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Biomedical subjects

C O Elson

Publications and source records attributed to C O Elson.

At least 55 records · Page 3Linked to original sources
PubMed1996

The effects of immunosuppressive agents on cytokines.

Controlled clinical trials have shown that several immunosuppressive drugs are efficacious in patients with inflammatory bowel disease. These drugs each have multiple effects on the immune system and the exact mechanism of their beneficial effect in inflammatory bowel disease is unknown. None of these agents directly inhibits the 'inflammatory cytokines' such as IL-1 beta, IL-6, IL-8, or TNF-alpha. However, they can all inhibit generation of leukocyte precursors in the bone marrow, that is, the cells that produce such cytokines. The effects of current agents on T-cell subsets and their associated cytokines remains unclear. Based on insights from novel mouse models of chronic colitis, the goal of 'immunotherapy' going into the next decade should be either to inhibit specifically the effector T cells mediating disease or to enhance the regulatory T cells that inhibit such effector cells or, ideally, to do both. Therapy meeting this goal, which will need to based on a more thorough understanding of the immunopathogenesis of inflammatory bowel disease, should allow a more specific or 'surgical' approach to immunotherapy and simultaneously reduce its risks and adverse effects.

Animals↗
PubMed1995

Differences in intraepithelial lymphocyte T cell subsets isolated from murine small versus large intestine.

Intraepithelial lymphocytes (IELs) have been extensively studied in the murine small intestine. However, to date no studies have assessed IEL in the large intestine, despite the marked differences in function and lumenal environment. In the present study, we isolated IEL from both small and large intestine of three mouse strains (BALB/c, C3H/HeN, C57BL/6) and determined the frequency of CD2, CD4, and CD8 expression on CD3+ IEL, as well as the frequency of alpha beta and gamma delta TCR usage and V beta distribution. Higher numbers of IEL/unit length were always isolated from the small intestine (20-30 x 10(6)/5 mice) compared with large intestine (1.1-2.5 x 10(6)/5 mice). Interestingly, IEL from the large intestine of all strains were predominantly alpha beta TCR+ whereas gamma delta TCR+ IELs predominated in small intestine. Large intestinal IELs were mainly CD4+, in both BALB/c and C3H/HeN mouse strains. IELs from large intestine of C57BL/6 mice were mainly CD8+; however, the CD4+ subset was fourfold higher when compared with small intestine IEL. Potential functional differences between IEL subsets was assessed by determining the relative levels of mRNA for IL-1, 2, 4, 5, 10, IFN-gamma, TGF-beta, and TNF-gamma. Similar patterns of IL-1, IFN-gamma and TNF-alpha were seen while more IL-2, IL-4, IL-5, and IL-10 mRNA was noted in large intestinal IEL. Stimulation of C3H/HeJ IEL with anti-CD3 also resulted in higher levels of IL-3/GM-CSF, IL-4, and IL-6 by IEL from large intestine. These results show that marked differences occur among the T cell subsets present in IELs from mouse small and large intestine.

Animals↗
PubMed1995

Morphologic and functional alterations of mucosal T cells by cholera toxin and its B subunit.

Despite the mucosal immunogenicity and adjuvanticity in vivo of cholera toxin (CT), both CT and CT B subunit are strong inhibitors of T cell activation in vitro. This study asked whether such T cell inhibition is relevant to the mucosal effects of CT in vivo. The activation of T cells pulsed in vitro for only 15 to 120 min with CT or CT B subunit, respectively, was inhibited, consistent with the expected short exposure times in vivo. Although both CD8+ and CD4+ T cells were inhibited in vitro, CD8+ T cells bound more toxin and were inhibited to a greater degree than were CD4+ T cells. Intestinal gavage of mice with 10 micrograms CT did not alter the overall composition of Peyer's Patch, mesenteric lymph node, or spleen but did cause a marked depletion of intraepithelial lymphocytes, mainly CD8+ T cells, and of lymphocytes in the dome epithelium over Peyer's Patch. To determine whether such inhibition of T cells was functionally relevant in vivo, T cells from mice fed keyhole limpet hemocyanin (KLH) were adoptively transferred into naive recipients, who were then parenterally immunized. T cells from mice fed KLH alone inhibited both the systemic IgG and secretory IgA anti-KLH response, but T cells from mice fed KLH plus CT did not, indicating that mucosally applied CT was able to abrogate the induction of this suppressor T cell. We conclude that one of the mechanisms of CT's mucosal effects in vivo is the inhibition of certain mucosal T cell functions and alteration of the regulatory T cell environment in gut-associated lymphoid tissue.

