Classical pathway,Alternative pathway and Lectin pathway

1. THE COMPLEMENT SYSTEMTHE COMPLEMENT SYSTEM
Presented by:Presented by:
Dipankar Das.Dipankar Das.
M.Sc Biotech 2M.Sc Biotech 2ndnd
semsem
Dept of Biotechnology,Dept of Biotechnology,
Pandu collegePandu college
Presented to:Presented to:
Dr. Kangkana katakiDr. Kangkana kataki

2. HISTORYHISTORY
 Research in complement system started in 1890sResearch in complement system started in 1890s
whenwhen Jules BordetJules Bordet at the institute Pasteur ofat the institute Pasteur of
Paris conduct experiment using sheep antiserum.Paris conduct experiment using sheep antiserum.
 He named those substances as Alexin.He named those substances as Alexin.
 Paul EhrilichPaul Ehrilich coined the term complement.coined the term complement.

3. INTRODUCTIONINTRODUCTION
 The complement system is a part of immune systemThe complement system is a part of immune system
 It enhances the ability of antibodies and phagocyticIt enhances the ability of antibodies and phagocytic
cells to clear microbes and damaged cells from ancells to clear microbes and damaged cells from an
organismorganism
 Promote inflamation,and attack the pathogen”s cellPromote inflamation,and attack the pathogen”s cell
membranemembrane
 The complement system protein mainly synthesis byThe complement system protein mainly synthesis by
liver cell and widely distributed among the body tissueliver cell and widely distributed among the body tissue
and fluids.and fluids.

4. EFFECT OF COMPLEMENTEFFECT OF COMPLEMENT
SYSTEMSYSTEM
Three main effect:Three main effect:
 Lysis of cell.Lysis of cell.
 Generation of mediator of inflamation.Generation of mediator of inflamation.
 Opsonization-enhancement of phagocytosis.Opsonization-enhancement of phagocytosis.

5. HOW IT IS ACTIVATEDHOW IT IS ACTIVATED
There are 3 pathwaysThere are 3 pathways
 Classical pathway(Antigen antibody reaction)Classical pathway(Antigen antibody reaction)
 Alternative pathway(Bacterial endotoxin)Alternative pathway(Bacterial endotoxin)
 Lectin pathwayLectin pathway

6. CLASSICAL PATHWAYCLASSICAL PATHWAY
 Main trigger of classical pathway is the antigen-antibody reaction.Main trigger of classical pathway is the antigen-antibody reaction.
 This reaction activate C1 component of complement system.This reaction activate C1 component of complement system.
 Then it cleave C4 component into a smaller component C4a andThen it cleave C4 component into a smaller component C4a and
C4b.C4b.
 C1 combined with C4b and active C2,which is hydrolyzed intoC1 combined with C4b and active C2,which is hydrolyzed into
C2a and C2b.C2a and C2b.
 C4b and C2b together make a complex which can convert theC4b and C2b together make a complex which can convert the
C3 into active form.The complex called C3 convertage.C3 into active form.The complex called C3 convertage.
 C4b,C2b,C3b(C5 convertage) active C5 and it is also hydrolizedC4b,C2b,C3b(C5 convertage) active C5 and it is also hydrolized
into C5a and C5b.into C5a and C5b.
 C5b open a special pocket where C6 bind then C7,C8,C9 bindC5b open a special pocket where C6 bind then C7,C8,C9 bind
and make a membrane attack complex.and make a membrane attack complex.
 The membrane attack complex swells and brusts the cell.The membrane attack complex swells and brusts the cell.

7. CLASSICAL PATHWAYCLASSICAL PATHWAY

8. MEMBRANE ATTACK COMPLEXMEMBRANE ATTACK COMPLEX
 C5bC6C7C8C9 togetherC5bC6C7C8C9 together
make a complex andmake a complex and
formed membrane attackformed membrane attack
complexcomplex

9. OPSONIZATIONOPSONIZATION
 Opsonization is theOpsonization is the
process where opsoninprocess where opsonin
molecule bind one sidemolecule bind one side
to the bacterial cell andto the bacterial cell and
other side bind with theother side bind with the
phagocytic cell.phagocytic cell.
 Example- C3b, IgG.Example- C3b, IgG.

