Corticosteroids inhibit murine macrophage Ia expression and interleukin 1 production

Corticosteroids have profound effects on functions of the macrophage associated with antigen presentation to T cells. The drugs inhibited the expression of surface I-region-associated (Ia) antigens by peritoneal macrophages both in vitro and in vivo, reduced the production of IL 1, and inhibited antigen presentation for T cell proliferation by macrophages. The doses of hydrocortisone and prednisolone that inhibited by 50% Ia expression in cultured macrophages ranged around 2 to 5 x 10(-8) M. These results could explain one mechanism by which corticosteroids suppress the induction of immune responses.     

Intestinal epithelial cell line induction of T cell differentiation from bone marrow precursors

The mechanism whereby the intestinal microenvironment promotes T cell development in the absence of the thymus is unknown. We show that the murine intestine-derived epithelial cell line, MODE-K, can induce T cell differentiation marker expression in vitro on bone marrow (BM) T cell precursors. Three-color flow cytometry analysis of T-cell-depleted C3H BM mononuclear cells (MNC) after 4 days of coculture on monolayers of MODE-K indicated that approximately 25% of MNC expressed CD3 and TCR alpha beta. Of these CD3+ cells, 36% were CD3loCD4-CD8- double negative (DN), 34% were CD3loCD4+CD8 alpha beta+ double positive (DP), and the remainder were CD3hiCD4+CD8- or CD3hiCD4-CD8 alpha beta+ single positive (SP). In addition, the T cells which developed in coculture with MODE-K expressed the early T cell differentiation marker CD24 (heat-stable antigen). These T cells subsets did not develop when BM was cocultured with the LTA fibroblast cell line or in medium alone. Interestingly, preventing cell contact between MODE-K and BM by culturing in Transwell plates did not interfere with the development of T cells expressing the DN, DP, or SP phenotypes. Double-positive T cells did not develop if splenic MNC were cocultured with MODE-K. These results suggest that the intestinal epithelial environment can induce and support the T cell development from bone marrow precursors.     

Interaction between interleukin 10 and interleukin 6 in human B-cell differentiation

Contrary to their opposing action on human T-lymphocytes and monocytes, both Interleukin (IL-)10 and IL-6 are potent differentiation factors of human B-cells. Both are known to induce immunoglobulin (Ig) production. The precise mechanism of this converging effect of IL-6 and IL-10 remains elusive, however. Here we investigated the role of IL-6 in the IL-10 dependent B-cell differentiation into Ig secreting cells. We found that co-stimulation of SAC-stimulated human peripheral B-lymphocytes with IL-10 and IL-6 exhibited no additive effect on Ig production over stimulation with IL-10 alone, and that IL-6 receptor blockade only mildly inhibited IL-10 induced Ig synthesis. In fact, we could show that stimulation of B-cells with IL-10 somewhat suppressed SAC induced autocrine IL-6 production. Despite this suppression IL-6 levels remained sufficiently high to stimulate its receptor, and IL-6 binding to the B-cell surface was not affected. The failure of IL-6 to exert an additional effect on SAC+IL-10 induced Ig production suggests that IL-10 may recruit components of the IL-6 intracellular pathway for Ig induction. In conclusion we could demonstrate that IL-10 acts on B-cell differentiation independently of autocrine IL-6 and that it had a considerably mild effect on B lymphocytic autocrine IL-6 secretion. This still allows an IL-6 effect in the presence of IL-10 which appears adaptive with a view to the converging effects of these two cytokines on human B lymphocytes. Our study thus adds to the appreciation of the complex cytokine regulation of the immune system.     

Effects of Ajoene on lymphocyte and macrophage membrane-dependent functions

An increasing flow of evidences collected on elementary forms of learning processes in selected animal models evidentiates some mechanisms which can represent the basic cellular principles underlying plastic changes: 1. 5HT and second messengers of nucleotide type (like cAMP) have a pivotal role in the learning process. 2. In almost all short-term learning processes the modifications are subserved by a mechanism of protein phosphorylation. 3. In various animal models the modulation of K+ and Ca2+ channels is the molecular mechanism for learning. Experiments performed in sensory T neuron of the leech indicate that the modulation of Na+/K+ electrogenic pump is one of the fundamental mechanism for learning. 4. In long-term plastic changes, the most important finding is that newly synthesized proteins are formed. 5. In addition to what has been observed in the Aplysia model, where changes in synaptic efficacy represent the basic principles of memory storage, in the leech it has been demonstrated that a molecular machinery present in a single neuron can adapt the activity of the cell to environmental stimuli.     

