Page 97 - Veterinary Immunology, 10th Edition

Canine C3 Deficiency, 35
VetBooks.ir Porcine Factor H Deficiency, 36

Other Complement Deficiencies, 37

LEARNING OBJECTIVES

After reading this chapter, you should be able to:
• Explain why the complement system is one of the most important innate defense

systems.
• Describe the three different pathways by which the complement system is
activated: two innate pathways, the alternative pathway and the lectin pathway;

and one adaptive pathway, the classical pathway.
• Explain how the innate complement pathways are activated by PAMPs, while the
classical pathway is activated when antibodies bind foreign antigens.

• Explain the significance of complement components, especially C3b, binding
covalently (and hence irreversibly) to invading microbes and opsonizing them.
• Explain how terminal complement complexes are constructed and their biological

significance.
• Understand how the complement system triggers inflammation by generating a

potent chemoattractant called C5a.
• Explain why deficiencies of some complement components result in increased
susceptibility to infections.
• Define complement, properdin, and anaphylatoxins.

The complement system is an essential innate defense system.
Although its main role is to kill pathogens immediately when they
enter the body, the complement system also alerts the immune
systems to the presence of invaders, regulates inflammation,

removes damaged or altered cells, and regulates adaptive immune
responses. It is involved in the clearance of antigen-antibody
complexes, blood vessel formation, mobilization of stem cells, tissue

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