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POM 4 Immunology > 4.5 Lymphocytes > Flashcards

4.5 Lymphocytes Flashcards

1
Q

What does adaptive immunity involve?

A

Expansion of antigen-specific lymphocytes and production of memory cells for long lasting immunity

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2
Q

When is an adaptive immune response generated?

A

Once the pathogen overwhelms innate defense mechanisms

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3
Q

What major event occurs in the peripheral lymphoid organs/tissues to initiate the adaptive immune response?

A

B or T lymphocytes encounter antigens for which their receptors have specific reactivity to

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4
Q

What is an antigen?

A

A molecule which is recognized by the specialised lymphocyte receptors, which acts to induce an adaptive immune response

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5
Q

State 3 characteristics of the adaptive immune response

A

Has memory

Needs time to develop

Improves efficacy of innate immune response

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6
Q

How is antigen receptor diversity generated in the adaptive immune response?

A

Each BCR chain is coded for by multigene clusters on different chromosomes

During B cell maturation, these genes are brought together and rearranged in VDJ recombination

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7
Q

What are the chains of the BCR receptor?

A

Kappa, lambda and heavy chain

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8
Q

Where does B cell maturation occur?

A

In the bone marrow

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9
Q

What are some problems with VDJ recombination to generate the high number of BCRs we need?

A

Autoimmunity – producing BCRs and TCRs that react with self-peptides

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10
Q

What is immunological memory?

A

Where memory lymphocytes exist in the blood that are able to recognize and bind to the same antigen upon subsequent infections and therefore induce an immune response

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11
Q

What are characteristics of a a secondary immune response?

A

Faster and larger response

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12
Q

What are the two primary cells involved in the adaptive immune response and which response are they involved in?

A

T cells – cell mediated
B cells – humoral

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13
Q

What are the differences between B cells and T cells? LAMAR

A

Location – B cells outside lymph nodes, T cells inside
Antibodies – B cells only
Maturation – B cells in bone marrow, T cells in thymus
Activation – T cells activate B cells
Receptors – T cells CD4 and CD8, B cells different

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14
Q

What are the three kinds of T cells?

A

Regulatory, helper, killer

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15
Q

What happens when an antigen binds to a TCR?

A

T cell proliferates and differentiates into T effector cells

Either killer, helper or regulatory

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16
Q

What are cytotoxic T cells?

A

They kill virus infected cells or intracellular pathogens that bear the specific antigen

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17
Q

What do helper T cells do?

A

Produce cytokines which activate functions of other cells

E.g. signals to B cells to produce antibodies

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18
Q

What do regulatory T cells do?

A

Suppress lymphocyte activity and limit immune response to reduce damage

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19
Q

Which CD do T helper cells have?

A

CD4

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20
Q

Which CD do T killer cells have?

A

CD8

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21
Q

What is the Th1 class of CD4 T helper cell?

A

Pro-inflammatory, boosts immune response

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22
Q

What is the Th2 class of CD4 T helper cell?

A

Pro-allergic, boosts multicellular response

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23
Q

What is the Th17 class of CD4 T helper cell?

A

Pro-inflammatory, controls bacterial or fungal infection

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24
Q

What is the Treg (Th0) class of CD4 T helper cell?

A

Anti-inflammatory, limits immune response

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25
Q

What is the Tfh class of CD4 T helper cell?

A

Pro-antibody

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26
Q

What does Th2 do specifically?

A

Involved in B cell class switching to IgE

For allergic reactions and parasitic infection

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27
Q

What does Th1 produce?

A

IL-1, 2, 3, 12
IFN-gamma
TNF-alpha

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28
Q

Which CD4 T helper cell class includes interleukins 4, 5 and 13?

A

Th2

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29
Q

Which class of CD4 T cells includes interleukins 6, 17 and 23?

A

Th17

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30
Q

Which class of CD4 T cells includes interleukin 21?

A

Tfh

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31
Q

In what way do T helper cells help B cells?

A

Surface proteins secrete cytokines so B cells proliferate into plasma and memory cells

Trigger immunoglobulin class switching to increase the antibody’s affinity to the antigen

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32
Q

How do CD8 cytotoxic T cells kill pathogens or infected cells?

A

Infected cells display viral peptides on MHC I

CD8 recognises non-self MHC, releases contents of granules

Perforin creates pores in membrane, granzymes trigger cascade leading to cell death

33
Q

What do cytotoxic T cells release when they want to kill an infected cell?

A

Perforin, granzymes, granulysin

34
Q

What does granzymes cause and how do they enter cells?

A

Cause apoptosis

Enter through pores created by perforin

35
Q

What two regions is the TCR made up of?

A

Variable region (top part)

Constant region (bottom region)

36
Q

What is an epitope?

A

The part of the antigen which the antibody binds to

37
Q

What makes up the epitope which the T cell receptors recognize?

A

The MHC

38
Q

What are MHC molecules?

A

Glycoproteins which bind and display pathogen peptide fragments on APCs for T cell recognition

39
Q

How do MHC I and MHC II differ?

