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Jack 2a > Immunology > Flashcards

Immunology Flashcards

1
Q

Describe 5 points on Innate immunity

A 
Non-specific 
Resistance is not improved by repeat infection (no memory)
Rapid response (hours)
Instinctive
Cells are phagocytes and NK cells
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2
Q

Describe 5 points on adaptive immunity

A 
It is specific
Requires lymphocytes
Antibodies involved
Resistance is improved by repeat infection (memory)
Slower response (days-weeks)
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3
Q

Describe some points of neutrophils

A

65% of WBC’s
Lifespan: 6-12hrs
Plays an important role in innate (phagocytosis)
Contain primary and secondary granules
Can kill microbes by secreting toxic substances (superoxides)

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4
Q

Describe some points of monocytes

A

Make up 5% of WBCs
Lifespan: Months
Play important role in innate (phagocytosis) and adaptive (Antigen presentation)
Differentiate into macrophages in tissues
Main role is to remove anything foreign
Have lysosomes containing peroxidase that can kill microbes

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5
Q

Describe some points of macrophages

A

Lifespan: Months/years
Different name in different tissues
Play important role in innate (phagocytosis) and adaptive (antigen presentation) to T cells
Most often the first line of non-self recognition
Remove foreign microbes and dead host cells
have lysosomes containing peroxidase

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6
Q

What 3 different receptors do these innate cells have?

A

Fc receptors for Fc region of antibodies
PRRs (TLRs)
Complement receptors

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7
Q

What is in each of the neutrophil granules (primary/secondary)?

A

Primary lysosomes - contain myeloperoxidase, acid hydrolases and defensins - combine with phagosomes containing microbes
Secondary granules contain lactoferrin and lysozyme

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8
Q

Describe some points of eosinophils

A

Make up 5% of WBCs.
Lifespan: 8-12 days
Mainly associated with parasitic infections and allergic reactions
Degranulation activates neutrophils (MBP) and induces histamine release from mast cells, also promotes bronchospasm

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9
Q

Describe some points of basophils

A

2% of WBCs
Lifespan: 2 days
Very similar to mast cells but circulate
Express high affinity IgE receptors, binding of which results in degranulation releasing histamine (allergic reaction)
Mainly involved in parasitic infections and allergic reactions

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10
Q

Describe some points of mast cells

A

Resisdent in tissues (not circulating)
Similar to basophils.
Express high affinity IgE receptors, binding results in degranulation releasing histamine
Mainly involved in parasitic infections and allergic reactions

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11
Q

Describe some points of T-lymphocytes

A 
10% of WBCs
Lifespan: Hours-years
Major role in adaptive immunity. 
Originate from bone marrow but mature in the thymus 
Recognise antigen displayed by APCs and bind via TCRs
This produces cytokines
Specifically kill infected host cells
Found in blood, lymph nodes and spleen
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12
Q

What are the 4 main types of T lymphocytes?

A

Th1
Th2
Cytotoxic
T reg

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13
Q

Describe some points of Th1 cells

A

Express CD4 receptors - bind to MHC1 and antigen
Help immune response for intracellular pathogens
Also help B cells make antibodies
Activate macrophages and NK cells
help development of cytotoxic T cells

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14
Q

Describe some points of Th2 cells

A

Express CD4
Help produce antibodies against extracellular pathogens
Help B cells make antibodies
Activate macrophages and natural kill cells
Help development of cytotoxic T cells

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15
Q

Name some differences between Th1 and Th2 cells (difference in cytokines and function)

A

Th1 produce IFN-gamma, Th2 produce IL-4

Th1 cells promote the effector functions of innate immune cells such as macrophages and dendritic cells
Th2 cells provide help for antibody formation

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16
Q

Describe some points of cytotoxic T cells

A

Express CD8 which binds to MHC1 specifically

Can kill infected host cells directly

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17
Q

Describe some points of Tregs

A

Regulates immune responses and acts to dampen them

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18
Q

Name primary, secondary and tertiary lymphoid organs

A

Primary - Bone marrow and thymus
Secondary - lymph nodes, spleen and tonsils
Tertiary - abnormal lymph nodes forming at site of chronic infection

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19
Q

Describe some points on B lymphocytes

A

Make up 15% of WBCs
Lifespan: hours to years
These originate and mature in the bone marrow
Recognise antigens on APCs
Express membrane bound antibody on cell surface
Differentiates into plasma cells that then makes antibodies

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20
Q

Describe NK cells

A

Accounts for 15% of lymphocytes
Expresses CD56
Found in spleen and tissues
Recongise and kill host cells (virus/cancer) via apoptosis

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21
Q

Describe dendritic cells

A

Professional antigen presenting cells
Only these cels have the capacity to induce a primary immune response in the inactive or resting T lymphocytes
They produce cytokines to active B cell differentiation
Found in tissue that has contact with outside environmnet (skin, linings of lungs and intestines)

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22
Q

Very briefly describe how complement works

A

Inactivate precusor turns into enzyme to cleave inactive precursors

The major purpose of the complement pathway is to remove or destroy antigens either by direct lysis or by opsonisation

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23
Q

What 4 things does complement do to help the immune respoonse?

