A retrospective analysis of early and late outcome of biodegradable stent placement in the management of refractory anastomotic colorectal strictures.

BACKGROUND: Benign colorectal strictures are treated conventionally by endoscopic dilation. Experience using SEMS for benign colonic strictures is limited, and outcomes to date have been disappointing. Refractory colorectal strictures remain challenging to be treated with surgery. Polydioxanone-based stent are biodegradable (BD) stent CE approved for esophageal strictures. This study was designed to investigate retrospectively the safety and the efficacy of these stents for the management of strictures refractory to multiple sessions of dilation. METHODS: Patients with postsurgical benign strictures located within 20 cm from anal verge, refractory to mechanical or pneumatic dilation (at least 3 sessions) were included in this analysis. Clinical success was defined as the absence of occlusive symptoms and the ability to pass through the stricture with a regular size colonoscope. All patients were predilated before stent placement. Stents were released under fluoroscopic control. All patients were under stool softeners for 3 months. Follow-up was scheduled with endoscopic and fluoroscopic controls within 90 days from stent deployment and afterwards by telephone interview and/or ambulatory consultation. RESULTS: Eleven patients (7 males, mean age 62.3 ± 8.5 years) were included. Technical success was achieved in all the patients. Stent migration was observed in four patients within the first 2 weeks after stent placement. Stent migration was followed by recurrence of stricture and obstructive symptoms in all the cases. Among the seven patients who completed the process of stent biodegradation, five of them had complete resolution of the stricture and relief of symptoms. Two of 11 patients required surgical treatment during the follow-up period (mean 19.8 (range 42-15) months). The overall success rate of the BD stent was 45 %. CONCLUSIONS: This retrospective analysis of a limited number of patients demonstrated that nondedicated esophageal BD stents are associated with high risk of migration and clinical success in less than 50 % of patients. Dedicated stents with large diameter and antimigration findings could potentially improve the outcome of patients with refractory benign colorectal strictures.

Safety of cold polypectomy for <10mm polyps at colonoscopy: a prospective multicenter study.

BACKGROUND: Cold polypectomy techniques (without electrocautery) by means of biopsy forceps or snare are widely adopted for the removal of subcentimetric polyps. However, few data are available on the safety of this approach. The aim of this study was to assess the safety of cold polypectomy for subcentimetric polyps, as well as the rate of advanced neoplasia in these lesions. PATIENTS AND METHODS: In a prospective multicenter trial, consecutive patients with at least one < 10-mm polyp at colonoscopy were prospectively included. All of the < 10-mm polyps detected within the study period were removed by cold polypectomy. The rates of immediate or delayed bleeding and other complications were assessed at 7 and 30 days after cold polypectomy by telephone calls. The rate of advanced histology was also assessed. Predictive variables of postpolypectomy bleeding or advanced neoplasia were identified by multivariate analysis. RESULTS: A total of 1015 < 10-mm polyps in 823 patients (15.5 % on antiplatelet agents) were removed. Of these, 822 (81 %) were ≤ 5 mm and 193 (19 %) were 6 - 9 mm. Immediate postpolypectomy bleeding occurred in 18 patients, corresponding to a per-patient and per-polyp bleeding rate of 2.2 % (95 % confidence interval [CI] 1.2 % - 3.2 %) and 1.8 % (95 %CI 1 % - 2.6 %), respectively. Therapy with antiplatelet agents (odds ratio [OR] 4; 95 %CI 1.5 - 10.6) and larger polyp size (OR 2; 95 %CI 1.1 - 6.9) were independent predictors of bleeding. Bleeding was successfully treated by endoscopic hemostasis in all cases and required no further medical intervention. Advanced neoplasia prevalence in polyps ≤ 5 mm was as high as 8.7 %. CONCLUSIONS: The results from this study showed the high safety of a cold polypectomy approach for subcentimetric polyps. This was due to the low rate of postpolypectomy bleeding and to the high efficacy of endoscopic hemostasis in its treatment. The high rate of advanced neoplasia in polyps ≤ 5 mm should prompt some caution on the management of these lesions following detection at computed tomography colonography or colon capsule endoscopy.

