September 3, 2015 - Humoral Immunity Flashcards
Common Markers of B Cells
CD19 and CD20
Somatic Recombination
Picking a V, D, and J region to combine together to make a unique variable region for the antibody.
There are 109 possible combinations.
Somatic Hypermutation
Restricted to B cells engaged with a matching antigen. Requires the help of a helper T cell and only occurs within the V-segment of the Ab gene.
Deliberate, random nucleotide substitutions in the Ab gene. Ones that lead to an inceased antigen affinity result in proliferation of the B cell and thus, a stronger antibody interaction.
B Cell - T Cell Crosstalk
B cells bind with a matching antigen, and then the B cell MHC Class II receptor binds with the T Cell Receptor (TCR).
T cells tell the B cells to proliferate and differentiate. This causes isotype switching, somatic hypermutation, maturation into memory or plasma cells, and communication via chemical signals.
Functions of Antibodies
- Neutralization
- Opsonization
- Complement activation
Opsonization
Marks a target for destruction. This is particularly important against encapsulated organisms such as H. influenzae, S. pneumoniae, N. meningitidis, K. pneumoniae .
Phagocytes bind the marked target through their Fc receptor.
Complement Activation
Antibodies bound to a target can induce C1 to become activated and initiate the complement cascade.
Professional Antigen Presenting Cells
Macrophages
Dendritic Cells
B Cells