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Infection and Immunity > Week 4 - Adaptive immunity > Flashcards

Week 4 - Adaptive immunity Flashcards

1
Q

What is MHC I?

A
  • Receptor on all nucleated cells which presents peptides from within the cell
  • Distinguishes self from non-self
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2
Q

What is MHC II?

A

-Receptor present on antigen presenting cells only which presents peptides from extracellular microbes which have been phagocytosed

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3
Q

What allows there to be high variety of MHC molecules within one person?

A

-Co-dominant expression of HLA genes

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4
Q

What is meant by HLA being polymorphic?

A

-Many alleles of HLA amongst the population allows presentation of different microbes and different susceptibilities in different people

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5
Q

Where is the variable region on an MHC molecule?

A

-Peptide binding cleft

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6
Q

Do MHC complexes have a narrow or broad specificity?

A

-Broad -> allows many peptides to be presented by same MHC molecule

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7
Q

What cell specifically recognises MHC I?

A

-CD8+ T Lymphocytes

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8
Q

What cell specifically recognises MHCII?

A

-CD4+ T Lymphocyte

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9
Q

What are the three steps of antigen presentation?

A
  • Capture
  • Processing
  • Presentation
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10
Q

What is specific about the location of APCs within the body?

A

-They are located in areas which allow them to interact with B and T cells eg mucous membranes, lymphoid organs and in the circulation

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11
Q

How do APCs capture pathogens?

A
  • Phagocytosis

- Macro-pinocytosis of soluble particles

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12
Q

How can APCs recognise so many different pathogens?

A

-Have a wide range of pathogen recognition receptors both extracellularly for bacteria and intracellularly for pathogens

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13
Q

What do Pathogen recognition receptors recognise?

A

-Pathogen Associated Molecular Patterns

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14
Q

Which type of adaptive immunity is activated by extracellular pathogens?

A

-Humoral

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15
Q

Which type of adaptive immunity is activated by intracellular pathogens?

A

-Cell-dependant

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16
Q

What is meant by humoral immunity?

A

-The immunity which does not involve cells directly in the defence eg antibodies and complement (although B cells are activated by T cells)

17
Q

What is meant by cell-dependant immunity?

A

-Cells are directly involved in the defence against the infection eg cytotoxic T cells and macrophages

18
Q

Name two clinical problems with MHC

A
  • Organ transplant rejection

- Cross reactivity

19
Q

Explain why MHC can be problematic in organ transplant rejection?

A

-HLA mismatch between donor and recipient causes destruction of donor tissue by recipient immune system

20
Q

What is cross reactivity of MHC?

A

-A microbe resembles human protein and cannot be distinguished eg strep pyogenes innoculates heart valve -> immune system cannot tell self from non-self and begins attacking own tissue ->rheumatic heart disease

21
Q

Describe antigen presentation to CD4+ cells and the response

A
  • Extracellular microbe phagocytosed and presented on MHC ii by APC
  • CD4+ cell binds to MHC ii and recognises non-self peptide
  • CD4+ cell activates B cell for clonal expansion and proliferation causing antibody production
22
Q

Describe antigen presentation to CD8+ cells and its response

A
  • Intracellular microbe displayed on MHC I and MHCii if APC
  • Activated CD8+ cell binds to MHC I on infected cell and recognises as non-self and causes cell lysis through perforins and granzymes to kill the cell
  • APCs with peptide displayed MHC i can activate CD8+ and also displaying peptide on MHC ii activates CD4+ cells which then activates CD8+ cells
23
Q

Where do T lymphocytes mature?

A

-Thymus

24
Q

What cytokines released by CD4+ induce macrophages?

A
  • IL-1

- IFN-g

25
Q

What co-receptor molecules on CD4+ are associated with extracellular microbes?

A
  • TH2

- TH17

26
Q

What co-receptor molecule on CD4+ are associated with intracellular microbes?

A

-TH1

27
Q

Name 3 types of APC and their location

A
  • Dendritic -> LNs, MMs and blood
  • Langerhan cells -> skin
  • Macrophages -> various
28
Q

Which APC can present to both T and B cells?

A

-Dendritic

29
Q

What are the role of T helper cells?

A

-Activate B cells, Macrophages,Eosinophils, Mast cells, Neutrophils and CD8+ cells

30
Q

Which TH type is associated with hypersensitivity?

A

-TH2 as activates mast cells

31
Q

What is the role of eosinophils?

A

-Kills parasites and associated with worms

32
Q

What is a primary and secondary antibody response?

A
  • Primary response when not encountered pathogen before -> take a while to recognise pathogen and make specific ab
  • Secondary response is much faster and stronger with specific antibody being produced much quicker
33
Q

Which antibody is described as natural antibody?

A

-IgM

34
Q

What is IgA associated with?

A

-Mucous membranes

35
Q

What is IgE associated with?

A
  • Allergies
  • Worms
  • Mast cell degranulation
36
Q

What are the immune functions of IgG?

A
  • Neonatal immunity
  • Complement activation
  • Toxin/virus neutralization
  • Phagocytosis
37
Q

What is isotype switching?

A

-A process whereby activated mature B cells change the class of antibody they are producing but with the same specificity eg from IgM to IgG -> IgG has different functions to igM

38
Q

What genes encode for MHC?

A

-HLA

Infection and Immunity (15 decks)

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