Chapter 13: Effector Mechanisms of Humoral Immunity Please recall that humoral immunity is one of the arms of adaptive immunity and involves antibodies. Unlike cell-mediated immunity, humoral immunity serves as a form of passive immunity (as is seen with breastfeeding mothers). In this chapter we will look at the many other ways that antibodies can be used (some have already been discussed). Additionally, we will revisit the complement cascade and discuss ways to inhibit this process. Overview of Effector Mechanisms of Antibodies Abbas, Lichtman and Pillai8_Figure 13-1; p.266TABLE 13-2: Functions of Antibody Isotypes (From Abbas, Lichtman and Pillai, 8th Edition; p. 267) Antibody Isotype Isotype-Specific Effector Functions IgG Opsonization of antigens for phagocytosis by macrophages and neutrophils Activation of the classical pathway of complement Antibody-dependent cell-mediated cytotoxicity mediated by natural killer cells Neonatal immunity: transfer of maternal antibody across the placenta and gut Feedback inhibition of B cell activation IgM Activation of the classical pathway of complement Antigen receptor of naive B lymphocytes* IgA Mucosal immunity: secretion of IgA into the lumens of the gastrointestinal and respiratory tracts IgE Mast cell degranulation (immediate hypersensitivity reactions) IgD Antigen receptor of naive B lymphocytes* ∗ These functions are mediated by membrane-bound and not secreted antibodies. Neutralization Abbas, Lichtman and Pillai8_Figure 13-2; p. 268Opsonization Opsonization can only be done by IgG (in this regard, IgG is referred to as an opsonin), but the process of phagocytosis can be done by neutrophils and macrophages. Antibody-Dependent Cell Mediated Cytotoxicity Clearance of Helminths ** PLEASE GO BACK AND REVIEW THE PATHWAYS OF THE COMPLEMENT CASCADE ** Abbas, Lichtman and Pillai8_Figure 13-4; p. 271 Abbas, Lichtman and Pillai8_Figure 13-5; p. 271A Refresher of the Complement Pathways: The Beginning of the Alternative Complement Pathway… Abbas, Lichtman and Pillai8_Figure 13-8; p. 275 Abbas, Lichtman and Pillai8_Figure 4-10; p. 70Abbas, Lichtman and Pillai8_Figure 13-7; p.274What Can Activate the Classical Complement Pathway? Abbas, Lichtman and Pillai8_Figure 13-11; p. 277Inhibiting the complement cascade It is important to inhibit the complement cascade from destroying normal, healthy host cells. Abbas, Lichtman and Pillai8_Figure 13-13; p.282 Abbas, Lichtman and Pillai8_Figure 13-14; p.282* PLEASE GO BACK AND REVIEW THE FUNCTIONS OF THE COMPLEMENT PROTEINS * Abbas, Lichtman and Pillai8_Figure 13-15; p.283 Abbas, Lichtman and Pillai8_Figure 13-16;
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