PubMed Health⌕ Search

Biomedical subjects

E C Ebert

Publications and source records attributed to E C Ebert.

At least 55 records · Page 3Linked to original sources
PubMed1993

Intestinal intraepithelial lymphocytes bind to colon cancer cells by HML-1 and CD11a.

Human intraepithelial lymphocytes (IEL), predominantly CD8+ T-lymphocytes located between intestinal epithelial cells (EC), may represent the first-line immune defense against colon cancer. The mechanism by which IEL bind to the colon cancer line, DLD-1, was evaluated. A larger fraction of IEL than peripheral blood mononuclear cells bound to DLD-1 monolayers (25 +/- 16 versus 8 +/- 4% binding, P < 0.05). Binding increased when DLD-1 monolayers were incubated with interferon-gamma but not with tumor necrosis factor-alpha. Similar numbers of IEL adhered to EC tumors, HT-29 and 5637, and the non-EC tumor, A375, but fewer bound to nonmalignant smooth muscle (HISM) and fibroblast (KD) lines (P < 0.01). Binding of IEL to DLD-1 was reduced by monoclonal antibodies to HML-1 and CD11a (47 +/- 9 and 26 +/- 13% inhibition, respectively) and was completely eliminated by both combined (93 +/- 4% inhibition). Anti-HML-1 also inhibited the binding of IEL to other EC tumors but did not affect binding to non-EC tumors or fibroblasts. To conclude, the binding of IEL to EC tumors is mediated by HML-1 and CD11a [A. I. Roberts, S. M. O'Connell, and E. C. Ebert. Binding of intraepithelial lymphocytes to colon cancer cells is mediated by HML-1 and LFA-1 (abstract). Gastroenterology, 102: A685, 1992].

Antigens, Neoplasm↗
PubMed1993

Lymphokine-activated killing by human intestinal lymphocytes.

Human intraepithelial lymphocytes (IEL), predominantly CD8+ T lymphocytes located between intestinal epithelial cells, may represent the first-line host defense against colon cancers. This study evaluates their lymphokine-activated killer (LAK) activity and compares it to that of lamina propria lymphocytes (LPL). The phenotypes of the precursor or effector LAK cells were determined by depleting IEL or LPL of specific subsets using antibody and complement lysis either before or after a 7-day culture with interleukin-2 (IL-2), respectively, and then measuring changes in lytic activity. The precursor and effector LAK cells in the IEL were mixed populations with some but not all expressing CD2, CD3, CD8, and NKHl. The LAK activity by LPL was due to CD2+CD3+CD4-CD8- precursor cells and CD8+ effector cells. Since the IEL LAK cells were heterogeneous, their lytic activity against two different target cell types was analyzed. The LAK activity against DLD-1 colonic adenocarcinoma cells was reduced by antibodies to CD2, CD11a, and HML-1, whereas LAK activity against K-562 cells was reduced by antibodies to CD2, CD11a, and CD54, but not HML-1, indicating a target-cell-specific mechanism. Cold competition experiments, however, showed that the same cytotoxic IEL bound to both target cells. In conclusion, LAK activity by IEL is due to a mixed population, whereas that by LPL is due to CD8- precursor cells and CD8+ effector cells. The same effector LAK IEL kill both DLD-1 and K-562 targets, but different mechanisms are involved.

Antigens, CD↗
PubMed1993

T-cell activation in human intestinal mucosa: the role of superantigens.

