Lecture 6: Self and Non-self Discrimination Flashcards Preview

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Flashcards in Lecture 6: Self and Non-self Discrimination Deck (37)
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1
Q

What is the major role of the immune system?

A

The immune system is designed to recognise and respond to pathogens

In this way the immune system is protective (good)

2
Q

What can inappropriate immune recognition lead to?

A

Inappropriate immune recognition and response can be damaging (bad)

Immunopathology = when things go wrong

3
Q

What is hypersensitivity?

A

Heightened or persistent response to exogenous antigen or innocuous antigen

eg allergy

4
Q

What are some examples of immunopathology?

A

Hypersensitivity
Autoimmune disease
Transplant rejection
Immunodeficiency

5
Q

Write some notes on autoimmune disease:

A

◦Breakdown in mechanisms that control self tolerance
◦Hypersensitivity to autoimmune antigens

Failure of self tolerance

6
Q

Write some notes on transplant rejection;

A

Antigens on the donor graft provoke a severe host reaction

7
Q

Write some notes on immunodeficiency;

A

◦Inadequate functioning immune system
◦persistent infection

I.e HIV results in common injections becoming lethal

8
Q

Describe the Response to Ag and deficient response to an infectious agent;

A

Antigen: Infectious Agent

Response to Ag: Protective immunity

Deficient Response: RECURRENT INFECTION

9
Q

Describe the Response to Ag and deficient response to an innocuous substance;

A

Antigen: Innocuous substance

Response to Ag: ALLERGY / HYPERSENSITIVITY

‘Deficient’ Response: No symptoms

10
Q

Describe the Response to Ag and deficient response to an organ graft;

A

Antigen: Organ Graft

Response to Ag: REJECTION

Deficient Response: Acceptance

11
Q

Describe the Response to Ag and deficient response to an self organ;

A

Antigen: Self Organ

Response to Ag: AUTOIMMUNITY

Deficient Response: Self Tolerance

12
Q

Describe the Response to Ag and deficient response to an tumour;

A

Antigen: Tumour

Response to Ag: Tumour Rejection

Deficient Response: CANCER

13
Q

Whats three examples of autoimmunity?

A

Chrons
Pernicious Anemia
Systemic Lupus Erythrmoamtus

14
Q

Write some notes on chrons;

A

Autoreactive T-cells cause intestinal inflammation and scarring

15
Q

Write some notes of pernicious anemia;

A

◦Antibodies damage to parietal cellsin stomach

◦Compromised vitamin B12 absorptionresulting in anaemia

16
Q

Write some notes on SLE;

A

◦Antibodies against DNA and nuclear antigens
◦Immune complexes lodge in kidneys, joints, skin
◦Complement-mediated tissue damage

17
Q

How does the immune system respond to antigens?

A

Immune system responds to antigens through activation of lymphocytes that bear specific receptors (sIg or TCR)

18
Q

What influences the antigen response?

A

Context

Context of antigen recognition facilitates differential immune responses and functions

19
Q

Describe that context factors that influence the antigen response;

A

The nature (protein, lipid etc) and concentration of the antigen

Site of entry/venue

How antigen is processed, presented to antigen-specific lymphocytes

Receptors class

The individual’s antigenic history

Associated soluble and cell-surface signalling events (Functional consequence)

20
Q

What are the possible sites of entry for antigens?

A

◦mucosa
◦peripheral tissues
◦circulation
◦secondary lymphoid organs

21
Q

What can result from antigen recognition?

A

Proliferation and differentiation

Effector functions
◦antibody production
◦cytotoxicity, inflammation

Recruitment of non-specific effectors(e.g. phagocytes)

Redistribution

Immunological memory

22
Q

What is immunological tolerance?

A

Immunologic tolerance is defined as ‘unresponsiveness to an antigen that is induced by a previous exposure to that antigen

23
Q

Why is immune system education necessary, where does it occur and what happens when it fails?

A

The immune system has to be “educated” not to recogniseself -in this way tolerance is “learned” i.e T and B cells

Immune system ”education” takes places in lymphoid tissue (primary and secondary tissue)

A failure of self tolerance results in autoimmunity

24
Q

What does central tolerance achieve?

A

Central tolerance in the primary lymphoid organs eliminates clones that recognise self

25
Q

What is peripheral tolerance?

A

It is a backup system that eliminates any cells that recognise self that have evaded central tolerance elimination

26
Q

What can happen in central tolerance to cells hat recognise self?

A

Strong self recognition

1) Apoptosis - deletion
2) Change in receptors ( B cel editing (ONLY))
3) Development of regulatory T cells (CD4 + T cells only)

Self recognition

1) Anergy
2) Apoptosis
3) Deletion

27
Q

What happens in peripheral tolerance?

A

Some self-reactive lymphocytes mature and enter peripheral tissues. There they may be inactivated or deleted by encounter with self antigens in these tissues, or are suppressed by the regulatory T cells (peripheral tolerance).

28
Q

What is an antigen?

A

Antigen-molecule that binds TCR or an antibody

29
Q

What do antibodies and TCR molecules recognise?

A
  • Antibodies and TCR can only recognisestructures of a certain size and these are called epitopes
  • An antigen is a ‘collection of epitopes’ on a single structure
  • B cell and T cell epitopes often differ
30
Q

Describe small protein antigen immunogenicity;

A

Decreased;

Small (<2500 Da)
Simple
Similar to self
Poor MHC binding

31
Q

Describe large protein antigen immunogenicity;

A

Increased:

Large
Complex
Many differences
MHC binding

32
Q

What are the types of epitopes?

A

Linear epitope

Conformational (assembled) Epitope

33
Q

Write some notes on T cell epitopes;

A

T cell epitopes are linear and therefore the antigen must be first processed and presented before recognition can occur.

The peptide fragment then binds a MHC molecule before it can bind a TCR (t cell receptor)

34
Q

Whats the ‘general scheme’ for dealing with foreign material?

A

Ingestion by phagocytic cells(egDCs)

Transport to secondary lymphoid organs

Processing and epitope presentation to lymphocytes

Specific lymphocyte activation

Immune response generation

35
Q

What do dendritic cells do?

A

Dendritic cells recognisepathogens via invariant receptors, ingest and display antigens to lymphocytes

36
Q

What is the purpose of DC?

A

The bridge the gap between innate and active immunity.

Act as APC

37
Q

What is APC functions?

A
Antigen collection and transport
Antigen concentration
Antigen processing
Antigen presentation
Co-stimulation
◦Surface molecules
◦Pro-inflammatory cytokines

Tolerance Induction