Immunoglobulin G Uptake Research Articles

IgG Leakage May Contribute to Neuronal Dysfunction in Drug-Refractory Epilepsies With Blood-Brain Barrier Disruption

Focal epilepsies are often associated with blood-brain barrier disruption. In 4 entorhinal cortex tissue samples and 13 hippocampal samples from patients with pharmacoresistent temporal lobe epilepsy, we observed immunoglobulin G (IgG) leakage in the parenchyma and IgG-positive neurons that had evidence of neurodegeneration, such as shrinkage and eosinophilia. These findings were not present in samples from 12 nonepileptic control subjects. To complement these findings, we used a rat in vivo model that mimics the development of limbic epilepsy with blood-brain barrier disruption. During epileptogenesis, IgG leakage and neuronal IgG uptake increased concomitantly with the occurrence of seizures. Immunoglobulin G accumulation in neurons was selective, particularly for interneurons and pyramidal neurons. Immunohistochemistry and electron microscopy showed that IgG uptake in the rat neurons was associated with eosinophilia, shrinkage, and ultrastructural degenerative changes. Moreover, IgG-positive neurons lost their NeuN immunohistochemical staining. Together, these observations suggest that IgG leakage is related to neuronal impairment and may be a pathogenic mechanism in epileptogenesis and chronic epilepsy.

Intestinal IgG uptake by small intestine of goat kid fed goat or lyophilized bovine colostrum

The immunoglobulin G (IgG) uptake and enterocyte nucleus position in the villous were studied in newborn goat kids fed goat or lyophilized bovine colostrum. Two groups of 15 newborn goat kids, each received 5% of body weight of goat colostrum (GC) or lyophilized bovine colostrum (LBC) containing 55mg/mL of immunoglobulin G (IgG) at 0, 7 and 14h of life. Three animals were sampled just after birth, receiving no colostrum intake, to be used as control. Samples of duodenum, medium jejunum and ileum were collected at 0, 18, 36 and 96h of life. IgG vacuoles were not observed in the duodenum throughout the experiment regardless of all the experimental time points. In this segment, at 0, 18 and 36h of life, nuclei were found in the apical, medial and basal positions in the enterocytes, and localized in the upper, medial and lower parts in the villous, respectively. At 96h, a basal nuclei position was observed in the enterocytes, throughout the villous. In jejunum, IgG vacuoles were distributed along the villous at 18 and 36h. In this segment at 0h the nuclei were positioned predominantly apically in the enterocytes, throughout the villous. At 18 and 36h, no consistent nuclei pattern was verified; however at 96h, the nuclei were positioned basally in the enterocytes, throughout the jejunal villous. In the ileum at 0, 18 and 36h, a great number of vacuoles without IgG were verified in the medial–apical part of the villous. In this segment, at 0h of life and 96h of life, the predominance of basal nuclei was observed. Nuclei were positioned in medial–apically part of the ileal enterocytes in the upper part of the villous at 18 and 36h. It was found that the jejunal epithelium was the most important segment related to absorption process. The IgG absorption and nucleus position in the newborn goats were dependent on the small intestine segments and experimental time points, regardless of the colostrum source, GC or LCB. Considering the IgG uptake mechanism observed in the present study, the lyophilized bovine colostrum might be used instead of goat colostrum.

Detection of inflammation/infection with human polyclonal immunoglobulin G labelled with 99Tcm.

Radiolabelled human polyclonal immunoglobulin G (IgG) has been successful in identifying inflammatory/infectious processes in human and animal models. We studied 71 patients with suspicion of inflammation of varied origin and location (44 of musculoskeletal location and 27 other) using 99Tcm. IgG images correctly identified 21/22 inflammatory sites of musculoskeletal origin and only 4/14 sites of soft-tissue location. Five false negative studies corresponded to granulomatous processes, three of them tuberculosis. Four false positive studies were obtained in the musculoskeletal group corresponding to three synovial tumours and a Charcot joint. No false positive results were seen in the soft tissue group. 99Tcm-IgG performs well in the identification of bone-joint lesions and rules out non-inflammatory conditions (with the important exception of tumours). The role of 99Tcm-IgG in soft-tissue inflammatory sites, especially in highly vascular organs is inferior, with a high yield of false negative studies. Granulomatous lesions probably represent situations of low or absent IgG uptake.