BACKGROUND: Superantigens are a class of potent T-cell mitogens that activate T cells using specific antigen receptor V regions. Superantigens have been implicated in the pathogenesis of several autoimmune diseases, including inflammatory bowel disease. The present study examines the role of superantigens in the human gastrointestinal immune response. METHODS: Human intestinal epithelial cells and T lymphocytes were obtained from surgical specimens and cultured in the presence or absence of exogenous superantigens. Activation of T cells and V region usage were measured by thymidine incorporation and by cell staining using a panel of monoclonal antibodies. RESULTS: Neither epithelial cells from normal nor diseased intestinal mucosa expressed virally encoded, endogenous superantigens. However, 50% of epithelial cell preparations could present exogenous bacterial superantigens to T cells. In the other 50%, a defect in this function was observed, which did not represent production of suppressive factors or absence of accessory cytokines. Mucosal T lymphocytes proliferated in response to superantigens in vitro, expressing increased transferrin receptor, interleukin-2 receptor, and HLA-DR. CONCLUSIONS: A superantigen-driven mucosal immune response may occur in health and in chronic inflammatory states. The intestinal epithelial cell may mediate this response, through presentation of superantigens to mucosal T lymphocytes.

Antigen-Presenting Cells↗
PubMed1993

Spontaneous cytotoxicity of intestinal intraepithelial lymphocytes: clues to the mechanism.

Human intestinal intraepithelial lymphocytes (IEL) demonstrate target cell-restricted spontaneous cytotoxic (SC) activity that is due to CD2+CD3+CD8+CD16-CD56- effector cells; they kill epithelial cell (EC) tumours (such as DLD-1 colon cancer cells), but not natural killer (NK)-sensitive K-562 cells. The present study shows that the measured levels of SC activities by IEL correlated with those of autologous lamina propria lymphocytes (LPL), but not with those of peripheral blood lymphocytes (PBL). Also, the susceptibilities of DLD-1 cell clones to lysis by IEL and PBL effector cells did not correlate, suggesting different mechanisms of lysis. Antibody blocking experiments showed that the main surface molecules involved in lysis depended on the effector cell type: alpha E beta 7 (HML-1) on IEL and CD16 on PBL. No antibody-dependent cell-mediated cytotoxicity (ADCC) was demonstrated by IEL, even after stimulation with interferon-gamma (IFN-gamma). Few IEL expressed Fc receptors for IgG. This study describes further differences between the SC activities of IEL and PBL.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1993

Ulcerative colitis serum recognizes the M(r) 40K protein on colonic adenocarcinoma cells for antibody-dependent cellular cytotoxicity.

Antibodies in ulcerative colitis (UC) serum promote antibody-dependent cellular cytotoxicity (ADCC) against colon cancer cells. The target molecules on the cells recognized by the antibody are unknown. This study examines the role of the M(r) 40K colon epithelial protein in this process. Serum from 29 UC patients, but not from 19 patients with Crohn's disease, significantly (p < 0.001) induced more cytotoxicity than did normal serum against DLD-1 colon cancer cells which are known to express the M(r) 40K protein. Peripheral blood lymphocytes but not polymorphonuclear leukocytes showed ADCC. Anti-M(r) 40K monoclonal antibodies significantly (p < 0.001) inhibited the UC-serum-induced ADCC, but not the spontaneous cytotoxicity. These results suggest the involvement of the M(r) 40K protein in ADCC induced by UC serum.

Adenocarcinoma↗
PubMed1992

Human lymphocytes lack substance P receptors.

Substance P (SP), a neuropeptide found in high concentrations in the gut, is reported to have many potent immunomodulatory actions. This study evaluated some effects of SP on human peripheral blood lymphocytes (PBL) and jejunal intraepithelial lymphocytes (IEL) and the expression of SP receptors on these and other lymphocytes types. In contrast to previous studies, SP (10(-8) or 10(-12) M) did not affect the proliferation (spontaneous or mitogen-induced) nor spontaneous cytotoxicity by PBL or IEL. To determine whether this unresponsiveness was due to an absence of SP receptors, the SP binding potential of these and other human lymphocyte types was determined by Scatchard analysis of radioligand binding. The IM-9 B lymphoblastoid cell line, used as a positive control, demonstrated 4838 +/- 603 or 3131 +/- 832 receptors per cell, with a Kd of 0.21 +/- 0.01 or 0.18 +/- 0.09 nM, using [3H]SP or 125I-SP, respectively. No receptors were found on PBL, polymorphonuclear leukocytes, splenocytes, IEL, or jejunal lamina propria lymphocytes using either radioligand. These findings dispute the presence of large numbers of SP receptors on lymphocytes in peripheral blood, spleen, or intestinal mucosa, and argue against any major effect of SP on T cell proliferation or spontaneous cytotoxicity.