Animals↗
PubMed1995

Transient protein S deficiency associated with cerebral venous thrombosis in active ulcerative colitis.

Cerebral venous thrombosis is an uncommon complication of ulcerative colitis. We report the case of a 29-yr-old female with a recent diagnosis of ulcerative colitis who suffered stroke secondary to thrombosis of the veins of Galen and straight sinus. A search for a hypercoagulable state revealed a nonfamilial transient protein S deficiency. Possible involvement of C4b-binding protein in this hypercoagulable state is discussed.

Acute Disease↗
PubMed1994

Oral tolerance in humans. T cell but not B cell tolerance after antigen feeding.

The purpose of this study was to investigate whether oral tolerance, defined as Ag-specific immunologic unresponsiveness after Ag feeding, could be induced in humans after prolonged Ag ingestion. Eight adult volunteers ingested a total dose of 0.5 g of keyhole limpet hemocyanin (KLH) followed by subcutaneous immunization with KLH. Eight controls received only the subcutaneous immunization. In the group fed KLH, there was a significant reduction in KLH-specific T cell proliferation (p = 0.04) and delayed skin test responses (p = 0.07) to KLH. KLH ingestion alone did not induce significant levels of Abs in either serum or secretions. However, after the subsequent subcutaneous immunization, the number of circulating IgG and IgM anti-KLH-producing cells, the titers of serum IgG, IgA, and IgM anti-KLH Abs, and the titers of IgA anti-KLH Abs in saliva and intestinal secretions were significantly greater in the KLH-fed group than in the nonfed group. We conclude that KLH feeding induced systemic T cell tolerance, but B cell priming, at both systemic and mucosal sites. These studies support the concept of using Ag feeding as a treatment for certain immune-mediated diseases.

Administration, Oral↗
PubMed1994

Dextran sulfate sodium-induced colitis occurs in severe combined immunodeficient mice.

BACKGROUND/AIMS: Oral administration of dextran sulfate sodium (DSS) has been reported to induce colitis in mice. The purpose of this study was to determine whether the possible pathogenic mechanism involved the acquired immune system. METHODS: Normal BALB/c and related C.B17 severe combined immunodeficient mice were fed 5% DSS (40 kilodaltons) in their drinking water for 7 days; controls were fed only water. Colons were scored for histological activity at various times. Cytokine production by cultures of colon and of draining lymph node cell was measured. The effect of DSS on the proliferation of the MCA-38 colonic epithelial cell line was assessed. RESULTS: DSS feeding resulted in a very reproducible acute distal colitis in both BALB/c and C.B17 severe combined immunodeficient mice. The lesions of BALB/c mice had an increased production of macrophage-derived cytokines, such as interleukin (IL) 1 beta, IL-6, tumor necrosis factor, and granulocyte-macrophage colony-stimulating factor, but not the T-cell cytokines IL-3 or interferon gamma. Draining lymph node cells produced these cytokines plus interferon gamma and IL-3. DSS inhibited MCA-38 cells at doses that would be easily achieved in the distal colon. CONCLUSIONS: Acute DSS-induced colitis does not require the presence of T cells or B cells because it occurred in C.B17 severe combined immunodeficient mice that lack these cells. Its induction may result from a toxicity of DSS for colonic epithelial cells.

Acute Disease↗
PubMed1994

Spontaneous, heritable colitis in a new substrain of C3H/HeJ mice.

BACKGROUND/AIMS: C3H/HeJ mice at the Jackson Laboratory have periodically been culled because of the occurrence of soft feces, perianal ulceration, and right-sided colitis. No pathogens have been isolated. The goal of the current study was to establish a substrain with a high incidence of this disease. METHODS: Affected male and female C3H/HeJ mice were bred. The clinical, pathological, microbiological, and genetic features of 216 mice of the resulting pedigree were characterized. RESULTS: A severely affected female crossed with a normal male resulted in a new substrain, denoted C3H/HeJBir, with a high incidence of right-sided colitis. Histologically, lesions occurred primarily in the cecum and proximal colon, characterized by acute and chronic inflammation, crypt abscesses, ulcerations, regenerative hyperplasia, and submucosal scarring. Such colitis peaked at 3-6 weeks; however, similar disease was found sporadically in animals more than 1 year of age. Small lesions at the anorectal junction were common throughout life. An extensive search for pathogens was negative. Genetic analysis of C3H/HeJBir mice suggested that the disease was inherited as a quantitative trait. CONCLUSIONS: C3H/HeJBir mice develop a spontaneous, heritable form of idiopathic inflammatory bowel disease and will be a valuable resource for genetic and immunologic studies of this disease.

