fos and Egr-1 when surface IgM and surface IgD were crosslinked. Further investigations of the mechanisms responsible for the different signals transduced through surface IgM and surface IgD will provide better understanding of immunodeficiencies and autoimmune diseases.