Search

High-dose intravenous immunoglobulin (IVIg) preparations are used currently for the treatment of autoimmune or inflammatory diseases. Despite numerous studies demonstrating efficacy, the precise mode of action of IVIg remains unclear. Paradoxically, IgG can exert both pro- and anti-inflammatory activities, depending on its concentration. The proinflammatory activity of low-dose IVIg requires complement activation or binding of the Fc fragment of IgG to IgG-specific receptors (FcγR) on innate immune effector cells. In contrast, when administered in high concentrations, IVIg has anti-inflammatory properties. How this anti-inflammatory effect is mediated has not yet been elucidated fully, and several mutually non-exclusive mechanisms have been proposed. This paper represents the proceedings of a session entitled ‘IVIg – Understanding properties and mechanisms’ at the 6th International Immunoglobulin Symposium that was held in Interlaken on 26–28 March 2009. The presentations addressed how IgG may affect the cellular compartment, evidence for IVIg-mediated scavenging of complement fragments, the role of the dimeric fraction of IVIg, the anti-inflammatory properties of the minor fraction of sialylated IgG molecules, and the genetic organization and variation in FcγRs. These findings demonstrate the considerable progress that has been made in understanding the mechanisms of action of IVIgs, and may influence future perspectives in the field of Ig therapy. [ABSTRACT FROM AUTHOR]

In this paper we describe the clinical and molecular features of a new case (GOR) of homozygous human TAP2 deficiency, analysing the phenotype and function of NK cells. The patient presented from infancy with recurrent sinopulmonary infections; a selective IgG2 deficiency, negative antibody response to polysaccharide vaccination and low level of cell surface expression of HLA class I antigens were found. The sequence of TAP2 gene identified a single mutation, a C to T substitution changing the CGA arg codon at amino acid 220 into TGA stop codon in exon 3. By using MoAbs for KIRs, CD94, CD94/NKG2A and ILT2 we observed, in agreement with others, that the latter two receptors were overexpressed on TAP2-deficient NK cells. The inhibitory CD94/NKG2A and triggering CD94/NKG2C NK receptors, specific for HLA-E, appeared to be functional in a limited number of NK clones that could be expanded in vitro. Expression of HLA-E was virtually undetectable in GOR B-LCL and very faint in PBMC, further supporting that interactions of class I leader sequence nonamers with HLA-E in the ER depend on a functional TAP complex. [ABSTRACT FROM AUTHOR]

Evidence accumulated over the last decade concerning human and experimental models suggests that an immunopathological mechanism may be involved in the pathogenesis of chronic Chagas' disease. In this paper we demonstrate the existence of two different circulating IgG in chagasic patients which bind with myocardial β1 and spleen cell β2 adrenoceptors, acting as non-competitive inhibitors. Both chagasic IgG against β1 and β2 adrenoceptor increased intracellular levels of cAMP that could be blocked by specific β1 and β2 adrenoceptor antagonists. The specificity for β1 and β2 adrenoceplors and the independence of other tissue reactive antibodies was demonstrated by IgG absorption with turkey red blood cell (TRBC), human lymphocytes (HL) or guinea pig red blood cells (GPRBC). The F(ab')2 fraction acted similarly. This supports the specificity of β1 and β2 adrenoceptors to the chagasic IgG and the independence of the other tissue reactive antibodies, such as EVI system. The probable pathogenic role of both β1 and β2 adrenergic chagasic antibody is discussed. [ABSTRACT FROM AUTHOR]

The presence of J chain in human immunocytes containing various immunoglobulin classes has already been reported and in this paper we investigated the presence of J chain in human myeloma cells using light and electron microscopy. Myeloma cells were positive for cytoplasmic J chain in thirteen cases six of fifteen IgG myeloma, two of seven IgA myeloma, two of nine B J myeloma and three of three primary macroglobulinaemia. None of the four with benign monoclonal gammopathy was positive for J chain. The ultrastructural localization of J chain in IgG myeloma cells was similar to that γ chain, i.e. around the nuclear membrane, in the endoplasmic reticulum (ER) and it the Golgi apparatus. The latter finding is compatible with the presence of J chain in the urine of the same patient. We examined the urine from nine patients with J chain-positive cells and secretion of J chain was confirmed in three patients two with IgG myeloma and one with B J myeloma. In none of twelve in whom the immunocytochemical findings were negative for J chain was there evidence of urinary J chain. [ABSTRACT FROM AUTHOR]