Evidence that natural murine soluble interleukin 4 receptors may act as transport proteins.

The present studies were undertaken to determine whether the interleukin 4 binding proteins (IL-4BPs) previously identified in the biological fluids of mice are soluble forms of IL-4Rs. We also studied the binding properties of IL-4BPs in order to gain insight into their physiological role in vivo. Affinity-purified IL-4BPs and recombinant soluble IL-4Rs generated similar one-dimensional (Cleveland) peptide maps after digestion with either Staphylococcus aureus V8 protease or trypsin, indicating structural similarities. Furthermore, a rat mAb directed against the murine IL-4Rs immunoprecipitated the IL-4BPs and completely inhibited binding of 125I-IL-4 to a purified preparation of IL-4BPs. Taken together these data indicate that the IL-4BPs are soluble IL-4Rs. At 4 degrees C the IL-4BPs competitively inhibited the binding of IL-4 to membrane IL-4Rs but their ability to prevent binding of IL-4 to cells at 37 degrees C, at the same concentrations, was significantly reduced. Kinetic binding studies of soluble IL-4BPs vs. membrane IL-4Rs disclosed important differences in their rates of dissociation from IL-4. Whereas dissociation at 4 degrees C was slow for both, dissociation of IL-4 from IL-BPs at 37 degrees C was considerably faster (t 1/2 of 2 min) than dissociation of IL-4 from membrane IL-4Rs (t 1/2 of approximately 69 min). Temperature-dependent changes in dissociation kinetics were reversible, and could not be accounted for by either inactivation of the IL-4BPs at 37 degrees C or receptor internalization. Additional experiments also demonstrated that when IL-4BPs bind to IL-4 at 37 degrees C, the IL-4/IL-4BPs complex can rapidly dissociate, allowing IL-4 to bind to membrane IL-4Rs. In addition, binding of IL-4 by the IL-4BPs protects IL-4 from proteolytic degradation. Taken together, these results suggest that the IL-4BPs are naturally occurring forms of soluble IL-4Rs and that some of their properties (fast dissociation kinetics and protection of IL-4 from proteolysis) are consistent with a potential role as carrier proteins for IL-4 in the circulation.

Memory T cells are anergic to the superantigen staphylococcal enterotoxin B.

We have used staphylococcal enterotoxin B (SEB) to study the role of naive and memory T cells in the induction of peripheral tolerance. After administration of SEB to mice, the numbers of naive and memory T cells increase, as does the proportion of memory T cells, which are unresponsive to further stimulation with SEB in vitro. In addition, memory T cells generated in response to conventional antigen, which proliferate and provide help to B cells in the presence of the conventional antigen, fail to respond to superantigen. Hence, memory T cells, in general, are anergized by SEB. These results suggest that SEB-induced activation and anergy reflect the combined responses of naive and memory T cells. The differential activation vs. anergy of naive and memory T cells by superantigen may be related to cytokine production and may play an important role in the etiology of autoimmune diseases or immunodeficiency diseases such as acquired immune deficiency syndrome.

A dichotomy between the expression of IgD on B cells and its requirement for triggering such cells with two T-independent antigens.

The majority of adult B lymphocytes in the mouse bear two immunoglobulin isotypes, IgM and IgD (mu(+)delta(+) cells) (1). A small population of IgM-bearing cells lacks, or expresses very low levels of IgD (mu- predominant [mup] cells) (1). These cells are believed to constitute a less mature subset of B cells analogous to neonatal B cells (2). Based on the time during ontogeny when responses to T-independent (TI) and T-dependent (TD) antigens appear (3, 4) and the ability to block in vitro responses with anti- mu or anti-delta (5, 6, D. Mosier, personal communication), it has been suggested that the precursors of two TI-1 responses, trinitrophenyl (TNP)- Brucella (TNP-BA) and TNP-lipopolysaccharide (TNP-LPS) are mup cells (5, 6), whereas the precursor for a TD response, TNP-sheep erythrocytes (TNP-SRBC), bears both IgM and IgD (6). However, the possibility cannot be excluded that IgD is present on some or all of the TI precursors, but that it is not obligatory for triggering. In the present experiments we have examined the phenotypes of TI and TD precursors by treating cells with C' and either anti-mu or anti-delta before stimulation with antigen. Our results suggest that the majority of B cells that respond to TNP-BA, TNP-LPS, and TNP-SRBC bear IgD, even though in the case of the two TI antigens, IgD is not required for triggering.