Humans↗
PubMed1992

Spontaneous cytotoxicity of human intraepithelial lymphocytes against epithelial cell tumors.

Human intraepithelial lymphocytes are T cells primarily of the CD8+ phenotype located between intestinal epithelial cells. The cytotoxic and suppressor activities of these lymphocytes are largely unexplored. The spontaneous cytotoxic activity of these cells is evaluated in this study. Jejunal intraepithelial lymphocytes spontaneously lysed a variety of epithelial cell tumor lines (colonic and pancreatic adenocarcinomas and bladder epidermoid carcinoma) but not the highly natural killer-sensitive K-562 cells. Cold target inhibition studies showed that these lymphocytes preferentially bind the DLD-1 colonic adenocarcinoma cells rather than the K-562 cells. Pretreatment of the effector cells with interferon-gamma did not change their cytotoxic activity. The cytotoxic cells are T lymphocytes (expressing CD2, CD3, and CD8). In contrast, the spontaneous cytotoxic activity of peripheral blood lymphocytes is directed against both epithelial cell targets and K-562 cells, is enhanced by interferon-gamma, and is effected by natural killer cells (expressing CD2, CD16, and NKH1). Thus, the spontaneous cytotoxicity of intraepithelial lymphocytes differs from that of peripheral blood lymphocytes in their target cell restriction, lack of response to interferon gamma, and effector cell phenotype. Lymphocytes in the intestinal epithelium may have a novel and important role in recognizing and destroying transformed epithelial cells and colon cancers.

Cytotoxicity Tests, Immunologic↗
PubMed1991

Oligoclonal expansion and CD1 recognition by human intestinal intraepithelial lymphocytes.

A human intestinal intraepithelial lymphocyte (IEL) T cell line was established from jejunum to characterize the structure and function of the alpha beta T cell antigen receptors (TCRs) expressed by this population. Single-sided polymerase chain reaction (PCR) amplification cloning and quantitative PCR amplification of the TCR chains from the cell line and from fresh IELs demonstrated that IELs were oligoclonal. The IEL T cell line exhibited CD1-specific cytotoxicity and a dominant IEL T cell clone was CD1c-specific. Thus, human jejunal intraepithelial lymphocytes are oligoclonal and recognize members of the CD1 gene family.

Amino Acid Sequence↗
PubMed1991

Human intraepithelial lymphocytes. Immunomodulation and receptor binding of vasoactive intestinal peptide.

This study evaluates the immunomodulation and receptor binding of vasoactive intestinal peptide on human peripheral blood lymphocytes and intraepithelial lymphocytes. Vasoactive intestinal peptide (VIP, 10(-8) and 10(-12) M) had no effect on the concanavalin A-induced proliferation or the spontaneous cytotoxicity against K-562 targets by either lymphocyte type. Human peripheral blood lymphocytes had a mean of 927 vasoactive intestinal peptide receptors per cell with a Kd of 1.12 x 10(-10) M, as demonstrated by the competitive displacement of [125I]peptide by unlabeled peptide using Scatchard analysis. In contrast, intraepithelial lymphocytes had no high-affinity receptors as shown by the negligible binding of 50 pM [125I]VIP. Peptide binding by peripheral blood lymphocytes, although reduced by exposure to dithiothreitol and ethylenediamine tetraacetic acid, was still greater than binding by intraepithelial lymphocytes. As intraepithelial lymphocytes are mainly CD8+ T cells, the possibility that this phenotype may not bind VIP at all was tested by specifically depleting peripheral blood lymphocytes by antibody and complement lysis. Peripheral blood lymphocytes expressing CD8, CD4, and/or CD2 were responsible for most of the binding, indicating that CD8+ T lymphocytes in the peripheral blood and in the intestinal epithelium differ in their capacity to bind VIP.

