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B J Underdown

Publications and source records attributed to B J Underdown.

At least 37 records · Page 2Linked to original sources
PubMed1990

Early expression in mice of genetic resistance to intestinal amebiasis.

Some strains of mice are known to be relatively resistant to hepatic or intestinal amebic infections. In order to know if the intestinal resistance is expressed few hours after infection, we inoculated axenic amebae in three inbred strains of mice either by direct intracecal injection or by infection of a washed-closed cecal loop. We found that amebae do not survive in conventional animals but they colonize longer in animals with the cecal loop. However, the survival was low after 24 hours postinfection. Balb/c mice were more susceptible and CBA mice more resistant. Our results suggest that genetic resistance to intestinal amebiasis is expressed in mice in the early phases of infection.

Animals↗
PubMed1988

Studies on the specificity of the IgA-binding lectin, jacalin.

The interactions of IgA with the jackfruit lectin, jacalin, were investigated with regard to the specificity of jacalin for species and subclasses of IgA. It was found that jacalin selectively bound to human IgA1, but not to human IgA2, mouse IgA or rat IgA. Binding studies with human IgA1 fragments produced by different IgA1 proteases revealed that jacalin bound to galactose-terminal oligosaccharides in the hinge region of human IgA1. Affinity chromatography employing jacalin-Sepharose provided a means to separate the subclasses of IgA in human whey.

Allergens↗
PubMed1988

Chronic giardiasis in B-cell-deficient mice expressing the xid gene.

The role of antibody in immunity to Giardia muris infection was investigated by studying B-cell-deficient CBA/N mice expressing the xid gene. After gastric administration of infective G. muris cysts, CBA/N male and female mice developed prolonged G. muris infection, whereas BALB/c mice eliminated their infection in 6 to 8 weeks. Male F1 progeny obtained from matings between female CBA/N mice and male BALB/c mice expressed the xid gene and developed prolonged infections. In contrast, all other F1 progeny of CBA/N and BALB/c matings, which did express the xid gene, eliminated G. muris. The link between the xid gene and prolonged infection was confirmed by studies of C57BL/6 mice congenic for the xid gene. When compared with BALB/c or F1 mice, CBA/N mice produced large quantities of immunoglobulin A (IgA) anti-G. muris antibody in serum and gut secretions during prolonged infection. Serum IgG anti-G. muris antibody levels were reduced in CBA/N and F1 male mice that expressed the xid gene. The inability of xid mice to eliminate G. muris is consistent with the importance of antibody in the development of immunity to G. muris. We hypothesize that mice bearing the xid gene fail to produce IgA antibody of appropriate specificity to an antigen or antigens whose recognition by antibody is critical for successful elimination of the parasite.

Animals↗
PubMed1987

Lymphocyte proliferation to antigen E: demonstration of the restriction of antigen E-specific T cells to ragweed-allergic donors.

Allergic sensitivity to ragweed is common among atopic individuals in North America and can be associated with symptoms of seasonal hay fever and increased airway reactivity in asthma. This sensitivity is mediated by IgE antibody to ragweed antigens that in turn is presumed to be the product of B-lymphocytes regulated by various T cell subsets. Proliferation in vitro by lymphocytes obtained from individuals allergic to ragweed and cultured in the presence of ragweed antigen E (AgE) has been repeatedly described, but a comprehensive study of this proliferation has questioned the specificity of this response. We have examined this question and found that in the first week of culture, the specific lymphocyte proliferation to AgE may be obscured by high background and mitogen-like proliferation. However, by carrying the cells for a longer period of time in culture and providing a second in vitro boost with AgE, specific proliferation could be clearly documented. Lymphocytes from atopic ragweed-allergic donors proliferated at levels 20 to 50 times beyond background in the presence of AgE. Cells from nonragweed-allergic donors (either nonatopic or atopic) did not do so. The AgE-responsive cells could be expanded in culture and demonstrated to be T cells. Moreover, AgE-responsive T cells could only be cloned from AgE-allergic donors and, after expansion and subcloning, demonstrated to respond to AgE but not partially purified dust mite antigen. In contrast, a clone of T cells from a dust mite-sensitive individual proliferated in response to the dust mite antigen but not AgE.

