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MSc IOVS > Cornea Lectures > Flashcards

Cornea Lectures Flashcards

1
Q

What are the two main divisions of the human immune system?

A

Innate immunity

Acquired (cell-mediated, humoral) immunity

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2
Q

What are the key characteristics of the innate immune system in terms of line of defence, mobilisation and pathogen exposure?

A

1st line of defence
Rapidly mobilised
No prior pathogen exposure needed

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3
Q

Does the innate immune system target specific pathogens? Which pathogens evade this system?

A

Non-specific

Intracellular pathogens not lysed

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4
Q

What physical barriers are in place to prevent pathogen entry? Which chemicals are produced in response to attempted entry?

A

Skin, eyelids, tears

Antibodies (from B cells), cytokines

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5
Q

What are the fluid and protein components of the innate immune system?

A

Blood, aqueous humor

Complement, mannose-binding lectin, lysozymes, anti-proteases

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6
Q

How does the complement cascade respond to detecting antigens?

A

Binding to antibodies

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7
Q

What is the action of lysozymes and what enzymes counteract their effect?

A

Lysing invading pathogens

Counteracted by anti-proteases

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8
Q

Which cells make up the innate immune system?

A

Phagocytes

Cytotoxic cells: Leucocytes, macrophages, natural killer cells

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9
Q

Which cells of the innate immune system are primary scavengers? What is their action?

A

Neutrophils

Attracted to inflammation sites by cytokines, release free radicals and proteases

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10
Q

What are the two main antigen-presenting cells in the innate immune system?

A 
Macrophages (MHC class II)
Dendritic cells
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11
Q

What are the main functions of macrophages?

A

Cell lysis, clearing antigen-coated cells
Active lymphocytes via cytokines
Trigger acquired immunity via lymphoid tissue

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12
Q

Where are dendritic cells of the innate immune system most often found?

A

High exposure sites: Respiratory system, digestive tract

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13
Q

After working on tissues where do dendritic cells recirculate to?

A

Lymph nodes

Spleen

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14
Q

Name a type of dendritic cell and where it can be found.

A

Langerhans cell

Skin, conjunctiva, cornea (stroma)

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15
Q

How does acquired immunity differ from innate immunity?

A

Antigen-specific
Forms immunological memory
Defends against both intracellular and extracellular pathogens

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16
Q

How do memory cells improve subsequent immune responses to the same invading pathogens?

A

Somatic mutations alter antibody, allowing better antigen recognition

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17
Q

Which cells make up the acquired immune system?

A

Lymphocytes
T cells, B cells
Natural killer cells

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18
Q

What are the functions of lymphocytes?

A

Recognise foreign antigens on pathogens and secrete cytokines

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19
Q

Which cells are activated by T cells and produce antibodies in acquired immunity? What do they do?

A

B cells

Counteract foreign antigens, activate other cells

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20
Q

Which polymorphic cells recognise antigens presented by MHC?

A

T cells

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21
Q

Which MHC classes do T helper cells and cytotoxic/suppressor T cells respond to respectively?

A 
T helper cells: MHC class II
Cytotoxic/suppressor T cells: MHC class I
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22
Q

How do cytokines affect macrophages, B and T cells?

A

T and B cells proliferate

Macrophages are activated

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23
Q

What do MHC classes determine?

A

Whether pathogen is intracellular or extracellular

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24
Q

Which antibodies are seen in the: (a.) Initial immune response, (b.) Secondary immune response, (c.) Mucosal immune system (e.g. tears)?

A

(a. ) IgM
(b. ) IgG
(c. ) IgA

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25
Q

Which circulating granulocytes do not need prior activation in acquired immunity?

A

Natural killer cells

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26
Q

Which cells are natural killer cells effective against? How do they destroy targets?

A

Tumour cells, virus-infected cells

Direct contact, antibodies

27
Q

What are the phases of the immune response?

A
  1. Afferent phase
  2. T cell activation
  3. Effector phase
  4. Secondary response
28
Q

What takes place in the afferent phase of the immune response?

A

Foreign antigen taken from entry site, presented to lymphocytes in lymphoid tissue by APC’s

29
Q

What do activated T cells do?

A

Produce cytokines

Stimulate cells to become cytotoxic

30
Q

What takes place in the efferent phase of the immune response?

A

T cells induce cytotoxic T cells, B cells and macrophages to remove antigen
Antigen-specific B and T cells appear

31
Q

How does the secondary immune response differ from the initial one?

A

More antigen-specific B and T cells recruited quicker

Type and specificity of antibody differs

32
Q

What do dendritic cells do?

