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POM 4 Immunology > 4.5 Lymphocytes > Flashcards

4.5 Lymphocytes Flashcards

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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
What is the Tfh class of CD4 T helper cell?
Pro-**antibody**
26
What does Th2 do specifically?
Involved in B cell **class switching to IgE** For allergic reactions and parasitic infection
27
What does Th1 produce?
IL-1, 2, 3, 12 IFN-gamma TNF-alpha
28
Which CD4 T helper cell class includes interleukins 4, 5 and 13?
Th2
29
Which class of CD4 T cells includes interleukins 6, 17 and 23?
Th17
30
Which class of CD4 T cells includes interleukin 21?
Tfh
31
In what way do T helper cells help B cells?
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
32
How do CD8 cytotoxic T cells kill pathogens or infected cells?
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
What do cytotoxic T cells release when they want to kill an infected cell?
Perforin, granzymes, granulysin
34
What does granzymes cause and how do they enter cells?
Cause apoptosis Enter through pores created by perforin
35
What two regions is the TCR made up of?
Variable region (top part) Constant region (bottom region)
36
What is an epitope?
The part of the antigen which the antibody binds to
37
What makes up the epitope which the T cell receptors recognize?
The MHC
38
What are MHC molecules?
Glycoproteins which bind and display pathogen peptide fragments on APCs for T cell recognition
39
How do MHC I and MHC II differ?
MHC I processes **extracellular pathogens** in the **cytosol** and present to **CD8** MHC II processes **intracellular pathogens** in **endosomes** and present to **CD4**
40
What is the structure of MHC 1?
Has a single variable alpha chain and a common beta-microglobulin
41
What is the structure of MHC 2?
Has two chains, alpha and beta
42
What cells are MHC I and MHC II present on?
MHC I – all nucleated cells MHC II – dendritic cells, B cells, macrophages
43
Which MHC will interact with TCR?
MHC II
44
What gene codes for MHC?
HLA gene
45
How is MHC expressed?
Co-dominant
46
What is meant by the fact that MHC is polygenic?
MHC contains 3 class I and 3 class II loci Thus everyone has MHC molecules with different peptide binding specificities
47
What is meant by the fact that MHC is highly polymorphic?
There are multiple variants or alleles of each gene within the population
48
What is a BCR?
A surface bound Antibody
49
What does the BCR do?
It encodes the antibody which the B cell will eventually make
50
What two pathways activate B cells?
Thymus dependent – T cells Thymus independent – antigens
51
Explain the thymus dependent pathway of B cell activation?
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
Describe the activation of B cells via the thymus independent pathway?
Thymus independent antigens directly activate B cells Second signal is sent by PAMPs (e.g. LPS)
53
What are thymus independent antigens and how do they work to induce antibody production?
They are antigens which cross link the BCR on B cells Only **IgM** antibodies are produced and **no memory cells**
54
What type of molecules are thymus independent antigens?
Highly repetitive molecules e.g. polysaccharides
55
What happens after B cells are activated?
Clonal expansion and clonal selection
56
What is clonal expansion of lymphocytes?
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
Which antibody type has the highest affinity and is most abundant?
IgG
58
Which antibody type is produced first?
IgM
59
Which antibody type is produced in allergic disease?
IgE
60
Describe the structure and function of IgG antibodies
Monomer Neutralisation, opsonisation, precipitation Pass through placenta to give baby **passive immunity**
61
Describe the structure of IgA antibodies and where they are found
Dimer Saliva, skin, GI mucosa, breast milk
62
Describe the structure and function of IgM antibodies
Pentamer and monomer (exists as BCR) Monomer activates complement for **MAC formation and opsonisation** Pentamer binds multiple antigens (e.g. mismatched transfusion reaction)
63
How many epitopes does the IgM pentamer have?
10
64
Describe the structure and function of IgE antibodies
Monomer **Anaphylaxis** (type I hypersensitivity) Tags **parasites** for **eosinophils** to destroy
65
Describe the structure and function of IgD antibodies
Monomer Acts as BCR
66
What part of the antibody determines its antigen-binding specificity?
The variable domains of the heavy and light chains
67
What are the three core functions of antibodies?
1. Neutralization 2. Opsonization 3. Complement activation
68
Describe the process of antibody neutralization?
Antibodies bind to viruses/bacterial toxins, so they cannot go and damage other cells
69
Describe the process of opsonization?
Antibodies coat a bacterium to better enable a phagocytic cell to ingest and destroy it
70
How do antibody opsonised bacterium bind to phagocytic cells?
Fc receptors on phagocytic cell binds to Fc region of antibody
71
Describe the process of complement activation?
Complement proteins on bacterium can be recognized by complement receptors on phagocytes Allows for stimulated phagocytosis and the bacterium to be destroyed
72
Increasing the numbers of what T helper cell will help with an autoimmune disorder?
Treg cells
73
What is somatic hypermutation?
Switching from IgM to IgG production Producing antibodies of **higher affinity**
74
What can lipopolysaccharides provide for B cell activation?
Primary and secondary stimuli
75
List the functions of interleukins 1-6 **HOT T-BO IS A CUTIE**
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
What does IL-8 stimulate?
Chemotaxis
77
What is IL-10 involved in and what class of CD4 T cell produces it?
Anti-inflammatory response Produced by Treg
78
What does IFN-gamma do?
Activates macrophages
79
What does TNF-alpha do?
Cytotoxic to tumor cells

POM 4 Immunology (14 decks)

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