Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This report describes studies of the mucosal antitoxic response in rats after enteric administration of several forms of cholera toxin or toxoid, proteins which differ primarily in their ability to bind to cell membranes and activate cellular adenyl cyclase. These two characteristics appeared to markedly enhance the local primary response to these antigens. A single dose of toxoid lacking these features was ineffective in local priming even though it was absorbed and induced a systemic immune response. Single dose mucosal priming occurred only with preparations which bind to cell membranes and was enhanced by those which also activate cellular adenyl cyclase. In contrast, single-dose mucosal boosting was best accomplished by materials with these properties but was also seen with a toxoid lacking both of these functions. The property of membrane binding appears to be most advantageous in mucosal priming, perhaps by increasing effective trapping of absorbed antigen in unprimed mucosal lymphoid tissue, whereas the ability to activate adenyl cyclase appears to enhance primary and secondary type responses about equally. Combinations of crude toxoid and toxin were also more effective in mucosal priming than purified materials, a finding which is unexplained. A single dose of this combination induced mucosal priming which was fully developed in 2 wk, undiminished after 4 too, and only modestly diminished after 8 mo, thus demonstrating relatively prolonged memory in the IgA mucosal immune system. Effective two-dose local immunizing regimens were developed, and it was shown that there was no correlation between the mucosal and systemic secondary antitoxin responses provoked by these regimens.
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PMID:The role of antigen form and function in the primary and secondary intestinal immune responses to cholera toxin and toxoid in rats. 67 Aug 85

Following incubation of murine epidermis in medium containing either interleukin-2 or interleukin-6, there is significant upregulation in the density of Ia+ epidermal Langerhans cells (to 159% and 175% of control, respectively). This cytokine-induced upregulation is abrogated by either rabbit or human IgG due to triggering of Fc gamma receptors. In contrast, human IgA does not inhibit the effect of interleukin-2 or interleukin-6. Using different isotypes of murine IgG, we have demonstrated that all subclasses are capable of inhibiting the cytokine-induced enhancement of Ia antigen, although IgG1 and IgG2b must be heat aggregated to be effective. The IgG-mediated events are dependent on prostaglandin synthesis because they can be blocked by the cyclooxygenase inhibitor indomethacin, 10 micrograms/ml. The responsible PG appears to be PGD2; in contrast to its known inhibitory effect on macrophages, PGE2 does not inhibit the upregulation of Ia antigen on Langerhans cells. In addition, these IgG-mediated events are dependent upon the generation of cAMP because they can be blocked by the adenylate cyclase inhibitor 2',5'-dideoxyadenosine, 1 mM. Despite the apparently central role of PGD2 and cAMP in this process, triggering of the Fc gamma R by different isotypes of IgG blocks upregulation of Ia via at least two different pathways. The inhibition caused by aggregated IgG1 or IgG2b, which bind to Fc gamma RII on Langerhans cells, is abrogated by para-bromophenacylbromide, an inhibitor of phospholipase A2. In contrast, the inhibition caused by monomeric IgG2a, which binds to Fc gamma RI most likely on keratinocytes, or monomeric IgG3, which probably binds to this same Fc gamma RI, is abrogated by staurosporine, an inhibitor of protein kinase C, as well as by W7, a calmodulin antagonist. Finally, 1,2 dioctanoyl-rac-glycerol, an activator of protein kinase C, mimics the Ig-mediated events. Based on these findings, as well as studies using monoclonal antibodies to the murine Fc gamma receptors I and II, we conclude that, as is the case in murine macrophages, triggering of an epidermal Fc gamma RI, most likely on keratinocytes, results in the generation of cAMP via a Ca(++)-dependent protein kinase C pathway, whereas triggering of an epidermal Fc gamma RII, most likely on Langerhans cells, results in the elevation of cAMP via a phospholipase A2-mediated pathway. In contrast to the situation for macrophages, PGD2 is a vital intermediate in both pathways, perhaps because Langerhans cells have receptors for only this prostaglandin.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effect of triggering epidermal Fc gamma receptors on the interleukin-2- and interleukin-6-induced upregulation of Ia antigen expression by murine epidermal Langerhans cells: the role of prostaglandins and cAMP. 165 69

