Host defense system

Endotoxin and Muramyl Dipeptide Derivatives. Bacterial cell wall constituents such as the Hpopolysaccharide endotoxin and muramyl dipeptide, which stimulate host defense systems, show radioprotective activity in animals (204). Although endotoxin is most effective when given - 24 h before irradiation, it provides some protection when adrninistered shortiy before and even after radiation exposure. Endotoxin s radioprotective activity is probably related to its Hpid component, and some of its properties may result from PG and leukotriene induction (204). 

Kateley JR, Insalaco R, Codere S, et al. 1982. Host defense systems in cattle exposed to... 

FU impairs the proliferation and differentiation of hematopoietic stem cells resulting in peripheral leukopenia. The above-mentioned indigenous infections should be attributable to the leukopenia-related impairment in the host defense system. 

Some of the best understood polyvalent interactions are found in immune and host defense systems as well as ligand-receptor activation. An example is the use of a polyvalent immunogen based on a synthetic peptide to elicit immune responses. The subsequent production of site-specific antibodies can then be employed to confirm the identity of proteins derived from recombinant DNA, to explore biosynthetic pathways, to define precursor-product relationships (e.g., proenzyme and preproenzyme), and to determine protein structural domains.19 ... 

For a number of overt, broad spectrum immunosuppressive xenobiotics (e.g., azathioprine) there is sufficient clinical experience to indicate the types of neoplasms for which there is an increased risk. These tumor types are listed in Table 27.1. Also listed are the tumors that occur in the unfortunate experiment of nature, namely patients infected with human immunodeficiency virus type 1 (HIV-1) and the tumors that may occur at higher incidence with more selective yet strong immunosuppressants (e.g., cyclosporin, sirolimus, and tacrolimus). Compared to the broad spectrum immunosuppressive agents listed above, most IMBPs express a highly selective regulatory influence on the immune system modulating the activity of host defense systems rather than mediating frank immunosuppression. 

Many animal models use infections artificially introduced into the animal either systemically or into specific organs or tissues. The behavior of infections and the efficacy of antibiotics in eliminating those infections differ, depending on the organ or tissue involved. The type of local pathology, the penetration and pharmacokinetics of antibiotics, the local host defense system, and the clearance rates for the bacterial inocula differ among the various organs and tissues of an animal. Therefore, to get a reliable prediction of how effective an antibiotic will be clinically it is... 

The interaction between an antimicrobial and a pathogen in the laboratory does not take normal host defense systems into account. Humoral and cell-mediated immune systems play a major role in pathogen eradication their contribution is underestimated in susceptibility reports. Antimicrobial agents act in concert with endogenous microbial inhibitors such as immunoglobulins, T lymphocytes, phagocytes, complement components, lactoferrin, lactoperoxidase and lysozymes. 

Secondary reactions provoked by pore-forming toxins are very diverse, and are probably responsible for short- and long-range effects in the host organism (for review, see Bhakdi ef al., 1994). Locally, PFTs can counteract the host defense system directly by killing phagocytes and lymphocytes, and they promote spread of infections by their cytocidal action on tissue cells (see e.g. Bhakdi et al., 1994 Paton et al., 1993 Trifillis et al., 1994 Welch, 1991 Welch et al., 1995 Welch et al., 1981). Mediators, derived for example from arachidonic acid, will provoke inflammation. 

Broekaert, W. F., Terras, F.R.G., Cammue, B.P.A., Osborn, R.W. Plant defensins novel antimicrobial peptides as components of the host defense system. Plant Physiol. 1995, 108, 1353-1358... 

P. aeruginosa infections [9]. This may be considered paradoxical, since laboratory susceptibility tests of these antibiotics have demonstrated them to be neither bactericidal nor bacteriostatic against P. aeruginosa at their usual therapeutic doses. It has been speculated, therefore, that the clinical efficacies of these macrolides may be due to an indirect result of the effects on the organism s virulence factors, host defense systems, or both. 

Targeting territories, organs, and tumors located outside the MPS organs can be achieved by triggering the host defense systems thanks to the modification... 

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