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Principles of Medicine (POM) - Block 2 > Lecture 15: Lymphocytes > Flashcards

Lecture 15: Lymphocytes Flashcards

1
Q

Why do we need adaptive immunity?

A
  • specificity to clear infections

- memory to protect against pathogens we’ve already encountered

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2
Q

What are memory responses characterised by?

A
  • more rapid and heightened immune reactions that serve to eliminate pathogens fast and prevent disease
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3
Q

What are the 2 types of adaptive immune response?

A
  • humoral(B cells)

- cell-mediated (T cells)

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4
Q

How do T cells recognise antigens?

A

They recognise linear epitopes in context of MHC (specific string of amino acids)

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5
Q

How do B cells/antibodies recognise antigens?

A

Antibodies recognise structural epitopes(3D structure)

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6
Q

What are antigens?

A

Molecules that act to induce an adaptive immune response

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7
Q

What is an epitopes?

A

The region of an antigen which the receptor binds to

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8
Q

How is antigen receptor diversity generated?

A

By recombination

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9
Q

What is the process called when during B cell maturation, gene segments are rearranged and brought together?

A

Immunoglobulin Gene rearrangement - generates diversity of lymphocyte repertoire

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10
Q

What does the T cell receptor recognise?

A

Antigen fragments presented by other cells

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11
Q

What does the major histocompatibility complex do (MHC)?

A

Presents antigens to T cells

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12
Q

What does it mean when you say MHC is polygenic?

A

It has several class I and class II loci

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13
Q

Describe MHC class I?

A
  • on all nucleated cells, although at various levels

- levels may be altered during infection, or by cytokines

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14
Q

Describe MHC class II?

A
  • normally only on ‘professional’ antigen regulating cells

- may be regulated by cytokines

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15
Q

What are the 2 families of T cells?

A

CD4 (helper) and CD8 (killer) -

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16
Q

How are the 2 T cell families defined?

A

Defined by cell surface molecules CD4 (which binds MCHII) and CD8 (which binds MCHI)
They are also functionally different

17
Q

What type of a pathogen/antigen uses CD4 T cells?

A

Extracellular pathogen/antigen

18
Q

What type of pathogen/antigen uses CD8 T cells?

A

Intracellular pathogen/antigen

19
Q

Where are intracellular antigens processed?

A

Cytosol

20
Q

Where are extracellular antigens processed?

A

Endosomes

21
Q

Each BCR receptor chain is encoded by what?

A

separate multigene families on different chromosomes

22
Q

How do CD8 (cytotoxic) T cells kill their targets?

A

By programmed cell death (apoptosis)

23
Q

What is apoptosis characterised by?

A

Fragmentation of nuclear DNA

24
Q

What is released after target recognition?

A

Cytotoxic granules which contain perforin, granzymes and granulysin (poisons)

25
Q

What do T helper cells produce?

A

Cytokines (family of inflammatory mediators)

26
Q

What do Th1 cells do?

A

Pro-inflammatory

- boost cellular immune response

27
Q

What doTh2 cells do?

A

Proxallergic

Boost multicellular response

28
Q

Describe the structure of an antibody.

,

A

It has 2 heavy chains and 2 light chains joined together by disqualified bonds and there is a variable region and a constant region

29
Q

What are the 3 core protective roles of antibodies?

A
  • neutralisation
  • opsonisation
  • complement activation
30
Q

B cells are the…?

A

Effector cells of humoral immunity

31
Q

What does the unique binding site of the BCR bind to?

A

Portion of antigen called antigenic determinant or epitope

32
Q

What 2 accessory signals do naive B cells require?

A
  • directly from microbial constituents

- from a T helper cell

33
Q

What are the 2 pathways by which antibody production can be be achieved by B cells?

A
  • T helper cell thymus dependent pathway

- microbial thymus independent

34
Q

What do thymus-independent antigens do?

A

Directly activate B cells without help of T

35
Q

What structure does the bacteria often need to have for thymus-independent antigens?

A

Repetitive structure

36
Q

What second signal is required for thymus-independent antigens?

A

Microbial constituent or by an accessory cell

37
Q

What type of antibodies does the thymus independent pathway produce?

A

Only IgM, no memory

38
Q

What type of antibodies are produced by B cells in the thymus-dependent pathway?

A

All IgG classes, memory

39
Q

Outline the 5 steps to B cell activation by T Cells

A
  1. Membrane bound BCR recognises antigen
  2. Receptor bound antigen is internalised and degraded into peptides
  3. Peptides associate with ‘self’ molecules (MHC class II) and expressed at cell surface
  4. Complex recognised by matched CD4 T helper cell
  5. B cell activated

Principles of Medicine (POM) - Block 2 (12 decks)

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