Immunocytochemical and labelled tracer approaches to uptake and intracellular routing of Immunoglobulin-G (IgG) in the human placenta

Isolated lobules of freshly delivered human term placenta were (a) subjected to an indirect immunoelectron ultracryo method in which the immunoreactivity of endogenous Immunoglobulin-G (IgG) to rabbit anti-human IgG antibody was localized with protein-A-colloidal gold and (b) extracorporeally perfused and human IgG molecules complexed to horseradish peroxidase (HRP) added to the maternal perfusate and the uptake of IgG-HRP over different perfusion durations visualized ultrastructurally by using diaminobenzidine cytochemistry. Immunoreactivity to anti-human IgG antibody was localized all along the apical plasmalemma, in apical coated and uncoated vesicles, in apical and juxtanuclear multivesicular bodies, and in basal vesicles of the syncytiotrophoblast layer of the placenta. The stroma separating the syncytiotrophoblast from the foetal endothelium as well as vesicles within the endothelium were immunoreactive. No immunoreactivity was localized in paracellular clefts of endothelia. A similar distribution of exogenous IgG-HRP was observed for the perfused placentae. When bovine IgG-HRP or HRP alone were used as control tracers no uptake was seen for the former whilst the latter was observed only in early endosomal vesicles of the syncytiotrophoblast. The pattern of localization visualized in both studies is consistent with receptor-mediated uptake of IgG by the syncytiotrophoblast and a vesicular transport of IgG across the foetal endothelium.

Intestinal uptake of IgG in suckling rats: Distinction between jejunal and ileal epithelial cells demonstrated by simultaneous ultrastructural localization of IgG and acid phosphatase

During the suckling period, the proximal small intestine of neonatal rats absorbs maternal milk immunoglobulin G (IgG) into the circulation by a receptor-mediated mechanism. At the same time, milk IgG enters vacuoles in the distal small intestine unaided by a receptor and is degraded. To help define the distinction between the handling of IgG by the proximal and distal neonatal small intestine, we simultaneously localized IgG (by peroxidase-labeled antibodies) and acid phosphatase (by a lead phosphate technique) at the ultrastructural level. In the proximal small intestinal epithelial cells, IgG-containing vesicles were separate from acid phosphatase-containing structures, whereas in the distal intestinal epithelial cells, IgG was present together with acid phosphatase in large supranuclear vacuoles. These observations are consistent with the hypothesis that IgG avoids degradation in the proximal intestinal cells because vesicles in which it is transported do not fuse with lysosomes, whereas IgG in the distal small intestine is degraded in lysosomal enzyme-containing organelles.

Inhibition of receptor-mediated endocytosis immunoglobulin G by enterocytes isolated from the neonatal rat jejunum

Abstract The effect of inhibitors of respiration (NaN 3 and DNP), glycolysis (2DG, IAA and NaF) and the microtubular-microfilament system (colchicine and cytochalasin B) on the uptake of rat immunoglobulin G (IgG) by enterocytes isolated from the neonatal rat gut has been assessed. After a 1 hour incubation, NaN 3 and DNP had significantly reduced IgG uptake by between 32% and 35% of the control, IAA and 2DG were less effective and NaF, colchicine and cytochalasin B had no effect at all. The findings show that (i) IgG is internalised by isolated enterocytes in vitro and (ii) that this internalisation is under metabolic control, (iii) that inhibitors of respiration are more effective in blocking uptake than inhibitors of glycolysis.

Receptor-mediated transport of IgG across the intestinal epithelium of the neonatal rat.

