Page 98 - Veterinary Immunology, 10th Edition

regeneration, and lipid metabolism.
VetBooks.ir invaders as rapidly as possible. A critical component of this early
Protection from infection requires that the body respond to

response is the complement system. It can detect and kill invaders

before other defenses have had a chance to respond. The
complement system is a network of interacting pattern-recognition
proteins, proteases, serum proteins, receptors, and regulators that
kills invaders fast (Fig. 4.1). The major complement proteins bind

covalently (and hence irreversibly) to the surface of invading
microbes and then destroy them. The complement system is
activated by the presence of either pathogen-associated molecular
patterns (PAMPs) or by antigen-bound antibodies. Because the

complement system is so potent, it must be tightly regulated and
controlled. Disturbances in this system may result in inflammation
or autoimmunity.

FIG. 4.1 The functions of the complement system. Complement
may either alter microbial membranes or trigger inflammation. Either
way, it hastens the elimination of microbial invaders and is thus a
key component of the innate immune system. It has multiple other
functions as well as those noted here.

The complement system consists of multiple proteins that are
activated in sequence. Once activated, the system generates

multiple effector molecules. The first step, complement activation,

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