Cell surface immunoglobulin. XVIII. Functional differences of B lymphocytes bearing different surface immunoglobulin isotypes.

Three populations of murine splenic B lymphocytes have been characterized previously (6, 7, 9) as those bearing only IgM, those bearing only IgD, and a population bearing both isotopes. These studies were designed to test the response of the IgM+ cells (IgM-only or IgM plus IgD) vs. the IgD-only cells to the B-cell mitogen, lipopolysaccharide. Results that after 1-4 days of culture, in the presence of mitogen, the IgM+ cells enlarge and elaborate an IgM polyclonal response. The IgD-only cells, in contrast, do not exhibit an IgM polyclonal response, but instead undergo blastogenesis and proliferation.

Studies on the murine Ss protein. I. Purification, molecular weight, and subunit structure.

The murine Ss protein has been isolated and purified. Using specific antisera, the radiolabeled protein has a mol wt of 120,000 in sodium dodecyl sulfate polyacrylamide gels. It is composed of two basic subunits of 23,000 and 14,000 daltons. The smaller molecular weight subunit contains a single disulfide bridge, is devoid of carbohydrate, and may represent the murine equivalent of beta2-microglobulin.

Cell surface immunoglobulin. IX. A new method for the study of synthesis, intracellular transport, and exteriorization in murine splenocytes.

A new method for the detection of cell surface immunoglobulin labeled with isotopic precursors is described. The method consists of the aggregation of surface Ig on cells with specific antibody (heterologous) and the subsequent removal of antigen-antibody complexes by the combination of high speed centrifugation and immunoprecipitation of remaining soluble complexes using antibody to the heterologous Ig. Using this method, the kinetics of appearance of cell surface Ig and its turnover were studied in murine splenocytes. The results suggest that cell surface Ig is synthesized and transported in the same manner as secretory Ig rather than being synthesized on the plasma membrane. The turnover of intracellular and cell surface Ig in lymphocytes is slow. In contrast, intracellular Ig in plasma cells is rapidly secreted and usually without a cell surface phase. Cell surface Ig was shown to be radiolabeled with [(3)H]glucosamine, -galactose, and -fucose. The proportion of cell surface to intracellular (nonsurface) Ig labeled with these precursors suggests the same sequence of addition of sugars to Ig destined to be on the surface of lymphocytes as with Ig which will be secreted by plasma cells. Results with this new method also confirm earlier conclusions based on experiments using cell surface iodination: 8S IgM is the predominant Ig on the surface of murine splenocytes and the molecule appears to be attached by its micro-chains.

Cytotoxic T cells specific for antigens expressed on surface immunoglobulin-positive cells.

C.B-20 mice were immunized with splenocytes or B leukemia cells (BCL1) from Ig H chain allotype congenic strains. Spleen cells from these immunized mice were rechallenged in vitro to generate H-2-restricted cytotoxic T cells that were specific for target antigens controlled by genes linked to the Ig H chain locus. The anti-Ig H cytotoxic T cells detected an antigen(s) expressed only on surface Ig+ cells. Thus, T cell lymphoblasts, eight BALB/c myeloma cell lines, and a T cell lymphoma were not lysed by the effector cells. In contrast, B cell lymphoblasts and the surface Ig+ BCL1 cells were sensitive to lysis. A surface Ig- hybridoma (which secretes the IgM from the BCL1 cells) generated by fusing BCL1 cells to X63 myeloma cells was not killed by the effector cells. These data indicate that cytotoxic T cells specific for antigenic determinants on either surface IgM+ or IgD+ or on a molecule that is coordinately expressed on IgM+ or IgD+ cells can be generated and that such cells might play a role in regulating the growth of normal B cells or surface Ig+ tumor cells in vivo.

