IL-25 induces IL-4, IL-5, and IL-13 and Th2-associated pathologies in vivo.

We have characterized a cytokine produced by Th2 cells, designated as IL-25. Infusion of mice with IL-25 induced IL-4, IL-5, and IL-13 gene expression. The induction of these cytokines resulted in Th2-like responses marked by increased serum IgE, IgG(1), and IgA levels, blood eosinophilia, and pathological changes in the lungs and digestive tract that included eosinophilic infiltrates, increased mucus production, and epithelial cell hyperplasia/hypertrophy. In addition, our studies show that IL-25 induces Th2-type cytokine production by accessory cells that are MHC class II(high), CD11c(dull), and lineage(-). These results suggest that IL-25, derived from Th2 T cells, is capable of amplifying allergic type inflammatory responses by its actions on other cell types.

Lessons from genetically engineered animal models. XII. IL-10-deficient (IL-10(-/-) mice and intestinal inflammation.

Interleukin (IL)-10(-/-) mice spontaneously develop intestinal inflammation characterized by discontinuous transmural lesions affecting the small and large intestine and by dysregulated production of proinflammatory cytokines. The uncontrolled generation of IFN-gamma-producing CD4(+) T cells (Th1 type) has been shown to play a causal role in the development of enterocolitis affecting these mutants. This article discusses studies of IL-10(-/-) mice that have investigated the role of enteric organisms in triggering intestinal disease, the mediators responsible for initiating and maintaining intestinal disease, the role IL-10 plays in the generation and/or function of regulatory cells, and the results of IL-10 therapy in experimental animal models of inflammatory bowel disease (IBD) and human patients with IBD.

Chronic colitis in IL-10-/- mice: insufficient counter regulation of a Th1 response.

IL-10-deficient (IL-10-/-) mice, generated by a gene-targeted mutation, develop abnormal immune responses as a result of uncontrolled interactions between antigen presenting cells and lymphocytes. The studies reviewed herein have focused on the enterocolitis that spontaneously develops in IL-10-/- mice. Not unexpectedly, heightened production of proinflammatory mediators accompanied pathologic changes in the gastrointestinal tract of young mutants. In a series of studies, the proinflammatory mediators responsible for initiating the pathogenic response were distinguished from those that were elicited as a consequence of persistent inflammation. We have also investigated the possibility that different mediators are involved in the inductive versus the maintenance phase of disease. The findings of these mechanistic studies as they relate to our understanding of progressive inflammatory disease and the role of IL-10 in controlling the acute and chronic stages are discussed.

[Comparison of infectious complications of long-term and short-term central venous catheterization]. / Comparaison des complications infectieuses des cathéters veineux centraux de courte et de longue durées.

OBJECTIVES: Risk factors for infectious complications of central venous catheters (CVC) were compared between CVC used for short and long periods to identify patients at risk. PATIENTS AND METHODS: A prospective study was conducted over a 6 month period in two general intensive care units (87 patients with short duration CVC) and in 4 medical units (110 patients with cancer or HIV infection for whom long duration CVC was scheduled). The first CVC inserted was followed to withdrawal or for a minimal 3 months. RESULTS: The mean duration of CVC use was 7.5 and 106 days for the short and long duration groups respectively. A CVC-related infection occurred in 6 patients in the short duration group and in 14 patients in the long duration group giving an incidence of 1.0/100 CVC days (95% CI: 0.4-2.0) for the short-duration CVC group and 0.13/100 CVC days (95% CI: 0.07-0.21) for the long-duration CVC group. Intensive care patients with a skin lesion far from the CVC insertion point had a higher incidence of CVC-related infection than patients without a skin infection. Taking into account the indications for CVC, patients with cancer or HIV infection had equivalent risk of infection. For both short and long duration CVC use, parenteral nutrition was found to be a major risk factor for infectious complications. CONCLUSION: Rigorous regular surveillance of nosocomial infections on central catheters should be centered on those inserted for parenteral nutrition.

The role of IL-10 in inflammatory bowel disease: "of mice and men".

