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L Mayer

Publications and source records attributed to L Mayer.

At least 37 records · Page 2Linked to original sources
PubMed2000

Antigen uptake and trafficking in human intestinal epithelial cells.

Primary intestinal epithelial cells, human colonic adenocarcinoma cell lines (DLD-1, Caco-2, and HT-29), and monocytes were used as model systems to study antigen uptake, antigen-presenting cell properties, as well as the kinetics of antigen uptake in intestinal epithelial cells (IEC). Intracellular staining of fluoresceinated tetanus toxoid was not evident in the IEC until after 30 min of incubation at 37 degrees C, whereas in monocytes intracellular punctate staining of fluoresceinated tetanus toxoid was evident after 5 mins. In polarized Caco-2 cells antigen could be internalized at both the apical and basolateral surfaces with polarized transport. When analyzed by electron microscopy, gold-labeled tetanus toxoid was internalized and found within endosomes and multivesicular bodies, but not within the lysosomal compartments by 60 min. By 2 hrs, gold-labeled tetanus toxoid was evident in the secondary lysosomes. These results demonstrate that tetanus toxoid follows an endocytic pathway in intestinal epithelial cells and that the kinetics of antigen uptake is slower than that of conventional antigen-presenting cells.

Antigens↗
PubMed2000

Factors affecting antigen uptake by human intestinal epithelial cell lines.

We assessed the role of size, solubility, and prophagocytic cytokines interferon-gamma (IFN-gamma), and granulocyte-macrophage colony stimulatory factor (GM-CSF) in antigen uptake and kinetics by intestinal epithelial cells using keyhole limpet hemocyanin and ovalbumin. Both fluoresceinated keyhole limpet hemocyanin (3000-7500 kDa) and fluoresceinated ovalbumin (45 kDa) were internalized by human colonic epithelial cell lines, with kinetics similar to those of fluoresceinated tetanus toxoid, and there was decreased uptake of insoluble immune complexes and no enhancement in the uptake of soluble immune complexes. In addition, neither IFN-gamma nor GM-CSF altered the kinetics of uptake nor enhanced antigen internalization by the intestinal epithelial cell lines. These data suggest that regardless of the size of the soluble antigen, the presence of prophagocytic cytokines, or the formation of soluble immune complexes, fluid phase endocytosis of antigen by intestinal epithelial cells appears to be a relatively stable process.

Antigen-Antibody Complex↗
PubMed2000

Modulation of benzo[a]pyrene diolepoxide-DNA adduct levels in human white blood cells by CYP1A1, GSTM1 and GSTT1 polymorphism.

The modulation of benzo[a]pyrene diolepoxide (BPDE)-DNA adduct levels by polymorphisms in the CYP1A1, GSTM1 and GSTT1 genes was assessed in leukocytes of Caucasian males. Eighty-nine coke oven workers (35 smokers, 36 ex-smokers and 18 non-smokers) were recruited from job categories with different exposure levels to polycyclic aromatic hydrocarbons (PAH), together with 44 power plant workers (all smokers) not exposed to PAH. BPDE-DNA adducts were detected in 69 of 133 (52%) DNA samples with a 100-fold variation (range 0.2-44 adducts/10(8) nt) and a median of 1.6 adducts/10(8) nt. All samples with the GSTM1 active genotype (n = 59) and five out of 74 samples with GSTM1*0/*0 (7%) showed non-detectable adducts (<0.2 adducts/10(8) nt) and 69 of 74 subjects with GSTM1*0/*0 (93%) had detectable adducts (>0.2 adducts/10(8) nt). The difference in adduct level between the GSTM1*0/*0 and GSTM1 active genotypes was highly significant (P < 0.0001). No significant difference in adduct level between the GSTT1*0/*0 and GSTT1 active genotypes was seen. All heterozygotes (CYP1A1*1/*2) from subjects of GSTM1 active type did not have detectable adducts. Among the GSTM1-deficient individuals (n = 69), 42 with the CYP1A1*1/*1 genotype showed a lower adduct level (median 1.3, range 0.2-4.1 adducts/10(8) nt) compared with 26 individuals with heterozygous mutated CYP1A1*1/*2 genotypes (median 2.5, range 0.4-6.1 adducts/10(8) nt, P < 0.015). One individual with low PAH exposure and the rare combination CYP1A1*2A/*2A-GSTM1*0/*0 showed an extremely high level of 44 adducts/10(8) nt. Significant differences in detectable adduct levels were found between the CYP1A1*1/*1 and CYP1A1*1/*2 genotypes in the exposed group low + medium (P = 0.01) and for all adduct levels, detectable and non-detectable (set at a fixed value), in highly exposed individuals and in ex-smokers (P = 0.03), whereas no such differences were observed in the control group. Mutated CYP1A1*1/*2 increased the adduct level in non-smokers from the exposed group (1.4 versus 2.2 adducts/10(8) nt), but had no effect on the smokers from the exposed group (2.3 versus 2.8 adducts/10(8) nt). When all variables were dichotomized, statistical evaluation showed that CYP1A1 status (P = 0.015), PAH exposure (P = 0.003) and smoking (P = 0.006) had significant effects on adduct levels which increased in the order: CYP1A1*1/*1 < CYP1A1(*1/*2 or *2A/*2A); environmental exposure < occupational exposure; non-smokers < smokers, whereby adducts increased with cigarette dose and the duration of smoking. Higher levels of BPDE-DNA adducts in individuals with the combined CYP1A1(1/*2 or *2A/*2A)-GSTM1*0/*0 genotype suggest that these genotype combinations are at increased risk for contracting lung cancer when exposed to PAH.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed2000

