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biosci > Cellular Immunity and Histocompatibility > Flashcards

Cellular Immunity and Histocompatibility Flashcards

1
Q

What are the two things that the T lymphocytes express

A

CD4 and CD8 surface antigens

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2
Q

What is CD4

A

Helper T cell that respond by secreting cytokines

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3
Q

What do T lymphocytes encounter on thymic epithelium

A

MHC class 1 and MHC class 2

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4
Q

What happens if a T lymphocyte responds to MHC class ll

A

They become CD4 helper T cells

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5
Q

What happens if a T lymphocyte responds to MHC class l

A

They become CD8 cytotoxic T cells (CTL)

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6
Q

What is CD8

A

Cytotoxic - they kill all other infected cells

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7
Q

What percentage of blood T cells are each CD4 and CD8

A

CD4 - 80%
CD8 - 20%

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8
Q

What are the functional subsets of CD4 helper T cells

A

Treg, Th1, Th2, Th17

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9
Q

What does Treg do

A

Suppresses the immune response

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10
Q

What does Th1 do

A

Promotes cell-mediated immunity

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11
Q

What does Th2 do

A

Promotes antibody mediated immunity

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12
Q

What does Th17 do

A

promotes inflammation

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13
Q

What is the thymus and where is it located

A

The thymus is a primary lyphoid organ that is largest at birth and shrinks with age. It sits at the top of the percardium above the heart.

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14
Q

Haemapoietic lymphoid precursors

A

Migrate from the bone marrow to the thymus where they mature into T lymphocytes

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15
Q

What is a viral infection

A

Infects epithelial tissue and replicates inside cells.

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16
Q

What are viral infections regulated by

A

A set of highly polymorphic genes that were first identified as controlling tissue transplantation.

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17
Q

What is a T cell receptor (TcR)

A

It is an Ig molecule on the surface of all T lymphocytes

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18
Q

What does the TcR gene locus undergo

A

Rearrangement (just like B cells)

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19
Q

What does the TcR recognise, and why

A

Only one antigen - which are the proteins of the Major Histocompatibility Complex (MHC) because the T cells were ‘selected’ during thymic development for their ability to respond to self MHC molecules

20
Q

Does the TcR undergo affinity maturation or not, and why?

A

It does not undergo affinity maturation because you dont want the affinity of TcR to increase to a self-antigen (MHC)

21
Q

How do T cells recognise foreign antigens from both virus and bacteria

A

Only when there are presented by MHC molecules on the surface of cells. This is how they detect host cells that have become virally infected.

22
Q

How do T cells pick up viral infections

A

They detect small fragments of virus picked up inside the cell and expressed in the binding groove of MHC molecules on the cell surface.

23
Q

MHC restriction means that T cells can see what two antigens at the same time?

A
  1. Foreign peptide antigen (non-slef) imbedded in MHC
  2. MHC molecules (self)
24
Q

Describe how and why TcR has affnity towards the combination of MHC

A

The antigen binding surface of the TcR (top molecule) binds to the top of MHC which represents the ‘peptide groove’ containing the foreign peptide antgien. Thus the TcR has affinity towards the combination of MHC.

25
Q

Label (3) of MHC restriction

A

TCR, peptide non-self, MHC (HLA) self)

26
Q

Where are HLA molecules expressed and where are they present

A

HLA molecules are expressed on most cells and present peptide antigens to T cells.

27
Q

Are HLA molecules weakly or highly polymorphic

A

Highly polymorphic

28
Q

What are HLA

A

Human kekocyte antigens - refers to the 6 different molecules expressed on human cells.

29
Q

What are the two forms of MHC

A

Class I and Class II

30
Q

What do Class I molecules do

A

Class I picks up antigens from inside the cell (intracellular) and presents them to CD8 cytotoxic T cells. Cd8 cells can then kill the presenting cell.

31
Q

What is the function of Class 2 MHC molecules

A

They pick up digested antigens from the phagolysosome (extracellular pathogens) and present them to CD4 helper T cells.

32
Q

What are CD4 and CD8

A

Accessory molecules on T cells that physically associate with the T cell receptor

33
Q

What do CD4 and CD8 both have

A

Intracellular tyrosine kinases associated with their cytoplasmic tails that initiate T cell signalling through phosphorylation.

34
Q

What are CD4 and CD8 crucial for

A

That activation of your adaptive immune response

35
Q

CD4 and CD8 bind to what

A

CD4 - MHC Class II
CD8- MHC Class I

36
Q

What does the CTL (CD8+ cytotoxic function) produce

A

Produces granzyme and perforins that punch holes in the target cell membrane and destroy cell viability.

37
Q

What is the CD4+ helper function

A

Proliferate and produce cytokines that “help” other cells.

38
Q

Peptide source for MHC class 1

A

Intracellular

39
Q

Peptide source for MHC class 2

A

Extracellular

40
Q

Peptide source for MHC class 1

A

Intracellular

41
Q

MHC class 1 and 2 work on viruses or bacteria

A

Class 1 - viruses
Class 2 - bacteria

42
Q

Restriction of polymorphism

A

Polymorphism is restricted to the protein domains that form the peptide groove

43
Q

What are the two important consequences of MHC polymorphism

A
  1. Tissue transplantation is difficult except for identical twins
  2. MHC polymorphism are strongly linked to many autoimmune diseases.
44
Q

What does it mean when MHC is polymorphic

A

It varies between individuals. T cells from the recipient recognises the donor MHC antigens as foreign.

45
Q

What part of the MHC is polymorphic

A

The locus

46
Q

How many polymorphic molecules are expressed on your cells

A

12 - 6 from mother and 6 from father.

biosci (28 decks)

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