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micr 386 > module 01 section 02 (innate immune system) > Flashcards

module 01 section 02 (innate immune system) Flashcards

1
Q

when does the innate immune system develop?

A

present at birth

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2
Q

what are 5 characteristics of the innate immune system?

A

(1) unchanging
(2) immediate
(3) nonspecific reactivities
(4) broad range of targets
(5) no memory

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3
Q

define “unchanging” with respect to the innate immune system

A

continuous protection without rearragement or alterations in the response

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4
Q

define “immediate” with respect to the innate immune system

A

response to patogens occurs within minutes

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5
Q

define “nonspecific reactivities” with respect to the innate immune system

A

innate immune reaction can be to a common component on multiple pathogens

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6
Q

define “broad range of targets” with respect to the innate immune system

A

any element which is identified as foreign will ellict a response

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7
Q

define “no memory” with respect to the innate immune system

A

this response is present from birth and is not improved through repeated exposure

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8
Q

the innate immune system has barriers that aim to keep foreign particles out of the body and prevent spreading, how many are there and what are they?

A

2

  • physical
  • chemical
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9
Q

what are the physical barriers of the innate immune system?

A
  • mucous membranes
  • cilia/hairs
  • epithelial barriers
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10
Q

what is the function of mucous membranes w respect to the innate IS?

A

trap pathogens and foreign materials

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11
Q

what is the function of cilia/hair w respect to the innate IS?

A

to move trapped pathogens out of the respiratory system via a concerted sweeping motion

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12
Q

what is the function of epithelial barriers w respect to the innate IS?
provide an example

A
  • skin, GI tract and respiratory tract all produce peptides with natural antibiotic funtion
  • e.g. defensins (cys rich peptides) are present in the skin and abundant in neutrophil wbc granules
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13
Q

which cells are most importatnt for the function of the innate IS?

A

wbcs (aka leukocytes)

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14
Q

what is the function of wbc’s?

A

protect the body by identifying and eliminating foreign invaders

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15
Q

how are wbc’s derived?

A
  • from hematopoietic stem cells in the bone marrow

- specialization results in several types of leukocytes

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16
Q

where are wbc’s found?

A

blood and lymphatic tissue

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17
Q

what are the possible groupings of leukocytes?

A

phagocytes, granulocytes and NK cells

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18
Q

can some cells be more than one type of leukocyte? why or why not?

A
  • yes: can be both phagocyte and granulocyte

- neutrophils are both !

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19
Q

what are phagocytes?

A

cells that ingest foreign particles, bacteria and dead/dying cells

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20
Q

what are granulocytes?

A

leukocytes with secretory granules in its cytoplasm

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21
Q

what are the three types of phagocytes?

A

neutrophils, macrophages and dendritic cells

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22
Q

define “neutrophils”

what percent of the innate IS cells corresponds to these?

A
  • the frist responding leukocytes to migrate to the site of infalmmation and to ingest microbes to be killed
  • they become increasingly segmented as they mature
  • 50-70% of cells in the innate IS
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23
Q

define “macrophages”

what percent of the innate IS cells corresponds to these?

A
  • most professional
  • ingest aged neutrophils and bacteria
  • secrete cytokines that stimualte inflammation and recruitment of other immune cells to the site of injury/infection
  • 1-6% of cells of the innate IS
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24
Q

define “dendritic cells”

what percent of the innate IS cells corresponds to these?

A
  • found on tissues in contact with the external environment

- serve as a link btwn the innate and adaptive IS’s

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25
Q

what are the types of granulocytes?

A

eosinophils, basophils, mast cells, neutrophils

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26
Q

define “eosinophils”

what percent of the innate IS cells corresponds to these?

A
  • secrete histamines and free radicals once activated by parasitic infection
  • important mediators for allergic responses
  • 1-3% of cells of the IS
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27
Q

what is the role of histamines?

A

vasoactive amine: causes contraction of sm and dilation of capillaries

28
Q

define “basophils”

what percent of the innate IS cells corresponds to these?

A
  • secrete heparin and histamine in response to parasitic and allergic inflammatory reactions
  • <1% of cells of the IS
29
Q

define “mast cells”

what percent of the innate IS cells corresponds to these?

A
  • role in allergy and anaphylaxis through heparin and histamine rich granules
  • have protective role in wound healing, angiogenesis and blood-brain barrier function
  • <1% of cells in the IS
30
Q

what is angiogenesis?

A

formation of new bvs

31
Q

define “NK cells”

A
  • large, granular, cytotoxic lymphocytes that do not have T or B cell receptors
  • play a fundemental role in surveillance of altered cells (cancer)
  • play a major role in the host-rejection of both tumours and virally infected cells
32
Q

do NK require activation to kill cells that they identify as non-self? explain.

A

no - they kill in an antibody independent manner

33
Q

can NK cells interact with antibodies? why or why not?

A
  • yes
  • during antibody-dependent cell mediated cytotoxicity for a faster immune response upon subsequent exposures to the antigen
34
Q

define “antibody-dependent cell mediated cytotoxicity”

A

a cell mediated rxn in which nonspecific cytotoxic cells that express Fc receptors recognize the bound antibody on the target cells and subsequently cause lysis of the target cell

35
Q

where are specialized NK cells found?

