Microbial antigens

Kadowaki N. Ho S. Antonenko S. Malefyt RW, Kastelein RA. Bazan F. Liu YJ Subsets of human dendritic cell precursors express different toll-hke receptors and respond to different microbial antigens. J Exp Med 2001 194 863-869. 

The mechanism most commonly invoked to explain the association of infection with autoimmune disease is molecular mimicry that is, the concept that antigens (or more properly, epitopes) of the microorganism closely resemble self-antigens.50 The induction of an immune response to the microbial antigen thus results in cross-reactivity with selfantigens and the induction of autoimmunity. Although epitope specific cross-reactivity has been shown in some animal models,48,51 53 molecular mimicry is clearly demonstrated to be the causative mechanism in few, if any, human diseases.3 54,55... 

The delayed type hypersensitivity response (DTH) is an assay frequently used to assess the T cell response to commonly encountered microbial antigens. It involves intradermal injection of antigens to which the majority of individuals are immune (known as recall antigens) such as vaccinia, herpes simplex, and mumps viruses, Candida, and tetanus toxoid. In normal individuals, after 24-48 hours, an inflammatory filtrate results in local edema and induration, the diameter of which can be measured. A negative reaction to all the antigens (anergy) is usually reflected by decreased lymphocyte function as measured in vitro and is frequently seen in AIDS and ARC patients. 

Shino A, Lujioka K, Manabe N, Yamaya S, Goto Y, Yasuhara M, Yamamoto K (2005). Simultaneous multicolor detection system of the single-molecular microbial antigen with total internal reflection fluorescence microscopy. Microbiol. Immunol. 49 461 —170. 

Newer techniques have equal sensitivity and greater specificity Enzyme-linked immunosorbent assay (ELISA) tests can identify C. trachomatis, HSV-1 and -2, and adenoviruses through the detection of microbial antigens. In the direct ELISA, an enzyme is covalently linked to an antigen-specific monoclonal or polyclonal antibody. 

Blander JM, Medzhitov R Toll-dependent selection of microbial antigens for presentation by dendritic cells. Nature 2006 440 808-12. 

One key hypothesis regarding the etiology of autoimmunity is that of molecular mimicry, where a microbial antigen may contain epitopes that are sufficiently similar to human molecular determinants, and for which the immune system cannot discriminate between.4756 The degree to which epitope mimicry occurs, under what conditions, and its pathological significance remains controversial.56 Criteria by which to demonstrate molecular mimicry-induced autoimmunity are outlined in a review by Ang et al.58... 

Among Austrian children living in a rural area, children living on a farm had less (hay fever) allergic rhinoconjunctivitis, asthma and other IgE-mediated allergies than those in a non-farming environment. Possible explanations include the development of immunotolerance or the stimulation of Thl cells and suppression of Th2 cells by increased exposure of farm children to microbial antigens in the stables or farmhouses [195(111)]. 

Melhotra I, Ouma J, Wamachi A, et al In utero exposure to helminth and microbial antigens generates cytokine responses similar to that observed in adults.. 1 Clin Invest 1997 99 1759-1766. 

Blood cultures usually should be performed in the acutely ill febrile patient. Blood culture collection should coincide with sharp elevations in temperature, suggesting the possibility of microorganisms or microbial antigens in the bloodstream. Ideally, blood should be obtained from peripheral sites as two sets (one set consists of an aerobic bottle and one set an anaerobic bottle) from two different sites approximately 1 hour apart. In selected infections, bacteremia is qualitatively continuous (e.g., endocarditis), so cultures may be obtained at any time. ... 

Y. Gao, G. Hu, P. Sherman, and D. Li, An automatic electrokinetically-controlled inununoassay lab-on-a-chip for simultaneous detection of multiple microbial antigens, BiomedMicrodevices, 1, 301-312 (2005). 

Suffia IJ, Reckling SK, Piccirillo CA, Goldszmid RS, Belkaid Y 2006 Infected site-restricted Foxp3 natural regulatory T cells are specific for microbial antigens. J Exp Med 203 777-788... 

The complex and sometimes redundant phagocyte signaling pathrrays that lead u> production of proinflanunatory, r ulatory and suppressive cytokines and/or chemoldnes, have been the subject of several recent reviews. In vertebrates, a second line of defense, (adaptive irmnunity) is initiated and modulated by the innate immune system throi h the interactions of antigen-presentii cells especially dendritic cells, with specialized B-cells and T-cells, which recognize a wide spectrum of microbial antigens. ... 

---