Cell surface immunoglobulin. II. Isolation and characterization of immunoglobulin from mouse splenic lymphocytes.

The proteins on surfaces of living splenic lymphocytes from normal BALB/c mice were iodinated enzymatically. Such cells were fractionated into two sub-populations: one composed almost exclusively of small lymphocytes and the other mainly of large lymphocytes and plasma cells. Specific immunoprecipitation of radiolabeled surface Ig obtained from lysates of these cell populations indicated that approximately 2-3% of the acid-precipitable radioactivity from the cell surface is Ig. Moreover, 95% of the H chain radioactivity from the Ig of the small lymphocyte fraction and 90% from the large lymphocyte-plasma cell fraction was characterized as micro by precipitation with anti-micro sera as well as by molecular weight determination on polyacrylamide gels in sodium dodecyl sulfate. The Ig was recovered from the cell surface in the form of an IgM monomer. Control experiments suggested that the monomer did not result from depolymerization of 19S IgM by the methods used to radiolabel and isolate the molecule. (3)H-tyrosine labeling of IgM produced by meyloma cells and radio-iodination of IgM in solution gave the same ratios of microL radioactivity as radiolabeling of IgM on cells, indicating that the tyrosine residues of L and micro-chains of cell surface IgM are available to the lactoperoxidase during the iodination. This is consistent with the hypothesis that cell surface IgM is entirely on the outside of the plasma membrane presumably attached to it by its Fc fragment. These results, together with previous reports by others, suggest that IgM, in its monomeric form, is the main antigen-specific receptor on lymphocytes of normal mice.

Interleukin 4 induces changes in the chromatin structure of the gamma 1 switch region in resting B cells before switch recombination.

Interleukin 4 (IL-4) can induce the expression of IgG1 in sIgG- murine B cells stimulated with mitogens or through a cognate interaction with T helper (Th) cells. We have investigated the molecular basis for the IL-4-induced switch to IgG1 in lipopolysaccharide (LPS)-stimulated murine B cells and have previously shown that IL-4 induces transcription of the gamma 1 switch region before switch recombination. We now demonstrate that IL-4 induces a DNase I hypersensitive site at the 5' end of the gamma 1 switch region in resting B cells. LPS is not required, but it enhances induction. Hence, the interaction of IL-4 with its receptor results in increased accessibility of the gamma 1 switch region. The more open chromatin structure and increased transcriptional activity may be important in the selection of this region for switch recombination.

Cell surface immunoglobulin. V. Release from murine splenic lymphocytes.

Turnover and release of cell surface Ig and secretion of total intracellular Ig has been studied in small lymphocytes from normal mouse spleen. The major findings to emerge are: (a) small lymphocytes secrete 8S IgM and IgG. A small portion of the 8S IgM, but virtually none of the IgG appears to have a cell surface phase. (b) Cell surface IgM is actively turned over with a half-life of 6-8 hr, and turnover can be accounted for by release into the incubation medium. Release is temperature dependent. (c) Released cell surface Ig is noncovalently bound to a fragment of plasma membrane. (d) H-2 antigens are not released during short-term incubation. Based on the above findings, we propose a model for the transport and release of both cell surface and conventionally secreted Ig.

The relationship between surface immunoglobulin isotype and immune function of murine B lymphocytes. I. Surface immunoglobulin isotypes on primed B cells in the spleen.