Allergens↗
PubMed1987

Alterations in protein transport events in rat liver after estrogen treatment.

The effects of 17 alpha-ethynylestradiol (EE) treatment on the hepatic processing of rat polymeric immunoglobulin A (IgA) and human asialoorosomucoid (ASOr) were studied. After 5 days of treatment with EE (5 mg/kg) or solvent alone, male rats were anesthetized and injected with tracer doses of the test proteins. Bile flow rates had been reduced by greater than 60% in the EE-treated animals. A previously reported radiolabeling strategy was used to monitor both the transport of intact protein to bile and the degradation of protein in lysosomes. Transport of intact IgA to bile was reduced by 43%, with transport peaking 27 min later in EE-treated animals compared with controls. There was a corresponding impairment of uptake of labeled IgA from blood. EE induced no kinetic change in the uptake or processing of ASOr. However, there was an increase in the proportion of ASOr reaching bile intact from 3% to 15-23% of the injected dose. The data indicate that EE disables the transport pathway for IgA and causes a partial change in the routing of ASOr after endocytosis in favor of direct transport to the bile canaliculus. These findings may have implications for the importance of membrane composition in protein transport events.

Animals↗
PubMed1987

The gastrointestinal tract as an immunologic organ--state of the art.

Mucosal as well as systemic immune responses are extensively influenced by the external environment. The maintenance of the physiologic integrity of the mucosa is complex and depends largely on local immune responses. The physiologic processes of the body are integrated and carefully regulated so that no single event can be considered in the absence of consideration of its interaction with its environment. These principles are perhaps best demonstrated by the models and concepts emerging to explain the apparent idiosyncrasies of the mucosal immune system. How these can be harnessed to promote protection and how they may be manipulated to prevent disease is the subject of extensive current investigation which we have attempted to summarize in this brief review.

Antibody Formation↗
PubMed1986

Cloned helper T cell for IgE: characterization of T cells cloned from an atopic donor with a high serum IgE.

T cells cloned from nonatopic and atopic donors were examined for the ability to help IgE production in vitro. Experiments with clones from nonatopic donors were unsuccessful in spite of isolation of four clones that promoted IgM and IgG when these were mixed with B cells from nonatopic donors and pokeweed mitogen. We reasoned that T cells regulating IgE might be found with greater frequency in atopic donors with very high serum IgE. Two T cell clones from an atopic donor with a serum IgE of 3000 IU/ml were found to drive atopic B cells to produce up to 10,000 pg/ml of IgE in vitro. This promotion of IgE secretion occurred in the absence of mitogen stimulus and appeared to decrease with higher ratios of T cells:B cells. One of the clones (A-H4) also promoted the production of IgM and IgG in addition to the IgE; however, when this clone was carried in culture for several months, this activity for IgM and IgG fell markedly, whereas help for IgE decreased less. We have speculated that these two T cell clones, with unusual activation properties, may be representative of a subset of atopic T cells responsible for maintaining the circulating B cells that spontaneously secrete IgE in vitro in patients with high serum IgE.

B-Lymphocytes↗
PubMed1986

Secretory component as the mucosal transport receptor: separation of physicochemically analogous human IgA fractions with different receptor-binding capacities.

