Metagenomic approaches are currently being used to decipher the genome of the microbiota (microbiome), and, in parallel, functional studies are being performed to analyze the effects of the microbiota on the host. Gnotobiological methods are an indispensable tool for studying the consequences of bacterial colonization. Animals used as models of human diseases can be maintained in sterile conditions (isolators used for germ-free rearing) and specifically colonized with defined microbes (including non-cultivable commensal bacteria). The effects of the germ-free state or the effects of colonization on disease initiation and maintenance can be observed in these models. Using this approach we demonstrated direct involvement of components of the microbiota in chronic intestinal inflammation and development of colonic neoplasia (i.e., using models of human inflammatory bowel disease and colorectal carcinoma). In contrast, a protective effect of microbiota colonization was demonstrated for the development of autoimmune diabetes in non-obese diabetic (NOD) mice. Interestingly, the development of atherosclerosis in germ-free apolipoprotein E (ApoE)-deficient mice fed by a standard low-cholesterol diet is accelerated compared with conventionally reared animals. Mucosal induction of tolerance to allergen Bet v1 was not influenced by the presence or absence of microbiota. Identification of components of the microbiota and elucidation of the molecular mechanisms of their action in inducing pathological changes or exerting beneficial, disease-protective activities could aid in our ability to influence the composition of the microbiota and to find bacterial strains and components (e.g., probiotics and prebiotics) whose administration may aid in disease prevention and treatment.

• MeSH
• Autoimmune Diseases etiology   microbiology   MeSH
• Gastrointestinal Tract microbiology   MeSH
• Germ-Free Life * MeSH
• Immunity MeSH
• Humans MeSH
• Metagenome immunology   MeSH
• Disease Models, Animal MeSH
• Neoplasms etiology   microbiology   MeSH
• Mucous Membrane immunology   MeSH
• Inflammation etiology   microbiology   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH

BACKGROUND: Mammals are essentially born germ-free but the epithelial surfaces are promptly colonized by astounding numbers of bacteria soon after birth. The most extensive microbial community is harbored by the distal intestine. The gut microbiota outnumber ~10 times the total number of our somatic and germ cells. The host-microbiota relationship has evolved to become mutually beneficial. Studies in germ-free mice have shown that gut microbiota play a crucial role in the development of the immune system. The principal aim of the present study was to elucidate whether the presence of gut microbiota and the quality of a sterile diet containing various amounts of bacterial contaminants, measured by lipopolysaccharide (LPS) content, can influence maturation of the immune system in gnotobiotic mice. RESULTS: We have found that the presence of gut microbiota and to a lesser extent also the LPS-rich sterile diet drive the expansion of B and T cells in Peyer's patches and mesenteric lymph nodes. The most prominent was the expansion of CD4+ T cells including Foxp3-expressing T cells in mesenteric lymph nodes. Further, we have observed that both the presence of gut microbiota and the LPS-rich sterile diet influence in vitro cytokine profile of spleen cells. Both gut microbiota and LPS-rich diet increase the production of interleukin-12 and decrease the production of interleukin-4. In addition, the presence of gut microbiota increases the production of interleukin-10 and interferon-gamma. CONCLUSION: Our data clearly show that not only live gut microbiota but also microbial components (LPS) contained in sterile diet stimulate the development, expansion and function of the immune system. Finally, we would like to emphasize that the composition of diet should be regularly tested especially in all gnotobiotic models as the LPS content and other microbial components present in the diet may significantly alter the outcome of experiments.

• MeSH
• Lymphocyte Activation MeSH
• Cell Differentiation MeSH
• Cytokines metabolism   MeSH
• Diet MeSH
• Germ-Free Life immunology   MeSH
• Immune System growth & development   microbiology   MeSH
• Immune Tolerance MeSH
• Lipopolysaccharides metabolism   MeSH
• Mice, Inbred BALB C MeSH
• Mice MeSH
• Cell Proliferation MeSH
• T-Lymphocytes, Regulatory cytology   immunology   metabolism   MeSH
• Intestines immunology   microbiology   MeSH
• Intestinal Mucosa metabolism   MeSH
• Th1 Cells cytology   immunology   metabolism   MeSH
• Th2 Cells cytology   immunology   metabolism   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• Cytokines MeSH
• Lipopolysaccharides MeSH

The development of levels of secretory immunoglobulins (SIgs) in newborns' saliva was examined under physiological conditions and after artificial colonization with nonpathogenic, probiotic bacterial strain E. coli O83. Higher levels of secretory immunoglobulin M (SIgM) and secretory immunoglobulin A (SIgA) were detected in the saliva of breast-fed children when compared with those of bottle-fed infants. SIgM was found earlier than SIgA, the levels of both SIgM and SIgA decreased after weaning. Breastfeeding actively stimulates local immunity on mucosal membranes of newborn infants. Early mucosal colonization with nonpathogenic E. coli bacteria stimulates the mucosal immune system to produce specific antibodies as well as nonspecific secretory immunoglobulins.

