Immunology 4- Acquired immune response and antibodies Flashcards
What two signals do B cells need to become fully activated and clonal proliferate?
- The antigen
- ‘helping’ signals
What do activated B cells differentiate into?
Plasma cells.
What are plasma cells?
Antibody secreting cells which are much larger than B cells and have many RER, meaning they can produce many antibodies.
In what ways can B cells mutate and produce better antibodies?
Switch from low to high affinity antibody production.
Switch the class of antibody they produce (e.g. IgM> IgG).
Differentiate into long-lived plasma cells and long-lived memory B cells.
Are IgM antibodies high or low affinity molecules?
Low affinity.
Which type of antibody do plasma cells first produce?
IgM antibodies.
What are the two signals needed from non-protein antigens for B cell activation?
1- BCR + antigen
2- PRR + PAMP
why do B cells not need a second signal for antigens with multiple antigenic epitopes?
There is enough interaction to activate the B cell without a secondary signal.
What do non-protein antigens and antigens with repetitive antigenic epitopes lead to?
- low affinity antibodies
- short lived plasma cells
- no memory cells
What are the two signals needed from protein antigens for B cell activation?
1- BCR binding to antigen
2- Help from Th cells
Through what process do B cells internalise protein antigens?
Endocytosis
What do B cells do to receive help from Tfh cells?
The peptides derived from chopping up protein antigens are presented on the B cell surface as an MHC-II peptide signal. The Tfh cell can then bind to this signal. Tfh helps by secreting co-stimulatory molecules to help the B cell.
How do Tfh cells help B cells?
They release co-stimulatory molecules. (help B cells produce antibodies)
What is the germinal centre reaction?
Rapid proliferation
What are the two parts of an antibody?
- The ‘recognition function’ at the top, mediates binding to antigen by variable region sites
- The ‘effector function’ at bottom, mediates clearance mechanisms by interaction of its heavy chain constant region and the effector molecules (complement or Fc receptors)