Endothelial and macrophage upregulation of urokinase receptor expression in human renal cell carcinoma

The binding of urokinase-type plasminogen activator (u-PA) to a specific cell surface receptor (uPA-R) has been shown to enhance plasminogen activation, a process involved in extracellular matrix degradation and cell migration during angiogenesis and tumor growth. We investigated the expression of u-PA and uPA-R in renal cell carcinomas (n = 11). By immunohistochemistry using monoclonal and polyclonal anti-uPA-R antibodies, we found that tumoral capillary endothelial cells (von Willebrand factor and CD31 positive cells) overexpressed uPA-R, whereas vascular endothelial cells of the normal human kidney do not. In addition, tumor-associated macrophages (CD68-positive cells) strongly expressed uPA-R. In contrast, few tumoral cells and stromal fibroblasts expressed uPA-R. By in situ hybridization using a cDNA S35-labeled probe specific for uPA-R, we confirmed the local expression of uPA-R messenger RNA. We also detected the induction of u-PA in tumoral capillary endothelial cells and in tumor-associated macrophages. In two cases, tumoral cells themselves were also stained by anti-u-PA antibodies in focal areas. Finally tissue-type plasminogen activator (t-PA) was also overexpressed by tumoral capillary endothelial cells as compared with endothelial cells of normal human kidney vessels. These findings indicate an active invasive phenotype of endothelial cells in renal cell carcinoma and suggest a role for the plasminogen activation system in tumoral angiogenesis and invasion.     

Effects of oxysterols upon macrophage and lymphocyte functions in vitro

Oxygenated derivatives of cholesterol (oxysterols), found in high concentrations in atherosclerotic lesions, are potent immunosuppressive agents inhibiting T-cell responses to different stimuli. The action of oxysterols on macrophage functions and macrophage-lymphocyte interaction has been poorly investigated. In this work, the effects of 25-hydroxycholesterol (25-OHCh) and 7-ketocholesterol (7-KCh) upon some functions of murine peritoneal macrophage (PM), such as generation of reactive oxygen intermediates (ROI), secretion of neopterin and interleukin-1 (IL-1)-like activity, Fc-receptor (FcR) activity, and murine and human lymphocyte functions, participating in lymphocyte-macrophage interactions, such as macrophage-activating factor (MAF) and Ia-inducing factor (IaIF) secretion, were studied in vitro. 7-KCh in concentration of 5 micrograms/mL culture medium only, but not 25-OHCh, significantly inhibited ROI generation by zymosan-stimulated PM. Pretreatment of PM for 22 h with 25-OHCh and 7-KCh led to the decrease of IL-1-like activity secretion. 25-OHCh and 7-KCh inhibited both FcR-dependent binding and phagocytosis of sheep red blood cells (SRBC). Oxysterols did not change both spontaneous and lipopolysaccharide-stimulated secretion of neopterin by PM. 25-OHCh dose-dependently and more efficiently than 7-KCh inhibited murine splenocyte secretion of MAF, which activity was determined by the ability of splenocyte-conditioned medium to stimulate ROI generation in PM. Both 25-OHCh and 7-KCh inhibited significantly proliferative activity of human mixed lymphocyte culture (MLC), as well as lymphocyte secretion of IaIF, which stimulates the expression of HLA antigens in cultured human monocytes. Purified Ch did not alter these parameters. These data showed, that some inflammatory functions of macrophages and lymphocytes may be modified by such environmental conditions as the presence of oxysterols.     