A

Lyse microbes directly using Membrane attack complex
Increase chemotaxis (C3a and C5a)
Enhance inflammation
Induce opsonisation C3b - macrophages have receptors for specific complement proteins

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24
Q

What is the difference between C3a and b or what does a/b indicate?

A

B is the major fragment of a complement protein. It has a site for binding to cell membranes and another for teh enzymatic cleavage of the next complement
A is the minor cleavage fragment and is important to enhance inflammation
C3 is inactive and generally C3b indicates active.

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25
Q

Which 3 pathways is C3 cleaved into C3b?

A

Classical pathway
Alternative pathway
Lectin pathway

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26
Q

Briefly describe the classical pathway

A

Antibody binds to microbe
Activation is antibody dependent
Generally C1 is activated by either IgM or IgG when it binds to the Fc region

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27
Q

Briefly describe the alternative pathway

A

Complement binds to microbe generating active C3 (C3a and C3b) without antibodies. It is activated by microbial cell surfaces.

Thus alternative pathway is responsible for innate defence against invading organisms

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28
Q

What is an antibody?

A

A protein produced in response to an antigen. It is specific.

They are soluble glycoproteins

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29
Q

What is an epitope?

A

The part of the antigen that binds to teh antibody/receptor binding site

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30
Q

What is affinity with regard to antibodies and epitopes?

A

A measure of binding strength between an epitope and an antibody binding site

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31
Q

What do Fab regions and Fc regions do on antibodies?

A

Fab - bind to specific antigens

Fc bind to complement, Fc receptors on phagocytes and NK cells

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32
Q

Describe the basic structure of antibodies

A

2 identical heavy and 2 identical light chains
The heavy chains determine the class of the antibody and physiological function
Variable regions binds antigen (is specific)
Constant are same for antibodies of the same type

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33
Q

Describe IgG

A

Forms the majority of immunoglobulins
Penetrates tissues easily
Is the only Ig to cross the placenta to protect the neonate

IgG usually has a much higher affinity for antigens compared to IgM hence takes longer to appear

34
Q

Describe IgA

A

Makes 15% of Igs

The predominant Ig in mucous secretions (saliva, milk, bronchiolar and genitourinary)

35
Q

Describe IgM

A

Accounts for 10% of Igs.
Mainly found in blood, pentamer so cannot cross the endothelium
Involved in primary response (initial contact with antigen as has lower affinity)
The major function is intravascular neutralisation of organisms. Also has mutliple complement-binding sites

36
Q

Describe IgE

A

Basophils and mast cells express IgE-specific receptor that has high affinity for IgE.
Binding antigen triggers release of histamine by basophils and mast cells
Associated with allergic response and defence against parasites

37
Q

What do antibodies do to help fight off infection?

A

Neutralise toxin by binding (IgG, IgA)
Immobilise motile microbes (IgM)
Increase opsonisation
Activate complement (IgG, IgM) using Fc receptors which activate complement

38
Q

Which cells express Fc receptors for each antibody type (ADEGM)?

A

Phagocytes (IgG, IgA) enhances phagocytosis
Mast cells (IgE) - release of inflammatory mediators
Natural killer cells (IgG) - enhanced killing of infected cells

39
Q

Definition for cytokines

A

Soluble proteins secreted by lymphocytes or macrophages/monocytes
that act as stimulatory or inhibitory signals between cells

40
Q

What is an interleukin and chemokine?

A

A cytokine that acts between cells of the immune system are called interleukins

Those cytokines that induce chemotaxis of leucocytes are called chemokines

41
Q

What are two features common of all cytokines?

A

Short half-lives/Rapid degradation

May affect multiple organs in the body

42
Q

What do interferons do?

What are the 2 types of interferon and which cells secrete them?

A

Induce a state of antiviral resistance in uninfected cells to limit the spread of a viral infection

IFN-alpha and beta are produced by virus-infected cells
IFN-gamma is released by activated Th1 cells

43
Q

What do interleukins do?

