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Flashcards in BC - L2 Deck (17):
1

Topics?

Distribution of lymphocytes
Immune response
early stages of B & T cell activation
Activities with the GC
HIGM
CVID

2

Describe B cell development in terms of location

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3

Describe the distribution of lymphocytes

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4

possible reasons for a failure to respond to an infection?

no B-lymphocytes (agammaglobulinaemia w/o B-cells)
no CD4 T-lymphocytes (severe combined immunodeficiency)
no B or T lymphocytes (severe combined immunodeficiency)
no signal from the CD4 to the B Cell
failure of the B cell to respond to T-cell signals
failure of the B cell to respond antigen

5

immune response and memory response to a protein antigen?

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6

early stage of B & T cell activation?

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7

Activities within GC?

proliferation (T cell driven)
isotype switching
somatic hypermutation
affinity maturation
memory formation

8

Describe isotype switching (including layout of heavy gene)

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9

Role of AID (how it works)?

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10

What targets AID to specific S regions?

T cell derived signal IL-4

11

Why make IgM and then change to IgG?

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12

Describe somatic hypermutation

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13

How does AID initiate somatic hypermutation?

converting cytosines in DNA to Uracil within IgV Genes, at both H and L chain loci

U is recognised as foreign in DNA by enzyme UNG (uracil N- glycosylase) and removed, creating a gap that is repaired by Base Excision Repair involving an error-prone Pol

the U/G mismatch is repaired by mismatch repair (MMR) pathway involving MSH2/6 (mismatch recognition heterodimer), mismatch Exonuclease 1 and error-prone Pol

U is not removed but replicated over = passive mutation

14

Describe the B-T cell help pathway
List possibel defects

blocking the NFkB pathway blocks:
B-cell proliferation
class switching and V gene mutation (no AID)
defects in AID and DNA repair also block CSR and SHM

15

Molecular basis of hyper-IgM immunodeficienies?

CD40L (CID)
CD40
AID
AID-cter
UNG
NFkB signalling

16

CVID?

most common type of PID
hypogammaglobulinaemia
genetic basis

17

common CVID mutations?

ICOS
CD19
TACI