Biological Significance of Fc Receptor-Bearing Cells Among Activated T Lymphocytes

Lethally irradiated mice injected with syngeneic thymocytes and immunized with protein antigens develop specific helper T cells. If injected with semiallogeneic thymocytes, such mice generate H-2 antigen-specific cytotoxic T cells. Most spleen cells from these chimeric mice possess Fc receptors The present results demonstrate that the development of Fc-rcceptor-bearing cells in thymocyte injected irradiation chimeras seemingly is due to the physiological conditions in the mice rather than to the specific immunization. As a corollary, both helper T cells and cytotoxic T tells did not have Fc receptors, at least not in their effector state. Thus, Fc receptors on T cells would seem irrelevant to their immune function.     

Suppressor Activity of T Cells Bearing Fc Receptors for IgG on Lymphoid Colony Formation

Human T lymphocytes, upon phytohaemagglutinin stimulation, are able to form colonies in semisolid media. Peripheral T cells bearing Fc receptors (T_G) were studied for their possible regulatory activity on lymphoid colony development. Although no substantial differences were observed between the cloning efficiency of unfractionated T cells (thus including T_G cells) and T cells depleted of T_G, a sharp suppression of colony formation occurred when positively selected T_G cells were readded to T_G-depleted suspensions. Therefore, T_G suppressor activity seems to be strictly dependent upon cell interaction with ox IgG immune complexes used for T_G cell isolation. Different experimental approaches failed to demonstrate, although did not exclude, that suppression in this system is mediated by soluble factors, γ-irradiation of T_G cells abrogated their suppressor capacity.     

Binding of Fc Receptors on Blood T and B Cells with IgG from Healthy Cows and Cows with Chronic Lympholeukemia

Pure population of T and B cells was obtained by a combined method consisting in lymphocyte fractionation through Nylon wool and precipitation of E-rosettes in 17% Verograffin density gradient. Scatchard analysis showed that T and B cells isolated from the blood of healthy cattle bind similar quantities of IgG molecules. Binding of IgG to Fc receptors of T and B cell isolated from animals with chronic lympholeukemia increases. The expression of Fc receptors for IgG is changed in cattle with chronic lympholeukemia.     

Increased Numbers of Suppressor-Cytotoxic Cells in a Patient with Carbamazepine Hypersensitivity

A patient is presented with a clinical syndrome of erythroderma, fever, liver function abnormalities, eosinophilia and atypical lymphocytosis due to carbamazepine hypersensitivity. Immunological analysis of peripheral blood mononuclear cells was performed using mouse monoclonal antibodies against T-cell and Ia antigens. A 12-fold increase in the absolute numbers of suppressor-cytotoxic T-cells was found, resulting in a reversed helper/suppressor ratio. Also the number of Ia-positive cells was greatly increased. Carbamazepine may induce a reversible proliferation and activation of the suppressor-cytotoxic subset of T-cells. Implications and pathogenetic possibilities are briefly discussed.     

Fc Receptors on Human T Lymphocytes: Loss of Fcμ and Expression of Fcγ Receptors by T Cells Stimulated in Mixed Lymphocyte Reaction

The consequences of allogeneic stimulation on the expression of Fc mu or Fc gamma receptors were analysed in T-cell populations responding in mixed lymphocyte reaction (MLR). Unfractionated T-cell populations were cultured with a pool or irradiated allogeneic T-depleted cells. The responder E-rosetting cells progressively lost Fc mu and acquired Fc gamma receptors. The change of the original Fc receptor phenotype is not the consequence of a preferential proliferative response of TG versus TM cells but is likely due to a de novo expression of Fc gamma receptors by T cells lacking detectable Fc receptors (T-null) and also to the loss of Fc mu and expression of Fc gamma receptors by TM cells. These data suggest that, after MLR, responder T cells can modify their Fc receptor phenotype.     

Clinical Significance of Immunoglobulin-secreting Cells in the Peripheral Blood in Patients with Multiple Myeloma

Immunoglobulin-secreting cells were enumerated in the peripheral blood of 31 patients with multiple myeloma, nine patients with so-called benign monoclonal gammopathy, and ten patients with polyclonal hypergammaglobulinaemia or idiopathic hypogammaglobulinaemia. Immunoglobulin-secreting cells were detected by a haemolytic plaque assay using protein-A-coated erythrocytes in the presence of class- or type-specific rabbit anti-human immunoglobulin antisera. In about two-thirds of patients with multiple myeloma, cells secreting the same light-chain isotype of their serum M-protein increased in number, whereas this was not the case in the patients with so-called benign monoclonal gammopathy. Follow-up studies of immunoglobulin-secreting cells in multiple myeloma revealed that these cells increased or decreased, correlating with the severity of the disease, and alterations were more rapid than other clinical features. This plaque assay is therefore useful in evaluating the response to chemotherapy in patients with multiple myeloma.     

Increased Number of IgG Fc Receptors on Monocyte-Enriched Peripheral Blood Leucocytes from Patients with Rheumatoid Arthritis

The number of free Fc receptors (FcR) per cell and the association constant (K_ass) for the binding of monomeric IgG were determined for monocyte-enriched peripheral blood mononuclear cells, isolated from 16 patients with active classical rheumatoid arthritis (RA) and from 15 normal healthy donors. The assay system was based on binding under equili brium conditions of ¹²⁵I-labelled monomeric rabbit IgG to monocytes purified from peripheral blood on a continuous gradient of Petcoll. Monocytes from 14 untreated RA patients (6 seropositive, 8 seronegative) expressed on the average 4.8±1.3 × 10⁴ FcR/cell. This number was significantly higher (P<0.01) than that found in the control group (3.46±0.7 × 10⁴ FcR/cell). There was also a significant difference between the mean K _ass of the RA group and the control group-2.1±0.7 × 10³1/mol and 2.6±1.0 × 10³ 1/mol, respectively (0.05 >P> 0.01). Two seropositive RA patients receiving systemic treatment with penicillamine expressed the same number of FcR/cell as the mean of the control group (3.6 ± 10⁴). Levels of circulating immune complexes (CIC) and of the complement-factor C3 split product C3d were also measured. No correlation was found between the number of FcR/cell and the concentration of C3d, but there was a weak correlation between the number of FcR/ccll and the level of CIC.     

