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Flashcards in L10 Deck (30)
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1

What Ab dominates primary exposure response to antigen? Secondary exposure?

Primary - IgM
Secondary - IgG or whatever isotype was selected for that pathogen in making memory cells (parasitic worms = IgE)

2

What parts of somatic diversification of B cells happens at the bone marrow? Describe it.

VDJ Recombination
- immature B cells ONLY
- RAG 1/2
- Antigen INDEPendent
1. Heavy chain recomb (allelic exclusion if needed)
2. Light chain (receptor editing if needed)

3

What parts of somatic diversification of B cells happens in secondary lymph organs?

1. Somatic hypermutation
2. Class switch recombination
- Both AID dependent
- MATURE B cells only
- Antigen dependent

4

What is SHM?

= affinity maturation
Point mutations made to heavy or light chain VARIABLE regions
- Where CDRs are coded

5

What is CSR?

= isotype switching
Recombination of HEAVY C genes

6

What chemokine receptor gets upregulated in naive B cells for movement to secondary lymph organs?

CCR7

7

What chemokine receptor gets upregulate in B cells to move into circulation/out of lymph organs?

CXCR5

8

What is the difference between how DC in T cell zones vs FDCs are made?

DC in T cell zones - from hematopoietic precursors
FDC - derived @ lymph node

9

What is the TAPPA receptor on B cells? What happens when this is bound?

CD19 + CD81 + CR2 (CD21)
Complement receptor
Signals via PI3 kinase
Lowers threshold of activation for B cell

10

Which cell surface molecule is distinguishing for B cells?

CD19

11

Which complement does CR2 bind?

3d & i3b

12

What 3 things happen after a B cell binds its BCR in the periphery?

Acts as an APC - phagocytosis of receptor + antigen
1. Mitosis --> clonal expansion
2. ↑CCr7 to move to lymph nodes
3. Low level IgM secretion

13

Why are antigen-specific B cells more likely to receive help from antigen-specifc T cells?

CONCENTRATION EFFECT
APC property of B cell to present on MHC2

14

How do you mount an immune response with memory against carbohydrates?

Couple with protein carrier
Alone would get B cell stimulation - but no memory

15

What is the difference between a primary vs secondary lymphoid follicle?

Secondary has germinal center!

16

How do Ab-antigen-complement complexes stimulate a response in the lymph node?

Enter via subcapsular sinus
Macrophages with CR3 bind iC3b molecules
Macrophages phagocytose the complex - present to naive B cells in follicle
Naive TAPPA complex binds
Passes complex to FDCs - present antigen on Fc gamma receptor or CD21
Antigen binds specific B cell

17

What happens once a specific B cell has bound an antigen-complement complex presented by FDC?

↑CCR7 to move to T/B border
↑CXC5 production (chemokine) to pull the T cells to the border too
↑CD40 expression for co-stimulation

18

What are the 2 paths that a B cell can take after meeting a T cell at the follicle border?

1. T cell saw B cell with high affinity receptor - good to go! Become a plasma cell and secrete those Abs
2. T cell saw B cell that needs a better BCR
- ↑CCR7 --> back into germinal center
- CSR & SHM

19

What 2 signals are needed to determine the recombination fate of B cells needing more maturity?

CD40L & appropriate cytokine
Upregulates AID
Cytokines det which switch boxes open for recomb of VDJ gene

20

What cytokine induces IgG B cells?

IFN gamma

21

What is the primary role of IgGs?

Opsonization for phagocytosis

22

What is the primary role of IgM?

Complement activation

23

What cytokine induces IgE B cells?

IL4

24

What cytokine induces IgA B cells?

TGF beta - those produced by mucosal tissues

25

What is the germinal center reaction?

@ light region of germinal center
Switched B cells present new receptor to FDCs to see if they pass the self test
Yes --> plasma/memory cells
No - anergy/apoptosis

26

What are centroblasts?

Dark region of germinal center
Where B cells are undergoing SHM and CSR
Cell division!!!

27

What are centrocytes?

Where B cells in germinal center have stopped dividing
Undergoing the germinal center reaction

28

What causes type 2 hyper IgM syndrome? Give symptoms.

AID deficiency due to inactivating mutation
Symptoms: repeated bacterial infections

29

WHAT IS THE CLASSIC HISTO FINDING for type 2 hyper IgM syndrome?

Histo: ENLARGED GERMINAL CENTERS
- Send B cells here for SHM & CSR but can't do anything about it!
- Only get primary IgM response from B cells - no class switching

30

What causes type 1 hyper IgM syndrome? Give symptoms? What is the primary histo finding?

CD40/CD40L mutations
No T-B cell interaction --> never send anything to GC
*NO GERMINAL CENTER FORMATION ON HISTO*
High IgM but no other isotypes
Same symptoms as type 2 - repeated bacterial infections