THE ADAPTIVE IMMUNE SYSTEM

II. HUMORAL IMMUNITY

A. WAYS THAT ANTIBODIES HELP TO DEFEND THE BODY

1. An Overview

The overall purpose of this Learning Object is to list the eight mechanisms by which antibodies remove or neutralize antigens during humoral adaptive immune responses .

LEARNING OBJECTIVES FOR THIS SECTION


Humoral Immunity refers to the production of antibody molecules in response to an antigen (def). These antibody molecules circulate in the plasma of the blood and enter tissue and organs via the inflammatory response. Humoral immunity is most effective microbes or their toxins located in the extracellular spaces of the body.

Antibodies or immunoglobulins (def) are specific glycoprotein configurations produced by B-lymphocytes and plasma cells in response to a specific antigen and capable of reacting with that antigen.

In this section we will look at how Antibodies help to defend the body.


A. Ways That Antibodies Help to Defend the Body: An Overview

The antibodies produced during humoral immunity ultimately defend the body through a variety of different means. These include:

1. Opsonization: Using antibodies to attach microbes to phagocytes or phagocytes to cells recognized as nonself.

2. MAC Cytolysis: Using antibodies to activate the classical complement pathway resulting in the lysis of gram-negative bacteria, viral envelopes, and host cells recognized as non-self by way of the membrane attack complex (MAC).

3. Antibody-dependent Cellular Cytotoxicity (ADCC) by NK Cells: Using antibodies to attach NK cells to infected cells and tumor cells and kill them via apoptosis.

4. Neutralization of Exotoxins: Using antibodies to prevent exotoxins from binding to receptors on host cells.

5. Neutralization of Viruses: Using antibodies to prevent viruses from adsorbing to receptors on host.

6. Preventing Bacterial Adherence to Host Cells: Using antibodies to prevent bacteria from binding to receptors on host.

7. Agglutination of Microorganisms: Using antibodies to clump microbes together for more effective removal by phagocytosis.

8. Immobilization of Bacteria and Protozoans: Using antibodies to against cilia and flagella to block motility.

9. Promoting an Inflammatory Response: Using antibodies to promote an inflammatory response in order to deliver defense cells and defense molecules to the infection site.


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Updated: July, 2012
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