Inflammatory bowel disease (IBD) is a generic term typically used to describe a group of idiopathic inflammatory intestinal conditions in humans that are generally divided into Crohn's disease and ulcerative colitis. Although the etiology of these diseases remains unknown, a number of rodent models of IBD have recently been identified, all sharing the concept that the development of chronic intestinal inflammation occurs as a consequence of alterations in the immune system that lead to a failure of normal immunoregulation in the intestine. On the basis of these models, it has been hypothesized that the development of IBD in humans may be related to a dysregulated immune response to normal flora in the gut. Immunodeficient scid mice injected with CD4+ CD45RB(high) T cells and mice deficient in interleukin (IL)-10 (IL-10-/-) are among the rodent models of IBD. In both models, there is inflammation and evidence of a Th1-like response in the large intestine, characterized by CD4+ T-cell and macrophage infiltrates, and elevated levels of interferon-gamma. Because IL-10 is an immunomodulatory cytokine that is capable of controlling Th1-like responses, the role of IL-10 was investigated in these models. IL-10 was shown to be important in regulating the development of intestinal inflammation in both models. These results provided key data that supported initiation of clinical trials evaluating the efficacy of IL-10 in patients with IBD.

A role for NK cells as regulators of CD4+ T cells in a transfer model of colitis.

Previous studies have shown that the chronic inflammation observed in the colon of IL-10-deficient (IL-10(-/-)) mice is mediated by CD4+ Th1 T cells and is dependent on the presence of IFN-gamma for its initial development. As CD4+ T cells from IL-10(-/-) mice will cause colitis when transferred into recombinase-activating gene (Rag)-deficient recipients, we considered the possibility that the recipients' NK cells could be an important source of IFN-gamma for the development of colitis. Therefore, the ability of IL-10(-/-) CD4+ T cells to cause colitis in Rag-deficient recipients that had been depleted of NK cells was tested. Contrary to our expectations, NK cell-depleted recipients of IL-10(-/-) CD4+ T cells developed accelerated disease compared with nondepleted recipients. Furthermore, CD4+ T cells from normal mice (IL-10(+/+)) also caused colitis in NK cell-depleted recipient mice, but not in nondepleted recipients. NK cells inhibited effector CD4+CD45RBhigh T cells, and subsequent experiments showed that this effect was dependent on perforin. Thus NK cells can play an important role in down-regulating Thl-mediated colitis by controlling the responses of effector T cells to gut bacteria.

[Central venous catheters. Prospective surveillance of a hospital]. / Cathéters veineux centraux. Surveillance prospective sur l'ensemble d'un hôpital.

OBJECTIVES: All the central venous catheters (CVC) inserted at the Saint-Antoine Hospital between December 5, 1994 and June 6, 1995 were prospectively studied in order to better define practices in the management of CVC and to determine the rate of catheter-related infections. METHODS: The following data were recorded for each CVC: insertion procedure, clinical data, catheter dressings, removal, catheter-related infections, bacteriological findings. Catheter-related infections were distinguished from probably catheter-related infections and localized skin infections. RESULTS: Among 325 patients, a total of 414 catheters were inserted. At the end of the surveillance period, 350 (85%) had been removed, 43 (10%) were still in place and 21 (5%) were lost to follow-up. Analysis of procedures such as cutaneous disinfection, routine replacement of the i.v. sets or changes of dressings showed wide variations between care units and within the same unit. The overall incidence of catheter-related infections was 0.24 per 100 days of catheterization. Infections occurred 29 +/- 34 days after insertion. Microorganisms responsible for catheter-related bacteremia were mostly Gram positive (84%) and Gram negative (16%). Sixty-two infections (15%) were clinically suspected by physicians, leading to the catheter removal in 84% of cases. Out of the 43 CVC sent to the laboratory, 29 (67%) were negative (i.e., "sterile") in quantitative culture of the tips as described by Brun-Buisson, suggesting that the CVC was unnecessarily removed. Bacteriological analysis ordered by physicians were not always relevant. For example, 76% of CVC received by the laboratory were systematically sent although they were not suspected of infections. Conversely, only 61% of exsudate formation at the insertion site were collected and analyzed. CONCLUSION: This study was designed to recall good guidelines to the hospital staff. Results will lead to the development of a better use of antiseptics and to the implementation of appropriate and standardized procedures to reduce risk infection.

Studies with IL-10-/- mice: an overview.

