Search

Background & Aims: Normal and neoplastic cells release microvesicles, whose effects on the immune system still need to be elucidated. Because human colorectal cancer cells are hypothesized to escape immune recognition by expressing proapoptotic molecules, we investigated whether microvesicles bearing Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand and inducing apoptosis of activated T cells are secreted by colorectal cancer cells both in vitro and in affected patients., Methods: Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand expression were analyzed in colorectal cancer cells and purified microvesicles by flow cytometry, Western blotting, and immunoelectron microscopy. Microvesicle tumor origin was assessed through simultaneous detection of lysosomal (CD63) and adenocarcinoma (carcinoembryonic antigen) markers. Proapoptotic activity of microvesicles was evaluated by annexin V/propidium iodide staining and caspase activation in T cells, including CD8+ T lymphocytes from colorectal cancer patients., Results: Colorectal cancer cells showed a granular pattern of tumor necrosis factor-related apoptosis-inducing ligand and Fas ligand expression, suggesting a secretory behavior. These proapoptotic molecules were detected on isolated microvesicles, together with class I HLA, CD63, and carcinoembryonic antigen. Microvesicles induced Fas ligand-mediated and tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis of activated CD8+ T cells generated from colorectal cancer patients. Microvesicles with comparable phenotypes and functions were found in plasma from patients with advanced disease, whereas vesicular structures expressing Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand were also detected in colorectal cancer specimens., Conclusions: These data show that colorectal cancer induces T-cell apoptosis through the release of Fas ligand-bearing and tumor necrosis factor-related apoptosis-inducing ligand-bearing microvesicles both in vitro and in vivo. This mechanism of immune escape has potential implications as a prognostic factor and could be targeted for the development of new antitumor therapies in colorectal cancer patients.

Background & Aims: Transmural perivascular mononuclear cell infiltrates are a feature of Crohn's disease. The aim of this study was a molecular characterization of the mechanisms leading to the formation of these infiltrates., Methods: Endothelial cell and leukocyte expression of the adhesion molecules directing leukocyte transendothelial migration were studied in situ by immunohistochemical analysis of 10 samples from patients with Crohn's disease and 10 samples from normal controls. Double-staining methods were used to characterize the cells forming the infiltrates., Results: CD11a+ and L-selectin-positive mononuclear cells seemed to be the major component of perivascular infiltrates. The vast majority of these cells were CD68+, CD31+ monocytes/macrophages surrounded by CD3+, L-selectin-positive, CD31+, CD45RA+, and/or CD45RO+ T lymphocytes. T lymphocytes within the vessels expressed both CD45RA and CD45RO markers. Endothelial cells were intercellular adhesion molecule 1 positive and mostly CD34+. Strong adhesion between L-selectin-positive and CD11a+ intravascular mononuclear cells and CD34+ and intercellular adhesion molecule 1-positive endothelial cells were observed., Conclusions: Data indicate that peripheral mononuclear cells are actively recruited in the submucosa of Crohn's disease tissue; endothelial cells express adhesion molecules highly permissive for transendothelial migration of monocytes and both naive and memory T cells contributing to infiltrates generation; and close membrane contact between migrated macrophages and naive T cells leads to the T-cell transition from naive to memory phenotype within Crohn's disease.

Background/aims: Vasoactive intestinal polypeptide (VIP) modulates the immunoglobulin (Ig) synthesis in the peripheral blood of humans and in various lymphoid organs of other species. Because VIP receptors have been shown on lamina propria mononuclear cells (LPMC), the effects of graded doses of VIP on the in vitro Ig production by normal human LPMC was investigated., Methods: Colonic LPMC were cultured with or without graded doses of VIP (1 pmol/L-1 mumol/L). The concentrations of Ig A, G, and M in the 12 days supernatants were quantitated by an enzyme-linked immunosorbent assay, and the effects of VIP were characterized by limiting dilution analysis (LDA)., Results: The addition of VIP was associated with a significant increase in the production of IgA, whereas IgG levels were significantly reduced. Both these effects were restricted to LPMC. LDA showed that the IgA-enhancing effect was associated with an increase in the number of IgA-producing precursor cells and with variation in the regulatory phenomena involved in IgA production., Conclusions: In humans, a major function of the mucosal immune system (i.e., the synthesis of IgA) is modulated by VIP. Data suggest that VIP may either act as an indirect switch factor or increase the clone size of pre-committed cells.

To examine the possible in vivo significance of the immunomodulatory effects of vasoactive intestinal polypeptide described in vitro, several parameters of peripheral blood lymphocyte function were studied in a patient with a pancreatic endocrine tumor and high circulating levels of vasoactive intestinal polypeptide. There was no imbalance of the circulating lymphocyte subpopulations, and the in vitro responses of the patient's lymphocytes to mitogens were normal. However, there was an increased number (32%) of peripheral lymphocytes expressing interleukin 2 receptor. Serum immunoglobulin M levels were higher than in controls, and the patient's lymphocytes exhibited a spontaneous in vitro immunoglobulin M production higher than normal. Comparable increases in both interleukin 2 receptor expression and immunoglobulin M production were induced in vitro in normal peripheral lymphocyte cultures by the addition of vasoactive intestinal polypeptide concentrations similar to that detected in the patient's plasma. These findings indicate that a modulatory effect of vasoactive intestinal polypeptide on lymphocyte activation and immunoglobulin synthesis may be operating in vivo. They also suggest that vasoactive intestinal polypeptide does not mediate major defects in peripheral blood lymphocyte function in vivo.

We investigated the ability of isolated human colonic epithelial cells to express the common acute lymphoblastic leukemia antigen (CALLA), the transferrin receptor, and the 4F2 antigen in response to different types of stimuli. The expression of these markers was assessed by immunofluorescence using monoclonal antibodies. Thirty-two percent of freshly isolated colonic epithelial cells from actively inflamed mucosa of patients with inflammatory bowel disease expressed the 4F2 antigen, 28% the transferrin receptor, and 13% the CALLA. Normal colonic epithelial cells were cultured and the kinetics of expression of the three antigens was studied. A significant increase in the expression of the three markers was observed throughout the culture period in response to the lectin phytohemagglutinin and the epidermal growth factor. The kinetics of expression of the 4F2 antigen and the CALLA after lectin stimulation appeared to differ from that observed after epidermal growth factor. At the end of the cultures one-third of the cells expressed the 4F2 antigen and the transferrin receptor, whereas one-fifth were positive for CALLA. Thus, after these cultures the expression of the three markers was quantitatively similar to that observed with freshly isolated cells from inflamed mucosa. gamma-Interferon markedly induced the 4F2 antigen but had no effect on the transferrin receptor and the CALLA. These data demonstrate that colonic epithelium is capable of expressing the 4F2 antigen and the CALLA in association with the transferrin receptor.