Chapter 21 - Section 21.5 - Study Guide - Assess Your Learning Outcomes - Page 845: 5

Antibodies combat antigens through a variety of mechanisms that collectively contribute to the immune response. Here are four key mechanisms by which antibodies work to neutralize and eliminate antigens: 1. **Neutralization:** Antibodies can neutralize antigens by binding to specific sites on the antigen's surface. This binding prevents the antigen from interacting with host cells and performing harmful activities. For example, antibodies can neutralize viruses by binding to their viral surface proteins, preventing them from attaching to and entering host cells. This mechanism reduces the ability of the antigen to cause infection or damage. 2. **Opsonization:** Opsonization is the process in which antibodies coat the surface of pathogens, making them more recognizable to immune cells such as phagocytes (macrophages and neutrophils). These immune cells have receptors for the constant region of antibodies (Fc region). When antibodies bind to antigens on the surface of pathogens, phagocytes can bind to the Fc region of the antibodies, facilitating the engulfment and destruction of the pathogen. Opsonization enhances the efficiency of phagocytosis. 3. **Complement Activation:** Antibodies can trigger the complement system, a group of proteins that work together to destroy pathogens. When antibodies bind to antigens, they can initiate the classical pathway of complement activation. This leads to the deposition of complement proteins on the surface of the antigen, which attracts immune cells and enhances phagocytosis. Additionally, complement activation can directly cause lysis (bursting) of certain pathogens by forming a membrane attack complex. 4. **Antibody-Dependent Cellular Cytotoxicity (ADCC):** ADCC involves antibodies binding to the surface of target cells, such as infected or cancerous cells. Natural killer (NK) cells, which have receptors for the Fc region of antibodies, recognize the antibody-coated target cells and subsequently release cytotoxic granules that induce cell death. ADCC is particularly important in eliminating cells that may not be effectively cleared by phagocytosis alone. In summary, antibodies play a crucial role in combating antigens through neutralization, opsonization, complement activation, and antibody-dependent cellular cytotoxicity. These mechanisms collectively contribute to the immune response by preventing infection, enhancing pathogen clearance, and facilitating the recognition and elimination of harmful cells and particles.

Antibodies combat antigens through a variety of mechanisms that collectively contribute to the immune response. Here are four key mechanisms by which antibodies work to neutralize and eliminate antigens: 1. **Neutralization:** Antibodies can neutralize antigens by binding to specific sites on the antigen's surface. This binding prevents the antigen from interacting with host cells and performing harmful activities. For example, antibodies can neutralize viruses by binding to their viral surface proteins, preventing them from attaching to and entering host cells. This mechanism reduces the ability of the antigen to cause infection or damage. 2. **Opsonization:** Opsonization is the process in which antibodies coat the surface of pathogens, making them more recognizable to immune cells such as phagocytes (macrophages and neutrophils). These immune cells have receptors for the constant region of antibodies (Fc region). When antibodies bind to antigens on the surface of pathogens, phagocytes can bind to the Fc region of the antibodies, facilitating the engulfment and destruction of the pathogen. Opsonization enhances the efficiency of phagocytosis. 3. **Complement Activation:** Antibodies can trigger the complement system, a group of proteins that work together to destroy pathogens. When antibodies bind to antigens, they can initiate the classical pathway of complement activation. This leads to the deposition of complement proteins on the surface of the antigen, which attracts immune cells and enhances phagocytosis. Additionally, complement activation can directly cause lysis (bursting) of certain pathogens by forming a membrane attack complex. 4. **Antibody-Dependent Cellular Cytotoxicity (ADCC):** ADCC involves antibodies binding to the surface of target cells, such as infected or cancerous cells. Natural killer (NK) cells, which have receptors for the Fc region of antibodies, recognize the antibody-coated target cells and subsequently release cytotoxic granules that induce cell death. ADCC is particularly important in eliminating cells that may not be effectively cleared by phagocytosis alone. In summary, antibodies play a crucial role in combating antigens through neutralization, opsonization, complement activation, and antibody-dependent cellular cytotoxicity. These mechanisms collectively contribute to the immune response by preventing infection, enhancing pathogen clearance, and facilitating the recognition and elimination of harmful cells and particles.