Current Opinion in Immunology - T cell tolerance and immunity to commensal bacteria. The commensal bacteria normally resident in the gastrointestinal tract represent an enormous pool of foreign antigen within the body. Although mechanical barriers limit entry of bacteria into the host, recent data suggest that T cells routinely interact with commensal bacteria using both antigen-specific and non-specific receptors. Depending on the bacterial species, either regulatory or effector T cell responses can be generated. For example, segmented filamentous bacteria (SFB) favor effector Th17 responses whereas Bacteroides fragilis and certain Clostridium species favor Foxp3+ regulatory T (Treg) cell responses. Thus, in contrast with the notion that only tolerogenic responses are required to self, gut homeostasis may require both tolerance and immunity to various constituents of the commensal microbiota. Highlights Copyright © 2012 Elsevier Ltd. Antimicrobial Host Defensins – Specific Antibiotic Activities and Innate Defense Modulation | Frontiers in Molecular Innate Immunity.
Current treatment of bacterial and fungal infections heavily relies on strategies which aim to inhibit and kill pathogens with high specificity. These strategies are very successful and antibiotics have contributed to increasing human life expectancy more than any other class of therapeutic drugs. However, antibiotics are losing efficacy as a result of high selection pressure and rapid resistance development. Thus, strategies that rely on boosting natural host defenses are gaining more attention, since compounds targeting host mechanisms should control infections regardless of the antibiotic resistance levels of pathogens. Antimicrobial peptides (AMPs) are considered as ideal candidates for such novel anti-infective strategies since they combine direct antibiotic activities with modulation of immune responses (Figure 1). However, AMPs frequently lack specific molecular targets and tend to have membrane disruptive activities, bearing risks of cytotoxicity.
Figure 1. Acknowledgments. Frontiers in NK Cell Biology. Home : Nature Immunology. The anti-inflammatory effects of exercise: mechanisms and implications for the prevention and treatment of disease : Abstract : Nature Reviews Immunology.