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Infection 5 Adaptive Immune System Flashcards

1
Q

Pathogen definition

A

Any microorganism that can cause disease in humans

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2
Q

Naive T cells definition

A

T cells that have not encountered the antigen before

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3
Q

Effector T cells definition

A

T cells that have encountered the antigen + are capable of performing effector function in immune response

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4
Q

What is the only way to activate T cells?

A

Antigen presenting cells

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5
Q

What do dendritic cells present pathogen to?
Where are they found?

A

Naive T cells

Lymph nodes, mucous membranes, blood

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6
Q

What do Langerhans cells present pathogen to?
Where are they found?

A

Naive T cells

Skin

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7
Q

What do macropages present pathogen to?
Where are they found?

A

Effector T cells

Various tissues

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8
Q

What do B cells present pathogen to?
Where are they found?

A

Effector + naive T cells

Lymphoid tissues

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9
Q

Function of dendritic cells

A

Present antigens to T cells

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10
Q

Function of langerhans cells

A

T cell response against most pathogens

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11
Q

B cell function

A

B cells > plasma cells > antibodies
(Humoral response)

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12
Q

Locations of APCs

A

Mucosal membranes
Skin
Blood
Lymph nodes
Spleen

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13
Q

Which cells are found on skin?

A

Langerhans cells
Dendritic cells

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14
Q

How do APCs capture pathogens?

A

Phagocytosis - whole microbes
Macropinocytosis - soluble particles

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15
Q

Phagocytosis meaning

A

Engulfing whole microbes/pathogen

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16
Q

Macropinocytosis meaning

A

Taking in soluble particles

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17
Q

What type of pathogen is sensed intracellularly?

A

Virus

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18
Q

What type of pathogen is sensed extracellularly?

A

Bacteria
Fungi
Protozoa

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19
Q

What does MHC stand for?

A

Major histocompatibility complex

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20
Q

Where are MHC class I + II expressed?

A
  • class I: all nucleated cells
  • class II: APCs
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21
Q

Differentiate between the type of response brought about by protection from extracellular and intracellular microbes
Examples of each

A

Extracellular microbes > humoral immunity
e.g. bacteria, parasites, worms, fungi

Intracellular microbes > cell dependent immunity
e.g. viruses

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22
Q

What gene complex encodes for MHCs?

A

Human leukocyte antigen

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23
Q

Function of MHC class I

A

Present peptides from intracellular microbes
e.g. viruses
Recognised by CD8+ T cells

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24
Q

Function of MHC class II

A

Present peptides from extracellular microbes
e.g. bacteria, fungi, parasites
Recognised by CD4+ T cells

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25
Q

What are MHC class I molecules recognised by?

A

CD8+ T cells

1x8=8 rule of 8

26
Q

What are MHC class II recognised by?

A

CD4+ T cells

2x4=8 rule of 8

27
Q

Describe the structure of MHC molecules

A
  • Peptide binding cleft - variable region with highly polymorphic residues
  • Broad specificity - many peptides are presented by the same MHC molecule
28
Q

Outline the responses of the immune system to extracellular pathogens

A

bacteria, fungi, protozoa
1- APC capture microbes
2- antigens presented by MHC class II to naive CD4+ T cells
3- humoral immunity
4- antibodies made

29
Q

Outline the responses of the immune system to intracellular pathogens

A

viruses
1- APCs capture microbes
2- present antigens by MHC class I to naive CD8+ T cells
3- cell mediated immunity > cytotoxic T cell response
3- humoral immunity > antibodies made

30
Q

Features of MHC molecules

A
  • Co-dominant expression - both parental genes are expressed > increased number of different MHC molecules
  • Polymorphic genes - different alleles among different individuals > increased presentation of different antigens
31
Q

Clinical importance of MHC molecules

A
  • host can deal with variety of microbes
  • no two individuals have the same set of MHC molecules > not being wiped out by single epidemic disease
  • different susceptibility to infection
32
Q

What produce B and T lymphocytes?

A

Bone marrow

33
Q

What are the two clinical problems associated with MHC molecules?

A
  • cause for organ transplant rejection
  • autoimmune diseases associated with HLA
34
Q

What do CD4+ cells become?