The absorptive epithelium of the neonatal rat is developmentally specialized to transfer maternal immunoglobulin G (IgG) intact to the circulation while other milk protein are digested. The epithelial cells of the duodenum and proximal jejunum which are responsible for IgG transfer represent a particular striking experimental model for study of receptor-mediated intracellular transport. Receptors located on the luminal plasma membrane selectively bind the Fc region of IgG. The IgG enters the cell by constitutive endocytosis within coated vesicles and is then released at the basolateral plasma membrane. Morphological evidence supports a model in which IgG crosses the cell as a ligand-receptor complex that dissociates only on exposure to a pH 7.4 environment found at the basolateral cell surface. Although uptake of IgG at the luminal plasma membrane is highly selective, small but significant amounts of other proteins enter the cell apparently non-selectively. Nevertheless, these latter proteins are not transferred across the cell. Double-tracer experiments indicate that IgG and these other proteins enter the cell simultaneously within the same endocytic vesicles, but that non-membrane-bound proteins are removed from the IgG transport pathway by an as yet poorly defined mechanism and sequestered within small apical vacuoles and lysosomes.

Examination of Streptococcus mutans for immunoglobulin G Fc reactivity.

Representative strains of oral streptococci were tested for Fc immunoglobulin G (IgG) reactivity by two different techniques, agglutination of rabbit-IgG sensitized sheep erythrocytes and uptake of human and rabbit 125I-radiolabeled IgG. None of the S. mutans serotypes a through e reacted with the Fc region of either human or rabbit IgG. Additionally, other streptococci such as S. sanguis, S. salivarius, S. faecalis, and S. mitis failed to show appreciable Fc reactivity as assayed by these techniques. The group A, C, and G streptococci, previously shown to possess Fc reactivity, proved to be reactive in these experiments, as did a protein A-containing strain of Staphylococcus aureus.

Heterogeneity of nonimmune immunoglobulin Fc reactivity among gram-positive cocci: description of three major types of receptors for human immunoglobulin G

Two hundred and thirty strains of various gram-positive cocci were tested for quantitative, nonimmune binding of radiolabeled human polyclonal immunoglobulin G (IgG). The majority of coagulase-positive staphylococci and streptococci belonging to serogroups C and G showed a high uptake of IgG. The binding of immunoglobulin to group A streptococci was considerably less, with a number of strains completely negative. None of the pneumococcal or the group B or D streptococcal strains displayed any binding capacity. Heterogeneity of the IgG reactivity of various reactive strains was studied in an inhibition assay using 10 different animal serum pools. Three different inhibition patterns were seen, each of them revealing a striking degree of homogeneity within single bacterial species. Staphylococcus aureus and group A streptococci, respectively, constituted two homogeneous groups which differed markedly from each other and from C and G streptococci. No differences were observed between group C and G streptococci. Based on the profound differences between these homogeneous groups, three major types of Fc receptors could be defined. Type I and II Fc receptors were found on S. aureus and on group A streptococci, respectively. Fc receptor type III represented the immunoglobulin-binding structure of both group C and G streptococci.

Radioglobulin localization and immunospecificity in the transplanted human choriocarcinoma

Human choriocarcinomas, transplanted into the hamster cheek pouch, concentrated both radiolabeled immune and nonimmune rabbit immunoglobulin G (IgG) as shown by autoradiography, immunofluorescence, and gamma spectrometric analysis. The intravascular activity and in vivo immunospecificity of the radioglobulin preparations was demonstrated by the use of nonlabeled whole rabbit sera as blocking agents. Nonlabeled rabbit anti-human chorionic gonadotropin serum was capable of blocking radio-uptake levels in the tumor and the ovary. In contrast, the use of nonlabeled, nonimmune rabbit sera influenced only the tumor radioactivity levels. Both immune and nonimmune blocking sera may have saturated IgG receptor sites in the tumor, thus reducing the uptake of radioglobulin IgG. Possible mechanisms for the indiscriminate uptake of IgG by the tumor have been discussed.