We investigated the ability of IgM-, IgD-, and IgG-bearing cells from the spleens of (BALB/c x C57BL/Ka)F1 mice primed to dinitrophenyl-bovine serum albumin (DNP-BSA) to restore the adoptive secondary anti-BSA and anti-DNP antibody responses. A rabbit anti-mouse IgD antiserum was prepared and the specificity documented by radioimmunoprecipitation, and cell surface staining. Purified populations of IgM-, IgD-, and IgG-bearing cells were prepared by immunofluorescent staining with isotype-specific reagents, and sorting on the fluorescence activated cell sorter. Bright or dull cells were transferred to irradiated syngeneic recipients which were challenged with DNP-BSA in saline. Unfractionated spleen cells restored an adoptive secondary serum antibody response which was all IgG (2-mercaptoethanol resistant). Purified IgM- or IgD-bearing cells restored both the secondary IgM and IgG antibody response. IgG-bearing cells restored only the IgG response. In addition, the IgG-bearing cells appear to suppress the adoptive secondary IgM response, since depletion of IgG-bearing cells from transferred spleen cells results in a marked increase in the adoptive IgM response.

The relationship between surface immunoglobulin isotype and immune function of murine B lymphocytes II. Surface immunoglobulin isotopes on unprimed B cells in the spleen.

We investigated the ability of IgM-, IgD-, and IgG-bearing cells from the spleens of unprimed (BALB/c x C57BL/Ka)F1 mice to restore the adoptive primary anti-BSA and anti-DNP antibody responses. Purified populations of isotype-specific cells were prepared by immunofluorescent staining and sorting on the fluorescence activated cell sorter. Bright or dull cells were transferred to irradiated syngeneic recipients which were challenged with DNP-BSA in complete Freund's adjuvant. Unfractionated spleen cells as well as IgM- and IgD-bearing cells restored the adoptive primary IgM and IgG antibody response. IgG-bearing cells restored a vigorous adoptive response which was all IgG (2-mercaptoethanol resistant). Depletion of IgG-bearing cells markedly increased the adoptive IgM response, and depletion of IgM-bearing cells markedly increased the IgG response. However, depletion of IgD-bearing cells resulted in a considerable reduction in the IgG response. The latter finding indicates that there is a subpopulation of IgD-bearing cells which express little or no surface IgM and which make a considerable contribution to the adoptive primary IgG response.

Cell surface immunoglobulin. XX. Antibody responsiveness of subpopulations of B lymphocytes bearing different isotypes.

Murine spleen cells were depleted of specific B-cell subpopulations bearing different immunoglobulin isotypes by means of complement-mediated cytolysis after treatment with antisera specific for micron- and gamma-chains. The functional effect of this depletion was measured by assaying both the primary and secondary plaque-forming cell responses of the residual cells after transfer to carrier-primed lethally irradiated hosts. The results suggest that cells bearing IgM are the progenitors of plaque-forming cells in the primary response and cells bearing IgG are the major progenitors of IgG plaque-forming cells in the secondary response. The quantity of IgM on progenitors of secondary IgM plaque-forming cells decreases markedly as the interval between primary immunization and antigenic challenge increases. Long-term memory cells for the secondary IgM response bear small amounts of both IgM and IgG.

Interactions between receptors for interleukin 2 and interleukin 4 on lines of helper T cells (HT-2) and B lymphoma cells (BCL1).

IL-2 and IL-4 induce a synergistic proliferative response in HT-2 cells, suggesting that IL-2Rs and IL-4Rs may interact. The purpose of this study was to examine the effect of IL-4 on the expression and function of IL-2Rs. Preincubation of HT-2 and BCL1-3B3 cells with IL-4 for 60 min at 4 degrees C or 37 degrees C resulted in a partial decrease in the number, but not the affinity of high affinity IL-2Rs as evidenced by Scatchard analysis of binding data. The decrease in the number of high affinity receptors correlated with decreased internalization of IL-2. After preincubation with IL-4, crosslinking of 125I-IL-2 to high affinity IL-2Rs also demonstrated a approximately 50% reduction in the number of high affinity IL-2Rs. Another lymphokine, IL-1, which acts on HT-2 cells, had no measurable effect on the affinity or number of IL-2Rs. Taken together, these results indicate that IL-4 downregulates the expression of high affinity IL-2Rs on some cells. It is not known whether this occurs by a direct ligand-mediated receptor interaction, by the sharing of a common receptor subunit, or by interaction of the two receptors with another membrane molecule or cytoskeletal component.

T cell-derived B cell differentiation factor(s). Effect on the isotype switch of murine B cells.

