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Micro - Immunology > Lec 3 Immunity > Flashcards

Lec 3 Immunity Flashcards

1
Q

What is immunity

A

A defense mechanism mediated by the immune system against infections and other diseases.

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2
Q

Main function of the immune system?

A

to prevent or limit infections and other diseases.

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3
Q

What is the defensive function performed by?

A

by various cellular and humoral components of the immune system, which interact with each other producing coordinated immune response that eliminates the pathogen.

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4
Q

What is the first line of immune defense?

A

innate or natural or non-specific immunity

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5
Q

What is the 2nd line of immune defenses?

A

Adaptive or acquired or specific immunity

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6
Q

Do the first and second line of defense operative independently of each other? If so, how?

A
  • innate and adaptive immunity do not operate in independence of each other
  • Their components can interact through various cytokines and adhesion molecules.
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7
Q

What is innate immunity defined as?

A

Immunity not acquired by contact with an antigen. It is the natural inborn immunity against invasion by microorganisms.

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8
Q

Where does innate immunity take place?

A

in any part of the body

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9
Q

What are the key features of innate immunity?

A
  • Non- specific(acts against any foreign invader)
  • Rapid(elements are in active state)
  • Does not react against self molecules
  • No immunological memory
  • No improvement upon subsequent exposures to the same microorganism.
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10
Q

What are the mechanisms of innate immunity?

A

1- First line of natural defenses

2- Second line of natural defenses

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11
Q

What is the first line of natural defenses?

A

include all the barriers at portals of entry of microorganisms that prevent entry of the microorganism

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12
Q

What is the second line of natural defenses?

A

reacts if the invading pathogen succeeds to get through the first line of natural defenses and enters the body tissues. Thereby it limits the infection.

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13
Q

What are examples of mechanical barriers? (1st line of natural defenses)

A
  • Intact skin (keratin layer)
  • Mucus membranes (trap microbes)
  • Mucus and ciliary apparatus.
  • Nasal hair
  • Coughing and sneezing
  • Eye lashes , blinking reflex and tears
  • Micturition reflex (flushing reflex)
  • Diarrhea and vomiting reflex (expels the microbe)
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14
Q

What are examples of chemical barriers? (2nd line of natural defenses)

A
  • Sweat and sebaceous secretions in skin(acidic pH,lysozyme and fatty acids)
  • Hydrolytic enzymes in saliva.
  • HCL in stomach secretions
  • Proteolytic enzymes in small intestine
  • Tears(lysozyme)
  • Acidic pH in adult vagina
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15
Q

What do cellular barriers include?

A

Normal flora

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16
Q

Where is the normal flora present?

A

portals of entry into the body

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17
Q

How does normal flora suppress growth of pathogens?

A
  • Competition for essential nutrients and site.

- Production of killing substances such as colicins or acids

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18
Q

What are the cells of innate immunity?

A
  • Phagocytic cells

- NK cells

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19
Q

What are examples of phagocytic cells?

A

Monocytes
macrophages
neutrophils
dendritic cells

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20
Q

What is the function of phagocytic cells?

A

Ingest and kill the microorganism (intracellular killing)

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21
Q

Describe shape of NK cells

A

large granular lymphocytes

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22
Q

What is the function of NK cells?

A

have a non-specific cytotoxic activity on virus-infected cells ,tumor cells and grafted cells (extracellular killing).

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23
Q

Examples of circulating proteins in serum and body fluids

A
  • Lysozyme
  • Complement proteins
  • Acute phase proteins
  • Interferons
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24
Q

What activates the complement proteins?

A

alternative pathway

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25
Q

What does activation of complement proteins promote?

A

promote inflammation and phagocytosis.

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26
Q

What are acute phase proteins produced by?

A

produced by macrophages

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27
Q

When are acute phase proteins produced?

A

when stimulated by microbial products

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28
Q

What is the function of acute phase proteins?

A

Can bind to microbes resulting in activation of complement.

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29
Q

What are interferons? What are their functions?

A

proteins released from virus-infected cells to protect uninfected cells.

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30
Q

Where are lysozyme present?

A

all body fluids

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31
Q

What are the cytokines of innate immunity?

A

Chemical mediators released from stimulated cells

32
Q

What is the function of cytokines?

A

Important for initiation of inflammation

33
Q

cytokines of innate immunity mainly include?

A

IL1,IL6,IL8 and TNF-alfa produced by macrophages

34
Q

What is IFN-y

A

produced by NK cells to activate macrophages.

35
Q

When are IFN-alpha and beta released?

A

released by virus-infected cells; inhibit viral replication and prevent its spread to uninfected cells.

36
Q

What is a fever

A

Thermal set- point altered in hypothalamus by pyrogens

37
Q

What does fever stimulate?

A

Stimulates leucocytes into action

38
Q

What does fever inhibit?

A

decreasing availability of iron and can kill the microbe.

39
Q

What are examples of exogenous pyrogens?

A
  • Endotoxin of Gram- negative bacteria
  • Staphylococcus enterotoxin
  • Streptococcus group- A Erythrogenic toxin
40
Q

Examples of endogenous pyrogens?

A

IL1, IL6 and TNF-alpha

41
Q

When does the inflammatory response occur?

A

Follows tissue damage caused by a wound or invading pathogen.

