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
Which antibody class is the smallest and thus able to cross the placenta?
IgG
Which antibody class is usually the first to be produced?
IgM
Which antibody class is the best at fixing complement?
IgM (IgG second place)
Which antibody class is secreted in milk?
IgA (makes it to baby gut lining)
Why do allergens require at least 2 exposures to cause an allergic or anaphylactic reaction?
On first exposure IgE is produced. On subsequent exposures, IgE is “primed” to degranulate mast cells
Anaphylaxis is associated with what type of antibody? What type of white blood cells?
IgE; Mast cells
Which antibody type marks cells for killing by NK cells in antibody-dependent cellular cytotoxicity?
IgG
If you have hypergammaglobulinemia, you have an excess of ________ in your blood.
IgG
What is the most abundant antibody found in the BODY?
IgA
What is the most abundant antibody found in the BLOOD?
IgG
Which complement molecule does IgM bind first to trigger the “classical” complement pathway?
C1
Which Ab class is typically thought of as the “first line” defense against bacteria and viruses?
IgM (first produced, interacts with complement and innate immune system)
What advantage does antibody binding bring to the complement system?
Can bind to a much broader range of surfaces and molecules on antigens/invaders
What are the names (letters) for the 3 portions of the heavy chains of the Fab? What are the 2 portions of light chains?
V, D, J for heavy chains; V&J for light chains
These antibodies are the redheaded stepchild class; there aren’t very many of them, and no one is really sure what they do.
IgD
Which proteins of the antibody make up the “prongs” of the “Y”? Which part makes up the tail?
Light and heavy chains (Fab); Fc
T-cell independent activation of B-cells requires an antigen with a _______ epitope
repeated/repetitive
What are the three major stages of B cell maturation?
- Class switching
- Somatic Hypermutation
- Career Decision
An antigen that binds and clusters B cell surface molecules together that are NOT BCRs is called a ________.
Mitogen
True or False: Polyclonal expansion of B cells by a mitogen is actually an example of the immune system gone wrong.
True. Some parasites express mitogens to “distract” the immune system from killing them in a more targeted manner.
CD40 is found on the ____ cell, and CD40L is found on the ____ cell.
B cell; T helper cell
True or False: The decision of whether an invader is dangerous or not is usually made by the adaptive immune system
False. Opsonization and danger signals, markers of danger, are usually functions of the innate immune system
True or False: complement receptor can decrease the threshold signal necessary to activate a B cell by 100 fold.
True. Called a “co-receptor”
B cells that have not been exposed to an antigen are known as _______
Naive/Virgin
True or False: each B cell has about 1,000 BCRs on its surface
False; the number is closer to 100,000
The tiny portion of cognate antigen that a BCR actually binds to is called its __________.
Epitope
True or False: each mature B cell produces only one type of antibody or BCR
True
True or False: The diversity of genes and proteins that make up the heavy and light chains of the Fab portions of antibodies are so diverse that they can likely recognize any organic molecules that exist
True
True or False: If, during gene rearrangement, the heavy and light chains of the BCR don’t align properly, the genes continually rearrange within the cell until proper alignment is achieved
False. The cell undergoes apoptosis
The production of memory B cells with daughter cells which display improved binding to the antigens that activated the original naive B cell is called _______.
Clonal selection (happens as a result of somatic hypermutation)
