Nonspecific mechanism, immune system

The immune system is divided into two defense mechanisms nonspecific, or innate, and specific, or adaptive, mechanisms that recognize and respond to foreign substances. Some of the important cellular components of nonspecific and specific immunity are described in Table 15.4. The nonspecific immune system is the first line of defense against infectious organisms. Its cellular components are the... 

There is a great deal of evidence that AmB can exert a number of effects directly on cells of the immune system, and particularly on macrophages to increase nonspecific defense mechanisms against pathogens and cancer cells. These mechanisms include the production of nitric oxide (NO) (32) and tumor necrosis factor alpha (TNF-a) (33), which could contribute to the antifungal and antiparasitic activity of AmB. However, excess TNF-a production could also be responsible for some of the side effects associated with AmB treatment, such as fever and chills. 

Preventative vaccines are increasingly used during pregnancy, with the intention of protecting the newborn baby from infectious disease, such as influenza, via conferred immunity from the mother (1). To date, no causal relationships have been demonstrated for adverse effects on pregnancy with any approved vaccine. However, potential mechanisms have been suggested by which an induced immune response could interfere with prenatal development. A nonspecific disturbance of the resting balance between the innate and humoral activities of the immune system, for instance, could result in abortion (2). Otherwise, the induced antibodies may have the potential to disturb normal development due to a specific... 

Mechanisms to control parasitic protozoa are similar to those utilized for other infectious agents they can be divided into non-specific mechanism(s) and specific mechanism(s) involving the immune system. The best studied non-specific mechanisms include those that affect the entry of parasites into the red blood cell. The sickle cell haemoglobin trait and lack of the Duffy factor on the erythrocyte surface make the red cell more resistant to invasion by Plasmodium. These traits are commonly found in populations from malaria-endemic regions. A second example of a non-specific factor is the presence of trypanolytic factors in the serum of humans which confer resistance to T. brucei, Although nonspecific factors can play a key role in resistance, usually they work in conjunction with the host s immune system. 

Thus, saponins are apparently able to stimulate or suppress the immune system by two different mechanisms. In one mechanism, saponins interact with cell membrane components to alter cell permeability, membrane-associated enzymes, cell-surface receptors, and other components, and thus result in a nonspecific stimulation (or suppression) of phagocytosis, phagocytic chemiluminescence, and other functions of phagocytic lymphocytes. These effects can take place in vivo or in vitro. In the other mechanism, formation of imines (Schiff bases) by carbonyl-containing saponins can provide a co-stimulatory signal necessary for specific immunopotentiation of T cells that leads to a CMI response. This second mechanism, which is known as an adjuvant effect, takes place only in vivo, and is discussed in more detail in subsequent sections of this article. From previous work [62,73], it is expected that, for saponins with appropriate structures, both mechanisms would take place. Perhaps, the best-known case where both mechanisms can take place is that of the saponins derived from Q. saponaria Molina, which are next discussed in more detail. 

Immune systems in plants are based on passive, struetural immunity, sueh as a waxy surface or cuticle, and active immunity exists in the expression of some chemicals. The mechanism of this system is to prevent infeetious agents fiom gaining access to plant cells. Plant immunity may also be protoplasmie. This means that the protoplast in cells is an unfavorable environment for pathogenic development. Plants do not, however, produce antibodies like animals do. The protoplasmic immunity is arranged generally by phytoalexins, nonspecific compounds whose concentrations increase in response to infections. Some alkaloids may act in a similar way to phytoalexins or in the direct chemical... 

Large quantities of polysaccharides are available in nature and many of them display a variety of biological functions [1 ]. There is an abundance of literature on the isolation of bioactive polysaccharides from botanical sources [1-5]. This area of research has attracted a lot of interest due to the fact that most of the bioactive polysaccharides are nontoxic with minimal side effects [4,5]. Hence, this class of biopolymers forms ideal candidates for therapeutic applications. Some of the notable bioactivities of botanical polysaccharides include antioxidant, immunomodulatory, and antitumor properties [4-10]. However, the mechanism of action of these biopolymers is not well understood. In general, one of the primary mechanisms of action of polysaccharides is nonspecific immunomodulation [8]. The key mechanism behind the immunomodulatory, anticancer, antibacterial, and other pharmacological activities of plant polysaccharides is to activate macrophages, which then leads to modulation of the complement system that activates the cells involved in innate immunity and improves host defense [1—4,11,12]. 

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