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Flashcards in Immunology Deck (11):

What is the immune system and what is the immune response?

The immune system is a network of cells, tissues and organs that function to defend the body against pathogens. The immune response is a coordination reaction of the immune system against a trigger.


What are the stages of an immune response?

- Adherence of pathogen (innate immunity)
- Penetrance of epithelium (innate immunity)
- Local infection of tissues (innate immunity)
- Lymphatic spread (adaptive immunity)
- Adaptive immunity


What are the different isotypes of the Fc (heavy chain) region of an antibody? Why is the Fc region important?

IgA, IgE, IgM, IgG and IgD
- The effector function of the antibody is largely derived from the constant region
- Interacts with other components such as complement


What is the Fab region?

Antigen binding, hypervariable - our antibody repertoire can bind an infinite array of antigens


How does antibody diversity come about?

- Gene recombination of the B cell receptor
- V, D and J segments of the heavy chain
- V and J segment of the light chain
- Only one of the V, D and J heavy chain genes and one of the V and J light chain genes are selected
- Deletion and insertions of nucleotides boosts number of antibodies


What is IgM?

• Expressed on naïve B cells
• Secreted form is a pentamer
• Linked by the J chain (not J gene segment)
• Very efficient at activating complement
• Pore forming protein complex that lyses bacteria and mammalian cells
• First antibody that you find
• 10 different binding sites - weak affinity


What is IgG?

• Major immunoglobulin class in serum
• Major class in secondary response
• Binds receptors (Fc receptors) expressed by monocytes, macrophages and NK cells
• Can activate complement
Can cross the placenta


What is IgE?

• Important in responses to parasites
• Can cause allergic reactions
Mast cells and basophils -> involved in the allergic response


What is IgA?

• Expressed on the cell surface as a monomer
• Secreted form is a dimer = held together by a J chain that binds to the secretory component
Secreted IgA is prominent in mucosal secretions = airways, gut, breast milk


What is IgD?

• Expressed on naïve B cells (coexpressed with IgM)
• Similar to IgG but cannot cross placenta
Does not activate complement


What are the two events that a B cell undergoes?

1. Isotype (class) switching -> switching out constant regions to change antibody type
2. Affinity maturations -> point mutations which allow for a tighter fit of the antigen

Isotype switching, affinity maturation -> memory cells, plasma cells