• MeSH
• Escherichia coli growth & development   immunology   MeSH
• Immunoglobulin A, Secretory analysis   MeSH
• Immunoglobulins analysis   MeSH
• Infant MeSH
• Breast Feeding MeSH
• Bottle Feeding MeSH
• Humans MeSH
• Infant, Newborn MeSH
• Probiotics * MeSH
• Antibodies analysis   MeSH
• Saliva immunology   MeSH
• Check Tag
• Infant MeSH
• Humans MeSH
• Male MeSH
• Infant, Newborn MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Immunoglobulin A, Secretory MeSH
• Immunoglobulins MeSH
• Antibodies MeSH

Despite the fact that target antigens and the genetic basis of several autoimmune diseases are now better understood, the initial events leading to a loss of tolerance towards self-components remain unknown. One of the most attractive explanations for autoimmune phenomena involves various infections as possible natural events capable of initiating the process in genetically predisposed individuals. The most accepted explanation of how infection causes autoimmunity is based on the concept of "molecular mimicry" (similarity between the epitopes of an autoantigen and the epitopes in the environmental antigen). Infectious stimuli may also participate in the development of autoimmunity by inducing an increased expression of stress proteins (hsp), chaperones and transplantation antigens, which leads to abnormal processing and presentation of self antigens. Superantigens are considered to be one of the most effective bacterial components to induce inflammatory reactions and to take part in the development and course of autoimmune mechanisms. It has long been known that defects in the host defense mechanism render the individual susceptible to infections caused by certain microorganisms. Impaired exclusion of microbial antigens can lead to chronic immunological activation which can affect the tolerance to self components. Defects in certain components of the immune system are associated with a higher risk of a development of autoimmune disease. The use of animal models for the studies of human diseases with immunological pathogenesis has provided new insights into the influence of immunoregulatory factors and the lymphocyte subsets involved in the development of disease. One of the most striking conclusion arising from work with genetically engineered immunodeficient mouse models is the existence of a high level of redundancy of the components of the immune system. However, when genes encoding molecules involved in T cell immunoregulatory functions are deleted, spontaneous chronic inflammation of the gut mucosa (similar to human inflammatory bowel disease) develops. Surprisingly, when such immunocompromised animals were placed into germfree environment, intestinal inflammation did not develop. Impairment of the mucosal immune response to the normal bacterial flora has been proposed to play a crucial role in the pathogenesis of chronic intestinal inflammation. The use of immunodeficient models colonized with defined microflora for the analysis of immune reactivity will shed light on the mode of action of different immunologically important molecules responsible for the delicate balance between luminal commensals, nonspecific and specific components of the mucosal immune system.

• MeSH
• Autoimmunity immunology   MeSH
• Autoimmune Diseases etiology   immunology   MeSH
• Infections immunology   MeSH
• Humans MeSH
• Mice MeSH
• Intestinal Mucosa immunology   microbiology   MeSH
• Immunologic Deficiency Syndromes immunology   MeSH
• Inflammation MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH

Remarkable interspecies differences in CD2 expression on B lymphocytes have been reported in mammals. Human and rat B cells lack CD2, whilst B lymphocytes in mice are CD2+. In pigs, B cells have been supposed not to express CD2. We show here, however, that CD2 is present at a low level on a prominent subset of porcine B cells. Moreover, we describe changes in the proportions of CD2+ and CD2- B-cell subsets during ontogeny. Before contact with microflora, the majority of peripheral surface immunoglobulin M+ (sIgM+) B cells express CD2 and sIgM+CD2- B cells are rare. Shortly after colonization of conventional (CV) piglets with complex intestinal microflora, numerous CD2- B cells appear in the periphery and their relative number increases with age in both CV and specific pathogen-free (SPF) pigs. However, monoassociation of germ-free (GF) piglets with a single Escherichia coli strain does not result in a significant increase of sIgM+CD2- B cells in the periphery. We suggest that CD2 is down-regulated in porcine B lymphocytes upon activation with microflora in mucosa-associated lymphatic tissues. In bone marrow (BM), we identified putative porcine B-cell precursors. These cells express CD2 at low density and do not bear either the common myelomonocytic antigen or T and B-lymphocyte receptors. Similar to mouse and human pre-B cells, this lymphocyte-sized subset expresses CD25 and class II antigens. CD2 positivity of these cells indicates that CD2 is expressed earlier than sIgM during B lymphopoiesis in pigs.