This paper describes the effects of a single dose of cyclophosphamide on specific IgG production in rats during an established secondary immune response. (PVG × Agus)F1 rats were immunized twice (days 0 and 28) with chicken erythrocytes (CRBC), received cyclophosphamide (100 mg/m² of body surface area) on day 33 and were killed 8 days later. The production of anti-CRBC IgG antibodies was assessed by testing the supernatants of spleen cell cultures in a cytotoxicity assay with 51Cr-labelled CRBC as target cells and normal rat spleen cells as effector cells. In observations of fifty-nine pairs of treated and untreated rats from eight separate experiments, the administration of cyclophospharnide resulted in: (1) a decrease in the number of spleen cell to a median of 108.63 from a median of 108.7 (P < 0.0025); (2) an increase in the anti-CRBC IgG antibody titre of the supernatants of cultured spleen cells to a median of 100.67 from a median of 100.27 (P < 0.0025); and (3) the calculated anti-CRBC IgG antibody production per spleen to be increased in the drug-treated rats to a median of 102.26 from a median of 102.0 (P < 0.005). In a cyclophosphamide dose-response study, it was shown that some enhancement of antibody production was induced by doses between 12.5 and 50 mg/m² and consistently elevated levels of antibody production were associated with doses between 100 and 400 mg/m². [ABSTRACT FROM AUTHOR]

In CD-1 mice infected with Trypanosoma musculi, the production of IgM and IgG antibodies in response to sheep erythrocytes (SRBC) was significantly suppressed when mice were immunized with SRBC once high parasitaemias had developed. In infected mice which were not immunized with SRBC, background plaque-forming responses of spleen cells to SRBC were significantly higher than in uninfected, unimmunized mice. Factors derived from T. musculi were found to be mitogenic m vitro for spleen cells taken from CD-1 mice. The mitogenic response to these factors by spleen cells from athymic mice was highly significant, whereas the response of spleen cells taken from CD-1 mice which had been pre-treated with cyclophosphamide was much less, suggesting that the B cell was the major target of the trypanosome-derived mitogen. In this paper we discuss the possible relationship of T. musculi-induced mitogenesis to the immunosuppression and non-specific antibody formation associated with T. musculi infections. [ABSTRACT FROM AUTHOR]

Investigation of the nature of the increased erythrocyte-antibody (EA) binding activity of peripheral blood lymphocytes (PHL) from rheumatoid arthritis (RA) patients reported in the preceding paper has revealed that IgG is the active class of antibody in this rosette formation. Some IgM binding also occurs. SRBC sensitized with F(ab)2 preparations of IgG do not give rosette formation even at high concentrations. EA binding is inhibited by prior incubation of lymphocytes with heat-aggregated human IgG but antigen-antibody complexes did not give significant inhibition. The majority of these rosettes were found to be stable at 4°C. and room temperature but labile at 37°C. Enzyme studies with pronase, trypsin, neuraminidase and treatment with sodium azide gave results strongly supporting the conclusion that the increased binding observed is increased Fc-receptor activity. This activity appears not to be a result of Fc binding by cell-bound rheumatoid factor. A range of titres of antibody and of IgG was used to sensitize erythroeytes to form EA and the enhanced EA-rosette formation by PBI, from RA patients occurred throughout the range of concentrations of sensitizing antibody. Significantly more EA were bound by individual lymphocytes from RA patients than control subjects. This data suggest that the Fc receptors on RA lymphocytes are more avid for FA than receptors on lymphocytes from healthy people. [ABSTRACT FROM AUTHOR]

Lymphocytes bearing complement receptors were separated from lymphocyte suspensions using C3-reacted Sepharose columns as solid phase immunoabsorbents. The retained CR + lymphocytes were recovered by elution of the column with IgG fraction purified from a rabbit antiserum to human C3. This paper describes the method, its specificity and the yields of cells obtained. [ABSTRACT FROM AUTHOR]

The 'skin window' technique in which the horny layer of the skin is abraded with a high speed grinder has been used to study the appearance of proteins with antimicrobial activity in the fluid accumulating in damaged human skin. The fluid was absorbed into paper discs and protein levels measured by radial diffusion. The skin exudates contained about 45%, as much IgG and IgM as the subjects' serum, but the amount of IgA (68% of the serum level) in the exudate was significantly greater, suggesting selective transport into the lesion. The fluid also contains complement proteins, lysozyme and lactoferrin. The methods used in this study may provide useful information about clinical situations in which susceptibility to cutaneous infection is increased. [ABSTRACT FROM AUTHOR]