We investigated the effects of the beta-adrenoceptor agonist isoproterenol (ISO) and the alpha- and beta-adrenoceptor agonist norepinephrine (NE) on murine B-cell activation. Cells were stimulated either by anti-mouse mu-chain antibodies (anti-mu), or by lipopolysaccharide (LPS), or a membrane proteoglycan of Klebsiella pneumoniae (Kp MPG), a T-independent polyclonal activator distinct from LPS, which induces B-cell proliferation and Ig synthesis. ISO and NE enhanced LPS- and Kp MPG-induced B-cell proliferation and maturation into IgM-, IgG- and IgA-secreting cells. The enhancement was prevented by prior addition of the beta-adrenoceptor antagonist propranolol but not by the alpha-adrenoceptor antagonist phentolamine. Earlier events in the LPS- and Kp MPG-stimulated B-cell activation, such as increases in Ia antigen expression and RNA synthesis, were not modified by the catecholamines. Unlike ISO and NE, the membrane-permeant cyclic adenosine 3',5'-monophosphate (cAMP) analogue dibutyryl cAMP (dbcAMP), and the potent adenylate cyclase activator forskolin did not enhance but even inhibited DNA synthesis and Ig secretion stimulated by LPS and Kp MPG. In addition, ISO and NE did not enhance but strongly inhibited anti-mu-induced B-cell proliferation, and these effects were mimicked by dbcAMP and forskolin. Collectively, the data demonstrate that beta-agonists differently modulate B-cell activation depending upon the polyclonal activator, and provide additional evidence for distinct biochemical mechanisms of B-cell activation by anti-mu and LPS. Moreover, our results indicate that beta-adrenergic stimulation up-regulates B-cell responses to LPS and Kp MPG by a novel and cAMP-independent pathway.
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PMID:Differential regulation of mouse B-cell activation by beta-adrenoceptor stimulation depending on type of mitogens. 215 73

Cholera toxin (CT) is a potent stimulator of IgA responses when administered orally and has been shown to promote IgA responses to a second protein such as keyhole limpet haemocyanin (KLH) if this is fed simultaneously. In this paper we show that whilst feeding 5 mg KLH with either 0.5 micrograms CT or 10 micrograms B subunit fails to stimulate a mucosal IgA response to KLH, feeding 0.5 microgram CT and 10 micrograms B subunit together with 5 mg KLH produces a local IgA anti-KLH response as great as that produced by 10 micrograms of whole CT. In addition to stimulating IgA responses in the lamina propria, preliminary results indicate that cellular responses are also stimulated, as we have demonstrated KLH antigen-driven proliferation of cells isolated from groups of mice fed either 10 micrograms CT + 5 mg KLH or 0.5 micrograms CT + 10 micrograms CTB + 5 mg KLH but not mice fed KLH alone or with either 10 micrograms CTB or 0.5 micrograms CT. These results indicate that the mucosal adjuvant action of CT is due to a synergistic effect involving both the GM1 binding of the B subunit and adenylate cyclase activation by the A subunit.
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PMID:Whole cholera toxin and B subunit act synergistically as an adjuvant for the mucosal immune response of mice to keyhole limpet haemocyanin. 233 68