Animals↗
PubMed1994

Intraperitoneal immunization of human subjects with tetanus toxoid induces specific antibody-secreting cells in the peritoneal cavity and in the circulation, but fails to elicit a secretory IgA response.

Five patients on continuous ambulatory peritoneal dialysis (CAPD) were immunized intraperitoneally with tetanus toxoid (TT) through an indwelling catheter. Four control patients on CAPD received the same dose of TT intramuscularly. Before immunization, virtually no anti-TT antibody-secreting cells (AbSC) were detected by the enzyme-linked immunospot (ELISPOT) assay in peripheral blood or peritoneal fluid from patients of either group. One to 2 weeks after immunization, high frequencies of TT-specific AbSC were detected in the circulation and peritoneal cavity. More than 80% of those cells were of the IgG isotype, with IgA accounting for most of the remainder. Patients receiving TT by the i.p. route showed significantly higher frequencies of specific IgG and IgA AbSC in the peritoneal cavity than patients immunized intramuscularly. Frequencies of AbSC in peripheral blood did not significantly differ between the two groups. Immunization with TT by both routes resulted in a significant increase of IgG anti-TT antibodies in serum, saliva and peritoneal fluid. A significant IgA antibody response was seen only in serum and peritoneal effluents. Therefore, i.p. immunization of human subjects with TT elicited both a localized response in the peritoneal cavity as well as a systemic response in serum, but did not induce a salivary IgA response.

Adult↗
PubMed1993

Helper T cell subsets for immunoglobulin A responses: oral immunization with tetanus toxoid and cholera toxin as adjuvant selectively induces Th2 cells in mucosa associated tissues.

Antigen-specific B cell responses to mucosally delivered proteins are dependent upon CD4-positive T helper (Th) cells, and the frequency of Th1 and Th2 cell responses after oral immunization may determine the level and isotype of mucosal antibody responses. We have used a protein-based vaccine, tetanus toxoid (TT), together with the mucosal adjuvant cholera toxin (CT), for oral immunization of mice to study the nature of antigen-specific Th cell subsets induced in Peyer's patches (PP) of the gastrointestinal (GI) tract and in the spleen (SP) during peak antibody responses. Mice orally immunized with TT and CT responded with antigen-specific secretory immunoglobulin A (S-IgA) antibodies in the GI tract, and with both IgG and IgA antibody responses in serum. PP and SP CD4+ T cells from mice orally immunized with TT plus CT were cultured with antigen-coated latex microspheres for induction of proliferative responses and for enumeration of cytokine producing CD4+ T cells. Interestingly, both PP and SP CD4+ T cell cultures showed increased numbers of IL-4- and IL-5 (Th2-type)-producing, spot-forming cells (SFCs) after 21 d of immunization, while essentially no interferon-gamma (IFN-gamma) or IL-2 (Th1-type) SFCs were noted. Cytokine-specific Northern blots and RT-PCR also revealed that significant IL-4 and IL-5 mRNA levels, but not IFN-gamma or IL-2 mRNA, were present in CD4+ T cells isolated from antigen-stimulated cultures. However, systemic immunization with TT and CT induced antigen-specific IgG and IgM but not IgA antibodies in serum. Further, both IL-2 and IFN-gamma-producing Th1-type cells as well as IL-4- and IL-5-secreting Th2-type cells were generated in SP. Our results show that oral immunization with TT and the mucosal adjuvant CT selectively induced antigen-specific Th2-type responses which may represent the major helper cell phenotype involved in mucosal IgA responses in the GI tract.

Administration, Oral↗
PubMed1993

Inhibition of murine T cell activation by cholera toxin B subunit is not mediated through the phosphatidylinositol second messenger system.

