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0V015 Biology & Pathology > Defence Against Pathogens L13 > Flashcards

Defence Against Pathogens L13 Flashcards

1
Q

What is the lifestyle of viruses?

A

Intracellular infection ( also extracellular)

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2
Q

What is the lifestyle of bacteria?

A

Largely extracellular with some exceptions

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3
Q

What is the lifestyle of Parasites?

A

Extracellular (and intracellular)

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4
Q

What is the lifestyle of fungi?

A

Extracellular

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5
Q

How can bacteria cause damage to cells?

A

They can cause damage by invading tissues and multiplying in them as well as releasing toxins that can damage cells

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6
Q

What are the body’s anti-bacterial mechanisms?

A 
Anatomical barriers e.g. skin
Phagocytosis 
Antibodies 
Complement 
T-cells
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7
Q

What are some examples of innate defence mechanisms against bacteria?

A

Barriers such as skin.
Acidic secretions on the surface of the skin.
Mucus which traps pathogens and prevent them binding.
External secretions such as tears contain anti-bacterial proteins.

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8
Q

What is special about IgA?

A

It can cross epithelium whereas other antibodies can’t ( with the exception of IgG which can only cross the placenta).

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9
Q

How can IgA cross endothelium?

A

It contains specific secretory components that allow it to do this.

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10
Q

What is the role of T-cells in an anti-bacterial mechanism?

A

Specific T cells recognise bacterial peptides expressed on a macrophage surface associated with MHC molecules.
These T-cells then produce cytokines which stimulate the macrophage to destroy intracellular pathogens.

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11
Q

Describe the viral life cycle.

A

The virus attaches itself onto a receptor on the surface of a cell.

It is then internalised by the cell ( i.e. maganges to penetrate the cell).

Inside the cell the proetin breaks away from the nucleic acid.

The nucleic acid migrates to the nucleus and instructs nucleus to produce viral proteins.

Viral proteins are then assembled within the cell before lysis occurs relseasing viruses.

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12
Q

What are some innate defence mechanisms against viruses?

A

Coughing and sneezing - these help to expel pathogens

Acidic secretions in the stomach are toxic to some pathogens.

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13
Q

What is a commensal?

A

An organism that is symbiotic

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14
Q

What is a symbiotic relationship?

A

A long term close relationship regardless of whether it is mutualistic, beneficial or parasitic

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15
Q

How is the phagocytosis of bacteria enhanced?

A

Phagocytosis is enhanced via coating the bacteria with antibodies or complement (or both). This makes it easier to phagocytose. This process is called opsonisation.

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16
Q

What are the roles of complement?

A

Opsonisation

Chemotaxis - complement attracts phagocytes to the site of injury.

Activation of phagocytes.

Formation of membrane attack complex - they can break a hole in a cell causing lysis.

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17
Q

What are the roles of antibodies?

A

Opsonisation
Preventing bacterial binding
Neutralising toxins
IgA are improtant for the defence of mucosal surfaces
IgG and IgM are important serum immunoglobulins

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18
Q

What are the roles of interferons in viral defence mechanisms?

A

When a cell is infected with a virus it is stimulated to produce alpha and beta interferons which signal neighbouring cells to produce anti-viral proteins.

Gamma interferon regulates the production of MHC class1 which present viral peptides to cytotoxic T- cells.

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19
Q

What is the role of T-cells in viral defence mechanisms?

A

Cytotoxic T-cells recognise association between MHC class1 and viral peptide fragments.
Cytotoxic T cells destroy virally infected cells via apoptosis.

T helper cells also recognise infected cells and produce gamma interferon.

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20
Q

Define innate defence mechanism

A

A non specific defence mechanism

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21
Q

Define adaptive defence system

A

A specific defence mechanism

22
Q

What are some antiviral mechanisms?

A 
Anatomical barriers 
Natural Killer cells 
Antibodies 
Interferons 
T-cells
23
Q

Are Natural killer cells part of the innate or adaptive defnce system?