A

Helper T cells

35
Q

What do CD8+ cells become?

A

Cytotoxic T cells

36
Q

Outline the exogenous pathway of extracellular microbes processing

A

bacteria, fungi, Protozoa
1- APCs phagocytes pathogen
2- degrade pathogen into small peptides
3- vesicles containing peptide fuse with MHC II molecules
4- present peptides to CD4+ T cells

37
Q

Outline the endogenous pathway of intracellular microbes processing

A

virus
1- viral protein present in cytosol
2- marked for destruction by protease on
3- viral peptide transported to ER by TAP proteins
4- fuse with MHC class 1
5- present peptides to CD8+ T cells

38
Q

How are T cells activated?

comes up often in exams

A

Via costimulation
1- MHC molecules interact with T cell receptor on CD4/8+ cell
2- B7 on APC activates CD28 on T cell
3- release of cytokines by APC
4- T cell becomes activated

39
Q

What do TH1 cells do?

A
  • differentiation of CD8+ T cells > cytotoxic T ells
  • recruit + active macrophages
  • trigger B cells to produce IgA or IgG
    cell mediated immunity
40
Q

What do TH2 cells do?

A
  • tigger B cells to produce IgE or IgG
  • tigger eosinophils to kill parasites
  • tigger mast cells for allergies
    humoral immunity with Th17
41
Q

What do TH17 cells do?

A

Recruit and active neutrophils
humoral immunity with Th1

42
Q

What to Treg cells do?

A

Regulate immune suppression

43
Q

What helper T cells brings about the best immune repsonse?

44
Q

What is the effector function of CD8+ T cells

A
  • Multiply to form many cytotoxic T cells
  • Migrate to peripheral tissues + kill infected cells
45
Q

What T helper cells cause CD8+ cell differentiation?

46
Q

What happens when B cells become activated?

A
  • antibody production - IgA/E/G/M
  • affinity maturation
  • memory B cells made
47
Q

Outline B cell activation

A

1- B cell receptor engagement:
- processes + presentation of antigen
- increases B7 receptors

2- T cell receptor engagement
- CD28 on T cell interacts with B7 on B cells
- CD4 on T cell interacts with MHC II on B cell

3- release of cytokines
- CD40L on T cells interacts with CD40 on B cell

48
Q

Function of IgG antibody

A
  • Phagocytosis
  • Complement activation
  • Neonatal immunity
  • Toxin neutralisation

Remains in body after infection > IgG positive = had infection before

49
Q

Function of IgE antibodies

A

Immunity against helminths - parasites
Mast cell degranulation&raquo_space; allergy response

IgE - allergE

50
Q

Function of IgA antibody

A

Mucosal immunity

51
Q

Function of IgM antibodies

A

Complement activation

52
Q

What antibodies are T helper independent?

53
Q

What antibodies are T helper dependent?

54
Q

What are presented via MHC class I vs II molecules?

A
  • class I: intracellular microbes viruses
  • class II: extracellular microbes bacteria, fungi, protozoa
55
Q

What type of MHC class are viruses presented via?

56
Q

What type of MHC class are bacteria presented via?

57
Q

What does a pattern of high IgG and absent IgM indicate?

A

A past infection

58
Q

What does a positive vs negative IgM test suggest?

A

positive: active or recent infection
negative: doesn’t rule out infection as levels may decline over time

59
Q

What does a positive vs negative IgG test suggest?

A

positive: previous exposure to pathogen or successful vaccination
negative no recent or past exposure

60
Q

What do each of these results suggest:
IgG + IgM +
IgG + IgM -
IgG - IgM +

A
  • IgG + IgM +: active or recent infection
  • IgG + IgM -: past infection or immunity
  • IgG - IgM +: early or acute infection
61
Q

Outline the primary antibody response

A
  • first encounter to new pathogen
  • primary antibody - IgM (less specific than IgG)
  • 5-10 days for peak primary immune response (slow)
62
Q

Outline secondary antibody response

A
  • exposure to pathogen before
  • primary antibody - IgG
  • 3-5 days to reach peak immune response
  • faster, stronger + lasts longer than primary response

Infection (16 decks)

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