This paper describes the separation and characterization of several IgA fractions from the same human monoclonal source, based on their ability to bind secretory component (SC). The study was undertaken to elucidate features of the immunoglobulin-binding site for SC, and to examine the dependence of mucosal transport on IgA-SC interaction. Enrichment or depletion of SC-binding activity was accomplished on an affinity adsorbant made with SC from human colostral whey. The affinity-purified human IgA fractions contained IgA polymers and were 77% active in rebinding to the adsorbant; this activity was diminished significantly by direct radioiodination. The non-adherent IgA fractions contained both polymer and monomer, and were only 8% active in rebinding to the adsorbant. When the polymer and monomer components were separated from each other, the non-adherent polymer was found to resemble the affinity-purified fraction by all criteria examined including J-chain content, except that the SC-binding capacity was greater than five-fold lower. These findings have two implications for the SC-binding site on human IgA: first, the presence of J-chain is insufficient to bestow IgA with SC-binding activity; second, a critical tyrosine participates in maintaining the SC-binding region, possibly on the IgA heavy chain. The relationship between SC binding and mucosal transport was tested in the rat hepatobiliary model. All radiolabeled human IgA fractions were captured rapidly from blood by the rat liver, but only the SC-binding fractions underwent substantial intact transport to bile (greater than 70% of the injected dose). Even though a nominal proportion of the SC-non-adherent IgA appeared in bile (4-15% of the dose), most IgA in these fractions was rapidly degraded within the liver. Thus, only a small amount of monomeric and polymeric IgA can use alternative receptors to get to bile by diversion from the degradative pathway. Polymeric IgA can undergo efficient transport across the cell, strictly conditional on a high binding capacity for SC. This demonstrates that membrane SC is the receptor conferring specificity on the mucosal-transport pathway.

Animals↗
PubMed1986

Human IgA as a heterovalent ligand: switching from the asialoglycoprotein receptor to secretory component during transport across the rat hepatocyte.

Asialoglycoproteins are taken up by the rat liver for degradation; rat polymeric IgA is taken up via a separate receptor, secretory component (SC), for quantitative delivery to bile. There is negligible uptake of these ligands by the converse receptor, and only a low level of missorting of ligands to opposite destinations. The two pathways are not cross-inhibitable and operate independently (Schiff, J.M., M. M. Fisher, and B. J. Underdown, 1984, J. Cell Biol., 98:79-89). We report here that when human IgA is presented as a ligand in the rat, it is processed using elements of both pathways. To study this in detail, different IgA fractions were prepared using two radiolabeling methods that provide separate probes for degradation or re-secretion. Behavior of intravenously injected human polymeric IgA in the rat depended on its binding properties. If deprived of SC binding activity by affinity adsorption or by reduction and alkylation, greater than 80% of human IgA was degraded in hepatic lysosomes; radioactive catabolites were released into bile by a leupeptin-inhibitable process. If prevented from binding to the asialoglycoprotein receptor by competition or by treatment with galactose oxidase, human IgA was cleared and transported to bile directly via SC, but its uptake was about fivefold slower than rat IgA. Untreated human IgA was taken up rapidly by the asialoglycoprotein receptor, but depended on SC binding to get to bile: the proportion secreted correlated 1:1 with SC binding activity determined in vitro, and the IgA was released into bile with SC still attached. These results demonstrate that human IgA is normally heterovalent: it is first captured from blood by the asialoglycoprotein receptor, but escapes the usual fate of asialoglycoproteins by switching to SC during transport. Since the biliary transit times of native human and rat IgA are the same, it is probable that the receptor switching event occurs en route. This implies that the two receptors briefly share a common intracellular compartment.

Animals↗
PubMed1986

Quantitative and temporal analyses of murine antibody response in serum and gut secretions to infection with Giardia muris.

We analyzed the appearance and level of Giardia muris-specific antibody of immunoglobulin A (IgA), IgG, and IgM isotypes, at weekly intervals, over the course of a 7-week infection in BALB/c and C57BL/6 mice. Using sensitive immunoradiometric assays, we observed that IgA antibody was the only detectable anti-G. muris antibody in intestinal secretions throughout the course of infection. No secreted IgG or IgM anti-G. muris antibody was detected even in concentrated intestinal secretions. The expulsion of G. muris by the mice was associated closely with the appearance and increasing levels of secreted anti-G. muris IgA antibody. Both IgG and IgA serum antibody to G. muris were detected, but no serum IgM antibody was detected. Serum IgA and IgG anti-G. muris antibody remained at high levels up to 10 weeks following clearance of the parasite. An interesting observation indicated that serum IgA antibody to G. muris developed more slowly in response to infection than secreted IgA antibody. An analysis of the molecular weight distribution of total serum IgA in infected mice determined that infection produced a transient but significant shift in serum IgA to high-molecular-weight (greater than or equal to dimeric IgA) forms. The results indicate that a substantial IgA antibody response occurs in sera and in gut secretions of G. muris-resistant mice and that IgA antibody is the dominant and possibly the only effector antibody active in intestinal secretions during G. muris infection in mice.

