MLT 115 Mod 2 Les 2: Complements

What is the primary role of the complement system in immunity?

It acts as a mediator and helper that enhances the immune response and is critical for inflammation.

What are the three pathways of the complement system?

1. Classic pathway, 2. Alternative pathway, and 3. Lectin pathway.

How are anaphylatoxins generated and what is their risk?

They are generated from activation of complement components from C3 onward; a buildup can lead to anaphylactic shock.

What activates the Classic Pathway?

The bond of an antigen-antibody, specifically involving IgM or IgG (IgM is most effective).

Which components make up the 'recognition unit' in the Classic Pathway?

C1q, C1r, and C1s.

At what point does the Classic Complement pathway reach its full amplitude?

When C3 is activated.

What components form the Membrane Attack Complex (MAC)?

C5bC6C7C8C9.

Which complement component has the highest circulating concentration in the body?

C3.

What is the most common complement deficiency in humans?

C2 deficiency, which can lead to repeated bacterial infections and autoimmune disorders.

What are the three stages of the Classic Pathway's antigen-antibody bond?

1. Recognition 2. Amplification or Enzymatic Activation 3. Membrane Attack

What is an alternative name for the Alternative Pathway?

The Properidin pathway.

Which Classic Pathway steps does the Alternative Pathway bypass?

It bypasses the activation of C1, C4, and C2.

What is the role of Factor B in the Alternative Pathway?

It acts as the 'Begin' factor, activating C3 to form the C3bBb complex.

How does Factor H control the Alternative Pathway?

Known as the 'Halt' factor, it prevents Factor B from binding with C3b, stopping the pathway.

What is Disseminated Intravascular Coagulation (DIC)?

A condition where small intravascular clots deplete coagulation factors and platelets, leading to uncontrollable and potentially fatal bleeding.

What is opsonization?

The process where cells that are coated with antibodies are identified and destroyed by macrophages.

What clinical risks are associated with decreased complement levels?

Increased susceptibility to bacterial infections (especially Streptococcus and Neisseria sps.), hemolytic syndrome, and autoimmune disorders.