B Cells Flashcards
What ligand/receptor is needed for T-cell dependent B-cell activation?
CD40
What are the two factors necessary for B cell activation?
Cross-linking of BCR and T-Cell costimulation (CD40)
Which factor replaces stimulation by a T-helper cell in T-cell independent B-cell activation?
“danger signal” (often repetitive antigen or ligand sequence on invader)
Which types of antibodies are primarily made by T-cell independent B-cell activation?
IgM
Which types of antibodies are primarily made by T-Cell dependent B-Cell activation? Which two CD40-dependent processes take place in the production of these antibodies?
IgG, IgE, IgA; Class switching and somatic hypermutation
Which two “careers” can a B cell choose?
Plasma cells vs Memory cells
Which type of B cells are “antibody factories”?
Plasma cells
Which has a longer lifespan, memory cells or plasma cells?
Memory cells
What are the two proteins that make up the signaling portion of the BCR?
Iga (alpha) and Igb(beta)
When an antibody switches classes, what part of the antibody changes, Fc, or Fab?
Fc
The type of antibody class produced during class switching is dependent on the ________ present in the local environment.
Cytokines
Why is T-cell independent B-cell activation so important to the immune system? Hint: what antigen types does it help the immune system recognize?
It helps the immune system react against carbohydrates and fats (the T-Cell dependent activation system primarily recognizes proteins)
How does somatic hypermutation select for B cells that are better able to defend against invaders?
Amplification of B cells is dependent on binding affinity for the antigen (the BCR that binds the best will proliferate the most)
How does class switching allow antibodies to be more effective in defending against invaders?
Each class of antibody is better suited to its target or location in the body (i.e. IgA, which is found in mucosa and intestines, coat antigens to prepare them for elimination in mucus or feces)
True or False: Memory cells are created when B cells are activated without help from T cells
False
True or False: B cells that make IgM antibodies have usually already undergone somatic hypermutation
False. IgM usually made by T-cell independent activation, somatic hypermutation is T-cell dependent
True or False: B cells that are activated without T cell help usually DON’T undergo class switching
True
Which part of the BCR/antibody is changed during somatic hypermutation, Fab or Fc?
Fab
Which antibody type, present in GI mucosal surfaces, is resistant to stomach acid?
IgA
Which antibody class stimulates mast cells to degranulate?
IgE