Mechanisms of intestinal epithelial cell injury and colitis in interleukin 2 (IL2)-deficient mice

Epithelial cell (EC) injury is a feature of all inflammatory bowel disorders (IBD). Although the mechanisms of EC injury are incompletely understood, it has been proposed that T-cell-mediated cytotoxicity and production of inflammatory cytokines are involved. This hypothesis was tested using the interleukin 2-deficient (IL2-/-) mouse model of IBD and cultures of primary colonic EC to determine if abnormal cytokine production or cytotoxicity by colonic T cells cause EC injury. Although capable of cell-mediated killing of allogeneic target cells, IL2-/- colonic T cells were unable to lyse syngeneic colonic EC. During disease progression, large numbers of IL4, TNF-alpha, and IFN-gamma-producing CD4+ and CD8+ cells accumulated within the intraepithelial spaces and lamina propria of the colon of IL2-/- mice. Although colonic EC expressed receptors for IFN-gamma and TNF-alpha, these cytokines did not adversely affect EC viability or growth in vitro consistent with these cytokines not being the primary mediators of EC injury in IBD. Our novel colonic EC culture system provides an in vitro accessible system in which to investigate further the nature of EC-lymphocyte interactions.     

CD10 is expressed on human thymic epithelial cell lines and modulates thymopentin-induced cell proliferation

Thymic hormones such as thymopoietin (TP) have been shown to regulate thymocyte differentiation and lymphocyte activation. However, it is not known whether thymopoietin affects thymic epithelial cell (TEC) functions. In this study we have examined the effect of a five amino acid active peptide (TP5), corresponding to amino acids 32-36 of TP, on the proliferation of nontransformed clones of human TEC. Our results indicate that TP5 induced reinitiation of DNA synthesis and potentiated fetal calf serum (FCS)-induced cell growth in postnatal and fetal-derived human TEC. We also found that TEC lines express high levels of endopeptidase 24.11, a cell-surface metallopeptidase also known as the CD10 antigen. We show that TP5 is cleaved by CD10 at the surface of TEC lines, indicating that this endopeptidase may regulate TP5-induced TEC proliferation. Phosphoramidon, a specific endopeptidase 24.11 inhibitor, consistently acts in synergy with TP5 to enhance FCS-induced TEC growth. Hence, we conclude that 1) TP5 alone or in combination with FCS supports the growth of TEC lines, and 2) TEC lines express high levels of CD10, which regulates TP5-induced TEC proliferation by acting as a thymic peptide degrading enzyme.     

Differential effect of interleukin 10 on interleukin 12- and interleukin 2-mediated killer induction from blood mononuclear cells

Symptomatic tarsal coalition is often considered to be synonymous with peroneal spastic flatfoot. The association of the cavovarus foot type with tarsal coalition is less well established and has been described only in children. This article describes a case of an adult female with symptomatic cavovarus feet with talocalcaneal coalition. The authors theorize about the pathology of muscle spasm and pain in patients with this condition.     

Expression of T lymphocyte adhesion molecules: regulation during antigen-induced T cell activation and differentiation

The pattern of lymphocyte traffic and migration in vivo is a composite of constitutive recirculation and transient changes induced by interaction with antigen. Naive T lymphocytes in their basal, unstimulated state continuously recirculate throughout the entire host, poised to react to specific antigens that they are programmed to recognize. After interaction with antigen, T cell traffic changes, first with the trapping of reactive cells in antigen-containing lymphoid tissue. Subsequently, the effector cells responding to antigen, accompanied by nonspecific T cells and monocytes, traffic in large numbers to sites of antigen localization, resulting in the localized inflammatory response. Then, as the immune response wanes, memory T cells develop, many of which exhibit still different routes of recirculation. The traffic and tissue localization of leukocytes is regulated by a series of cell surface adhesion molecules that recognize specific ligands on endothelial cells and in the extracellular matrix. Modulation of the expression of these adhesion molecules results in the changes in T cell traffic that are characteristic of each stage of T cell differentiation. Thus, during T cell activation and differentiation, the down-regulation of adhesion receptors specific for lymphoid tissue endothelium and up-regulation of integrins facilitate the targeting of effector cells to sites of inflammation. Subsequent changes in adhesion receptors regulate the traffic of the antigen-specific memory cells. T cell adhesion molecule expression is therefore regulated as a function of the stage of activation and differentiation and, in addition, is influenced by cytokines and the local lymphoid microenvironment.     

