Opsonization, phagocytosis and

Complement system. A group of serum proteins with the capacity to interact with each other when activated. The chain reaction of the activated complement components results in formation of a lytic complex and several biologically active peptides of low molecular weight (anaphylatoxins). The system can be activated by antigen-antibody complexes (classical pathway) and by other components, e.g. bacteria (alternative pathway). As an effector mechanism of the humoral immune response, the activated complement system facilitates opsonization, phagocytosis, and lysis of cellular antigens. Some defects in components of complement are associated with autoimmune diseases (see complement deficiency). 

Opsonization. As mentioned in the introduction, the presence of opsonic proteins is required to elicit CL mediated by challenge particles. Non-opsonized particles do not stimulate light emission (English, 1976), and Grebner (1977) has shown that complement amplifies opsonization, phagocytosis and CL in parallel fashion. Hill (1977) revealed a progressive decline in CL with serial dilutions of serum. 

Binds polysaccharides in many bacteria, fungi, and protozoal parasites Can initiate opsonization, phagocytosis, and lysis of invading cells In presence of Ca + binds phosphorylcholine, lecithin, nucleic acid CRP is closely related to serum amyloid P No genetic abnormalities... 

A common characteristic of most CNS bacterial pathogens (e.g., H. influenzae, Escherichia coli, and N. meningitidis) is the presence of an extensive polysaccharide capsule that is resistant to neutrophil phagocytosis and complement opsonization. 

Humoral immunity is characterized by the production of antigen-specific antibodies that enhance phagocytosis and destruction of microorganisms through opsonization. Thus, deficiencies of humoral immunity (B lymphocytes) may lead to reduced antibody titers and are typically associated with acute gram-positive... 

Soluble antimicrobial and fungicidal proteins produced by epithelial cells may cause direct killing of inhaled fungal spores. In addition, opsonizing soluble products may facilitate phagocytosis and killing of Aspergillus by alveolar... 

Poloxamers and other polymeric materials such as albumin may coat the micro- or nano particle, alter their surface characteristics and reduce their phagocytosis and opsonization by the reticuloendothelial system following IV injection. Such surface modifications often result in prolongation in the circulation time of intravenously injected colloidal dispersions.Poloxamers also have been used to stabilize suspension such as NanoCrystal . ... 

Le CV, Carreno S, Moisand A, et al. (2002) Complement receptor 3 (CDl lb/CD18) mediates type I and type II phagocytosis during nonopsonic and opsonic phagocytosis, respectively. J Immunol 169 2003-2009... 

Seth, V., and Chandra, R. K., Opsonic activity phagocytosis and bactericidal capacity of polymorphs in undernutrition. Arch. Dis. Child. 47, 282-284 (1972). 

The concentrations of C-reactive protein increase up to 1000 -fold in inflammatory conditions and in tissue necrosis. In addition, it can initiate reactions of agglutination, precipitation, and opsonization for phagocytosis and can activate the complement system. Other biological activities with platelets and lymphocytes have also been described, but the full biological functions of CRP have not yet been completely elucidated. Review of CRP and the acute phase response H. Gewurz el aL. Advan. Int. Med. 27, 345 -372 (1982). Review of structure and function M. B. Pepys. Bur. J. Rheumatol Inflammation S, 386-397 (1982). Book Arm. N. Y. Acad. Set 389, entitled "C-Reactive Protein and the Plasma Protein Response to Tissue Injury , I. Rushner et al, Eds. (1982) 482 pp. 

As stated previously, pSi particles are targets for internalization by cells of the mononuclear phagocyte system, and stealthing with PEG delays their uptake. For third-generation delivery systems, the first level of targeting for intravascularly administered particulates is the vascular endothehum. In vitro, vascular endothelial cells are able to internalize micron-sized pSi particles by phagocytosis and macropinocytosis (R.E. Serda et al, unpublished results). This is more compHcated in vivo, where serum opsonization coats the microparticles and alters their ability to adhere to the vascular wall. In this section we describe cellular uptake of pSi nanoparticles and microparticles, and examine the characteristics of pSi microparticles which alter this phenomenon. 

Both globulins exert their effect by depletion of circulating lymphocytes either by complement-dependent lysis or by phagocytosis after opsonization. However, antilymphocyte globulin (ALG) and antithymocyte globulin (ATG) are nonhuman polyclonal antibodies. To prevent sensitization application is restricted to a time period of several days only. 

It has the ability to cross the placenta and therefore provides a major line of defence against infection for the newborn. This can be reinforced by transfer ofcolostral IgG across the gut mucosa of the neonate. It diffuses readily into the extravascular spaces where it can act in the neutralization of bacterial toxins and can bind to microorganisms enhancing the process of phagocytosis (opsonization). This is due to the presence on the phagocytic cell surface of a receptor for Fc. 

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