Retention of Immune Complexes by Fc Receptors on Mouse Follicular Dendritic Cells

Follicular dendritic cells (FDC) are located inside lymph follicles and are mainly characterized by their capacity to retain antigens. We investigated this aspect in mice lymph nodes by using bovine serum albumin (BSA) labelled with 5-nm colloidal gold particles and homologous anti-BSA antibodies bound to 20-nm gold particles. Gold-labelled BSA injected alone in non-immunized mice was only rarely found in FDC cytoplasmic interdigitations. Injected in the form of immune complexes, it was retained by FDC. Antigen-free anti-BSA antibodies injected under similar conditions as immune complexes were always found in draining lymph nodes in the same locations as BSA-anti-BSA immune complexes. F(ab')2 from mouse immunoglobulins linked to colloidal gold particles were very rarely found between the FDC extensions, whereas it was intensely phagocytosed by macrophages. Our study permitted precise ultrastructural localization between FDC cytoplasmic extensions or inside macrophages and other cells of the lymph nodes, but it also pointed out that homologous antibodies linked to colloidal gold particles might be retained by FDC in the absence of antigens. These observations, carried out with colloidal gold, were checked by using 125I-labelled anti-BSA antibodies. Complement activation determinations of gold-labelled antibodies or immune complexes showed that antibodies or immune complexes fixed on colloidal gold particles do not activate the complement. This observation enabled us to conclude that Fc receptors play a significant part in the retention of gold-labelled antibodies or immune complexes by FDC of lymph nodes.     

多发性骨髓瘤患者血清IL-18和sVCAM-1的水平及临床意义

目的探讨多发性骨髓瘤患者血清白细胞介素18（IL-18）和可溶性血管细胞黏附分子-1（sVCAM-1）的水平及临床意义。方法应用ELISA法检查15例多发性骨髓瘤患者治疗前的血清IL-18和sVCAM-1的水平,并与正常对照进行比较。结果多发性骨髓瘤患者血清IL-18和sVCAM-1的水平[（1154.6±299）pg/ml和（1704.5±405.86）ng/ml]明显高于正常对照组[（256.39±59）pg/ml和（538.16±91.21）ng/ml]。结论多发性骨髓瘤患者血清IL-18、sVCAM-1含量明显增高,可能与多发性骨髓瘤的发病机制有关。     

Role of IgA and IgA Fc Receptors in Inflammation

Introduction  

Signals delivered by serum monomeric IgA (mIgA) are essential in controlling the immune system by preventing the development of autoimmunity and inflammation. However, IgA can also, when aggregated, be deleterious to the host, inducing inflammatory diseases. This Janus-like nature of IgA is mainly due to their heterogeneity in molecular forms and their interaction with IgA receptors.     

Inhibition of B Lymphocyte Activation by Interaction with Fc Receptors

Much early work indicated that specific antibody can play an inhibitory role in the immune response. This inhibitory activity was found to be dependent on an intact Fc portion of the antibody used, both in vivo and in vitro. Thus a role for lymphocyte Fc receptors in regulation of the immune response was suggested. However, soluble antigen-antibody complexes, which bind to Fc receptors, do not appear to inhibit B cell activation. Recent experiments have demonstrated that antigen-antibody complexes immobilized on a surface strikingly inhibit LPS induced B cell mitogenesis and polyclonal antibody synthesis. Mechanisms for Fc receptor-mediated inhibition of B cell activation have been considered, and a model proposed to explain many of these findings as well as allow for antigen specific inhibition.     

Inhibition of B Lymphocyte Activation by Interaction with Fc Receptors

Much early work indicated that specific antibody can play an inhibitory role in the immune response. This inhibitory activity was found to be dependent on an intact Fc portion of the antibody used, both in vivo and in vitro. Thus a role for lymphocyte Fc receptors in regulation of the immune response was suggested. However, soluble antigen-antibody complexes, which bind to Fc receptors, do not appear to inhibit B cell activation. Recent experiments have demonstrated that antigen-antibody complexes immobilized on a surface strikingly inhibit LPS induced B cell mitogenesis and polyclonal antibody synthesis. Mechanisms for Fc receptor-mediated inhibition of B cell activation have been considered, and a model proposed to explain many of these findings as well as allow for antigen specific inhibition.     

Increased T cells lacking immunoglobulin Fc receptors and increased spontaneous morphological blast transformation in a patient with phycomycosis

A 64-year-old diabetic man had phycomycotic infection withRhizopus and expired following surgical debridement. Extensive immunological evaluation revealed normal cellular and humoral immune responses including anin vivo response toRhizopus antigen following delayed hypersensitivity skin testing. Evidence for increasedin vivo lymphocyte activation consisted of increased spontaneous morphological blast transformation and increased T non-mu non-gamma cells. This work extends the previous findings of normal immunological responsiveness includingin vitro reactivity toRhizopus antigen in such patients.