Epithelial cell antigen presentation.

For decades intestinal epithelial cells were thought of as passive barriers to luminal contents, cells involved in nutrient absorption and electrolyte secretion. Studies during the past 10 to 15 years have changed that concept as our understanding of mucosal immunity has evolved and as we have come to understand that the regulation of this system is unique in terms of cellular interactions and factors produced. The intestinal epithelial cell has moved to the forefront of these studies where it has been shown to be an active participant in mucosal immunoregulation and inflammation. Results of the earliest studies suggested that epithelial cells might be involved in immune regulation because they expressed a series of cell surface molecules that correlate with classical antigen presentation (class I and II MHC molecules). Later on, the expression of nonclassical class I molecules was identified on these cells as well, raising the possibility of novel forms of interactions with unique cell populations. This was followed by the observation that epithelial cells secrete cytokines and chemokines, which not only regulate mucosal immune responses but also regulate inflammatory responses. By such processes, the IEC has been proposed as being a bridge between innate and adaptive immunity. The recent description of Toll-like receptors on IECs adds further support to this concept. Clearly there is growing appreciation of the multifaceted role that the IEC plays in the gut. The work on IECs in the past year has helped to refine this role.

Journal Article↗
PubMed2000

Mucosal immunity and gastrointestinal antigen processing.

The intestine is the largest lymphoid organ in the body by virtue of lymphocyte numbers and quantity of immunoglobulin produced. This is largely related to the enormous antigen load to which these cells are exposed on a daily basis. However, despite this, the mucosa-associated lymphoid tissue appears to be regulated by unique mechanisms, and this is reflected in specific phenomena (oral tolerance, controlled or physiologic inflammation) as well as unusual lymphoid populations (intraepithelial lymphocytes) that respond to alternative pathways of activation. This, coupled with the existence of novel antigen-presenting cells (intestinal epithelial cells) sets the scene for distinct immune responses. It is these distinct regulatory factors that support immunosuppression or tolerance rather than active immunity at a site juxtaposed to the external environment. This review defines these novel interactions and suggests how alteration in normal function may result in allergic or inflammatory responses. A clearer understanding of mucosal immunoregulation may lead to new therapeutic approaches for these diseases.

Antigen Presentation↗
PubMed2000

IBD: immunologic research at The Mount Sinai Hospital.