Adjuvants, Immunologic↗
PubMed1991

Induction of suppressor cells by Mycobacterium paratuberculosis antigen in inflammatory bowel disease.

We studied the M. paratuberculosis-induced proliferation and suppressor cell generation by peripheral blood lymphocytes from patients with inflammatory bowel disease. Peripheral blood lymphocytes were separated from 33 patients with Crohn's disease, 18 with ulcerative colitis, nine with other intestinal diseases, and five with autoimmune disorders. Proliferation of peripheral blood lymphocytes from normal individuals in response to 10 micrograms/ml of M. paratuberculosis antigen was reduced by depletion of CD4+ T cells. The ability of M. paratuberculosis antigen to suppress concanavalin A-induced proliferation (expressed as a percentage suppression) was reduced by depletion of CD8+ T cells. This suppression was the same whether peripheral blood lymphocytes were from normal individuals, patients with intestinal diseases other than inflammatory bowel disease, or patients with autoimmune disorders (47 +/- 14%, 44 +/- 24%, and 30 +/- 26%, respectively). In contrast, the suppression induced by M. paratuberculosis for patients with Crohn's disease and ulcerative colitis (66 +/- 22% and 67 +/- 22%) was much greater than that for normal individuals (P less than 0.001). In particular, lymphocytes from patients with active Crohn's disease demonstrated little proliferation in response to this antigen but marked suppressor activity (79 +/- 13%). How the immunomodulatory effects of this antigen relate to the pathogenesis of the inflammatory bowel diseases remains to be determined.

Adolescent↗
PubMed1990

Selective immunosuppressive action of a factor produced by colon cancer cells.

A soluble substance (HT29 factor) produced by HT29 colon cancer cells markedly suppresses mitogen-induced T-cell proliferation and interleukin-2 production. In this study the range of T-cell functions susceptible to the inhibitory effects of the HT29 factor was evaluated. Serum-free conditioned medium was collected from confluent cultures of HT29 cancer cells, concentrated, and subjected to gel filtration chromatography and anion exchange chromatography, resulting in 24.4-fold purification of the HT29 factor with 31% yield. This factor abolished the development of lymphokine-activated killer cells when present during activation of peripheral blood lymphocytes by interleukin-2 but did not affect the lysis of target cells by normal effectors when added in the lysis stage only. The HT29 factor did not affect the generation of concanavalin A-induced suppressor lymphocytes, even though it markedly inhibited synthesis of DNA, RNA, and protein as well as expression of the CD25 (Tac) antigen during mitogen activation of T-cells. The HT29 factor itself did not induce suppressor cells. These results indicate that the immunosuppressive action of the HT29 factor is selective.

Colonic Neoplasms↗
PubMed1990

Intra-epithelial lymphocytes: interferon-gamma production and suppressor/cytotoxic activities.

Human intraepithelial lymphocytes (IEL) proliferate minimally in response to phytohaemagglutinin (PHA), but produce as much interleukin-2 (IL-2) as do peripheral blood lymphocytes (PBL). The addition of sheep erythrocytes during activation of IEL with PHA markedly augments both T cell functions. This study evaluates the ability of IEL to produce interferon-gamma (IFN-gamma) and to develop suppressor and cytotoxic activities when stimulated with mitogens in the presence or absence of sheep erythrocytes. PHA-activated IEL produced as much IFN-gamma as did PHA-activated peripheral blood CD8+ T lymphocytes. IEL activated by concanavalin A (Con A) demonstrated less suppressor activity directed against T cell proliferation than did Con A-activated peripheral blood CD8+ T lymphocytes. IEL generated less mitogen-induced cellular cytotoxicity and lymphokine-activated killer cell activity than did peripheral blood CD8+ T lymphocytes. The addition of sheep erythrocyte lysates during mitogen stimulation of IEL markedly enhanced their proliferation and lymphokine production but did not affect their suppressor or cytotoxic activities.