We have raised polyclonal antibodies in rabbits against the FSH receptor, purified from calf testis and isolated the IgG fraction from the immune serum (immune IgG) by protein A affinity chromatography. When the immune IgG was incubated with purified, radioiodinated FSH receptor, the resulting complex could be immunoprecipitated by goat anti-rabbit gamma globulin. The immunoprecipitate, after dissociation of receptor from antibody, separation by SDS-PAGE under reducing conditions, and autoradiography, showed the presence of a approximately 60 kDa protein previously identified as a component of the FSH receptor. Binding of 125I-hFSH to membrane-bound receptors was inhibited in a concentration-dependent manner by immune IgG (Ed50 = 90 micrograms/ml). Nonimmune serum or IgM/IgA fractions from immune serum had no effect. 125I-labeled immune IgG bound specifically to testis membranes and the binding could be inhibited in a concentration-dependent manner by ovine FSH. These results suggest that the FSH-binding site and the antibody-binding site on the receptor are proximate or identical. Immune IgG mimicked the ability of FSH to stimulate basal adenylate cyclase activity and conversion of androstenedione to estradiol in cultured immature rat Sertoli cells. Stimulatory but submaximal effects of FSH were augmented by immune IgG. Rat Sertoli cells treated with IgG fractions from immune serum showed an intense fluorescent staining of plasma membrane receptor. No fluorescent staining of receptor was seen when preimmune IgG was used or in the presence of excess ovine FSH. These observations suggest that the polyclonal receptor antibody capable of recognizing FSH receptor behaved as an FSH binding competitor, but was also active as an agonist producing the biological effect of FSH in vitro. The effectiveness of antibodies against FSH receptor in stimulating estradiol synthesis suggests that the information needed for FSH signal transduction resides in the membrane receptor rather than in the hormone molecule. Such antibodies may offer a useful probe for further study of FSH receptor structure and mechanism of hormone action.
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PMID:Polyclonal antibodies against follitropin (FSH) receptor interfere with hormone binding, but mimic the effects of FSH. 240 17

Cholera toxin (CT), either mixed with or conjugated to unrelated protein Ag, is known to enhance the intestinal IgA response of rodents toward the unrelated Ag. Although relatively low doses of CT exert this gut mucosal adjuvant effect, the inherent toxicity of CT is a hindrance to its use in humans. Our report demonstrates that CT treated with 20 mM glutaraldehyde retains adjuvant properties but exhibits more than 1000-fold lower toxicity than untreated toxin. Glutaraldehyde was also used in a one-stage conjugation procedure to couple CT covalently to Sendai virus. Again, toxicity was reduced more than 1000-fold. This drop in toxicity is consistent with an observed 100-fold loss in binding capacity of the CT B subunit and a 20- to 50-fold reduction in adenylate cyclase activation by the CT A subunit. Oral administration of this virus-toxoid conjugate resulted in increased gut antiviral IgA titers compared with oral administration of either virus alone or of virus mixed with glutaraldehyde-treated toxin. This marked decrease in toxicity may afford a practical approach for the use of CT as a mucosal adjuvant.
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PMID:Cholera toxin as a mucosal adjuvant. Glutaraldehyde treatment dissociates adjuvanticity from toxicity. 254 46

Cholera toxin (CT) is a powerful oral immunogen and adjuvant that elicits strong IgG and IgA antibody responses. In our study we investigated whether this property of CT was associated with an effect on B cell isotype differentiation. Initially, we determined the effect of CT on normal LPS-induced Peyer's patch B cells and found that whereas CT is strongly inhibitory of IgM production, it increases by approximately three-fold the number and frequency of IgG- and IgA-producing cells. Subsequently, using cell sorting technology, we demonstrated that CT acts on membrane (m)IgM+, mIgG/mIgA- B cells rather than mIgG/mIgA+ B cells. In addition, we showed that CT does not cause selective inhibition of mIgM, or enhancement of mIgG/mIgA B cell proliferation. In parallel studies we determined the effect of CT on the differentiation of a clonal B cell population, CH12.LX cells, i.e., a population comprised mainly of mIgM+ cells (98%) admixed with a small subpopulation of mIgA+ cells (2%). Here we found that CT (in the absence of LPS) causes a rapid decrease (24 h) in the intensity of mIgM expression as well as a marked increase in the size of the subpopulation expressing mIgA. In addition, we found that CT (in the presence of LPS), inhibits CH12.LX IgM production while increasing the absolute number and frequency of IgA-producing cells. In contrast, CT inhibits IgA production by CH12.LX.A2 cells, a subclone of CH12.LX cells that bears only IgA. Finally, we demonstrated that CT is equally inhibitory of the proliferation of CH12.LX cells and CH12.LX.A2 cells. Taken together, these effects of CT on normal B cells and a clonal B cell line indicate that CT induces substantial numbers of mIgM+ cells to undergo isotype differentiation into mIgG+ or mIgA+ B cells. In a final series of studies we showed that the effect of CT on isotype differentiation was mimicked by the B subunit of CT, i.e., the subunit that does not activate intracellular adenylate cyclase; thus the induction of isotype differentiation by CT is not mediated by a perturbation in cAMP level.
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PMID:Cholera toxin promotes B cell isotype differentiation. 278 65