Our studies have elucidated, in part, the mechanism whereby persistent stimulation by normal enteric antigens leads to the development of chronic enterocolitis in interleukin 10-deficient (IL-10-/-) mice. This disease is mediated by IL-10-/- CD4+ T cells as evidenced by their ability to transfer colitis to immunodeficient RAG-2-/- mice. Furthermore, the CD4+ T cells recovered from the affected colons of IL-10-/- mice consisted of a highly polarized Th1-like population because they produced interferon-gamma (IFN-gamma) but not IL-4. We found that enterocolitis could be prevented if 3-week-old mutants were treated for 6-8 weeks with either anti-IL-12 or anti-IFN-gamma monoclonal antibodies (mAb). These results were consistent with the findings of in vitro studies suggesting that IFN-gamma and, in particular, IL-12 direct the differentiation of naive T cells toward a Th1 phenotype. Apparently, the uncontrolled production of IL-12 and IFN-gamma by accessory cells and T cells, respectively, in IL-10-/- mice ultimately resulted in the excessive generation and activation of Th1 cells, hence, immunopathology. IL-10-/- mice have also been used to evaluate the importance of IL-10 in regulating immune responses outside of the gastrointestinal (GI) tract. In these studies, IL-10-/- mice were challenged with a variety of foreign antigens using different routes of administration. In general, the results repeatedly demonstrated that a major function of IL-10 is to protect the host from the harmful side effects of an overly zealous immune-inflammatory response. However, other studies have confirmed speculations that the potent immunosuppressive activities of IL-10 may, under certain circumstances, increase the host's susceptibility to infection with certain types of pathogenic organisms.

Can bone marrow-derived thymic stromal cells mediate the positive selection of class I-restricted T cells?

Positive selection of T lymphocytes expressing self. MHC-restricted T cell receptors is mediated by MHC molecules expressed on thymic stroma. Among the more controversial aspects of this process is the relative role of MHC molecules on epithelial versus bone marrow-derived stromal elements (BM-APC). For CD4+ T cells, the weight of evidence suggests that positive selection is driven solely by MHC class II molecules expressed on thymic epithelial cells. In contrast, recent experiments have been interpreted to show that CD8+ T cell development can be driven by MHC class I molecules expressed on BM-APCs as well as epithelial cells. To directly address this issue, we have examined the development of T cells expressing a transgenic, MHC class I-restricted TCR in mice deficient in the rearrangement of endogenous TCR genes. Since the transgenic TCR is the only TCR expressed, this system is extremely sensitive and specific for detecting even inefficient events in T cell development. Our experiments demonstrate that MHC class I expression exclusively on BM-APC is incapable of driving positive selection of CD8+ T cells. This finding, together with earlier experiments for MHC class II, suggests a qualitatively unique function of thymic epithelial cells in mediating positive selection.

T helper cell 1-type CD4+ T cells, but not B cells, mediate colitis in interleukin 10-deficient mice.

Mice rendered deficient in the production of interleukin 10 (IL-10-/-) develop a chronic inflammatory bowel disease (IBD) that predominates in the colon and shares histopathological features with human IBD. Our aim was to identify which cell type(s) can mediate colitis in IL-10-/- mice. We detected an influx of immunoglobulin-positive cells into the colon and the presence of colon-reactive antibodies in the serum of IL-10-/- mice. To assess a pathogenic role for B cells, we generated a B cell-deficient (B-/-) strain of IL-10-/- mice. B-/-IL-10-/- mice acquired a severe colitis analogous to that IL-10-/- mice, implying that B cells were not the primary mediator of IBD in this model. A series of cell transfer experiments was performed to assess a pathogenic role for T cells. When IL-10-/- T cell-enriched lamina propria lymphocytes (LPL) or intraepithelial lymphocytes (IEL) were transferred into immunodeficient recombinase-activating gene (RAG)-2-/- recipients, a mild to severe colitis developed, depending on the cell number transferred. Lymphocytes recovered from the colon of transplanted RAG-2-/- mice with colitis were predominantly alpha beta TCR+CD4+, including a large proportion of CD4+CD8 alpha + cells. These cells were also CD45RB-/low and CD44+, indicative of an activated/memory population. Individual populations of CD4+CD8 alpha-, CD4+CD8 alpha + and CD4-CD8 alpha + T cells were then isolated from the lamina propria compartment of IL-10-/- mice and transferred into RAG-2-/- recipients. Only IL-10-/- CD4-expressing LPL, including both the CD4+CD8 alpha- and CD4+CD8 alpha + populations, induced colitis in recipient mice. Interferon-gamma, but little to no IL-4, was produced by CD4+CD8 alpha- and CD4+CD8 alpha + LPL recovered from the inflamed colons of RAG-2-/- recipients implicating alpha T helper cell 1 (TH1)-mediated response. We thus conclude that colitis in IL-10-/- mice is predominantly mediated by TH1-type alpha beta TCR+ T cells expressing CD4 alone, or in combination with the CD8 alpha molecule.