A 
Pinocytosis in ECM
Lyses cells in acidic vacuole, puts their antigens on surface via MHC class II
33
Q

Which immune cells recognise MHC class I (found in all cells) and for which antigens?

A 
CD8 cytotoxic T cell
Intracellular antigens (viral, self)
34
Q

Which immune cells (a.) present, (b.) recognise MHC class II and for which antigens?

A

(a.) Macrophages, dendritic cells
(b.) CD4 helper T cell
Extracellular antigens (bacteria, fungi)

35
Q

What are the key characteristics of T cell receptors?

A

Unique to every T cell to recognise different antigens

via embryonic gene rearrangment

36
Q

Which are the most important cytokines for T cells? Which one is lost in proliferation?

A

IL-2, 4, 7

IL-2 lost (activated cytotoxic T cells)

37
Q

What are the key characteristics of B cell receptors?

A

Unique immunoglobulin surface antigen receptor
Excreted as soluble antibody
Marks foreign antigens recognised by identical T cell receptor for removal by innate immunity

38
Q

What is the first stage of the antibody response?

A

Antigen broken up
Picked up by APC and processed
Presented to T helper cell

39
Q

What is the second stage of the antibody response?

A

B cell picks up antigen via antibody, more processing

Activated to divide

40
Q

What is the third stage of the antibody response?

A

Antibody-forming cells produce soluble antibody

Some remain on B cell surface membrane

41
Q

What is the initial immune response to injury and infection?

A

Inflammation

Pathogen removal by innate immune system

42
Q

Why are immune cells attracted to the injury site?

A

Tissue component changes (blood vessels, ECM)

43
Q

How is acquired immunity activated following injury?

A

Degraded pathogen antigen transported to lymphoid tissue

44
Q

What is seen in the first stage of the injury and infection response at the site?

A

Vascular leaks

Leucocyte activation, adhesion, migration

45
Q

What occurs after antigen migration in the first stage of the injury and infection response?

A

Acquired immune system activation in the lymphoid tissue

Inflammation

46
Q

What is seen in the second stage of the injury and infection response?

A

Phagocytosis

ECM changes

47
Q

What is seen in the third stage of the injury and infection response?

A

Inflammation resolution

Tissue remodeling

48
Q

What is the definition of immune privilege?

A

The ability to tolerate the introduction of antigens without eliciting an inflammatory immune response

49
Q

Which bodily organs demonstrate immune privilege?

A 
Brain
Ovaries
Testes
Pregnant uterus
Placenta
Eye
50
Q

Which factors affect immune privilege?

A

Avascularity, blood ocular barrier (iris, ciliary body, retina)
Local immunosuppressive neuropeptides, cytokines
Less MHC expression, class II APC’s, Langerhans cells
Anterior chamber associated immune deviation, apoptosis

51
Q

Which immunosuppressive factors are in the aqueous humor?

A

TGF-beta, alpha-MSH
VIP, CGRP, cortisol
NK Cell Inhibitory Factor
Soluble Fas ligand

52
Q

What role does TGF-beta play in the immune response?

A

Inhibits B/T cell proliferation
IL-2 receptor expression
Antibody production

53
Q

What role does alpha-MSH play in the immune response?

A

Suppresses pro-inflammatory cytokines (IFN-gamma, IL-1, TNF-alpha)

54
Q

What role does VIP play in the immune response?

A

Inhibits IL-2 to suppress lymphocyte proliferation

55
Q

What role does CGRP play in the immune response?

A

Inhibits delayed-type hypersensitivity

56
Q

What role does NK Cell Inhibitory Factor play in the immune response?

A

Protects corneal endothelium from attack by NK cells

57
Q

What role does the soluble Fas ligand play in the immune response?

A

Downregulates inflammatory cytokines (IFN-gamma, IL-1, TNF-alpha)
Kills active lymphocytes

58
Q

What does ACAID stand for? Which intact organs are required?

A

Anterior chamber associated immune deviation

Eye, spleen

59
Q

Which cells begin the process of ACAID? How do they do so?

A

Dendritic cells

Antigen presentation via the lymphatic system

60
Q

Which two processes occur in ACAID?

A

Antibody response induction

Suppression of delayed type hypersensitivity

61
Q

How is ACAID triggered?

A

TGF-beta (aqueous humor, tears)
APC response
Thrombospondin

62
Q

What phases are involved in ACAID?

A

Ocular phase
Splenic phase A
Splenic phase B

63
Q

How is the ocular phase of ACAID carried out?

A

Antigen in anterior chamber captured by indigenous APC’s

64
Q

Where does the antigen travel to in the ocular phase of ACAID?

A

Trabecular meshwork to blood to marginal zone of spleen

MSc IOVS (4 decks)

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