Although cholera toxin B subunit is a potent mucosal immunogen in vivo, its predominant effect in vitro is inhibition of T cell and B cell activation. We reported earlier that this inhibition was not mediated through activation of adenylate cyclase and increases in intracellular cAMP. There is increasing evidence that T cell activation is initiated through the phosphatidyl inositol second messenger system in which phosphatidyl inositol bisphosphate is hydrolyzed by phospholipase C, producing inositol trisphosphate (IP3) and diacylglycerol. IP3 increases cytosolic calcium and diacylglycerol binds, translocates, and activates protein kinase C (PKC). These signals lead to a complex series of events eventuating in activation of a number of genes important in cell proliferation. In this study, we asked whether the mechanism of T cell inhibition by B subunit of cholera toxin (CT-B) was due to interference with the phosphatidyl inositol second messenger system. We found that substitution of ionomycin and PMA for IP3 and diacylglycerol, respectively, in culture induced T cell proliferation but only if both were present simultaneously. Such proliferation was inhibited by CT-B even if added hours after the start of culture. An assay for cytosolic PKC activity demonstrated that PMA translocation of PKC from cytosol to membrane was not inhibited by CT-B, indicating that CT-B does not inhibit activation of PKC. There was no inhibition of Con A-stimulated T cell phosphoinositol turnover. Moreover, Con A added to Fura-2 AM-loaded cells caused a rapid rise in cytosolic calcium, which CT-B preincubation did not alter. These results indicate that CT-B did not inhibit IP3 generation or action. We next looked at expression of genes involved in T cell proliferation. CT-B inhibited the production of IL-2 by mitogen-activated T cells; Northern analysis showed that this inhibition was associated with decreased levels of IL-2 mRNA. Expression of IL-2R and of transferrin receptors was only modestly reduced. Despite the presence of IL-2R on the T cells exposed to CT-B, the addition of exogenous IL-2 to the cultures did not reverse the CT-B-induced T cell inhibition. We conclude that the T cell inhibition by CT-B is not mediated by interference with the activation of the phosphatidylinositol second messenger system but occurs at a later stage of T cell activation.

Animals↗
PubMed1993

Low-dose oral methotrexate in refractory inflammatory bowel disease.

The purpose of this study was to evaluate the efficacy and safety of low-dose weekly, oral methotrexate in patients with steroid-dependent or steroid-refractory inflammatory bowel disease (IBD). Oral methotrexate was given weekly at 15 mg/week. The primary criterion of response was based on steroid withdrawal. Of the 10 patients with Crohn's disease, daily prednisone dosage dropped from a mean of 37 +/- 9.6 mg to 8.3 +/- 2.1 mg/day (P < 0.02); two had a complete withdrawal and four a partial response (< 7.5 mg/day). In the eight patients with ulcerative colitis, daily prednisone dose dropped from a mean of 26.3 +/- 3.2 mg/day to 12.7 +/- 2.0 mg/day (P < 0.001); three had a partial response. Adverse effects due to methotrexate were mild in both groups. We conclude that oral methotrexate may be useful and reasonably safe as a steroid-sparing agent in patients with refractory IBD.

Administration, Oral↗
PubMed1993

Comparative effectiveness of the cholera toxin B subunit and alkaline phosphatase as carriers for oral vaccines.

The purpose of this study was to determine whether the B subunit of cholera toxin (CtxB) has adjuvant activity over and above serving as a carrier protein for orally administered vaccines. An oligonucleotide that encodes an antigenic determinant (GtfB.1) from the glucosyltransferase B gene (gtfB) of Streptococcus mutans was genetically fused to the 5' terminus of either the CtxB gene (ctxB) or the Escherichia coli alkaline phosphatase gene (phoA). The resulting chimeric proteins were expressed in a phoA mutant strain of E. coli and then purified. The antigenicities of the proteins were confirmed by immunoblotting analysis using antisera specific for GtfB, CtxB, or PhoA. An equimolar amount of peptide on each carrier was administered by gastric intubation to mice three times at 10-day intervals. Antibody titers to the peptide, CtxB, and PhoA (in the serum, intestine, vagina, saliva, and bronchus) were determined by enzyme immunoassay. Antibody to the peptide was detected only in the sera of mice immunized with the peptide fused to CtxB. No antipeptide antibody was detected in mice immunized with the peptide fused to PhoA. The lack of detectable levels of antipeptide antibody in intestinal lavage fluid was attributed to dilution of the sample beyond the sensitivity of the assay. This was confirmed by cultivation of Peyer's patch and mesenteric lymph node tissue from mice orally immunized with the GtfB.1::CtxB chimera. Using this method, antipeptide antibody was detected in the culture fluid. We conclude that CtxB possesses unique properties that allow it to act as more than a simple carrier protein.

Administration, Oral↗
PubMed1993

Optimizing oral vaccines: induction of systemic and mucosal B-cell and antibody responses to tetanus toxoid by use of cholera toxin as an adjuvant.