This paper describes immunofluorescence studies on liver cell surface localization of hepatitis B surface antigen (HBsAg) and of IgG in acute and chronic hepatitis and in cirrhosis. In acute hepatitis B, HBsAg was found at the surface of hepatocytes in an early phase of the disease, hut not during the recovery. This finding is consistent with the hypothesis that immune reactions to HBsAg may be responsible for the liver cell lysis. In HBsAg-positive chronic hepatitis and cirrhosis the antigen was found in the cytoplasm, but not on the surface of the hepatocytes, while in HBsAg-negative cases the antigen could not be detected in the liver cells. Both in HBsAg-positive and in HBsAg-negative chronic active hepatitis (CAH) and cryptogenic cirrhosis, IgG bound to the membrane of the hepatoeytes could be detected, suggesting a role of antibodies in the pathogenesis of the disease. [ABSTRACT FROM AUTHOR]

Mitogen-transformed human peripheral blood lymphocytes and tonsil blasts were examined by rosette formation to detect the presence of membrane-bound immunoglobulin (Ig) and surface receptors for fixed IgG and fixed C3. In addition, the capacity of these cells to rosette with sheep erythrocytes was evaluated as a reaction characteristic of T lymphocytes. In order for clear morphological recognition of the rosetting transformed lymphocytes and the rosetting tonsil blasts a cytocentrifuge technique was developed and used in conjunction with autoradiography and/or with Romanowsky stains. Using these techniques and the culture methods described in this paper phytohaemagglutinin, pokeweed mitogen, streptococcal filtrates and purified protein derivative stimulated predominantly T cells in the peripheral blood of man. A minority of the transformed cells in these mitogen-stimulated cultures (<24%) did rosette with B lymphocyte markers and presumably represent a B-cell response. No significant differences were found between the T- or B-cell specificity of the mitogens investigated. Lymphoid preparations from tonsils excised from normal donors with recurrent tonsillitis were found to contain 6-15% lymphoblasts and the iarge majority of these cells formed rosettes with the B-cell markers, less than 20% of these lymphoblasts formed spontaneous sheep erythrocyte rosettes. Using a mixed rosetting technique a small proportion (<5%) of PHA-transformed cells and tonsil lymphoblasts were found to have combined sheep Fc or combined sheep C3 receptors. The investigation of B- and T-lymphocyte surface markers on mitogentransformed lymphocytes was extended to neopiastic lymphocyte populations and it was found that the majority of transformed cells (>70%) present in chronic lymphocytic leukaemia cultures stimulated with PHA after 6 days incubation were transformed T lymphocytes. [ABSTRACT FROM AUTHOR]

This paper confirms results showing that TA3 tumour cells coated in vivo with immunoglobulins, lose some of the coat upon transfer to in vitro conditions. By labelling IgG isolated from the ascitic fluid of TA3 tumours it was found that the immunoglobulin coating TA3 cells is dynamically exchanged with immunoglobulin in the corresponding ascitic fluid. Some of the released immunoglobulin is in a degraded state as judged from the fact that most of the released material lost the antigenicity of intact immunoglobulin and has a lower capacity to precipitate with ammonium sulphate at 50% saturation. The degraded immunoglobulin has a higher binding efficiency to tumour cells. In vivo experiments demonstrated that the ascitic fluid of mice bearing TA3 and MCIM tumours contains a material which has some of the physicochemical properties of IgG but which does not precipitate with antisera directed aguinst IgG. [ABSTRACT FROM AUTHOR]

Evidence is provided which supports the concept that a previously characterized monoclonal IgA-λ rheumatoid factor with a medium-binding avidity reacts with a select Fc region antigenic determinant. The interaction between this rheumatoid factor and anti-Rh-coated human erythrocytes is inhibited by IgG1 Fc fragment, IgG1 heavy chains, and a single peptide pool isolated from this tryptic digest by paper chromatography. Cyanogen bromide cleavage of the isolated heavy chains abolishes this reactivity. A methionine residue is assumed to be near, involved in, or necessary for reactivity between the IgA and its antigenic determinant. The data thus provide further evidence for a specific autoantigenic, rheumatoid factor-reactive determinant. [ABSTRACT FROM AUTHOR]

In this paper the specificity of the skin-reactive guinea-pig immunoglobulin in the homologous PCA test has been reconsidered. Extensive purification of this immunoglobulin by chromatographic methods results in the isolation of a small fraction or medium speed immunoglobulins that contains all skin reactivity. No correlation could be found with the 7S immunoglobulins IgGγ1 and Igγ1A suggesting a separate class of biologically active immunoglobulins. The PCA active antibody belongs to either an IgG subclass or is a heat stable homocytotropic antibody. Rabbit and chicken antisera against isolated fractions of guinea-pig immunoglobulins show the existence of 7S subclasses. Some suggestions for a revised nomenclature are given. [ABSTRACT FROM AUTHOR]