Response to Bacterial Infection

Polymorphs are small, less complex cells that are of extreme importance to the immune system, as they are highly specific and short-lived, and can be rapidly produced by the body and delivered to the tissues by chemotactic response. Like the macrophages, they operate in association with complement and antibody through their respective C3 and Fc receptors. 

The complement system has been reviewed151,152 it is composed of a series of proteins, C1-C9, present in normal human serum, that serve as important mediators in the host defense. The terminal components, C3-C9, are involved in the destruction of invading microorganisms, but, in order to achieve this, they have to be activated. This activation process can be divided into two pathways, the alternative pathway and the classical pathway, although both pathways can occur simultaneously in the host defense-mechanism. 

Surface carbohydrates of micro-organisms are able to activate the al- 

Capsular polysaccharides are actively involved in the mediation of complement, in that they are able to suppress the activation of the immediate, alternative-pathway mechanism, thus forcing the immune system to use the classical pathway this is an important factor in the virulence of bacteria (see Section VI,1). 

An important distinction must be made between the humoral response to a pure, capsular polysaccharide, and to the same polysaccharide when it is an integral part of the bacterium. Thus, the immunity received on recovery from infection by encapsulated bacteria, in terms of the polysaccharide antigen, differs from that generated by purposeful immunization with purified capsular-polysaccharide vaccines. Fortunately, with the exception of infants, the polysaccharide vaccines still stimulate protective-antibody levels in humans, despite these differences. In infants, due to the immature nature of their immune systems, these polysaccharide vaccines are of only marginal benefit.7 Some insights into the nature of these different responses in humans can be found in studies on the cellular basis of the immune response to polysaccharides. However, for the purposes of this Chapter, it would be inappropriate to provide a lengthy description of this incompletely understood mechanism in-depth reviews of this burgeoning field of research can be referred to.144-147,162-166 

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Pyuria The presence of white blood cells in the urine, a known marker of inflammatory response to bacterial infection. 

MacMicking, J.D. et al., Altered responses to bacterial infection and endotoxic shock in mice lacking inducible nitric oxide synthase, Cell, 81, 641, 1995. 

When tested, the antibiotic compounds killed or inhibited the growth of two varieties of E. coli but had no effect on several other types of cells. These results show that in response to bacterial infection the ants elaborated an antibiotic that was selectively toxic to the pathogen. Their defense was tailored closely to their need. It is too soon to know more, but it seems that looking for new antibiotics in ants is a promising idea. Further research should establish whether ant antibiotics will lead to drugs for human use and also reveal whether other crowded species also synthesize antibiotics. 

Immunotoxicity. No studies were located assessing the potential effect on the immime system during 3,3 -dichlorobenzidine exposure. Studies that examine antibody levels and responses to bacterial infections after exposure to 3,3 -dichlorobenzidine would provide valuable information on the immune system. Also, evaluation of morbidity among individuals exposed to 3,3 -dichlorobenzidine in the workplace may provide important indirect evidence regarding their immime status. 

Lipopolysaccharides are the dominant surface feature of the outer membrane of gram-negative bacteria such as Escherichia coli and Salmonella ty-phimurium. These molecules are prime targets of the antibodies produced by the vertebrate immune system in response to bacterial infection and are therefore important determinants of the serotype of bacterial strains (serotypes are strains that are distinguished on the basis of antigenic properties). The lipopolysaccharides of S. typhimurium contain six fatty acids bound to two... 

The importance of capsular polysaccharides in the immune response to bacterial infection is due to their location on the outer surface of the bacteria. They are at the interface of the many host-bacte-... 

Endotoxin pyrogen induces fever by an indirect process. On entry into the circulatory system, endotoxin is bound to LPS-binding protein (LPB) that transports it to receptor cells in the reticuloendothelial system. The main target cells are circulating mononuclear cells, which produce proinflammatory cytokines such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-a (TNFot). These cytokines are involved in acute and chronic inflammation, induce fever, and modulate the host s response to bacterial infection. ° ... 

Although OxPL generated at sites of inflammation might be able to prevent overwhelming inflammation in settings of sterile inflammation, impairment of the innate immune response to bacterial infections by OxPL is detrimental for the outcome of host defense reactions. 

A bacterial flavohemoglobin, which contains a globin domain fused to a flavin/NADH binding domain, functions enzymatically as a nitric oxide dioxygenase, using a catalytic cycle similar to that in Figure 10. The role of this enzyme is apparently to detoxify nitric oxide produced by the body in response to bacterial infection. The distal pocket of flavohemoglobins more closely... 

ANALYSIS OF THE HOST IMMUNE RESPONSE TO BACTERIAL INFECTION... 

Kluger, M. J. and Rothenburg, B, A. (1979) Fever and reduced iron their interaction as a host defense response to bacterial infection. Science 203 374-376. 

LAUTH X, BABON JJ, STANNARD JA, SINGH S, NIZET V, CARLBERG JM, et al. BaSS hepcidin synthesis, solution structure, antimicrobial activities and synergism, and in vivo hepatic response to bacterial infections. I Biol Chem 2005 Mar ll 280(10) 9272-82. 

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