Lecture 15 Flashcards
What can B cells recognize?
Pathogens in their native form
What can T cells recognize?
Can only recognize pathogens that have been processed/presented by APCs
What does B cell activation require?
requires signals from B cell co receptor
What are the 2 B cell co-receptor signals and which is expressed in all mature B cells?
- CR2
- CD19
-CD19 is expressed in all mature B cells
Explain what the binding of CR1 and C3b leads to?
C3b and CR1 lead to further cleavage of C3b and makes a C3d fragment
-the C3d fragment allows for the CR2 part of the B cell co-receptor to bind to each other
What does CD19 and CR2 increase?
Increases signal & B cell sensitivity to antigen
What does stimulation of BCR and co-receptor result in?
Phagocytosis of BCR antigen complex which leads to MHC II pathway
What additional stimulation do B cells need besides CD19 and C3b
- T Independent (TI-1 and TI-2)
- T Dependent
What is T Independent (TI-1)
Antigen binds to BCR and TLRs
What is T independent (TI-2)
Antigens composed of repetitive epitopes
What is T Dependent (TD)
Antigens are recognized by both T and B cells
How do TI-1 and TD differ?
They differ in their 2nd signal
-TI-1 has a BCR co-receptor signal and an additional receptor like TLR
-TD antigen has a BCR signal and a Tfh cell that brings a 2nd signal CD40/CD40L
T-dependent
-What is the chemical structure
-Does it do isotype switching
-Affinity maturation somatic hypermutation (Yes/no)
-Memory B cells (yes/no)
-proteins
-yes
-yes
-yes
T-Independent
-What is the chemical structure
-Does it do isotype switching
-Affinity maturation somatic hypermutation (Yes/no)
-Memory B cells (yes/no)
-antigens, polysacharides, glycolipids, nucleic acids
-no
-no
-no
Where and how does B and T cell collaboration occur?
Secondary lymphoid organs
True or false: B and T cells are activated by antigens after their interaction
False
-B and T cells are activated by antigens BEFORE their interaction
What changes are made after B cell activation that prepares them for optimal interaction with T cells?
Increased
-proliferation
-B7-1 and 2
-IL-2
-CCR7
What attracts T cells to the B cells area?
CXCR5
What are cognate T cells?
Helper T cells that are primed by dendritic cells that present the SAME antigen peptide that the B cells present
What is linked recognition?
B cell that is activated by helper T cells that are physically linked
-doesn’t need to be the same epitope it just needs to be physically linked to same part of molecule
Are helper T cells cognate T cells?
yes
What are haptens?
A small molecule that only has an immune response when attached to a large carrier protein
Can haptens induce an antibody response on their own?
No they are too small and need to be on a carrier to have an immune response
What is the primary focus of clonal expansion and where does it happen?
FIrst wave of antibody (IgM) response
-occurs in medullary cords
-Cognate pairs migrate to medullary cords then differentiate & make IgM
What is the secondary focus for clonal expansion and where does it happen?
Makes IgG w/ higher affinity
-occurs in germinal center