A

Can cause cells to divide, differentiate and secrete factors

44
Q

What do colony stimulating factors (CSF) do?

A

Directing the division and differentiation of bone marrow stem cells - the precursors of leukocytes

This controls how many of each cell will be made

45
Q

What do tumour necrosis factors (alpha and beta) do?

A

Mediate inflammation and cytotoxic reactions

46
Q

What are the 2 types of chemokine and what do they do?

A

CXCL - attracts neutrophils (also lymphocytes)

CCL - attracts monocytes, lymyphocytes, eosinophils and basophils

47
Q

What 5 barriers make up innate immunity?

A 
Skin (secretions pH3-5)
Mucous membranes - saliva, mucous, cilia, commensal colonies
Physiolgical barriers - temperature
Chemical barrier - pH
Phagocytic cells
Serum proteins
48
Q

What are PAMP’s?

A

Pathogen associated Molecular Patterns - how foreign microbes are recognised by the innate immune system.

A classic PAMP is lipopolysaccharide

49
Q

What does activation of PPRs do?

A

Drives cytokine production by antigen presenting cells that can increase the likelihood of a successful T cell activation

50
Q

Name some circulating PRRs

A

Antimicrobial peptides (defensins)
Lectins/collectins
Pentraxins (proteins like C-reactive protein)

51
Q

Name some cell-associated PRRs

A

TLRs - found on macrophages, dendritic cells and neutrophils. Binding causes release of IL-1, IL-2 and TNFa.
They induce a response by secondary messengers

NLRs - detect intracellular microbial pathogens

52
Q

What are the 2 methods of killing by macrophages and neutrophil polymorphs?

A

O2 dependent uses reactive oxygen intermediates (ROI) such as Superoxides and Nitric oxide

O2 independent - enzymes such as defensins and lysozyme

53
Q

Describe the MHC, its function, and what it does

A

This presents antigens to T cells.
The antigen specific receptor of an individual T cell will only recognise antigen as part of a complex of antigen and an individuals MHC

It acts as a safety mechanism, preventing the immune system being activated too easily

54
Q

Describe MHC1 and MHC2

what they present, where they are found and what they bind

A

MHC1:
Binds antigens from intracellular pathogens
Found on the surface of all body cells except RBCs
Cytotoxic T cells (CD8) require an antigen to be associated with MHC1 before they kill the cell containing the pathogen

MHC2
Extracellular pathogens with antigens from phagocytosis
Found mainly on surface of APCs (macrophages, B cells and dendritic cells)
Helper T cells (CD4) require MHC2 with antigen before they help B cells make antibodies

55
Q

Are T cell receptors specific?

Do TCRs bind to soluble antigens

A

Yes - TCR recognises antigens if bound complexed with MHC1 (for cytoxic) or MHC2 (for Th2). The structure is similar to the Fab region on Igs.

The T cell only binds to antigens with MHC so not soluble antigens

56
Q

Describe the steps in humoral immunity

A

1) Bacteria enter lymph nodes
2) Eventually it will bind to a specific Ig on a B cell, extra cytokines needed to activate B cell
3) In tissues APCs present antigens (complexed to MHC2)
4) The specifc CD4 receptor eventually binds causing the T cell to release IL-2 causing proliferation
5) Th cells migrate to lymph nodes and stimulate B cells to differentiate into plasma cells releasing antibodies

57
Q

Describe the steps in cell-mediated immunity

A

1) An infected/cancer cell produces antigens complex to MHC1
2) Correct CD8 cytotoxic T cell recepto binds but again extra stimulates in required
3) In tissues APCs present antigens (complexed to MHC2)
4) The specifc CD4 receptor eventually binds causing the T cell to release IL-2 causing proliferation
5) IL2 activates cytoxic T cells

58
Q

What does Th1 do?

A

Binds to APC with MHC2 antigen to turn from naive to Th1 cell.
Migrates to secondary lymphoid tissue, undergoes clonal expansion
These T cells then help B cells make IgG and produce cytokines (interferon gamma)
It also has the correct CD4 receptor to bind to the specific antigen and MHC2 so it binds via TCR to cause cytokine release and interferon gamma production

59
Q

What do Th2 do?

A

Produce IL’s, activate eosinophils and mast cells and induce B cells to make IgE

They help protect agains allergies and extracellular microorganisms

60
Q

What do cytotoxic CD8 cells do after maturing from naive cells?

A

They are activated by antigens with MHC1.

Release pro-inflammatory/macrophage activating cytokines
Kill infected cells via perforins and granulysin)
Can also induce apoptosis

61
Q

What are some clinical signs to allergy?