Animals↗
PubMed1985

Low level transport of IgA to bile via the asialoglycoprotein receptor.

The rat and rabbit transport IgA from blood to bile by a highly efficient transcellular pathway mediated by secretory component (SC). Other mammals do not express SC on liver hepatocytes, but they do transport a small amount of IgA to bile. In the first part of this study, human polymeric IgA was radiolabeled and depleted of SC binding activity by successive affinity adsorption. Transport of this preparation intact to rat bile was 4%, but was reduced to 2% when 50 mg unlabeled asialoglycoprotein was preadministered. The 2% decline corresponds to the percent of asialo-orosomucoid diverted to bile from the lysosomal pathway. In guinea-pigs, missorting of asialo-orosomucoid intact to bile was 10% of the injected dose. Transport of normal human IgA to bile was 1-2%, even though guinea-pigs do not express SC in the liver. Excess unlabeled asialofetuin reduced the transport of asialo-orosomucoid by 10-fold and IgA by 6-fold. This demonstrates that the asialoglycoprotein receptor can mediate transport of IgA to bile in small amounts, but that this transport may be only a biological artifact resulting from limited fidelity of intracellular protein sorting.

Animals↗
PubMed1985

Secretory component in breast cancer. Analysis of the levels in primary and metastatic disease.

Levels of secretory component (SC) were measured in breast tumors from 95 patients with primary or metastatic cancer. Tumor cytosols were prepared by polytron disruption and high speed centrifugation (105,000 g X 30 min) and SC was measured using a sensitive radioimmunoassay which detects primarily free SC. In frozen samples stored for up to 5 months SC resisted degradation and could be measured quantitatively without interference. In primary tumors from patients between ages 28 and 97, SC positive samples ranged from 4 ng/mg protein to 600 ng/mg protein. In metastatic lesions, SC positive samples ranged no higher than 46 ng/mg protein. The studies indicate that SC can be measured quantitatively in both primary and metastatic tumors and that prolonged storage does not interfere with measurements of SC. The wide variation in SC levels in primary tumor samples may be related to a susceptibility to metastasis. Further, the low levels of SC in metastatic lesions could indicate a potential for SC involvement in immune regulation of tumor growth.

Adult↗
PubMed1985

Chronic Giardia muris infection in anti-IgM-treated mice. I. Analysis of immunoglobulin and parasite-specific antibody in normal and immunoglobulin-deficient animals.

To investigate the role of B cells and antibody in the immune response of mice to the murine intestinal parasite Giardia muris, we used mice treated from birth with rabbit anti-IgM antisera (aIgM). Such mice developed in serum and in gut secretions extreme Ig deficiency (IgM, IgA, and IgG) relative to control animals. The aIgM-treated mice showed no anti-G. muris antibody in serum or in gut wash material. Infections of G. muris in these mice were chronic, with a high load of parasite present in the small bowel, as reflected by prolonged cyst excretion (greater than 11 wk) and high trophozoite counts. In contrast, normal, untreated mice or NRS-treated animals developed anti-parasite IgA and IgG antibody in serum, demonstrated IgA antibody against the parasite in gut washings, and expelled the parasite within 9 wk. These effects of aIgM treatment on the murine response to primary infection with G. muris were demonstrated in two strains of mice: BALB/c and (C57BL/6 X C3H/He) F1. It was also observed that the response to G. muris infection in untreated animals was characterized by higher than normal total secretion of IgA into the gut and a concomitant increase in the serum polymeric IgA level. Mice treated with aIgM had a marked decrease of both monomeric and polymeric IgA in serum, and little detectable IgA in the intestinal lumen. These experiments provide the first demonstration that anti-IgM treatment suppresses a specific intestinal antibody response to antigen, and provide evidence that B cells and antibody play a role in the development of an effective response to a primary infection with G. muris in mice.