Cholera toxin (CT) is an effective mucosal antigen and acts as an adjuvant when given orally with various antigens; however, few studies have compared the levels of antibody responses to CT and coadministered protein in systemic and mucosal tissues. In this study, we used tetanus toxoid (TT) for assessment of immune responses. Time course and dose-response studies established that 250 micrograms of TT given orally with 10 micrograms of CT three times at weekly intervals induced high serum and gastrointestinal tract anti-TT and anti-CT antibody responses. Oral immunization with TT alone induced no detectable mucosal immunoglobulin A (IgA) antibodies in fecal extracts and only weak serum IgG anti-TT responses. The coadministration of CT and TT induced peak serum IgG anti-TT responses following two oral doses that remained constant after the third oral immunization, while optimal mucosal IgA responses were seen after the third oral immunization. The serum anti-TT response obtained with CT and TT proved protective against TT challenge (100 minimum lethal doses), whereas mice orally given CT or TT alone died. Antigen-specific B-cell responses were assessed with an isotype-specific Elispot assay of isolated lymphoid cells from the spleen, Peyer's patches, and the small intestinal lamina propria. Interestingly, approximately fourfold-higher numbers of IgA anti-CT than of anti-TT antibody-producing (spot-forming) cells occurred in lymphocytes from the lamina propria of mice orally immunized with both TT and CT. The adjuvant CT did not induce polyclonal B-cell responses in mice given CT by the oral route, since no significant differences in total numbers of B cells producing IgA, IgG, or IgM were found compared with the numbers in mice given TT alone. The results clearly indicate that serum and mucosal antibody responses develop with different kinetics and that protective TT-specific antibody responses are generated in the systemic compartment when TT is administered with CT via the oral route.

Adjuvants, Immunologic↗
PubMed1993

Enhancing effect of cholera toxin on interleukin-6 secretion by IEC-6 intestinal epithelial cells: mode of action and augmenting effect of inflammatory cytokines.

Oral administration of cholera toxin (CT) induces a strong mucosal immune response to CT as well as having a potent adjuvant effect. Since one of the first cell types to encounter CT during cholera infection or after oral administration is the epithelial cell, we studied the effect of CT on interleukin-6 (IL-6) secretion by the rat intestinal epithelial cell line IEC-6. CT was found to rapidly enhance IL-6 secretion and IL-6 gene expression by these cells. The addition of dibutyryl cyclic AMP (cAMP) to cultures of IEC-6 cells had little effect on IL-6 secretion, yet mRNA levels were elevated, suggesting that the response may have been regulated by cAMP. Purified B subunit of CT did not significantly enhance IL-6 secretion or mRNA expression. CT and transforming growth factor beta 1 synergistically enhanced IL-6 secretion in IEC-6 cells. The addition of CT with either IL-1 beta or tumor necrosis factor alpha gave even greater synergistic enhancement of IL-6 secretion, and dibutyryl cAMP could mimic CT's synergy with IL-1 beta. These results indicate that the intestinal epithelial cell is capable of secreting high levels of IL-6 after encountering CT, especially in the presence of inflammatory cytokines. This high level of IL-6 secretion could be a very important component of the mucosal immune response to CT and may also account for a portion of the adjuvant effect of CT.

Animals↗
PubMed1993

Reduction in oral immunogenicity of cholera toxin B subunit by N-terminal peptide addition.

The mucosal adjuvanticity of cholera toxin and the potential of the B subunit of cholera toxin (CtxB) to serve as an oral vaccine carrier have prompted interest in the coupling of immunogenic peptides to this protein. The purpose of this study was to determine how such fusions affect the function of CtxB. Oligonucleotides were genetically fused to the 5' terminus of the ctxB gene to encode additional amino acids of 8, 12, and 24 residues in length. None of these additions affected the ability of CtxB to oligomerize, as determined by nondenaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Circular dichroism revealed no difference in conformation between the modified B subunits, regardless of the length of the addition. However, when compared with native CtxB, additions to the N terminus induced a consistent change in the net conformation of the protein. By using a competitive enzyme immunoassay, the affinity of the modified B subunits for GM1 ganglioside was shown to gradually decrease with increasing length of the N-terminal addition. A similar pattern was observed for the ability of the chimeras to inhibit proliferation of concanavalin A-stimulated spleen cells in vitro, which is a previously described functional property of CtxB that is dependent on its binding to cells. Lastly, the oral immunogenicity of these chimeras was found to be less than that of native CtxB. These results indicate that large fusions to the N terminus of CtxB can significantly affect its biological properties and could reduce its value as a mechanism for effective mucosal immunization.

Administration, Oral↗