innate immunity part 2 video 1

What roles does the complement system play?

• collection of proteins in the bloodstream and tissue fluids

• usually in an inactivated state but when activated there is an enzymatic cascade

  • lysis of foreign cells

  • opsonization

  • inflammatory response

How is complement activated? all of them end with the same product

1. alternative pathway: starts with the presence of C3b and then binds to surface of invader and sets of formation of C3 convertase

2. lectic pathway: bacteria have mannose sugar and we don’t. Our mannose-binding protein will bind to mannose sugars which results in C3 convertase

3. Classical pathway: antibodies are sensors that will bind to microbial invaders to form C3 convertase

What occurs after C3b is form?

next in the cascade is C5 convertase with makes C5a and C5b

What are the consequences of complement activation?

1. cell lysis: when C5b is created it will then bind to the membrane and then other proteins in the complement will also bind resulting in circular pore form called membrane attack complexes (MAC) which results with a hole in the membrane

2. Opsonization: process by which microbe is coated with a molecule makes it easier for phagocytes to attach to it

   1. ex: C3b coats microbial cells, phagocytes have C3 receptors

3. Inflammation response: C3a and C5a promote vascular permeability and chemotaxis of phagocytes

Which one would have the most resistance to complement? Gram + or -

Gram negative have less resistance than gram positive because gram positive has a layer of peptidoglycan

What are anaphylotoxins and which microbe produces enzyme that degrade it?

they are C3a and C5a that promote inflammation

Pseudomonas aeruginosa

why is opsonization so important

genetic variations that limit opsonization lead to chronic recurring infections and early death

How do host cells protect themselves from compliment?

Decay accelerating factor (DAF) protects host cells by disruption membrane-bound C3 convertase

what is paroxysmal nocturnal hemoglobinuria

red blood cells killed by C3 convertase