Topic 7: B Cell Immunity and Effector Mechanisms

Question 1

What are the phases of a humoral immune response?

Answer 1

1. Antigen recognition
2. Activation of B lymphocytes (from antigen recognition plus helper T cells and other stimuli)
3. Proliferation
4. Differentation into effector cells

Question 2

Describe a T-dependent antibody response:

Answer 2

1. T cells must recognise the antigen peptide presented by APCs in the T cell zone of a lymphoid organ
2. Once activated the effector T cells will migrate towards the follicle
3. B cells must also recognise the antigen within the follicle causing it to become activated and migrate towards the T cell zone
4. The migration of the activated B and T cells towards eachothers respective zones makes them likely to interact with eachother
5. Activated B and T cell interaction (the B cell can also present some internalised antigen on MHC II to the CD4 cell confirming that it is the correct B cell
6. The B cells will proliferate and differentiate and migrate into germinal centres where affinity maturation occurs

Question 3

What are the 3 functions by which antibodies protect us from disease?

Answer 3

1. Neutralisation: antibody binds microbe/toxin and prevents it from completing its pathogenic role
2. Opsonisation:
   the antibody binds to the microbe and the Fc region of the antibodies bind to CD64 on neutrophils and macrophages
3. Complement system activation