A

Innate system

24
Q

What can natural killer cells do to stop viral infections?

A

Recognise and destroy virally infected cells

25
Q

What is immuno surveillance?

A

Checking whether a cell is infected

26
Q

What are the role of antibodies in a viral defence mechanism?

A

IgA synthesised locally in the lungs and nose protects against viral infections.

IgG and IgM are effective against blood-borne viruses.

Antibodies neutralise viruses by binding to viral surface antigens and blocking their entry.

27
Q

What are the three types of Interferon?

A

Alpha
Beta
Gamma

28
Q

What are interferon alpha and beta produced by?

A

Leukocytes , fibroblasts ans virally infected cells

29
Q

What is the immune response to parasitic worms?

A

Eosinophils granules contain substances that are toxic to parasitic worms.

TH2 cells and macrophages direct immune activity and control activationand degranulation of eosinophils.

Mast cell and basophil degranulation also occurs.

30
Q

How could commensals be beneficial in pathogen prevention?

A

They compete with the pathogen for food.

31
Q

What does the occular surface comprise of?

A

The cornea and conjunctiva

32
Q

Why is the occular surface vulnerable?

A

It is exposed to the external environment

33
Q

What are the three ways defence mechanisms can be classified?

A

Mechanical
Anatomical
Immunological

34
Q

What are the role of the eyelids?

A

To blink - this is important for preotection ( as a reflex) and to replenish tear film layer.

35
Q

What are the roles of the eyelashes?

A

The lashes trap microbes preventing access to the globe.

They are inherently oily to trap micro-organisms, dust and other debris.

36
Q

What is the role of the tear film?

A

The washing action of the tears reduces microbial adhesion and removes cells that have been shed.

Tear film mucins have anti-microbial properties.

37
Q

What proteins with antimicrobial properties are present in tears?

A

Lysozyme, Lactoferrin, IgA, Beta lysin and lipocalin.

38
Q

What is Lysozyme?

A

An enzyme produced by the lacrimal gland which has the ability to lyse bacterial cell walls.

39
Q

Which antibody is predominant in tears?

A

IgA

40
Q

What is IgA in tears produced by?

A

Plasma cells within the connective tissue surrounding lacrimal acini

41
Q

Why is IgA beneficial in ocular surfaces?

A

It inactivates bacterial toxins.

It prevents binding of viruses and bacteria to ocular surface.

42
Q

When are IgM and IgG found in tears?

A

When inflammation has occured. (Healthy eyes only have IgA in tears).

43
Q

Why do closed eyes show a 50 fold increase in concentration of IgA?

A

As there is no blinking action eyes are more succeptible to deisease therefore production of IgA is increased to compensate.

44
Q

What is the role of the conjunctiva?

A

It forms a part of the EALT ( eye associated lymphoid tissue).

It plays an important role in the immune protection of the ocular surface and its mucosal adnexa.

45
Q

What does the EALT consist of ?

A

It consists of a diffuse lymphoid tissue of T lymphocytes and IgA secreting plasma cells.

46
Q

What are predominant in the conjunctival epithelium?

A

Cytotoxic T cells

47
Q

In the stroma of the conjunctiva, what are predominant?

A

T helper cells

48
Q

Why is there a high success rate in corneal transplants?

A

Due to avascularity of the cornea and lack of immune activation.

49
Q

How can rejection to a corneal transplant occur?

A

Neovascularisation could occur and therefore the immune system responds to attack the foreign (donor) antigens.

Here T cells and macrophages infiltrate the tissue and secrete a variety of cytokines.

50
Q

In high risk corneal grafts what two strategies are used?

A

HLA matching of donor and recipient.

Immunosupressive therapy.

51
Q

What is neovascularisation?

A

Natural formation of new blood vessels.

0V015 Biology & Pathology (57 decks)

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