Page 156 - Textbook of Pathology, 6th Edition

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SECTION I

Figure 6.10 Inter-relationship among clotting, fibrinolytic, kinin and complement systems.

anaphylatoxins (C3a, C4a and C5a), and membrane attack evident in hypersensitivity conditions. Such self-damaging

complex (MAC) i.e. C5b,C6,7,8,9. effects are kept in check by the host mechanisms in order to
The actions of activated complement system in resolve inflammation. These mechanisms are as follows:
General Pathology and Basic Techniques
inflammation are as under: i) Acute phase reactants. A variety of acute phase reactant
C3a, C5a, C4a (anaphylatoxins) activate mast cells and
basophils to release of histamine, cause increased vascular (APR) proteins are released in plasma in response to tissue
trauma and infection. Their major role is to protect the normal
permeability causing oedema in tissues, augments cells from harmful effects of toxic molecules generated in
phagocytosis. inflammation and to clear away the waste material. APRs
C3b is an opsonin. include the following:
C5a is chemotactic for leucocytes.
Membrane attack complex (MAC) (C5b-C9) is a lipid i) Certain cellular protection factors (e.g. α -antitrypsin, α -
1
1
dissolving agent and causes holes in the phospholipid chymotrypsin, α -antiplasmin, plasminogen activator
2
membrane of the cell. inhibitor): They protect the tissues from cytotoxic and
proteolytic damage.
REGULATION OF INFLAMMATION ii) Some coagulation proteins (e.g. fibrinogen, plasminogen, von
Willebrand factor, factor VIII): They generate factors to
The onset of inflammatory responses outlined above may replace those consumed in coagulation.
have potentially damaging influence on the host tissues as
iii) Transport proteins (e.g. ceruloplasmin, haptoglobin): They
carry generated factors.
iv) Immune agents (e.g. serum amyloid A and P component,
C-reactive protein): CRP is an opsonising agent for
phagocytosis and its levels are a useful indictor of
inflammation in the body.
v) Stress proteins (e.g. heat shock proteins—HSP, ubiquitin):
They are molecular chaperons who carry the toxic waste
within the cell to the lysosomes.
vi) Antioxidants (e.g. ceruloplasmin are active in elimination
of excess of oxygen free radicals.
The APR are synthesised mainly in the liver, and to some
extent in macrophages. APR along with systemic features of

Figure 6.11 Pathway of kinin system. fever and leucocytosis is termed ‘acute phase response’.