Antibodies opsonization

Microorganisms are more readily phagocytosed when coated with antibody (opsonized). This is due to the presence on the white blood cells of receptors for the Fc fragment ofIgM and IgG (discussed in Chapter 14). Avoidance of opsonization will clearly enhance the chances of survival of a particular pathogen. A substance called... 

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. 

IgG Main antibody in the secondary response. Opsonizes bacteria, making them easier to phagocytose. Fixes complement, which enhances bacterial killing. Neutralizes bacterial toxins and viruses. Crosses the placenta. 

Wang TT, Fellows PF, Leighton TJ et al (2004) Induction of opsonic antibodies to the gamma-D-glutamic acid capsule of Bacillus anthracis by immunization with a synthetic peptide-carrier protein conjugate. FEMS Immunol Med Microbiol 40 231-237... 

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...

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... 

Opsonization by complement components also represents a potential barrier for intravenous gene delivery. Cationic charges of the particles activate the complement, which then takes part in particle elimination. This hurdle is possibly limited by using short hydrophobic chains, reducing the particle size, and eventually PEG insertion into lipoplexes (18). The interaction effect between the lipoplex and the complement might not be such a limitation. Indeed, it was reported that depletion of complement by injection of cobra venom factor and anti-C3 antibodies in mice indicated no differences upon intravenous injection of lipoplexes, neither in terms of tissue distribution nor in lipofection efficiency (19). 

Particles are most efficiently phagocytized when they are opsonized with complement components or immunoglobulins. This is accomplished by incubating the particles with autologous or normal human pooled serum, or with specific antibodies that recognize antigens on the particle surface. 

Immunity What the patient does to the pathogen. For example, a patient with AIDS who is exposed to tuberculosis may develop the disease in spite of receiving a course of postexposure prophylactic antituberculosis chemotherapy, which would be effective in a patient with an intact immune system. Immunity includes both nonspecihc complement-mediated opsonization and specihc antibody- and cell-mediated immunity. 

It consists primarily of IgG and contains trace amounts of IgA and IgM. y-Globulin provides the patient with passive immunity and does not require time for the development of an antibody response. It is believed to inhibit viral penetration of host cells, opsonize viral particles, activate complement, and stimulate cell-mediated immunity. 

IgG y K or X 150 Toxin neutralizing, agglutinating, opsonizing, bacteriolytic (with aid of complement system) antigen-IgG antibody complexes may cause tissue injury. Serum, amniotic fluid... 

However, when PMNs were stimulated, not by antibody on the surface of the tumor cell, but instead by Concanavalin Aor by opsonized zymosan myeloperoxidase did appear to mediate the killing azide and cyanide inhibited the killing, halides were required, catalase inhibited, and PMNs from patients with either hereditary deficiency of myeloperoxidase or chronic granulomatous disease were... 

IgG Immunoglobulin G is present in lymph fluid, blood, cerebrospinal fluid and peritoneal fluid. It is composed of 2 y chains of 50 kDa and 2 L chains (k or ) of 25 kDa with a total molecular weight of 150 kDa. The functions of IgG include agglutination and formation of precipitate, passage through placenta and thus conferring immunity to fetus, opsonization, antibody-dependent cell-mediated cytotoxicity (ADCC), activation of complement, neutralization of toxins, immobilization of bacteria and neutralization of virus. 

Figure 18. Specific antibodies induced with derivatives of the capsular polysaccharide overcome bacteriaI self-defense by opsonization.

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. 

In addition, macrophages are able to opsonize antibody-bound cells. 

Human serum containing anti-group A streptococcus carbohydrate (GAS CHO) antibodies were opsonic for different M protein-carrying serotypes. 

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