42
Q

What does the inflammatory response include?

A
  • vasodilatation of capillaries leading to redness and increase of tissue temperature.
  • increased capillary permeability and influx of fluids and cells into the tissues causing oedema
  • influx of phagocytes from the capillaries into the site of tissue damage. Phagocytes ingest and kill the microbe.
43
Q

What factors affect immunity?

A

1- Race or genetic make up: certain races are more susceptible than others to certain microbes.
2-Age: extremes of age more susceptible to diseases
3-Nutritional status: undernutrition and malnutrition
4-Hormones and steroids
5-Diseases: Diabetes mellitus patients, cancer patients, renal failure
6- Radiation
7-Chemotherapy
8-Immunosuppressive and cytotoxic drugs.

44
Q

What are the events of infection?

A

1- Entry of pathogen
2- Recognition of pathogen by the immune system
3- Phagocytosis and killing of the pathogen
4- Induction of inflammation
5- Attraction of immune cells to site of infection
6- Elimination of pathogen and or
7- Activation of adaptive immune response

45
Q

How does recognition of pathogen by innate immune system take place?

A
  • Takes place by a number of receptors including cell-surface receptors on immune cells.
  • These receptors recognize and bind to ligands present only on cell surface of the pathogen and not found on human cells, or bind to soluble molecules produced by the microbe e. g toxin
46
Q

What are the recognition receptors of innate immune cells known as?

A

PATTERN RECOGNITION RECEPTORS (PRRs)

47
Q

What are pattern recognition receptors?

A

A genetically stable set of receptors programmed to non-self structures.

48
Q

What are pattern recognition receptors present as?

A

Present as extracellular proteins or membrane-bound proteins on innate immune cells .

49
Q

What do PRRs recognize and bind to?

A

recognize and bind PATHOGEN-ASSOCIATED MOLECULAR PATTERNS ( PAMPs

50
Q

Where are PAMPS present?

A

present only on cell surface of pathogen.

51
Q

What can PAMPS be?

A

sugars, proteins, lipids and nucleic acids of microbes

52
Q

What are some examples of PAMPS?

A

lipopolysaccharide,peptidoglycan of bacteria.

53
Q

What else to PRRs bind to?

A

-they bind to structures produced by host cells in response to stress(MICA and MICB)

54
Q

What is an example of the structures produced by host cells in response to stress that PRRs bind to?

A

-infection or injury or to soluble host proteins coating the pathogen such as complement C3b or Fc of IgG.

55
Q

What are categories of PRRs?

A 
1-Toll-like receptors(TLRs)
2-Killer activation receptors(KARs):
3-Killer inhibition receptors (KIRs):
4-Complement receptors:
5-Fc receptors
6-Mannan-binding lectin(MBL)
7-Scavenger receptors
56
Q

Where are TLRs present?

A

Present on a variety of immune cells such as macrophages, monocytes and dendritic cells.

57
Q

What do TLRs do once bound to amps?

A

they mediate cytokine production to promote inflammation and attraction of phagocytes to site of infection.

58
Q

Where are KARs present?

A

surface of NK cells

59
Q

What do KARs recognize?

A

presence of stress-related molecules(MICA and MICB) expressed by abnormal host cells such as virus- infected cells or cancer cells.

60
Q

What does binding of MICA and MICB by KARs induce?

A

Binding of MICA and MICB by KARs induces the NK cell to attach and kill the infected host cell.

61
Q

Where are KIRs found?

A

on surface of NK cells

62
Q

Why are KIRs used by NK cells?

A

to monitor MHC I molecules normally present on cell surface of all nucleated cells.

63
Q

What happens if cell surface on all nucleated cells is sub-normal?

A

the NK cell proceeds to kill the cell.

64
Q

What can decrease amount of MHC 1 on an affected cell?

A

Viral infection and neoplastic changes on cells decrease the number of MHC I on the affected cell.

65
Q

Where are complement receptors displayed?

A

Proteins displayed on phagocytic cells and B-cells.

e.g.C3b receptor on phagocytic cell.

66
Q

What do complement receptors bind to?

A

Can bind to microbial surfaces and tag the microbe for destruction by the phagocytic cell

67
Q

What is binding of CRs to microbial surfaces done through?

A

complement proteins such as C3b which is an opsonin that coats the pathogen.

68
Q

What is the relationship between complement receptors and phagocytes?

A

Can attract phagocytes to site of infection to kill the microbe.

69
Q

What are FC receptors expressed on?

A

Expressed on surface of phagocytes.

70
Q

What is the function of FC receptors? What is the process known as?

A

Can bind the Fc portion of IgG-bound to a microbe and induce the phagocyte to ingest and kill the microbe.
Process is known as opsonization and IgG is an opsonin

71
Q

What is the function of MBL?

A

enables phagocytes to recognize and bind to sugar residues on surface of some pathogens.

72
Q

Where are scavenger receptors found?

A

phagocytes

73
Q

Where are FC receptors for IgG expressed?

A

Expressed on surface of phagocytes.

74
Q

What is opsonization?

A

process of coating a microorganism by an opsonin to facilitate phagocytosis.

75
Q

What do the opsonins include?

A
  • The immunoglobulin IgG

- Complement proteins C3b,iC3b and C4b.

Micro - Immunology (6 decks)

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