A 
Eczema, itching, reddening
Excessive mucus production
Airway constriction
Abdominal bloating, vomiting diarrhoea
Anaphylaxis
Lowered blood pressure
62
Q

What 3 things does histamine cause?

A

Arteriolar dilation
Capillary leakage
Induces bronchoconstriction/bronchospasms

63
Q

Name 5 (types of) substances in histamine granules

A

Histamine
Chemtactic factors (IL-4)
Proteases (Tryptase)
Prostaglandin D2 (smooth muscle constriction)
Platelet Activating Factor - activates platelets and increases vascular permeability

64
Q

Name and describe each tpye of Gell and Coombs classification

A

Type 1 - Allergic/acute. This is IgE mediated. requires prior exposure (hay fever is an example)
Type 2 - Cytotoxic reaction (IgG/IgM bound to cells interact with antigens examples include transfusion reactions and autoimmune disease)
Type 3 Immune complexes (IgG antigen complexes build up, e.g. SLE)
Type 4 - delayed type hypersensitivity (TB)

65
Q

Describe process of initial sensitisation and re-exposure that occurs during type 1 hypersensitivity

A

Initial exposure to antigen leads to antibody synthesis and B memory cells.

Second exposure leads to more powerful response
Antigen binds to pre-made IgE on mast cells
This causes more IgE synthesis requiring T helper cells
T helper cells are also involved in activating mast cells to secrete inflammatory mediators and chemokines

66
Q

What is the difference between type 1 hypersensitivity and anaphylaxis?

A

If mast cells secrete lots of mediators they enter the circulation causing systemic symptoms (hypotension, vasodilation, bronchoconstriction and mucous hypersecretion) which is anaphylaxis

67
Q

What is passive immunisation? Why is it given?

A

Transfer of preformed (natural/aritifical) antibodies

This is given to people with B cell defects, immunocompromised where there is no time for active immunisation

Can also give anti-sera to neutralise toxins

68
Q

Name some diseases we treat with passive immunisation

A 
Botulism - anti-toxin
Tetanus - anti-toxin
Diptheria - anti-toxin
Hepatitis - prophylatic use
Measles - prophylatic use
Rabies - prophylatic use
69
Q

Name some draw backs of passive immunisation

A

Does not activate immunological memory so no long term protection
There is a possibility of reaction to antisera (it is non-self) leading to anaphylaxis

70
Q

How does active immunity work?

A

Stimulates immune system to produce high affinity antibodies (IgG) against the immunogen.
The goal of immunisation is to achieve initial exposure without risks of infection

71
Q

Name different types of (active) vaccines

A

Whole organism - either live attenuated or killed, inactivated pathogen
Purified subunit - either toxoids, antigenic extracts or recombinant proteins
DNA vaccines
Recombinant vector vaccine

72
Q

Describe advantages/disadvantages of live attenutated, whole-organism vaccines - give examples of these kinds of vaccine

A

Live attenutated vaccine - TB, Polio, Typhoid
+ Gives full natural immune response (T and B cells) (less likely to need repeat doses)
- There is a risk of infection (in immunocompromised patients) and needs to be kept cold.

73
Q

What are adjuvants?

A

Any substance that is added to a vaccine to stimulate the immune system (Toxioids, proteins, chemicals)

74
Q

What is immunodeficiency?

A

Deficiency in the immune response, can be either acquired (HIV) or inherted.

It can be deficiency in innate or acquired cells, barriers, complement, antibodies etc.

75
Q

Is ulcerative colitis an organ specific auto-immune disease?

A

No

76
Q

What is thymic/central tolerance?

A

T cells which recognise self are destroyed in the thymus very early in life. This can fail leading to some auto-immune disease

77
Q

How is peripheral tolerance achieved?

A

CD4 T cells only recognise antigens in associate with MHC2.

78
Q

Describe advantages/disadvantages of killed/inactivated, whole-organism vaccines - give examples of these kinds of vaccine

A

Inactivated pathogen - Anthrax, Cholera, Hep A
+ There is no risk of infection
- Usually only the humoral response is activated, as such repeated booster vaccines may be required

79
Q

What 3 kinds of things can be used in a sub-unit vaccine

A

Toxioids - inactive (still immunogenic) exotoxins
Antigenic extracts
Recombinant proteins

80
Q

What are advantages/disadvantages of using subunit vaccines?

A

+ Safer than handling live pathgoens, easier to store

- Less powerful response (boosters required)

81
Q

What kinds of things are adjuvants for vaccines?

A

Toxoids, proteins, chemicals or whole organisms

This is to try and improve/trigger the immune response.

Jack 2a (8 decks)

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