A

in the placenta - may play a role in pregnancy

36
Q

list 4 important proteins of the innate IS

A

(1) complement proteins
(2) mannose-binding lectin (collectin)
(3) c-reactive proteins (pentraxin)
(4) coagulation factors

37
Q

define the role of complement proteins

A

mark pathogens for destruction (opsonization or cell lysis)

38
Q

define “opsonization”

A

process by which a pathogen is marked for phagocytosis and may occur in different immune responses

39
Q

define “opsonins”

A

proteins that coat the pathogen and promote attachement of phagocytes

40
Q

define the role of mannose-binding lectin

A

involved in opsonization of microbes and activation of complement system via the lectin pathway

41
Q

define the role of c-reactive proteins

A
  • involved in opsonization of microbes and activation of complement system
  • these are a member of the acute phase proteins that are secreted by hepatocytes of the liver in response to inflammation
42
Q

define the role of coagulation factors

A

involved in coagulation of blood and repair of damaged vessels

43
Q

what occurs following infection?

A
  • an acute inflammatory response as an inflammatory barrier alongside coagulation
  • there will be swelling of the capillaries near the infection
44
Q

what are the signs of inflammation?

A
  • erythema (tissue redness)
  • edema (tissue swelling)
  • heat
  • pain
45
Q

define “phagocytosis”

A

an important method of eliminating invading pathogens

46
Q

what is phagocytosis activted by?

A

the recognition of PAMPs

47
Q

what are PAMPs?

A
  • i.e. pathogen-associated molecular patterns

- small molecule motifs conserved within a group of pathogens that are recognized by phagocytes of the innate IS

48
Q

define the role of opsonins in phagocytosis

A

these can act as attachment sites for receptors that aid in the phagocytosis of pathogens

49
Q

explain the state of neutrophils and macrophages after phagocytosis

A
  • neutrophils are short-lived and form pus

- macrophages are long-lived and continue to form lysosomes

50
Q

what are the 5 steps of phagocytosis

A

(1) attachment
(2) ingestion
(3) fusion
(4) digestion
(5) release

51
Q

define the “attachment phase”

this phase of phagocytosis is dependent on what?

A
  • (initiation of phagocytosis)
  • attachment phase = recognition and binding of the microbe
  • macrophages and neutrophils express many cell surface receptors that may bind microbes for subsequent phagocytosis
  • the attachment phase is dependent on these specific receptors recognizing a variety of microbes
52
Q

explain the role of LPS receptors in the initation (attachment phase) of phagocytosis

A
  • most highly conserved component of gram-neg bacteria
  • LPS binding to the LPS receptor is the innitation of an inflammatory singnalling cascade
  • LPS receptor = CD14-toll-like receptor 4
53
Q

explain the role of scavenger receptors in the initation (attachment phase) of phagocytosis

A
  • these are a family of receptors that are integral to the removal of any foreign substances and waste materials
  • they bind to a wide variety of ligands, including LDLs
54
Q

explain the role of monnose receptors in the initation (attachment phase) of phagocytosis

A
  • monnose expression is exclusive to microbes

- this receptor acts as a pattern regonition receptos (PRR) that is capable of recognizing several different microbes

55
Q

define “PRRs”

A
  • proteins expressed on cells of the innate IS that identify two classes of molecules:
    (1) pathogen-associated molecular patterns: associated with microbial pathogens
    (2) damage-associated molecular patterns: associated with cell components released during cell damage or death
56
Q

explain the role of N-formyl methionyl receptors in the initation (attachment phase) of phagocytosis

A
  • bacteria produce f-met-leu-phe (fMLP) proteins that have an amio-terminal N-formylated met
  • fMLP will also recruit inflammatory cells such as neutorphils
57
Q

define “unenhanced attachment”

what does this?

A
  • type of attachment done by LPS, monnose and the N-formyl methionyl receptors
  • it is the nonspecific innate recognition of PAMPs through PRRs
  • the attachment step can be enhanced such that phagocytosis of a microbe is more efficient and specific
58
Q

define “enhanced attachment”

what does this?

A
  • attachment of an opsonized microbe to the phagocyte
  • opsonization can occur via IgG antibodies, complement proteins or acute phase proteins such as mannose binding lectin and C-reactive proteins
59
Q

list the receptors that may innitiate phagocytosis upon attachment

A

LPS, N-formyl methionyl, mannose, scavenger

60
Q

list the opsonins we have covered

recall opsonins are proteins that coat pathogens to promote the attachment of phagocytes

A

complement proteins, mannose-binding lectins, C-reactive proteins, coagualtion factors

61
Q

describe ingestion

A
  • (encapsulation of the microbe)
  • following attachment, pseudopods surrond and engulf the microbe placing it in a phagosome (endocytic vesicle)
  • an electron pump brings protons into the phagosome
  • this lowers the pH to ~4, preparing for the next steps of phagocytosis
62
Q

describe fusion

A
  • (creating the phagolysosome)
  • phagocytes contain lysosomes which travel along microtubules within the phagocyte and fuse with the phagosomes to create phagolysosomes
63
Q

what is a lysosome?
where are they created?
where can they be found?

A
  • organelle containing proteolytic/digestive enzymes

- derived from the golgi apparatus and are found in the cytoplasm

64
Q

describe digestion

A
  • (killing of the microbe)
  • microbes are broken down by lysosomal enzymes in the phagolysosome
  • phagocyte oxidase in the phagolysosome membrane generates reactive o2 intermediates (ROI) which are strong oxidizing agents
  • inducible nitric oxide synthase (iNOS) synthesizes nitric oxide which creates oxidative toxins that further damage the biological molecules
65
Q

describe release

A
  • (residual body exocytosis)
  • the indigestible materials remaining in vesicles = residual bodies
  • these can be released via exocytosis or displayed via MHC-antigen complexes through the exogenous antigen processing pathway
66
Q

define “MHC-antigen complexes”

A

the interaction of self molecule detecting protein MHC with a self or non self molecule (antigen)

67
Q

define “exogenous antigen processing pathway”

A

an antigen processing pathway used by specialized antigen presenting cells to present peptides derived from proteins that the cell has endocytosed

micr 386 (31 decks)

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