A

MHC I processes extracellular pathogens in the cytosol and present to CD8

MHC II processes intracellular pathogens in endosomes and present to CD4

40
Q

What is the structure of MHC 1?

A

Has a single variable alpha chain and a common beta-microglobulin

41
Q

What is the structure of MHC 2?

A

Has two chains, alpha and beta

42
Q

What cells are MHC I and MHC II present on?

A

MHC I – all nucleated cells
MHC II – dendritic cells, B cells, macrophages

43
Q

Which MHC will interact with TCR?

A

MHC II

44
Q

What gene codes for MHC?

A

HLA gene

45
Q

How is MHC expressed?

A

Co-dominant

46
Q

What is meant by the fact that MHC is polygenic?

A

MHC contains 3 class I and 3 class II loci

Thus everyone has MHC molecules with different peptide binding specificities

47
Q

What is meant by the fact that MHC is highly polymorphic?

A

There are multiple variants or alleles of each gene within the population

48
Q

What is a BCR?

A

A surface bound Antibody

49
Q

What does the BCR do?

A

It encodes the antibody which the B cell will eventually make

50
Q

What two pathways activate B cells?

A

Thymus dependent – T cells
Thymus independent – antigens

51
Q

Explain the thymus dependent pathway of B cell activation?

A

BCR recognises antigen

Antigen internalised and degraded into peptides

Peptides displayed on MHC II, complex recognised by CD4 T cells

Tfh produces cytokines and co-stimulatory markers, activating B cells

52
Q

Describe the activation of B cells via the thymus independent pathway?

A

Thymus independent antigens directly activate B cells

Second signal is sent by PAMPs (e.g. LPS)

53
Q

What are thymus independent antigens and how do they work to induce antibody production?

A

They are antigens which cross link the BCR on B cells

Only IgM antibodies are produced and no memory cells

54
Q

What type of molecules are thymus independent antigens?

A

Highly repetitive molecules e.g. polysaccharides

55
Q

What happens after B cells are activated?

A

Clonal expansion and clonal selection

56
Q

What is clonal expansion of lymphocytes?

A

Activated B cells divide and give rise to clones with identical progeny and MHC

This maintains antigen specificity as the progeny differentiate into effector cells

57
Q

Which antibody type has the highest affinity and is most abundant?

A

IgG

58
Q

Which antibody type is produced first?

A

IgM

59
Q

Which antibody type is produced in allergic disease?

A

IgE

60
Q

Describe the structure and function of IgG antibodies

A

Monomer

Neutralisation, opsonisation, precipitation

Pass through placenta to give baby passive immunity

61
Q

Describe the structure of IgA antibodies and where they are found

A

Dimer

Saliva, skin, GI mucosa, breast milk

62
Q

Describe the structure and function of IgM antibodies

A

Pentamer and monomer (exists as BCR)

Monomer activates complement for MAC formation and opsonisation

Pentamer binds multiple antigens (e.g. mismatched transfusion reaction)

63
Q

How many epitopes does the IgM pentamer have?

A

10

64
Q

Describe the structure and function of IgE antibodies

A

Monomer

Anaphylaxis (type I hypersensitivity)

Tags parasites for eosinophils to destroy

65
Q

Describe the structure and function of IgD antibodies

A

Monomer

Acts as BCR

66
Q

What part of the antibody determines its antigen-binding specificity?

A

The variable domains of the heavy and light chains

67
Q

What are the three core functions of antibodies?

A
  1. Neutralization
  2. Opsonization
  3. Complement activation
68
Q

Describe the process of antibody neutralization?

A

Antibodies bind to viruses/bacterial toxins, so they cannot go and damage other cells

69
Q

Describe the process of opsonization?

A

Antibodies coat a bacterium to better enable a phagocytic cell to ingest and destroy it

70
Q

How do antibody opsonised bacterium bind to phagocytic cells?

A

Fc receptors on phagocytic cell binds to Fc region of antibody

71
Q

Describe the process of complement activation?

A

Complement proteins on bacterium can be recognized by complement receptors on phagocytes

Allows for stimulated phagocytosis and the bacterium to be destroyed

72
Q

Increasing the numbers of what T helper cell will help with an autoimmune disorder?

A

Treg cells

73
Q

What is somatic hypermutation?

A

Switching from IgM to IgG production

Producing antibodies of higher affinity

74
Q

What can lipopolysaccharides provide for B cell activation?

A

Primary and secondary stimuli

75
Q

List the functions of interleukins 1-6
HOT T-BO IS A CUTIE

A

1 – hot, fever
2 – T cell stimulation
3 – bone marrow stimulation
4 – IgE class switching from IgM
5 – IgA, eosinophils
6 – acute phase protein production

76
Q

What does IL-8 stimulate?

A

Chemotaxis

77
Q

What is IL-10 involved in and what class of CD4 T cell produces it?

A

Anti-inflammatory response

Produced by Treg

78
Q

What does IFN-gamma do?

A

Activates macrophages

79
Q

What does TNF-alpha do?

A

Cytotoxic to tumor cells

POM 4 Immunology (14 decks)

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