Concanavalin A↗
PubMed1989

Proliferative responses of human intraepithelial lymphocytes to various T-cell stimuli.

Human intraepithelial lymphocytes (IEL) are CD8+ T cells located between intestinal epithelial cells, capable of only minimal proliferation to mitogens but brisk proliferation to mitogens combined with sheep red blood cells. This study examines this differential response of IEL. Both IEL and CD8+ T lymphocytes from the peripheral blood are predominantly CD2+, CD3+, CD4-, CD5+, CD8+, and express the alpha beta subunits of the T-cell receptor. Human IEL express the same densities of the CD2, CD3, and CD8 antigens but a lower density of the CD5 antigen than do peripheral blood CD8+ T cells. The proliferation of IEL is significantly less than that of peripheral blood CD8+ T lymphocytes in response to phytohemagglutinin, to concanavalin A, or to anti-CD3 antibody bound to Sepharose (p less than 0.05). Supplementing IEL with interleukin-1, interleukin-2, or autologous peripheral blood macrophages does not completely reconstitute the proliferative response of IEL to these stimuli. Rather, the low proliferation of IEL to these stimuli is due to incomplete activation, as demonstrated by the low percentage of CD25 (Tac)+ lymphocytes with concanavalin A or the low density of the CD25 antigen with phytohemagglutinin. Both IEL and peripheral blood CD8+ T lymphocytes proliferate minimally in response to alloantigens or to interleukin-2, but briskly in response to stimuli of the CD2 receptor such as the combination of anti-T11(2) and anti-T11(3) antibodies or mitogen and sheep red blood cells. The sheep red blood cells enhance the mitogen-induced response of IEL by augmenting events of activation, both interleukin-2 production and interleukin-2 receptor expression. Thus, IEL represent an unusual compartment of CD2+, CD3+ T lymphocytes that are activated more completely by stimuli of the CD2 receptor than by stimuli of the CD3 receptor or by T-cell mitogens.

Antigens, Differentiation↗
PubMed1989

Characterization of activated lymphocytes in colon cancer.

The percentages of activated lymphocytes in colon cancers were compared to clinical features of the tumors and to functional characteristics of the tumor-infiltrating lymphocytes (TIL) in order to evaluate the role of activated TIL in controlling tumor growth. The TIL isolated from colon cancers contained 80 +/- 6% T cells [cluster designation (CD) 2+], 42 +/- 9% CD4+ cells, 27 +/- 9% CD8+ cells, 17 +/- 5% cells (surface immunoglobulin or SIg+), 6 +/- 2% null cells (CD2-, SIg-), 6 +/- 4% Leu 7+ cells, 1 +/- 0% macrophages (CDw 14+), and no plasma cells (PCA+). The lamina propria lymphocytes (LPL) isolated from adjacent colonic mucosa contained a similar distribution but with fewer CD8+ (10 +/- 5%) and Leu 7+ (0.6 +/- 0.3%) lymphocytes (P less than 0.05). More TIL than LPL expressed the interleukin-2 (IL-2) receptor (9 +/- 8% vs 1 +/- 0.8% CD25+ cells; P less than 0.05) and the transferrin receptor (4 +/- 5% vs 0.3 +/- 0.6% T9+ cells; P less than 0.05). Those TIL expressing activation antigens were CD2+, SIg-. The percentage of TIL that were CD25+ did not correlate with the extent of tumor spread, with the degree of tumor differentiation, nor with the percentage of HLA-DR+ tumor cells. However, there were significantly more CD25+ TIL from tumors located in the left colon, particularly small lesions, than from tumors located in the right colon (P less than 0.05). The proliferation of TIL preparations cultured with medium alone, with mitogens, or with IL-2 did not vary according to the percentage of CD25+ lymphocytes in the TIL. T cells may be activated by foreign surface determinants on tumor cells, particularly in small, left-sided lesions.

Adenocarcinoma↗
PubMed1987

Characterization of an immunosuppressive factor derived from colon cancer cells.

