Phagocytosis Opsonization

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. 

CRP content indicates a persistent proinflammatory stimulus in the body. CRP binds to host or bacterial phosphocholine, and the complex activates a group of plasma proteins called complement (Sect. 3.3.2). The complement system resembles the blood clotting system, except that proteolytic cleavage of its components results in peptide fragments that to attract and enhance the phagocytosis (opsonization) of CRP- or antibody-bound material by macrophages (like IL-1 or IL-8). CRP is part of the innate immune response, and the antibody response is part of the acquired immune response (Sect. 12.1.4). Many bacteria of the successor microbiota induce an antibody response that is increased in periodontitis compared with gingivitis or healthy subjects. 

The complement system consists of approximately 30 plasma proteins and is involved in hypersensitivity through a variety of immunologic responses, including enhancement of phagocytosis (opsonization of target cells), cell lysis, and generation of anaphylatoxins (C3a, C4a, and C5a), which can cause non-IgE-mediated activation of mast cells and release of inflammatory mediators. 

McArthur, J. D. and Walker, M. J. (2006) Domains of group A streptococcal M protein that confer resistance to phagocytosis, opsonization and protection implications for vaccine development. Mol. Microbiol. 59, 1-4. 

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. 

Figure 8.9 Increased expression of IgG Fc receptors on phagocytes results in enhanced phagocytosis. These receptors will retain opsonized (i.e. antibody-coated) infectious agents at their surface by binding the Fc portion of the antibody. This facilitates subsequent phagocytosis...

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... 

After opsonization, add particle snspensions to the phagocytosis assay mixture to a final concentration of =5% sernm. Adjust particles to a density of 10 /mL (see Notes 3 and 4). 

Not all KCs are phagocytic to the same extent periportal KCs generally have a higher level of phagocytic activity than those in other regions of the liver [49]. Prior to phagocytosis, particulate material like viruses, bacteria and erythrocytes may be opsonized and bound by specific receptors, but this is not essential for phagocytosis [50]. 

H. J. Jorbeck, S. B. Svenson, and A. A Lindberg, Artificial Salmonella vaccines Salmonella typhimurium O-antigen-specific oligosaccharide-protein conjugates elicit opsonizing antibodies that enhance phagocytosis, Infect Immun., 32 (1981) 497-502. 

Complement proteins opsonize bacteria for phagocytosis via integrin family, a(3 het-erodimeric CRs on the macrophages. Unlike the FcR-mediated process, GR-mediated... 

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... 

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