Classical complement pathway, Alternative pathway, Lectin mediated pathway ?

Classical complement pathway:

-        after entry of antigen in the blood IgM and IgG type of antibody bind to its surface, other type of antibody’s [ IgD, IgE, IgA ] can not activate.

-        Ones IgG and IgM antibody bind to surface of antigen conformation changes occur in Fc region of antibody bn Fc region of antibody due to this conformation changes

-        A pocket is created for the binding of complement protein known as clqr2s2 after binding to Fc region of antibody clqr2s2 get activated and it gets photolytic activity clqr2s2  bar has to substrate

-        C2 protein and C4 protein it clues C4 into C4a and C4b in which C4b is longer factor and C4a is smaller than smaller fragment dissociated and the larger fragment C4b bind to the surface of antigen it clues C2 into C2a and C2b in which C2a is longer fragment and C2b is smaller larger fragment C2a bind to C4b bond to antigen forming a dimer C4b2a.

-        C4b2a bar gains the activity to degrade C3 protein therefore it is also known as C3 convertase clues 3a and C3b. C3a is smaller fragment which is dissociated in the serum C3b is larger fragment bind to C3a convertase (C3b2a) forming trimer C4b2a3b bar this trimer has ability to degrade C5 protein therefore it is known as C5 convertase.

-        C5 convertase Can clues C5 protein into C5a and C5b is smaller fragment which is again dissociated and larger C5b protein sequence bind it to forming complex (C5bC6C7C8) C5b6789 complex has to ability gent inserted into membrane of antigen after getting the inserted into membrane multiple molecule of C9 protein bind to this complex forming C5b678 polynight this complex is also known as membrane attack complex which is form longer pore in the membrane of antigen and hence antigen is lised and killed.

 

Alternative Pathway: -

                              Antigen antibody complex for its activation the pathway starts with the autohydrolysis of complement protein C3 into C3a and C3b the rate of this autolytic reaction is very slow the C3a component is dissociated into serum while C3b which is larger factor it bind to it surface after its binding another serum protein joint to its which is known as factor B then factor D this complex and it clues factor B into fragment Ba and Bb, Ba is smaller factor which is dissociated Bb is larger which remain associated with C3b resulting in the dimer C3Bb factor D is dissociated after the cleavage of factor B C3bBb bar has ability to degrade C3 and therefore it is known as C3 convertase of alternative pathway this C3 convertase it clues C3 complement protein into C3a and C3b, C3b joins the dimer resulting in the complex C3bBb this is complex is also known as C5 convertase it clues C5 protein into C5a and C5b the larger C5b bind to the surface of antigen C5b678 polynight (9) this complex is also known is known as MAC which is form larger pore in the membrane of antigen and hence antigen is killed.

 

Lectin mediated pathway: -

                          Many bacteria and viral antigen have carbohydrate residues present on their surface this carbohydrate can be specifically recognize by serum protein host serum protein known as lectin. Such serum protein are also involved in immune activation

For example: -In human serum a protein known as [MBL] mannose binding lectin. Mannose residue present and form antigen and activate complex system.

Antigen bearing mannose residue comes in the body serum protein known [MBL] bind to mannose residue then two serum protein bind to MBW called as MASP-1, MASP-2 [MBL associated serum protein 1 and 2] MASP 1 and 2 have 2 substrate C2 and C4 compliment protein they clues then C4a and C4b and C2a and C2b, C4b and C2a forms complex of surface on antigen which is also called as C3 convertase C4b2a bar gains the activity to degrade C3 protein therefore it is also known as C3 convertase clues 3a and C3b. C3a is smaller fragment which is dissociated in the serum C3b is larger fragment bind to C3a convertase (C3b2a) forming trimer C4b2a3b bar this trimer has ability to degrade C5 protein therefore it is known as C5 convertase. C5 convertase Can clues C5 protein into C5a and C5b is smaller fragment which is again dissociated and larger C5b protein sequence bind it to forming complex (C5bC6C7C8) C5b6789 complex has to ability gent inserted into membrane of antigen after getting the inserted into membrane multiple molecule of C9 protein bind to this complex forming C5b678 polynight this complex is also known as membrane attack complex which is form longer pore in the membrane of antigen and hence antigen is lised and killed