Current Immunology Reviews (Discontinued) - Volume 8, Issue 3, 2012

The intestinal tract represents the first barrier to ingested chemicals or food contaminants and is also the first line of defense against intestinal infection. Because of their location, intestinal epithelial cells could be exposed to high doses of food contaminants. Among natural food contaminants, mycotoxins are regarded as an important risk factor for human and animal health as up to 25% of the world's crop production may be contaminated. The Fusarium genus produces high quantities of toxins (fusariotoxins) in temperate northern countries (North America, Europe or Asia) and the trichothecenes are the most prevalent toxin detected. An increasing number of studies suggest that intestinal epithelial cells are important targets for mycotoxins and in humans, various adverse digestive symptoms are observed on acute exposure. In animals, trichothecenes induce pathological lesions, including necrosis of the intestinal epithelium. They affect the integrity of intestinal epithelium through alterations in the barrier function, cell morphology and differentiation. Moreover these toxins modulate the activity of intestinal epithelium in its role in immune responsiveness. They affect the cytokine production by intestinal or immune cells and are supposed to interfere with the cross-talk between epithelial cells and other intestinal immune cells. This review summarizes our current knowledge of the effects of a class of mycotoxins, the trichothecenes, on the intestine.

Jaagsiekte sheep retrovirus (JSRV) is a retrovirus which infects small ruminants and is responsible for a natural lung cancer. This virus bears an oncogenic envelope inducing epithelial cell transformation from the deep lung. The cells, main target of the infection and constitutive of the tumors, are alveolar type II cells in the alveoli and Clara cells in the bronchioli. The immune response to JSRV infection is poorly understood. The specific humoral response is limited and the cell-mediated response is marked by CD4+ lymphocytopenia, neutrophilia, and macrophage invasion of the tumor. The mechanisms of viral immune evasion could be explained by the direct and indirect immunosuppressive effects of the virus, and by the immune tolerance of the infected hosts due to the presence in the sheep genome of endogenous viral forms (enJSRV).

Dairy propionibacteria are gram positive, aerotolerant and mesophilic bacteria found in dairy products, and in diverse habitats such as soil, plants, and digestive tracts of ruminants. They are essential as ripening culture in the manufacture of Emmental cheese and other types of Swiss cheeses so they are consequently ingested in high amounts by the consumers. Dairy propionibacteria are also considered for their probiotic use. Indeed, they are species with low nutritional requirements, and with high adaptability and tolerance toward stresses, including acid and bile salts. Some strains (species) were shown to survive in the human gut, where they may have health-promoting effects. In this review, we summarize the knowledge on the interactions between probiotic dairy bacteria and the intestinal epithelium. We focus on the metabolites that are likely to play a probiotic role in the colon, as well as propionibacteria adhesion to intestinal mucus and epithelial cells. Then, among the probiotic potentialities, the immunomodulatory properties of dairy propionibacteria are given detail in.

The endothelium is the thin layer of cells that lines the lumen of blood and lymphatic vessels. Endothelial cells (ECs) from different locations have distinct and characteristic expression patterns that persist during in vitro culture. Although gene expression patterns in cultured cells clearly reveal the molecular heterogeneity of these ECs, their corelation with their in vivo counterparts remains to be defined. Situated at the interface between blood and tissues, the endothelium plays a central role for critical functions and represents a physical barrier for both blood-borne pathogens and immune cells, which must cross this barrier for trafficking between the bloodstream and tissues. Endothelial cells are target cells for several infectious agents, including Anaplasma, Bartonella, Orientia and Rickettsia. The lack of appropriate spontaneous or experimentally-induced animal models is a serious limitation for the study of pathogen-ECs interactions and is the major justification for the use of ECs cultures. Bartonella adherence to ECs is mediated by type-IV like pili and some outer membrane proteins. Some differences exist among Bartonella species adherence mechanisms. ECs are invaded either by an endocytic uptake or by engulfment of Bartonella. The activation of ECs by chronic inflammation and direct or indirect action of some Bartonella species leads to proliferation, angiogenesis and vasoproliferative tumor growth. Interactions between Anaplasma, Orientia, Rickettsia and ECs are less documented than Bartonella but differ significantly from the mechanisms described for Bartonella. At the least, they do not induce vasoproliferation. This review summarizes our understanding of the diversity of ECs, the vector borne bacterium-ECs interactions and the mechanisms of bacterial virulence and persistence.

Our gastrointestinal tract (GIT) is colonized by the intestinal microbiota, a vast community of commensal bacteria which plays an important role in host gut health. Some food products contain live bacteria which transit through our GIT and could exert beneficial effects on our health. Major efforts are focused on these bacteria (known as probiotics) since the last 10 years. Among the numerous proposed health benefits attributed to probiotic and commensal bacteria, their capacity to interact with the host immune system (crosstalk) is now well demonstrated. In this review, we give an overview on the recent developments and perspectives in the study of the role of probiotic and commensal bacteria in human through their crosstalk with the host.

Fungi are the most important eukaryotic infective agents in Europe which largely overpass parasite infections. Total number of people dying of fungal infection is increasing and this trend is likely to continue due to the increase in immunosuppressive treatments. The opportunistic pathogen Aspergillus fumigatus (Af) is a saprophytic filamentous fungus that can cause invasive pulmonary diseases in immuno-compromised hosts. In veterinary medicine aspergillosis is also a recurrent problem since it infects various species, birds are particularly susceptible. It propagates through airborne conidia (spores), which are inhaled into the small airways where they may germinate and initiate an infection. The host epithelium has permanent contact with the environment and a multitude of diverse microorganisms, resulting in a network of the host’s defense mechanisms. Pathogens use various strategies to invade epithelial barriers, to exploit eukaryotic host function to their own benefit and disseminate throughout the host using the epithelium as a reservoir. The current revue will discuss the ways how epithelial and innate immunity cells can contlol Af infection. We will focus on Af strategies for the host’s invasion, antifungal innate immune response and antimicrobial activities of the respiratory epithelial cells.