Animals↗
PubMed1985

A role for the spleen in the appearance of IgM in the bile of rats injected intravenously with horse erythrocytes.

The i.v. injection of the particulate antigens horse red blood cells (HRBC) and Salmonella enteritidis into rats results in the appearance of high levels of IgM agglutinating antibody in the serum and bile. This is in contrast to the appearance of specific IgA antibodies in bile after the injection of antigen into the Peyer's patches. At the height of the response, a fivefold to 10-fold increase in total IgM was found in bile, whereas there was no increase in IgA or in total protein levels. The biliary IgM was not associated with secretory component. Studies aimed at revealing the source of the IgM showed that neither immunized nor nonimmunized rats were able to transport 131I-rat IgM, but both groups were equally efficient at transporting 125I-rat IgA. Furthermore, specific anti-HRBC antibody could not be detected in the bile of rats that were injected with a high titer serum, indicating that blood is unlikely to be the source. Splenectomy of rats at the time of the injection of antigen, at 3 days after immunization had abrogated the biliary response, and at 5 days resulted in rapid decline in existing specific antibody level. Involvement of the spleen was additionally implicated when it was shown that injection of animals with immune spleen cells gave rise to specific antibodies in serum and bile. On the basis of these experiments, it is proposed that antigen entering the blood stream can stimulate a population of cells in the spleen that emigrates to the liver, where the cells localize and secrete IgM into bile.

Animals↗
PubMed1984

Characterization of a long-term T-helper-cell line which produces IL-2 and induces immunoglobulin secretion.

Six OKT4+ human T-cell lines that require continuing PHA stimulation and TCGF for continuous growth were established. The cells from all six of these T-cell lines became smaller in size and lost the cell surface Ia antigen when they were grown in phytohemagglutinin (PHA)-depleted growth factor. These cells were unable to survive in the absence of PHA even if exogenous factor was present in great abundance. One of the cell lines (FL) was capable of providing helper functions. In the presence of PHA and phorbol myristate acetate, FL cells produced a growth factor, tentatively identified as Interleukin 2 (IL-2) by its ability to promote the proliferation of an IL-2-dependent murine T-cell line. Moreover, when FL cells were cocultured with B cells, pokeweed mitogen-induced immunoglobulin production was enhanced.

Antibodies, Monoclonal↗
PubMed1984

Receptor-mediated biliary transport of immunoglobulin A and asialoglycoprotein: sorting and missorting of ligands revealed by two radiolabeling methods.

In the rat, all receptor-bindable immunoglobulin A (IgA), and 1-4% of injected asialoglycoprotein (ASG), are transported from blood to bile intact. The major fraction of the ASG is degraded in hepatic lysosomes. The study described here was designed to elucidate the sorting that occurs in hepatocytes subsequent to receptor binding of ligands not sharing the same fate. We show that conjugation of protein with the Bolton and Hunter reagent can be used as a probe for the lysosomal pathway, since 50% of the reagent is released into bile after lysosomal degradation of internalized protein. Radiolabeling by iodine monochloride was alternatively used to follow the direct pathways that deliver intact IgA and ASG to bile. After intravenous injection of labeled proteins, first intact ASG and IgA, and then radioactive catabolites from degraded protein, were released into bile. No proteolytic intermediates were detected, and the transport of IgA or ASG directly to bile was not affected by the lysosomal protease inhibitor leupeptin. These observations indicate that divergence of the direct biliary transport pathways from the degradation pathway occurs at a stage preceding delivery to lysosomes, possibly at the cell surface. Competition studies showed that all three pathways (including the biliary transport of intact ASG) are receptor mediated, but even at supersaturating doses the uptake and processing of IgA and ASG occur independently. We propose that IgA and ASG receptors are not frequently in juxtaposition on the plasma membrane, but that ASG, after binding to its receptor, is occasionally missorted into the biliary transport pool.

Animals↗