B Flashcards

1
Q

Key phases of infection

A
  1. establishment of infection
  2. induction phase - adaptive threshold
  3. effector phase
  4. Memory - threshold lowered when reencountered
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2
Q

Why does adaptive immune response take time

A

requires cell to move, interact & produce cytokines: effector.
APC takes up antigen, travels from site of infection to lymph node: activates T cells -> activate B cells. Both return to site of infection via circulation

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3
Q

where does T/B precursor rearrange receptor genes

A

Thymus: -ve & ive selection of naive cell

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4
Q

Immature T cells can be

A

receive survival signals - if recognise MHC

clonal deletion: interact strongly w/self

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5
Q

where do mature T/B cells encounter antigen

A

peripheral lymphoid: are activated

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6
Q

MHC-I recognises which kind of cells

A

CD8+ intracellular antigens e.g. virus (endogenous)

- all of self except RBC can present to CD8+

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7
Q

MHC-II recognises which kind of cell

A

CD4+ extracellular: extracellular bacteria, soluble antigens, virus particles. e.g. dendritic cells/ pinocytosis

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8
Q

How does MHC polymorphism affect antigen recognition by T cells through

A

influencing peptide binding & contacts between T cell + MHC

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9
Q

Th1 induces & is induced by

A

Macrophage activation & delayed type hypersensitivity

induced by: IL-12, IFNy, IL-18

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10
Q

Th2 induces & is induced by

A

antibody production & allergic response.

induced by: IL-4, IL-5

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11
Q

what signals do APC deliver to naive T cells

A
  1. activation 2. survival 3. Differentiation
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12
Q

B cell activation

A

Antigen recognised by BCR -> antigen internalised via receptor mediated endocytosis -> peptides presented to MHC
if CD4 also recognises antigen will provide help via CD4 & cytokines

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13
Q

what provides flexibility to antibody

A

Hinge region of Ig when binding to multiple antigens

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14
Q

what happens when IgE recognises antigen

A

variable region of IgE binds antigen & constant region binds FCeR1 - crosslinks receptors = degranulation of mast cells

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15
Q

3 main functions of antibodies protection

A
  1. neutralisation: antibody binds & blocks toxin from
    cell receptor
  2. opsonisation: antibodies bind to bacterium, label it foreign. Fc region antibody binds Fc phagocytic cell & is digested.
  3. complement: recognises certain features of microbial surfaces allowing it to be lysed and ingested.
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16
Q

Central tolerance involves

A

occurs at young age
+ve selection: cells lacking affinity - dont receive survival signals
-ve: removes T cells which bind too strongly, ensure autoreactive deleted by apoptosis: clonal deletion
Fates: 1. death by neglect 2. +ve selection 3. clonal deletion

17
Q

describe Peripheral tolerance

A

occurs throughout lifetime in periphery
ensure self-reactive T&B cells which escaped central tolerance don’t cause autoimmune disease
e.g. antigens not present in thymic selection: sex hormones & food antigens, autoantigen, good bacteria

18
Q

which mechanisms of peripheral tolerance exist to ensure mature T cells don’t activate inappropriately

A
  1. co stimulation signal & specific signals: activates T cell
  2. specific signal alone (MHC bound) - T cell becomes anergic
  3. co stim signal alone - no effect on T cell (no antigen)
    B. CTLA-4 binds to B7 more than CD8: inhibits T activity
    C. Treg: IL-10 & TGFb: inhibit self reactive T cells
19
Q

What happens if T cells escapes clonal deletion

A

can become activated

  • to non harmful antigens: allergy
  • to self antigens: autoimmunity
20
Q

What happens when tolerance fails

A

immunodeficiency (immune evasion by pathogens)
1y - genetically acquired
2y - infections, metabolic dysregulation, therapeutically induced