An evolution in our understanding of the inflammatory bowel diseases (IBD), ulcerative colitis and Crohn's disease, correlates with increased knowledge of the function of the mucosal immune system. In the early 1960s and 1970s, IBD was considered to be an autoimmune disease in which there was a directed attack by humoral and cellular elements of the immune system against intestinal tissues. These studies did not withstand the test of time, and from the 1970s through the 1990s there was a growing appreciation that defects in cellular immunity, not auto-reactive in nature, played a larger role in disease pathogenesis. Research at Mount Sinai focused in on these cellular T cell defects and helped pave the way for the current model of disease pathogenesis.

Allergy and Immunology↗
PubMed1999

The nonclassical class I molecule CD1d associates with the novel CD8 ligand gp180 on intestinal epithelial cells.

Previous studies have shown that normal intestinal epithelial cells (IECs) are able to selectively activate CD8(+) T cells with suppressor activity, inducing proliferation associated with the activation of both the CD8-associated kinase p56(lck) and the T cell receptor (TCR)-associated kinase p59(fyn). This process appears to relate in part to a 180-kDa IEC surface glycoprotein, gp180, which binds to CD8 and activates CD8-associated p56(lck). However, purified gp180 alone is unable to induce T cell proliferation and does not activate p59(fyn). Because the class Ib molecule CD1d is expressed by IECs and monoclonal antibodies (mAbs) against CD1d inhibit IEC-induced proliferation of CD8(+) T cells, co-immunoprecipitation and enzyme-linked immunosorbent assay studies were performed, which demonstrated an association of gp180 and CD1d on the IEC surface. Interestingly, the activation of p59(fyn) in IEC-T cell co-cultures was blocked by the anti-CD1d mAb D5 but not by the anti-gp180 mAb B9. Conversely, treatment of IECs with mAb B9 inhibited IEC-induced activation of p56(lck) but not p59(fyn). More directly, a human CD1d cDNA (FO-1 D5) transfectant was able to activate p59(fyn) but not p56(lck). These data suggest that the CD1d-gp180 complex on the surface of IECs can be recognized by the TCR-CD8 co-receptor, resulting in the activation of CD8(+) T cells.

Antibodies, Monoclonal↗
PubMed1999

Infliximab for the treatment of fistulas in patients with Crohn's disease.

BACKGROUND: Enterocutaneous fistulas are a serious complication of Crohn's disease and are difficult to treat. Infliximab, a chimeric monoclonal antibody to tumor necrosis factor alpha, has recently been developed as a treatment for Crohn's disease. We conducted a randomized, multicenter, double-blind, placebo-controlled trial of infliximab for the treatment of fistulas in patients with Crohn's disease. METHODS: The study included 94 adult patients who had draining abdominal or perianal fistulas of at least three months' duration as a complication of Crohn's disease. Patients were randomly assigned to receive one of three treatments: placebo (31 patients), 5 mg of infliximab per kilogram of body weight (31 patients), or 10 mg of infliximab per kilogram (32 patients); all three were to be administered intravenously at weeks 0, 2, and 6. The primary end point was a reduction of 50 percent or more from base line in the number of draining fistulas observed at two or more consecutive study visits. A secondary end point was the closure of all fistulas. RESULTS: Sixty-eight percent of the patients who received 5 mg of infliximab per kilogram and 56 percent of those who received 10 mg per kilogram achieved the primary end point, as compared with 26 percent of the patients in the placebo group (P=0.002 and P=0.02, respectively). In addition, 55 percent of the patients assigned to receive 5 mg of infliximab per kilogram and 38 percent of those assigned to 10 mg per kilogram had closure of all fistulas, as compared with 13 percent of the patients assigned to placebo (P=0.001 and P=0.04, respectively). The median length of time during which the fistulas remained closed was three months. More than 60 percent of patients in all the groups had adverse events. For patients treated with infliximab, the most common were headache, abscess, upper respiratory tract infection, and fatigue. CONCLUSIONS: Infliximab is an efficacious treatment for fistulas in patients with Crohn's disease.

Adult↗
PubMed1999

Efficacy and safety of retreatment with anti-tumor necrosis factor antibody (infliximab) to maintain remission in Crohn's disease.