Culturing BALB/c B cells for 6 d at low cell density in the presence of lipopolysaccharide (LPS) results in the appearance of a small number of IgG plaque-forming cells (PFC). The addition of supernatants from concanavalin A (Con A)-induced alloreactive (AKR anti-B6) long-term T cell lines (PK 7.1.1a and 7.1.2) or a T cell hybridoma (FS7-6.18) to LPS-treated B cells resulted in a marked increase in IgG PFC (3--10-fold higher than in cultures treated with LPS alone. The number of induced IgG PFC was not affected by removing IgG-bearing cells on the fluorescence-activated cell sorter, indicating that T cell-derived B cell differentiation factor enhances isotype switching of sIgG- cells, rather than selecting and expanding pre-existing subpopulations of sIgG+ cells. We also investigated the subclass of IgG produced in the absence or presence of T cell factors and found that PK 7.1.1a, PK 7.1.2, and FS7-6.18 supernatants selectively increased IgG1 production. Several other T cell supernatants containing a variety of lymphokines had no effect, suggesting that PK 7.1.1a, PK 7.1.2, and FS7-6.18 lines produce factor(s) that can specifically enhance the recovery of IgG secreting cells in culture in the presence of LPS. These factors, which we have termed B cell differentiation factors, are different from interleukin 1, interleukin 2, T cell-replacing factor, colony-stimulating factor, macrophage-activating factor, and immune interferon. Our results suggest that soluble factors produced by T cell lines and hybridomas can markedly influence both the class and subclass of Ig produced by B cells.

Beta 2-microglobulin is selectively associated with H-2 and TL alloantigens on murine lymphoid cells.

We have used a rabbit antiserum prepared against purified rat beta2-microglobulin to immunoprecipitate molecules from lysates of radioiodinated murine thymocytes and splenocytes. All the molecules that are reactive with this serum have subunits of 44,000 and 12,000 and can be identified as H-2 and TL antigens. Thus, the anti-beta2mu serum can deplete lysates of the majority of the TL and H-2 atigens which can be subsequently recognized by alloantisera. If TL and H-2 are precipitated from the lysates before the addition of anti-beta2mu, no beta2mu-reactive molecules remain. Our results indicate that Ia antigens cannot be depleted from the lysates with anti-beta2mu. The studies also suggest that TL and H-2 heavy chains can exist as both monomers and dimers. These observations are discussed with regard to previous studies concerning the native structure of H-2 and TL antigens.

Biochemical evidence linking the GIX thymocyte surface antigen to the gp69/71 envelope glycoprotein of murine leukemia virus.

It is known that the thymocyte surface antigen GIX is found in some strains of mice and not others, and that its expression in mice of strain 129, in which most extensive genetic studies have been made, is controlled by two unlinked cellular chromosomal loci. We have now isolated a protein with a mol wt of approximately 70,000 daltons from the surface of thymocytes from 129 mice, which have antigenic and biochemical properties characteristic of the gp69/71 envelope component of murine leukemia virus. Our evidence is compatible with the conclusion that it carries the GIX antigen.

Expression of murine leukemia virus envelope glycoprotein gp69/71 on mouse thymocytes. Evidence for two structural variants distinguished by presence vs. absence of GIX antigen.

Thymocytes of several mouse strains were tested for expression of the gp69/71 envelope component of murine leukemia virus by surface iodination, followed by immunoprecipitation and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Theses strains included two congenic lines differing from their partner stocks with respect to expression of GIX antigen demonstrable in the cytoxicity assay. We conclude that:(a) two structural variants of gp69/71 can be expressed on mouse thymocytes, (b) these are distinguishable by a small difference in mobility in SDS gels, (c) one carries GIX antigen and the other not, (d) they are coded, or their expression is regulated, by different chromosomal loci that are not closely linked, and (e) both can be expressed together on the thymocytes of inbred mice. In the intact thymocyte plasma membrane, the sites of group-specific antigen shared by the two gp69/71 variants, unlike the GIX type specificity carried by only one of them, are probably inaccessible to antibody.