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Microbiology, Immunology, and Genetics > Immunology Lecture 11 > Flashcards

Immunology Lecture 11 Flashcards

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1
Q

What are dendritic cells, and how do they act?

A

They are antigen presenting cells, where they phagocytose pathogens, and present their antigens on their surface.

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2
Q

Where do dendritic cells go to present antigens?

A

After phagocytosing, they go to the lymph node to present antigens to a lymphocyte.

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3
Q

Name 4 characteristics of specific immunity.

A

Specificity
Memory
Diversity
Discriminates self from non-self

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4
Q

What are the two branches of specific immunity, and what are they mediated by?

A

Humoral - B cell antibody mediated.

Cellular - T cell mediated.

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5
Q

Define acquired immunity.

A

Specific immunity developed after exposure to an antigen, or transfer from a donor.

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6
Q

What is an epitope?

A

Recognition site for an antigen.

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7
Q

What is a multivalent antigen?

A

Antigen with multiple epitopes.

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8
Q

Define hapten. What are they used for?

A

Small molecule that becomes immunogenic if coupled to a carrier.
Used to make conjugated vaccines.

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9
Q

What molecular class are antibodies?

A

Glycoproteins.

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10
Q

What 3 fluids are antibodies typically found in?

A

Blood, lymph, and mucosal fluid.

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11
Q

Describe the structure of antibodies.

A

Y shape composed of two heavy chains.

On each fork, hands off a smaller light chain.

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12
Q

What is the V region of an antibody?

A

Site where the epitope binds to the antigen, V= variable.

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13
Q

What is the V region of antibodies encoded by?

A

Certain segments of DNA, that are able to be randomly selected, allowing for huge diversity to the V region.

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14
Q

Where on the Y do the heavy and light chains bond together?

A

At the fork.

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15
Q

What are antibodies made by?

A

B cells.

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16
Q

Where are B cells made (2), and where do they migrate to mature?

A

Made in the foetal liver, and bone marrow.

Mature in the bone marrow.

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17
Q

What is an antibody before it is activated?

A

A receptor on a B cell.

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18
Q

What shape is IgG? Is it monomeric, dimeric, or pentameric?

A

Y shaped, monomeric.

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19
Q

Where is IgG found?

A

Blood, lymph, and intestines.

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20
Q

Does IgG cross the placenta?

A

Yes, allowing for maternal transfer.

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21
Q

What shape is IgM? Is it monomeric, dimeric, or pentameric?

A

Y shaped, pentameric, so 10 binding sites, 2 per Y.

22
Q

What is IgM particularly effective for, and why?

A

Good for early infections, due to the number of arms, allowing quick agglutination.

23
Q

How can a measure of IgM and IgG all one to distinguish whether an illness is recent or a past infection?

A

A recent infection will have a high IgM count.

Past infection will have a high IgG count.

24
Q

Is IgM stable or unstable?

A

Unstable, doesnt last long.

25
Q

Where is IgM found?

A

Blood, lymph.

26
Q

What shape is IgA, and is it monomeric, dimeric, or pentameric? What important characteristic does this confer to IgA?

A

Y shaped, dimeric. Dimerism protects it from being digested, allowing it to be passed maternally via breast milk.

27
Q

Where is IgA found?

A

In secretions, such as tears, saliva, breast milk.

Also in blood/lymph.

28
Q

Is IgD monomeric, dimeric, or pentameric?

A

Monomer.

29
Q

Where is IgD found?

A

Blood/lymph.

30
Q

What is the role of IgD?

A

Serum function unknown.

Present of B cell surface during immune response initiation.

31
Q

Is IgE monomeric, dimeric, or pentameric?

A

Monomeric.

32
Q

What is the function of IgE?

A

Fights parasites.

33
Q

What connection does allergies have to IgE?

A

It is believed that allergic people produce IgE instead of IgG to an allergen.
IgE binds to a mast cell, causing it to release histamines.

34
Q

How can allergic individuals be desensitised to an allergen?

A

They are given minute quantities of the allergen. In 50% of individuals, the body resets to IgG from IgE.

35
Q

Why do some people fail to desensitise to allergens?

A

Unknown why.

36
Q

Explain the activation of B cells in detail.

A

Antigen fragment is presented to a B lymphocyte.
B lymphocyte attaches antigen to an MHC class 2 receptor, and presents it to a Th cell.
Th cell activates to release cytokines.
Cytokines induce the B lymphocyte to change to a B plasma cell.
Some become B memory cells.

37
Q

What is the function of a B plasma cell?

A

They produce large quantities of antibodies to the antigen that was presented to the Th cell.

38
Q

Define clonal expansion.

A

Rapid division of a B plasma cell to make a large quantity that produces the specific antibody.

39
Q

During an infection, which immunoglobulin appears first? What comes next?

A

IgM is the first to appear.

Followed by IgG

40
Q

What is the difference in IgG and IgM levels between a first and second infection? Why is this so?

A

IgM has low affinity. On second exposure, much more IgG is made, and has higher affinity.

41
Q

What are CD molecules?

A

Cell surface proteins that act as a cluster of differentiation molecules.

42
Q

Where are CD2, CD4, and CD8 receptors found?

A

CD2 - all T cells
CD4 - on Th cells
CD8 - on cytotoxic T cells

43
Q

Where do T cells mature?

A

Thymus.

44
Q

What kind of receptors do T cells have?

A

Antigen specific T cell receptor - TCR

45
Q

What structure do TCRs have?

A

Are like antibodies, very high diversity, but arent forked, single arm.

46
Q

Can TCRs recognise native antigens?

A

No, it must be presented by another immune cell.

47
Q

How are antigens presented to T cells?

A

Broken to a short polypeptide, and attached to an MHC class 2 receptor.

48
Q

Define MHC class 1 markers, and where they are found. Define what recognises them, and what happens when a cell with MHC1 is infected.

A

Present on all nucleated cells. Present internally synthesised peptides.
Recognised by CD8 cells, no reaction.
If infected, antigens are presented on MHC1 markers, which the CD8 will recognise and induce apoptosis.

49
Q

Define MHC class 2 markers, and where they are found. Define what recognises them.

A

Found only on antigen presenting cells. They present antigens they phagocytose.
Recognised by CD4 cells.

50
Q

Can an antigen on an MHC2 marker found on an antigen presenting cell activate a Th cell? Explain.

A

Yes. It requires a second costimutation through CD28.

51
Q

Name and describe the four kinds of immunity.

A

Natural active – acquiring the infection naturally through environment

  • Artificial active – injection of infective agents (vaccine)
  • Artificial passive – injection of antiserum from immune individuals
  • Natural passive – transfer of maternal antibody to a foetus via the placenta or breast milk

Microbiology, Immunology, and Genetics (24 decks)

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