BACKGROUND & AIMS: Infliximab, an anti-tumor necrosis factor monoclonal antibody, rapidly reduces signs and symptoms of active Crohn's disease. The aim of this study was to determine whether repeated infusions of infliximab would effectively and safely maintain the remitting benefit. METHODS: The efficacy, safety, pharmacokinetics, and immunogenicity of 4 repeated treatments with 10 mg/kg infliximab given every 8 weeks were compared with the effects of placebo in a randomized, double-blind, placebo-controlled, parallel group trial. Seventy-three patients with active Crohn's disease who had not adequately responded to conventional therapies and then had demonstrated a clinical response (>/=70-point decrease in the Crohn's Disease Activity Index) to an initial infusion of infliximab (or placebo) were studied. RESULTS: Retreatment with infliximab maintained the clinical benefit through the retreatment period and 8 weeks after the last infusion in nearly all patients retreated with infliximab. Median values for Crohn's Disease Activity Index, inflammatory bowel disease questionnaire (a quality of life measurement), and serum C-reactive protein concentration were maintained at remission levels with infliximab retreatment, but not with placebo retreatment. Retreatment with infliximab every 8 weeks maintained serum infliximab concentration and was well tolerated with a low incidence of immunogenicity. One case of lymphoma and 1 case of suspected lupus were reported; the complete long-term safety profile of infliximab requires additional clinical investigation. CONCLUSIONS: Long-term treatment with infliximab showed efficacy and tolerability in managing symptoms of patients with active Crohn's disease not responding to conventional treatments.

Adolescent↗
PubMed1999

Correlation of clinical parameters and immunological function with human immunodeficiency virus plasma viremia in children.

Studies of immune function in human immunodeficiency virus (HIV)-infected children are important, because functional abnormalities can precede CD4+ T-cell loss and are associated with the development of opportunistic and bacterial infections. We sought to correlate clinical parameters and immunological function with HIV RNA plasma levels in 20 children. HIV RNA levels were measured by a polymerase chain reaction assay. We analyzed T-cell responses to mitogens (phytohemagglutinin, concanavalin A, and pokeweed [PWM]) and antigens (tetanus toxoid and Candida albicans); T-cell suppressor activity; and humoral immunity to Haemophilus influenzae, hepatitis B, tetanus, and diphtheria vaccines. The median age of the children was 6 years. Eight children had HIV RNA levels less than 200 to 9621 copies per milliliter (group I). Four children had 37,970 to 82,630 copies per milliliter (group II). Eight children had 102,100 to 191,200 copies per milliliter (group III). There were no differences in the HIV-related complications between group I and II children. Group I/II children had significantly higher CD4+ T-cell counts (P = 0.02), less symptomatic HIV disease (P = 0.005), and more detectable protective vaccine immunity (P = 0.014) compared with group III children. Responses to mitogens were conserved in most children. Group I children tended to have higher responses to tetanus toxoid than group II children and significantly higher responses than group III children (P = 0.01). Group I had significantly higher responses to C. albicans than groups II (P = 0.016) and III (P = 0.001). Group I/II children tended to have lower suppressor activity compared with group III children (median, 0 vs 64%). We demonstrated that humoral and cellular immune dysfunction exists at all stages of disease in HIV-infected children but was most severe in children with greater than or equal to 100,000 HIV RNA copies per milliliter. Function was the most intact in children with less than 10,000 copies per milliliter.

Adolescent↗
PubMed1999

The intestinal epithelial cell: processing and presentation of antigen to the mucosal immune system.

The immunologic tone of the intestinal tract is one of suppressed or highly regulated responses. While there are several components (intrinsic and extrinsic to the gut-associated lymphoid tissue) responsible for this immunologically suppressed tone, the intestinal epithelial call (IEC) has been proposed as a key player in this process. IECs can take up and process antigen but distinct surface molecules and restriction elements allow them to present these antigens to unique regulatory T cells. These include the expression of the class Ib molecule CD1d as well as a novel CD8 ligand, gp180. These molecules come together to activate a subpopulation of CD8+ regulatory cells whose function is to suppress immune responses in an antigen non-specific fashion most likely through cognate interactions. This form of regulation may be unique to the gut-associated lymphoid tissue which is consistent with the unusual demands upon this part of the immune system.