10. ALTERNATIVE PATHWAYALTERNATIVE PATHWAY
 Alternative pathway triggered by bacterial endotoxin,it is aAlternative pathway triggered by bacterial endotoxin,it is a
polysaccerides compound which is found in outer membrane ofpolysaccerides compound which is found in outer membrane of
gram negative bacteria.gram negative bacteria.
 C3b activated by surface molecule, it will make a domain whichC3b activated by surface molecule, it will make a domain which
interact with another protein B.interact with another protein B.
 Protein B also hydrolyzed into Ba and Bb.Protein B also hydrolyzed into Ba and Bb.
 C3b and Bb together act as C3 convertage and bind with anoterC3b and Bb together act as C3 convertage and bind with anoter
C3b component.C3b component.
 C3bBbC3b(C5 convertage), C5 hydrolysed into C5a and C5bC3bBbC3b(C5 convertage), C5 hydrolysed into C5a and C5b
 C5b open a special pocket where C6 bind then C7,C8,C9 bindC5b open a special pocket where C6 bind then C7,C8,C9 bind
and make a membrane attack complex.and make a membrane attack complex.
 The membrane attack complex swells and brusts the cellThe membrane attack complex swells and brusts the cell

11. ALTERNATIVE PATHWAY FIG:ALTERNATIVE PATHWAY FIG:

12. MANNAN BINDING LECTINMANNAN BINDING LECTIN
PATHWAYPATHWAY
 Some bacteria have Mannan molecule.Some bacteria have Mannan molecule.
 From our blood special protein called mannan binding lectinFrom our blood special protein called mannan binding lectin
present.present.
 They bind with mannan molecule of bacteria.They bind with mannan molecule of bacteria.
 MBL activate C4 into C4a and C4b.MBL activate C4 into C4a and C4b.
 They also activate C2b.They also activate C2b.
 C4b and C2b together make a complex which can convert theC4b and C2b together make a complex which can convert the
C3 into active form.The complex called C3 convertage.C3 into active form.The complex called C3 convertage.
 C4b,C2b,C3b(C5 convertage) active C5 and it is also hydrolizedC4b,C2b,C3b(C5 convertage) active C5 and it is also hydrolized
into C5a and C5b.into C5a and C5b.
 C5b open a special pocket where C6 bind then C7,C8,C9 bindC5b open a special pocket where C6 bind then C7,C8,C9 bind
and make a membrane attack complex.and make a membrane attack complex.
 The membrane attack complex swells and brusts the cell.The membrane attack complex swells and brusts the cell.

13. LECTIN PATHWAY FIGLECTIN PATHWAY FIG

14. INFLAMATIOINFLAMATIO
 C3a and C5a activate mast cell.C3a and C5a activate mast cell.
 Mast cell produce histamin and vesodilation intoMast cell produce histamin and vesodilation into
injured area.injured area.
 More blood mean more monocytes, antibodies,More blood mean more monocytes, antibodies,
nutrophylls, more complement protein.nutrophylls, more complement protein.
 They amplify the inflametory response.They amplify the inflametory response.

15. conclusionconclusion
 The complement system complement ourThe complement system complement our
immune system.immune system.
 Classical pathway need antibody to activateClassical pathway need antibody to activate
complement system, so it is acquired immunity.complement system, so it is acquired immunity.
 Alternative and lectin pathway no need antibody,Alternative and lectin pathway no need antibody,
so it is innate immunity and provied First line ofso it is innate immunity and provied First line of
deffence.deffence.

16. REFERENCEREFERENCE
 DrNajeeblectures.com.DrNajeeblectures.com.
 en.wikipedia.org.en.wikipedia.org.

17. THANK YOUTHANK YOU