Ingestive behavior and body temperature of pigeons during long-term cold exposure.

Pigeons well adapted to living in 21 degrees C ambient temperature (T(a)) were continuously exposed to cold T(a) for 6 days (Experiment 1) or 30 days (Experiment 2). The pigeons lived on a 12:12 L:D cycle where they could obtain short access to food and water at any time in the light phase by making 12 keypeck responses. Across the two experiments, the levels of cold exposure were 6 degrees C, 1 degrees C, and 0.6 degrees C. In cold, total daily food intake increased gradually across the first few days of the exposure, and the new level of food intake was inversely related to T(a). The daily ratio of total water drunk to total food eaten averaged approximately 1.3 in 21 degrees C, fell to approximately 1.0 on day 1 of cold exposure, and remained at that level for as long as 30 days. The day-night cycle in core body temperature was not changed by cold exposure. The bimodal temporal pattern of feeding in the light phase, which is characteristic of pigeons in moderate T(a), was preserved in the cold although the absolute level of feeding activity was enhanced. An analysis of the ways individual pigeons achieved total daily food intake by combining a number of feeding episodes with an average amount eaten per episode revealed considerable variation between birds, but a relatively constant feeding style within bird over time. In the colder temperatures used, however, the pigeons all increased the number of feeding episodes per day. The results provide the first detailed analysis of cold-induced changes in ingestive behavior in the pigeon and raise several questions about the behavioral expression of cold-sensitive regulatory processes.

Genetic variability in HIV-1 gp120 affects interactions with HLA molecules and T cell receptor.

The propensity of HIV-1 to undergo sequence variation, particularly in the envelope glycoprotein gp120, complicates vaccine development and may enable the virus to evade ongoing immune responses in infected individuals. We present here a molecular analysis of the effects of this variability on human T cell recognition of HIV-1 gp120. Synthetic peptides representing a defined CD4+ human T cell epitope in gp120 were used to survey gp120 molecules from various HIV-1 strains for the capacity to be recognized in the context of a single human MHC molecule, DR4. Variation affected recognition at two levels. For some strains, variation in this epitope was sufficient to alter the interaction of Ag receptors on gp120-specific human T cell clones with peptide-DR4 complexes on APC. In the case of two strains, the natural variation was sufficient to prevent the critical initial interaction between the relevant gp120 peptides and DR4 on the APC. However, these strains were highly divergent from the reference strain. Thus it is encouraging to note that the range of natural sequence variation in this T cell epitope falls, for the most part, within the range of peptide sequences that can be accommodated by the relevant human MHC molecule.

A comparison of three nucleoside analogs with anti-retroviral activity on immune and hematopoietic functions in mice: in vitro toxicity to precursor cells and microstromal environment.

A number of 2'3'-dideoxynucleosides have been reported to markedly inhibit the in vitro growth of HIV, the causative agent of acquired immunodeficiency syndrome (AIDS). Clinical trials have shown that the continued therapeutic use of these nucleoside derivatives can be associated with adverse side effects. Since these side effects include myelotoxicity, as occurs in many patients treated with zidovudine (AZT; 3'-azido'3-deoxythymidine), and AIDS patients already represent an immunologically compromised population, we examined the immunological effects of three nucleoside inhibitors, including zidovudine, 2'3'-dideoxycytidine, and 2'3'-dideoxyadenosine (DDA) in a mouse model. Additional studies were conducted to further determine and characterize the potential toxic effects associated with these drugs on the hematopoietic system. Of the three dideoxynucleosides examined, only DDA altered immune functions following a 30-day subchronic exposure in mice. This was evidenced by a marked suppression of the antibody plaque-forming cell response and a slight alteration in macrophage function. None of the nucleoside derivatives affected bone marrow function following in vivo exposure, although AZT produced a mild macrocytic anemia in vivo and was myelotoxic when added in vitro to bone marrow cell cultures. In vitro studies indicated that AZT was capable of affecting both proliferating stem cells as well as the stromal cell microenvironment, both of which play a role in hematopoiesis. These data indicate that, although the mice may not develop the identical toxicities associated with nucleoside therapy in humans, certain adverse immunological and hematological effects were readily discerned which could have relevance to humans.