Opsonization complement-mediated

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. 

In humans, there are five isotypes of antibodies, IgG, IgA, IgD, IgE, and IgM, which are defined by the structures of their heavy chains and their abilities to form multimers (Figure 10.1) [8], IgG is the most abundant isotype present in serum with average serum concentrations ranging from 0.5 to 9mg/ml depending on the IgG subtype. This is followed by IgA (3mg/ml), IgM (1.5mg/ml), IgE (0.05 mg/ml), and IgD (trace). Each antibody isotype has unique functions. Critical functions of IgG include opsonization, complement activation, antibody-dependent cell-mediated cytotoxicity (ADCC), passive immunity, and regulation of B cells. Both IgM and IgD act as antigen receptors on naive B cells, and soluble, multimeric forms of IgM are involved in complement activation. IgA is involved in mucosal and passive neonatal immunity, while IgE is involved in immediate hypersensitivity [8],... 

Recently, streptococcal colh n-like protein Sell.6 of M6-type GAS was charaaerized as a FH/FHL-1 bindii protein. Scll.6-bound FH retained cofactor activity for factor I-mediated cleavage of C3b su esdng a role in GAS evasion of complement-mediated opsonization. ... 

Complement. Complement is an extensive series of glycoproteins and protein inhibitors whose function includes major cytolytic effects, mediation of opsonization, and modulation of inflammatory responses. Activation of this system plays an important role in host defense leading to destruction of microorganisms. It also results in generation of anaphylotoxins which induce mediator release and "split products" that mediate membrane damage, either directly through structural alteration or indirectly, via cell chemotaxis and regulation. 

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 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. 

IFN-y also induces the costimulatory molecules on the macrophages, which increases cell-mediated immunity. As a consequence, there is activation and increase in the tumoricidal and antimicrobial activity of mononuclear phagocytes, granulocytes and NK cells. The activation of neutrophils by IFN-y includes an increase in their respiratory burst. IFN-y stimulates the cytolytic activity of NK cells. It is an activator of vascular endothelial cells, promoting CD4+ T lymphocyte adhesion and morphological alterations, which facilitates lymphocyte extravasation. IFN-y promotes opsonization by stimulating the production of IgG subclasses that activate the complement pathway. A summary of the characteristics of selected cytokines is shown in Table 2.3. 

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

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... 

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. 

Complement components Inflammatory mediators Opsonization, chemotaxis, and mast cell... 

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