Antibodies effector functions mediated

Another effector function is the cell-mediated cytotoxicity. Infected cells that were recognized and opsonized by specific antibodies can be lysed by natural killer cells which are the classical K cells. These properties are highly determined by the Fc part of antibodies. IgGl and IgG3 have the highest capacity for cell-mediated cytotoxicity. The effector function of an antibody is frequently used as a mean of antibody recognition. This is especially the case with bacterial proteins such as protein A and protein G that specifically interact with the same domain. Therefore purification can interfere with the antibody effector function. 

Administration of Tyv-specific monoclonal antibodies to rat pups already infected with intestinal larvae causes larvae in the epithelium to be expelled (Carlisle et al, 1990). Only the LI stage is susceptible to expulsion once the larva has moulted to L2 it resists the effects of the antibodies (Carlisle et al, 1990). Expulsive immunity is transferred by three IgG isotypes, F(ab )2 fragments, as well as IgM (Carlisle et al., 1991a). These findings argue against a role for Fc-mediated effector functions and imply that antibodies against Tyv can disturb the larva s niche in a direct fashion. 

For complement-dependent cytotoxicity, a complex cascade of protein binding and cleavage occurs that culminates in final complement mediated effector functions of phagocytosis, recruitment and activation of leukocytes, and osmotic lysis. It has been reported that Rituximab (anti-CD20) utilizes a complement-dependent mechanism for tumor cell destruction [14], If the desired effect of a therapeutic antibody is complement-dependent activity, the isotype subgroup chosen should be one that binds to complement proteins (IgGl or IgG3). 

The effector function of an antibody is defined as the mediation of other host-defense mechanism besides antigen recognition. It is highly determined by the carbohydrate structure of the heavy chain. 

IgA is the principal antibody present in a number of secretions and is the major antibody associated with the external immune system. IgA lacks the effector functions identified previously and acts mainly in immune exclusion (prevention of entry of potentially infectious entities into the body). As noted previously, there are differences in the immune effector mechanisms associated with the internal immune system or systemic immunity and the external immune system or local immunity. Systemic immunity is mediated by IgM and IgG, the latter is the major form of Ig found in the blood. Local immunity is mediated primarily by IgA and IgE. The contribution by the external immune system should not be underestimated because about half of the body s lymphocytes are associated with this system. 

The basis for the effector function by antigen-specific lymphocytes - especially antibody-secreting B cells, Td cells, and Tc cells - and the participation of other cellular components of the immune system in acquired immunity - including NK cells, macrophages, and neutrophils - have already been emphasized in other sections of this volume. It has also been emphasized that Th cells play an important effector role in acquired immunity as regulators in the growth and differentiation of B cells and Tc cells. In this regard, it is important to note that both populations of T cells whose participation in an acquired immune response is mediated by the secretion of lymph-okines, that is, Th and Tq cells, are characterized by the expression of CD4. 

The lymphocyte populations also arise from bone marrow progenitor cells. The B lymphocytes mature or differentiate in the bone marrow before leaving to circulate in the blood and lymph, while T lymphocytes undergo maturation in the thymus. Antibodies mediating the effector functions of the... 

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