Animals↗
PubMed1999

Randomized phase II study of high-dose paclitaxel with or without amifostine in patients with metastatic breast cancer.

PURPOSE: To determine whether the neurotoxicity of paclitaxel 250 mg/m(2) given over 3 hours every 3 weeks could be reduced by pretreatment with amifostine 910 mg/m(2). Secondary objectives included comparing myelosuppression, myalgias, and response rates of the two groups. PATIENTS AND METHODS: Forty women with metastatic breast cancer were randomized to receive either paclitaxel alone (arm 1) or paclitaxel preceded by amifostine (arm 2). All were assessable for toxicity, and 37 were assessable for response. At baseline and after each cycle, all patients completed questionnaires for neurologic symptoms and had standardized neurologic examinations, including objective assessments of power and vibration sense. In addition, standard follow-up assessments for other toxicities and tumor response were undertaken. Changes from baseline after courses 1, 2, and 3 were assessed. The sample size was sufficient to detect a 50% improvement in the expected determination in sensory change. RESULTS: There were no differences observed in any of the measures of neurotoxicity. Other toxicity was similar in arms 1 and 2, including hair loss (95% v 90%), neurosensory changes (100% v 100%), fatigue/lethargy (85% v 90%), myalgia (95% v 90%), and grade 4 neutropenia (47% v 60%). Nausea, vomiting, dizziness, hypotension, and sneezing were more common in the amifostine arm. Response rates (22.2% v 36.8%) and paclitaxel pharmacokinetics were not significantly different. CONCLUSION: There was no protection from paclitaxel-related neurotoxicity or hematologic toxicity in this study. These results suggest that the mechanism of action of paclitaxel-related toxic effects is not amenable to the cytoprotective action of amifostine.

Adult↗
PubMed1998

The regulation and functional consequence of proinflammatory cytokine binding on human intestinal epithelial cells.

Products of an activated immune system may affect cells within the immune system as well as nonlymphoid cells in the local environment. Given the immunologically activated state of the intestinal tract, it is conceivable that locally produced cytokines could regulate epithelial cell function. To assess whether epithelial cells are targets for particular cytokines, we initiated studies on the binding of a panel of proinflammatory cytokines in freshly isolated epithelial cells from normal and inflammatory bowel disease (IBD) patients as well as in cell lines. Isolated intestinal epithelial cells (IEC) were stained with phycoerythrin-conjugated or biotinylated cytokines to determine the expression and density of receptors for IL-1beta, IL-6, granulocyte-macrophage CSF (GM-CSF), and TNF-alpha. Receptors for IL-1beta, IL-6, and GM-CSF were readily detectable in all epithelial cell preparations at levels equal to (GM-CSFR) or lower than those seen on monocytes. However TNFalpha-R were not detectable on freshly isolated IECs. Receptor density was greater in surface vs crypt epithelial cells, but no significant differences were seen between normal and IBD epithelial cells. Expression of IL-1R and IL-6R was enhanced by LPS and IFN-gamma. Functionally, IL-1beta enhanced proliferation of the IEC cell line, DLD1, whereas GM-CSF treatment of de-differentiated crypt-like DLD1 and HT29 cells resulted in enhanced expression of ICAM-1. Furthermore, TNF-alpha treatment enhanced the secretion of IL-8 and GRO-alpha in HT29 cells, but not in freshly isolated IEC cultures. The differential binding and function of proinflammatory cytokines on IEC support the hypothesis that these cytokines may be involved in normal physiological processes as well as in regulating mucosal immune responses.

Antigen-Presenting Cells↗
PubMed1998

Relationship between blood antioxidants and occupational exposure to polycyclic aromatic hydrocarbons in coke oven workers.