Intestinal epithelial cells down-regulate macrophage tumor necrosis factor-alpha secretion: a mechanism for immune homeostasis in the gut-associated lymphoid tissue

BACKGROUND: The gut lumen contains more than 10(6) organisms per gram of luminal contents. The mechanisms that limit the response of macrophages in the lamina propria to these microbial antigens are unknown, although an intrinsic defect in this mechanism may contribute to the development of inflammatory bowel disease. Intestinal epithelial cells (IEC) may play an important role in mediating tonic down-regulation of local immune cell activation. The purpose of this study was to discern whether IEC might modulate macrophage activation in response to a variety of microbial stimuli. METHODS: Thioglycollate-elicited murine peritoneal macrophages were activated by endotoxin, zymosan, Escherichia coli, and Candida albicans in the presence or absence of IEC from the rat intestinal epithelial cell line IEC-6. Macrophage tumor necrosis factor-alpha (TNF-alpha) secretion was determined by enzyme-linked immunosorbent assay. RESULTS: Lipopolysaccharide or zymosan-activated macrophages in coculture with IEC secreted significantly less TNF-alpha than macrophages cultured alone. The inhibitory effect of the IEC was dependent on their activation by lipopolysaccharide. Interleukin-1 alpha production was not affected. IEC-mediated suppression of macrophage TNF-alpha secretion was reversed by indomethacin but not by neutralizing antibody to TGF-beta. CONCLUSIONS: Lipopolysaccharide-activated IEC down-regulate macrophage TNF-alpha secretion in response to microbial stimuli through a prostanoid-mediated mechanism. IEC may mediate tonic down-regulation of immune cell activation in the gut-associated lymphoid tissue and may thereby regulate local and systemic inflammatory responses.     

Advanced colorectal cancer is associated with impaired interleukin 12 and enhanced interleukin 10 production

Interleukin 12 (IL-12) is a heterodimeric cytokine that has been demonstrated to have a major role in stimulating a cell-mediated antitumor response. IL-10, a product of T helper 2 lymphocytes, is its most potent inhibitor. The aim of this study was to investigate whether patients with colorectal cancer had an imbalance in production of IL-12 and IL-10 preoperatively, and whether this was associated with advanced disease at surgery. Blood was obtained before surgery from 60 patients with colorectal cancer and from 30 controls. Peripheral blood mononuclear cells were incubated with Staphylococcus aureus Cowan's strain 1 in vitro for 24 h to assess IL-12 expression after stimulation, and serum was used for IL-10 measurement. IL-12 and IL-10 levels were assessed by ELISA. A single pathologist staged the tumors according to the tumor-node-metastasis (TNM) and Dukes' classifications. Patients with colorectal cancer had significantly lower levels of IL-12 (P <0.001) and higher levels of IL-10(P = 0.004) compared to controls. In addition, lower levels of IL-12 were detected in those patients who were node positive (P<0.05), had Dukes' C lesions (P < or = 0.001), and T3 or T4 lesions (P<0.033) when compared to controls. Patients with Dukes' B and C lesions (P<0.01) and T3 and T4 lesions (P<0.05) also had higher levels of IL-10 compared to controls. This study is the first to demonstrate that patients with colorectal cancer have decreased IL-12 production and increased serum IL-10. This suggests an impaired T helper 1 cell-mediated antitumor response and provides some justification for exogenous IL-12 therapy or anti-IL-10 therapy in these patients.     

Down regulation of gene expression by the vaccinia virus D10 protein

Vaccinia virus genes are expressed in a sequential fashion, suggesting a role for negative as well as positive regulatory mechanisms. A potential down regulator of gene expression was mapped by transfection assays to vaccinia virus open reading frame D10, which encodes a protein with no previously known function. Inhibition was independent of the promoter type used for the reporter gene, indicating that the mechanism did not involve promoter sequence recognition. The inhibition was overcome, however, when the open reading frame of the reporter gene was preceded by the encephalomyocarditis virus internal ribosome entry site, which excludes the possibility of nonspecific metabolic or other antiviral effects and suggests that capped mRNAs or cap-dependent translation might be the target of the D10 product. The inducible overexpression of the D10 gene by a recombinant vaccinia virus severely inhibited viral protein synthesis, decreased the steady-state level of viral late mRNA, and blocked the formation of infectious virus.