The colon cancer cell line, HT29, produces a soluble substance (HT29 factor) that blocks mitogen-induced T cell proliferation and the production of interleukin 2 (IL 2). Inhibition of T cell proliferation by the HT29 factor is reversible and is not due to a decline in cell viability or an alteration in the kinetics of T cell proliferation. It occurs even when the HT29 factor is added only 24 hr before terminating the T cell cultures, indicating that the factor affects cell division after activation of T cells has already occurred. No inhibitory activity was found in medium conditioned by human colonic epithelial cells or fibroblasts. The factor has an apparent m.w. of 56,000 and an isoelectric point of 7.9. It is sensitive to endopeptidases, heating to 56 degrees C, and extremes of pH. The HT29 factor also suppresses IL 2 production by T cells. However, low IL 2 availability alone cannot account for the suppressive effect of the factor on T cell proliferation, because the addition of exogenous IL 2 does not reverse the inhibition. This block in IL 2 responsiveness is not primarily due to a decrease in IL 2 receptors because Tac expression on activated T cells is minimally decreased during a 24-hr exposure to the HT29 factor. In addition, IL 2-induced proliferation of mitogen-activated T cells is inhibited only slightly by the HT29 factor, indicating that a block in the interaction of IL 2 with its receptor is not its main mechanism of action. Thus the inhibition of T cell proliferation is likely to be due primarily to a mechanism independent of IL 2.

Cell Line↗
PubMed1986

Intestinal epithelial cells rosette with sheep red blood cells.

A large fraction of colonic epithelial cells (45 +/- 15%) formed rosettes with sheep red blood cells (RBC) but not with bovine or human RBC. This interaction was independent of the T11 receptor since it was not inhibited by anti-T11 antibody or trypsin treatment of the epithelial cells. The binding was also not due to surface immunoglobulin reactive with sheep RBC since antibodies to immunoglobulin light chains did not block the interaction. Sheep RBC rosettes formed around colonic and jejunal epithelial cells, a few percent of colonic adenocarcinoma cells, but not around uterine epithelial cells. Sheep RBC rosette formation should not be used to quantitate or isolate intestinal mucosal T cells if epithelial cells are present.

Animals↗
PubMed1986

T cells in patients undergoing chronic hemodialysis: mitogenic response, suppressor activity, and interleukin-2 production and receptor generation.

The functional response of peripheral blood T lymphocytes was studied in patients with end-stage renal disease treated by chronic hemodialysis for over 1 year. Proliferation after phytohemagglutinin stimulation of patients' peripheral blood mononuclear cells and of T lymphocyte fractions isolated by either sheep erythrocyte rosetting or by use of a nylon wool column was significantly reduced as compared with that of corresponding fractions from healthy control subjects (P less than 0.001). The induction of suppressor cell activity by concanavalin A in rosetted T cell fractions was higher with cells of hemodialyzed patients than with control cells (P less than 0.025). The expression of class II MHC antigen (HLA-DR) by the T8 lymphocyte subset after concanavalin A induction, as determined by staining with monoclonal antibodies and two-color fluorescence analysis by flow cytometry, was also higher in hemodialyzed subjects (P less than 0.025). Since contamination by non-T cells in such cell fractions and increases in proliferation after indomethacin treatment of peripheral blood mononuclear cells were similar in hemodialyzed and control subjects, it is unlikely that the depressed T lymphocyte responses and the increased suppressor cell activity can be attributed to increased peripheral blood monocyte counts observed in patients undergoing hemodialysis. Studies of the biological events associated with the activation of lymphocytes of hemodialyzed patients revealed a reduction in expression of interleukin 2 receptor in the plasma membrane of phytohemagglutinin-stimulated lymphocytes as determined by staining with monoclonal antibody (P less than 0.01). In addition, a very low secretion of interleukin 2 by stimulated peripheral blood mononuclear cell populations was observed in about one-half of patients receiving hemodialysis.

Adult↗