BACKGROUND: We investigated if blood Cu++/Zn++ superoxide dismutase, glutathione peroxidase, and catalase activities are increased and total plasma antioxidant concentration is decreased in coke oven workers exposed to polycyclic aromatic hydrocarbons. METHODS: Ninety-six coke oven workers participated in the study. Nonexposed workers (n = 105) were randomly sampled among power plant workers in the same age range. The examination included a questionnaire on health status, occupational history, smoking, and dietary habits. Blood samples completed the examination. Coke oven workers were classified into low-, middle-, and high-exposure groups based on the benzo[a]pyrene (B[a]P) air concentrations and were further classified into the categories "topside" and "non-topside," according to their proximity to the ovens. RESULTS: Erythrocyte glutathione peroxidase activity increased with age (r = 0.18, P = 0.061) in power plant workers, whereas plasma glutathione peroxidase activity decreased with age (r = -0.18, P = 0.068) and erythrocyte glutathione peroxidase activity was inversely correlated with the number of cigarettes per day (r = -0.28, P = 0.08) in coke oven workers. Comparison of blood antioxidant enzyme activities and total plasma antioxidant concentration between coke oven and power plant workers showed that erythrocyte glutathione peroxidase activity was significantly lower in coke oven workers, even after adjustment for potential confounding factors. No differences were found either in other blood antioxidant enzyme activities or in total plasma antioxidant concentration between coke oven and power plant workers. Moreover, no trends toward decreased glutathione peroxidase activity among the three subgroups of B[a]P exposure were observed, and no differences either in blood antioxidant enzyme activities or in total plasma antioxidant concentration between the two groups of job categories were found. CONCLUSIONS: Production of reactive oxygen species seems not to be increased in coke oven workers.

Adult↗
PubMed1998

IL-10 production in common variable immunodeficiency.

Common variable immunodeficiency, (CVI) is a heterogeneous primary immunodeficiency disease in which there are T and B cell defects. Since IL-10 in conjunction with anti-CD40 promotes secretion of IgG, IgA, and IgM by CVI B cells, these studies were performed to investigate IL-10 production in CVI. Mitogen or anti-CD3 stimulated CVI peripheral blood mononuclear cells, or isolated T cells produced an insignificant amount of IL-10 over background levels. CVI monocyte IL-10 production was substantial and greater than that of normal controls. Anti-IL-10-neutralizing antibody strongly enhanced CVI T cell proliferative responses to PHA, but only to an insignificant extent, soluble antigens. IL-2 plus anti-IL-10 enhanced CVI proliferative responses to antigens significantly more over baseline than for cells of similarly tested normal controls. These data suggest that CVI T cell secretion of IL-10 is deficient, but that monocyte-derived IL-10, plus a relative lack of IL-2 production, could contribute to the defects of cell proliferation in this disorder.

Adolescent↗
PubMed1998

Differential expression of interleukin 1 receptor antagonist isoforms in human intestinal epithelial cells.

BACKGROUND & AIMS: Regulatory cytokines mediate intestinal epithelial cell (IEC) participation in mucosal immune responses. The aim of this study was to investigate the expression of secretory and intracellular isoforms of interleukin 1 receptor antagonist (IL-1Ra) in human primary IECs and carcinoma-derived cell lines. METHODS: Primary IECs were isolated from patients with Crohn's disease or ulcerative colitis and from normal controls. Isoform-specific IL-1Ra messenger RNA (mRNA) and protein were assessed by reverse-transcription polymerase chain reaction and Western blot analysis. Expression during cellular differentiation was determined by in situ immunohistochemistry on sequentially released, native IECs and in vitro differentiated cell lines. Intracellular IL-1Ra I function was analyzed by permanent transfection of Caco-2 cells. RESULTS: Intracellular IL-1Ra I protein accumulated in surface IECs with extension to the crypts during inflammation. Secretory IL-1Ra and intracellular IL-1Ra II mRNA, but not the corresponding protein, was detected. Transcription of intracellular IL-1Ra I mRNA was significantly up-regulated with inflammation and in vitro by phorbol myristate acetate and interleukin 1beta. In vitro differentiated cells had higher constitutive intracellular IL-1Ra I protein content. Intracellular IL-1Ra I expression in Caco-2 cells decreased IL-1beta-stimulated interleukin 8 secretion. CONCLUSIONS: Native human IECs and certain cell lines constitutively express intracellular IL-1Ra type I, which is up-regulated by inflammation, inflammatory stimuli, and cellular differentiation. Constitutive expression of this anti-inflammatory cytokine may contribute to mucosal protection.

Cell Differentiation↗