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MICRO2209 > adaptive immunity > Flashcards

adaptive immunity Flashcards

1
Q

What is the Major Histocompatibility Complex?

A

genes encoding proteins that enable the host to distinguish self and non-self

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2
Q

What is the human MHC?

A

human leukocyte antigen (HLA)

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3
Q

What does it mean when the HLA genes are codominant?

A

both parental alleles of each MHC gene are expressed

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4
Q

What do MHC molecules bind to?

A

only peptides

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5
Q

Proteins in the cytosol of nucleated cells display what MHC class?

A

class I MHC molecule

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6
Q

Extracellular proteins, internalised by APCs and processed late endosomes and lysosomes display what MHC class?

A

class II MHC molecule

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7
Q

What are class I MHC molecules?

A

identify all nucleated cells of the body as “self”
e.g. leukocytes, epithelial cells, mesenchymal cells
endogenous antigen processing

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8
Q

What happens when class I MHC molecules bind to peptides?

A

signals to the immune system that it is an infected host cell

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9
Q

What do class II MHC molecules bind to?

A

antigens

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10
Q

What happens when class II MHC molecules bind to antigens?

A

degraded as a consequence of phagocytosis or receptor mediated endocytosis

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11
Q

What type of processing is MHC class II molecules?

A

exogenous (antigen processing)

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12
Q

What type of T cells do class II MHC molecules interact with?

A

CD4+ T cells

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13
Q

Why are CD4 and CD8 molecules useful on T cells?

A

stabilise interaction of TCR and MHC/peptide

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14
Q

What is immunologic tolerance?

A

lack of response to antigens that is induced by exposure of lymphocytes to these antigens

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15
Q

What is central tolerance?

A

death of immature T cells and the generation of CD4+ regulatory T cells

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16
Q

What is peripheral tolerance?

A

functional inactivation or death, or suppression of self-reactive T cells by regulatory T cells

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17
Q

What are the two types of TCR?

A

αβ
γδ

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18
Q

What is the antigen-recognising domains of the TCR called?

A

variable regions

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19
Q

True or false: every individual T cell has a different TCR specificity?

A

true

20
Q

TCR diversity allows for?

A

identification of a plethora of antigens

21
Q

How is TCR diversity generated?

A

by combining the distinct variable (V), diversity (D), and joining (J) gene segments

22
Q

The vast amount of TCR clones can be formed due to…

A

recombination, random insertion, deletion and substitution

23
Q

What does the variable region of each TCR contain?

A

complementary determining regions (CDRs)

24
Q

How can T cells die or become unresponsive when exposed to antigens?

A

no co-stimulation

25
Q

What happens in the presence of co-stimulation of T cells?

A

rapid secretion of IL2 = increase expression of IL-2R (increases sensitivity)

26
Q

What are the main functions of IL2?

A

stimulate the survival and proliferation of T cells

27
Q

What are the 3 signals needed to activate a T cell?

A
  1. TCR binding to peptide-MHC antigen + co-receptor (CD4/CD8)
  2. APC molecules (B7-1 + B7-2) bind to costimulatory receptors (CD28)
  3. cytokines induce the expression of transcription factors
28
Q

During immune synapse DCs trigger what cell?

A

naive T cells (TH0)

29
Q

What are the different subset of TH0 cells?

A

TH1, TH2, TH17, T(reg)

30
Q

Cytokines released by activated T cells are used to?

A

communicate with other cell types

30
Q

Cytokines released by activated T cells are used to?

A

communicate with other cell types

31
Q

TH17 cells are activated due to?

A

response to extracellular bacterial and fungal infections

32
Q

Regulatory T cells main function is to?

A

suppress immune response
- block immune cells
- block B7 on APCs
- consume IL-2

33
Q

What is the role of TH1 cells?

A

increase the ability of macrophages to kill phagocytosed microbes

34
Q

How are TH1 cells developed?

A

DCs produce INF-γ and IL-12

35
Q

How does the release of IFN-γ by TH1 cells help in phagocytosis?

A

recruitment of monocytes and granulocytes
activates anti-microbial activity of macrophages

36
Q

What does TH2 cells stimulate?

A

antibody responses, and defend against helminth parasites

37
Q

What cytokines released by DCs produce TH2 cells?

A

IL-4

38
Q

What cytokines do TH2 cells release?

A

IL-4, IL-5 and IL-13

39
Q

What do TH2 cytokines inhibit?

A

the activation of classical macrophages

40
Q

What do TH2 cytokines stimulate?

A

the alternative pathway (important in tissue repair and fibrosis)

41
Q

What are TH2 cells involved in?

A

allergic reactions (trigger mast cells and eosinophil activation)

42
Q

What is the role of CD8 T cells?

A

recognition of peptides on infected cells or tumour cells expressed by MHC-1 molecules

43
Q

What are a ways CD8 T cells are activated to induce differentiation?

A

cross-presentation = DCs sufficiently activated
require additional help from CD4 cells

44
Q

How does CD4+ cells help differentiate CD8+ T cells into cytotoxic T cells?

A

B7 expressed by DC activates CD4+ T cells to express IL-2 and CD40 ligand
CD40 ligand binds to CD40 on DC = increase B7 expression
increase co-stimulatory signals to CD8+ T cell
IL-2 acts to promote effector cell differentiation

45
Q

What is perforin?

A

disruption of the integrity of target cell plasma membrane and endosomal membranes

46
Q

What is granzymes?

A

activate enzymes called caspases which induce apoptosis

MICRO2209 (16 decks)

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