Innocent bystander reaction

Another type of reaction that may affect the formed elements in blood is the innocent bystander reaction. With this type of reaction, antigen-antibody complexes formed in blood adhere nonspeciflcally to cells. Complement is then activated, resulting in ceU lysis. 

Thallium(i) salts have long been used in reactions with organic and organometallic halide complexes as a means of activating the halide by removal as insoluble T1X. However, the thallium ions proved not to be innocent bystanders, and numerous examples were reported in COMC (1995) where the metal-bound thallium complexes were formed. Deliberate reactions of thallium(i) and thallium(m) salts with metal carbonyl anions have yielded a variety of complexes of the form T1 MLJ3. In the past decade, new examples of metal carbonyl derivatives of thallium have been prepared (see Table 2). In addition, the propensity for Tl+ to form adducts with 16-electron noble metal complexes has been exploited. 

Non-IgE-antibody-mediated immunological reactions Modification of erythrocyte surface components due to binding of beta-lactams or their metabolic products is thought to be the cause of the formation of antierythrocyte antibodies and the development of a positive Coombs test implicated in the development of immune hemolytic anemia (211). About 3% of patients receiving large doses of intravenous penicillin (10-20 million units/ day) will develop a positive direct Coombs test (212). However, only a small fraction of Coombs positive patients will develop frank hemolytic anemia (213). Antibody-coated erythrocytes are probably eliminated by the reticuloendothelial system (extravascular hemolysis) (214), or less often by complement-mediated intravascular erythrocyte destruction (215). Another mechanism implicates circulating immune complexes (anti-beta-lactam antibody/beta-lactam complexes), resulting in erythrocyte elimination by an innocent bystander mechanism (82). Similar mechanisms have been implicated in thrombocytopenia associated with beta-lactam antibiotics (216,217). 

Besides this hapten or penicillin-type of drug-induced hemolysis, a second less frequent mechanism, the so-called innocent bystander mechanism can occur (46,49,50). Penicillin-antibody complexes are only loosely bound to erythrocytes and activate complement, which can be detected on the erythrocyte surface with the complement antiglobulin test ( complement or nongamma type). This mechanism plays a part in immune hemolytic anemias due to various drugs other than penicillins. The hemolytic reaction can continue for weeks after withdrawal of penicillin, that is as long as sufficient penicillin-coated erythrocytes and specific antibodies remain in circulation. 

Given the strong connectivities in many ILs, it can be expected that strong cooperative effects are often observed in ILs. Indeed, several studies have also addressed cooperativity in ILs [110, 111], Kossman et al. have studied cooperative effects in Dmim-Cl ILs by quantum chemical calculations [109], Moreover, it has been shown that ILs are not (always) innocent bystanders of a reaction but much rather that ILs can interact in many ways with solutes. These developments have recently been reviewed [132],... 

There are times when the MOM group is not such an innocent bystander and participates in some unexpected and surprising reactions. ... 

The following example shows that the methoxybenzylidene acetal is not always an innocent bystander. During an attempted Barton deoxygenation the benzylidene acetal participated in a 1,5-hydrogen shift when the reaction was run under dilute conditions, but this could he obviated by running the reaction in neat BusSnH. ... 

The second mechanism of immune-mediated agranulocytosis is called the innocent bystander phenomenon. In this reaction, the drug combines with a drug-specific antibody. The complex is... 

The most widely employed heteroatom ligands are the phosphines. Although they are largely spectators and do not participate directly in bond formation (and when they do, the result is often highly undesirable), they are not innocent bystanders. The size and electronic nature of the three groups attached to phosphorus have a profound effect on the course of the reaction and may make the difference between success and failure. An example is with the Grubbs catalyst (Chapter 8). The bis(triphenylphosphine) complex is of little use. The bis(tricyclohexylphosphine) complex is Nobel-prize winning. 

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