THE COMPLEMENT SYSTEM in immunology.pptx

Immunology, immunesystrm complement system

1. THE COMPLEMENT SYSTEM By Sneha S MSc Biological Sciences 1

2. INTRODUCTION Antibodies protect the body from invading organisms in two ways: 1. By direct actions 2. Through complement system. The Direct Actions of Antibodies directly inactivate the invading organism by any one of the following methods: Agglutination, precipitation, neutralization, lysis The indirect actions of antibodies (through the complement system) are stronger than the direct actions and play a more important role in the defense mechanism of the body than the direct actions. Complement was discovered by Jules Bordet. The complement system refers to an extremely complex group of proteins present in normal human and animal serum. It is an integral part of the body’s immune system that has various abilities. Chemically complement is a group of proteins associated with some carbohydrates and phospholipids. 2

3. NOMENCLATURE Complement components are designated as C1 to C9 The product of the reaction designated as Ag-AB C (for example Ag–Ab C1423) Components that acquire enzymatic activity are indicated by a bar over the components. Fragments of C cleaved during the reaction are indicated by lowercase letters (for example C3a ) Inactivated forms of C components are indicated by the suffix ‘I’ (for example – C3i) 3

4. COMPONENTS OF THE COMPLEMENT SYSTEM Components of the complementary system are from C1 to C9 (not all the components of the complementary system have similar characteristics – each has different properties) These proteins work in a cascade to attack the surfaces of pathogen. C1 is made of 3 protein subunit and is sensitive to heat. C2 is heat labile. C3 is the largest protein which are heat stable and can combine with yeast cell wall. C4 is also heat stable . C5 to C9 are terminal components of membrane attack pathway which plays important role in cytolysis. 4

5. FUNCTIONS After initial activation, the various complement components interact, in a highly regulated cascade, to carry out a number of basic functions including: Lysis of cells, bacteria, and viruses. Opsonization, which promotes phagocytosis of particulate antigens. Binding to specific complement receptors on cells of the immune system, triggering specific cell functions, inflammation, and secretion of immunoregulatory molecules. Immune clearance, which removes immune complexes from the circulation and deposits them in the spleen and liver. 5

6. CLASSICAL PATHWAY 6

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