Complement system activation

Figure 31-8 Pathways for activation of the complement system. Active proteases are designated by abbreviations in boldface.

Nephritis is an autoimmune disease caused by activation of the complement system. Cinnamon cortex and cinnamon oil inhibited complement formation in vitro. Cinncassiol C, and its glucoside, the cinncassiols C2 and C3 and cinncassiol D, and its glucoside were reported to possess anticomplementary activity. A water-soluble polysaccharide isolated from the cinnamon extract showed complement system activity (Tang and Eisenbrand, 1992). 2-Hydroxycinnamaldehyde and 2-benzyloxy cinnamaldehyde isolated from the stem bark of cinnamon possessed immunomodulatory effects (Koh et al., 1999). 

A decrease in lysis may result from either activation or inhibition of the complement system. Activated components are consumed and therefore removed so that the effect on the total system resembles that of inhibition. The exact mechanism of action can only be elucidated by specific reactions with the individual complement components. 

Significant protection of mice by several polysaccharides other than glucan isolated from S. cerevisiae has been described (209). A 2.16-fold protection in the LD q q is observed for one modifier, MNZ, when given 15 min prior to irradiation. Glucan protects 2.25-fold in this same protocol. Many of these polysaccharides may act through activation of the complement system, rather than directiy on ceHs. 

Plasma Inhibitors, In Vivo Anticoagulants. Fourteen naturally occurring compounds that normally exert an inhibiting effect on the activity of coagulation, platelet function, and fibrinolytic activity and complement systems have been identified within the circulating blood. 

Mediators derived from activated plasma protein cascades Complement system... 

Already in 1988 and 1991, Gao et al. [65,66] detected four different polysaccharides present in the leaves of Panax ginseng that had an effect on the complement system, but only two of them, the neutral, GL-NIa, and one of the acidic ones, GL-AIa, had potent activities at low concentrations. GL-NIa was found to be mainly an arabinigalactan type II polymer. GL-AIa was a polysaccharide with a rhamnogalacturonan core with neutral side chains of the AG-II type, confirmed by a strong reaction with the Yariv reagent and the methylation results. It was shown that the crude polysaccharide fraction contained KDO and DHA, suggesting the presence of Rhamnogalacturonan II in... 

The structure that appears to be important for the effect on the complement system is most probably the complex galactan ohgomer being composed of separate 1,3- and 1,6-hnked galactose chains with branch points being of 1,3,6 nature. These units have been proposed as the active sites for... 

The mechanisms of the allergy-like reactions to RCM are still a matter of speculation (table 2). Anaphylaxis to RCM has been discussed to be due to a direct membrane effect possibly related to the osmolality of the RCM solution or the chemical structure of the RCM molecule (pseudo-allergy) [2], an activation of the complement system [27], a direct bradykinin formation [28], or an IgE-mediated mechanism [3]. 

Histamine Serotonin Platelet-activating factor (PAF) Eicosanoids (various prostaglandins and leukotrienes) C3a, C4a, and C5a from the complement system Bradykinin and fibrin split products from the coagulation system... 

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