complement Flashcards
What are the two main subdivisions of the immune system?
Humoral and cell-mediated
The immune system can also be divided into innate and adaptive.
What is humoral immunity?
Involves combating pathogens with molecules in body fluids, including antibodies produced by B lymphocytes.
What is cell-mediated immunity?
Primarily involves T lymphocytes and also includes phagocytes like neutrophils and macrophages.
What are the components of innate immunity?
Physical and chemical barriers, serum proteins, and various immune cells
Key cells include phagocytes, natural killer cells, mast cells, basophils, and dendritic cells.
What is the response time of the innate immune system?
Minutes to hours.
What is the specificity level of innate immunity?
Limited specificity.
List beneficial molecules found in plasma during an immune response.
- Clotting factors
- Antibodies
- Proteins of complement pathways
- Nutrients
- Lysozyme & beta-defensins
- Transferrin
What is the function of clotting factors during an immune response?
To localize infection, stop bleeding, and attract phagocytes.
What role does transferrin play in the immune response?
Deprives microbes of needed iron.
What activates the complement system?
A biochemical cascade of around 30 small plasma proteins.
What are the three pathways of the complement system?
- Classical complement pathway
- Alternative complement pathway
- Mannose-binding lectin pathway
What is the key enzyme produced by all three complement pathways?
C3 convertase.
What activates the classical complement pathway?
Requires antibody bound to antigen.
Which antibodies primarily activate the classical complement pathway?
IgG or IgM.
What is the function of C1 in the classical complement pathway?
Cleaves C4 into C4a and C4b.
What is the role of C4b2a in the classical complement pathway?
Functions as a C3 convertase.
What does C3b do in the immune response?
Attaches antigens to phagocytes for opsonization and improves phagocytosis.
What is the role of C5a in the complement system?
Triggers inflammation and acts as a chemoattractant for phagocytes.
What is the Membrane Attack Complex (MAC)?
A complex that puts pores into lipid bilayer membranes of human cells leading to cell lysis.
Describe the alternative complement pathway.
A non-specific pathway continuously active at low levels, activated by pathogens without requiring antibodies.
What initiates the alternative complement pathway?
Spontaneous activation and attachment of complement protein C3 to a pathogen.
What is the function of properdin in the alternative pathway?
Stabilizes the C3 convertase.
What is the first step in the mannose-binding lectin pathway?
Mannose-binding lectin binds to mannose on the surface of the pathogen.
What is the role of MBL-associated serine protease (MASP) in the mannose-binding lectin pathway?
Cleaves C4 and C2 in a manner similar to C1 in the classical pathway.