Thyroid-stimulating hormone (TSH) receptor antibodies and antibodies stimulating adenyl cyclase were measured in 47 relatives of patients with Graves' hyperthyroidism from two families with a high prevalence of the disease, in whom bioassays for the long-acting thyroid stimulator (LATS) had been performed 10 years earlier. Tests were also carried out in six propositi from the two families and age- and sex-matched normal subjects from six families. There had been no new cases of hyperthyroidism since the first study, although one subject was clinically and biochemically hyperthyroid at the time of study and two more were biochemically borderline hyperthyroid but clinically euthyroid. Levels of serum T4 thyrotropin, and percentage T3 resin uptake and free thyroxine indices were similar for relatives and normal subjects, although the mean serum T3 level for relatives was significantly greater than that for the normal subjects. Antibodies were not detected by either assay in any relative. Significant titers of antithyroglobulin antibodies were demonstrated in 4 of 44 relatives but in none of 46 normals tested, while thyroid cytoplasmic antibodies were detected in 8 of 44 relatives and 3 of 45 normals. The mean serum IgG for Graves' relatives was significantly greater than that for the normals, although the mean IgM and IgA levels for the two groups were not significantly different.
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PMID:Thyroid-stimulating hormone (TSH) receptor antibodies and antibodies stimulating adenyl cyclase in relatives from two families with a high prevalence of Graves' hyperthyroidism: a ten-year follow-up study. 628 89

Mice were immunized perorally with cholera toxin (CT), cholera B-subunit (CB), or buffer as control. The response of anti-CT antibodies of the IgG, IgA and IgM class in bile, IgA being predominating, were similar in both immunized groups. The same number of anti-CT containing plasma cells (ACC) were determined in the intestinal lamina propria of CT - as well as of CB-immunized mice 20 days after the last immunization, while ACC at day 4 in the CB group were 50% higher than in the CT group. In contrast to the vigorous antibody response to CT in both groups of immunized mice, only animals immunized with CT displayed resistance to CT-induced intestinal hypersecretion and to CT stimulation of adenylate cyclase. The CB-treated group responded to CT with fluid accumulation and enzyme activation similar to controls. The results suggest that intestinal resistance to CT in mouse is due to desensitization of adenylate cyclase rather than to CT-neutralizing antibodies.
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PMID:Intestinal resistance to cholera toxin in mouse. Antitoxic antibodies and desensitization of adenylate cyclase. 672 17

Intestinal mucosal as well as extramucosal antibody responses were studied in mice after peroral immunizations with cholera toxin or cholera B subunit. The immunizations with cholera toxin gave rise to a marked response with antitoxin-secreting cells (PFC) in Peyer's patches (PP), mesenteric lymph nodes (MLN) and spleen showing isotype distribution of IgG greater than IgA greater than IgM and with PFC kinetics in MLN and spleen that suggested migration of cells from PP after peroral administration rather than cells stimulated in situ by adsorbed antigen. Highest numbers of PFC were obtained after 2 immunizations, and further administrations resulted in a decrease in the PFC response in MLN and spleen, while the PP responsiveness was relatively unchanged, and interestingly, protective immunity and IgA-dominated antitoxin titers in intestinal washings increased markedly by the additional boosters. Animals immunized with cholera B subunit, which lacks the adenylate cyclase-stimulating capacity of cholera toxin, showed similar PFC responses in extramucosal organs as those receiving cholera toxin but were poorly protected and had correspondingly lower IgA antitoxin titers in intestinal washings. These results suggest that the mucosal IgA antitoxin predominance is mainly due to regulatory mechanisms operating on the end-stage differentiation of the committed B cells in lamina propria and that this differentiation, as judged from the different results with cholera toxin and its B subunit, might be influenced by cyclic AMP.
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PMID:IgA isotype restriction in the mucosal but not in the extramucosal immune response after oral immunizations with cholera toxin or cholera B subunit. 687 6


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