• MeSH
• CD2 Antigens metabolism   MeSH
• Cell Differentiation immunology   MeSH
• Antigens, Differentiation metabolism   MeSH
• Germ-Free Life MeSH
• Immunophenotyping MeSH
• Escherichia coli Infections immunology   MeSH
• Bone Marrow immunology   MeSH
• Leukocytes, Mononuclear immunology   MeSH
• B-Lymphocyte Subsets immunology   MeSH
• Swine immunology   MeSH
• Flow Cytometry MeSH
• Aging immunology   MeSH
• Intestines microbiology   MeSH
• Animals MeSH
• Check Tag
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• CD2 Antigens MeSH
• Antigens, Differentiation MeSH

Mucosal surfaces covered by a layer of epithelial cells represent the largest and most critical interface between the organism and its environment. The barrier function of mucosal surfaces is performed by the epithelial layer and immune cells present in the mucosal compartment. As recently found, epithelial cells, apart from their participation in absorptive, digestive and secretory processes perform more than a passive barrier function and are directly involved in immune processes. Besides the well known role of epithelial cells in the transfer of polymeric immunoglobulins produced by lamina propria B lymphocytes to the luminal content of mucosals (secretory Igs), these cells were found to perform various other immunological functions, to interact with other cells of the immune system and to induce an efficient inflammatory response to microbial invasion: enzymic processing of dietary antigens, expression of class I and II MHC antigens, presentation of antigens to lymphocytes, expression of adhesive molecules mediating interaction with intraepithelial lymphocytes and components of extracellular matrix, production of cytokines and probable participation in extrathymic T cell development of intraepithelial lymphocytes. All these functions were suggested to influence substantially the mucosal immune system and its response. Under immunopathological conditions, e.g. during infections and inflammatory bowel and celiac diseases, both epithelial cells and intraepithelial lymphocytes participate substantially in inflammatory reactions. Moreover, enterocytes could become a target of mucosal immune factors. Mucosal immunosurveillance function is of crucial importance in various pathological conditions but especially in the case of the most frequent malignity occurring in the intestinal compartment, i.e. colorectal carcinoma. Proper understanding of the differentiation processes and functions of epithelial cells in interaction with other components of the mucosal immune system is therefore highly desirable.

• MeSH
• Autoimmune Diseases immunology   pathology   MeSH
• Bacteria immunology   MeSH
• Celiac Disease immunology   pathology   MeSH
• Cytokines physiology   MeSH
• Adult MeSH
• Epithelium immunology   MeSH
• Epithelial Cells MeSH
• Fungi immunology   MeSH
• Inflammatory Bowel Diseases immunology   pathology   MeSH
• Immunoglobulins immunology   MeSH
• Integrins physiology   MeSH
• Colorectal Neoplasms immunology   pathology   MeSH
• Humans MeSH
• Lymphoid Tissue cytology   immunology   MeSH
• Membrane Glycoproteins physiology   MeSH
• Mice, Knockout MeSH
• Mice MeSH
• Peyer's Patches immunology   MeSH
• Antigen Presentation MeSH
• Intestines microbiology   MeSH
• Intestinal Mucosa cytology   immunology   MeSH
• Animals MeSH
• Check Tag
• Adult MeSH
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Cytokines MeSH
• Immunoglobulins MeSH
• Integrins MeSH
• Membrane Glycoproteins MeSH

The cellular immune response (MIF, E-rosette formation and changes in nucleolar morphology of lymphocytes) was followed as related to age and antigenic stimulation. MIF in healthy infants increased from the 2nd to the 12th week of life as compared with the first week, probably due to BCG vaccination. The total and active E-rosette formation did not change during the whole period of investigation. Ring-shaped nucleoli increased gradually from the second week of life. Active nucleoli increased up to the 4th week, i.e. after BCG vaccination and then slowly decreased. Micronucleoli being high in the first week, decreased during 24 weeks of life. After artificial colonization of the intestine the production of MIF was slightly lower in colonized infants than in controls from the 2nd to the 12th week. The other parameters followed were not influenced by colonization.

• MeSH
• BCG Vaccine immunology   MeSH
• Immunity, Cellular * MeSH
• Cell Nucleolus ultrastructure   MeSH
• Escherichia coli growth & development   MeSH
• Leukocyte Migration-Inhibitory Factors biosynthesis   MeSH
• Infant MeSH
• Humans MeSH
• Lymphocytes immunology   ultrastructure   MeSH
• Lymphokines biosynthesis   MeSH
• Infant, Newborn MeSH
• Intestines microbiology   MeSH
• Rosette Formation * MeSH
• Vaccination MeSH
• Check Tag
• Infant MeSH
• Humans MeSH
• Infant, Newborn MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• BCG Vaccine MeSH
• Leukocyte Migration-Inhibitory Factors MeSH
• Lymphokines MeSH