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Veterinary Immunology > Lecture 5 - Phagocytosis > Flashcards

Lecture 5 - Phagocytosis Flashcards

1
Q

What is phagocytosis

A

ability of some cells to ingest foreign particles

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2
Q

What are phagocytes

A

class of cells which are capable of ingestion and
killing of microorganisms that incite inflammatory response

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3
Q

What cells are the first to accumulate around invaders and initiate phagocytosis

A

neutrophils

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4
Q

What are the second cells to migrate to the tissue site and intiate phagocytosis

A

local and blood-borne macrophages

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5
Q

Neutrophils and macrophages are sometimes referred to as _____ for their roles in phagocytosis

A

professional phagocytes

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6
Q

What are the 2 professional phagocytes

A

neutrophils and macrophages

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7
Q

What are the 4 steps of phagocytosis

A
  1. chemotaxis
  2. adherance
  3. ingestion
  4. destruction
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8
Q

What is chemotaxis (in regards to phagocytosis)

A

delivery of phagocytic cells to the infection site

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9
Q

What is adherance (in regards to phagocytosis)

A

phagocytic adherance to the target

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10
Q

What is ingestion (in regards to phagocytosis)

A

engulfment of the target particle

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11
Q

What is destruction (in regards to phagocytosis)

A

intracellular killing and digestion of the target

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12
Q

What part of phagocytosis is only in the case of macrophages

A

egestion

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13
Q

What can neutrophils phagocytose

A

anything more HYDROPHOBIC than itself

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14
Q

What is opsonization

A

coating of a hydrophilic material
with opsonins that include IgG, IgM, C3b, etc

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15
Q

What happens after opsonization of a hydrophilic substance

A

allows neutrophils to bind it

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16
Q

What bacteria can neutrophils NOT phagocytose until they are opsonized

A

bacteria with HYDROPHILIC capsules (Staphylococcus, Streptococcus, Klebsiella)

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17
Q

Why are mycobacteria sp. easily phagocytosed by neutrophils

A

have hydrophobic capsules

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18
Q

What 2 neutrophil membrane receptors are important for phagocytosis

A

Fc and C3b

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19
Q

What do Fc receptors bind

A

antibody that is bound to an antigen, especially IgG antibody

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20
Q

What do C3b receptors bind

A

to C3b when it is coating bacteria, ect.

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21
Q

What happens once neutrophils bind to opsonized material

A

it is readily engulfed, forming phagosome

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22
Q

What is a phagosome

A

membrane bound vesicle containing the ingested microbe or material

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23
Q

What happens when a phagosome migrates into the cytoplasm and collides with lysosomal granules

A

lysosomal granules explosively discharge their contents into the membrane-enclosed vesicle (phagosome)

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24
Q

What is formed when membranes of the phagosome and lysosome fuse

A

digestive vacuole called phagolysosome

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25
Q

What can fuse with the phagolysosomes

A

other lysosomes

26
Q

What occurs within the phagolysosome

A

killing and digesting of the engulfed microbe

27
Q

What does it mean when the killing process is confined to the phagolysosome?

A

none of the toxic substances and lethal activities of the phagocytes are turned against themselves

28
Q

What is the first detectable effect on bacterial physiology after phagolysosome formation; and how fast does it occur after engulfment

A

loss of viability; within a few minutes

29
Q

What happens 10-30 minutes after ingestion

A

many pathogenic and nonpathogenic bacteria are killed followed by lysis and digestion of the bacteria by lysosomal enzymes

30
Q

What are the 3 killing processes

A
  1. lytic enzymes and antimicrobial peptides from granules
  2. oxidative metabolism (respiratory burst)
  3. neutrophil extracellular traps
31
Q

What are stored in primary and secondary granules

A

lytic enzyme and antimicrobila peptides

32
Q

Where are lytic enzymes and antimicrobial peptides stored

A

primary and secondary granules

33
Q

What are the 4 primary granules?

A
  1. hydrolases
  2. lysozyme
  3. defensins
  4. myeloperoxidase
34
Q

What are hydrolases

A

breaks covalent bonds by adding water, important
for degrading dead bacteria or dead tissues

35
Q

What are lysozymes

A

breaks down peptidoglycan in Gram-positive bacteria. Found in many secretions in the body

36
Q

What are defensins

A

small cationic proteins that kill bacteria, especially
Gram-positive bacteria; 29-42 amino acids long; hydrophobic outside and hydrophilic interior and insert into a membrane and form a pore

37
Q

What is another name for defensins

A

antimicrobial peptides

38
Q

What is a myeloperoxidase

A

enzyme that has an important role in the oxygen mediated killing mechanism

39
Q

What are the 3 secondayr granules

A
  1. lysozymes
  2. lactoferrin
  3. collagenase
40
Q

What is lactoferrin

A

chelates iron- bacteria need iron for survival

41
Q

What is collagenase

A

degrades connective tissue, so it can move through to the site of inflammation

42
Q

What is the most potent killing mechanism of a neutrophil

A

oxygen mediated killing mechanism

43
Q

Where does oxygen mediated killing occur

A

phagolysosome

44
Q

What are the killing products of the respiratory burst

A
  1. hypochlorite
  2. hydrogen peroxide
  3. aldehydes
  4. oxygen radicals (superoxide anion and hydroxyl radical)
45
Q

What s chronic granulomatous disease

A

fatal disease causes by defective oxidative enzyme

46
Q

What are neutrophil extracellular traps (NETs)

A

Stimulated neutrophils release nuclear material and granular proteins extracellularly

47
Q

What are NETs neutrophils stimulated by

A

CXCL8 or LPS

48
Q

What nuclear material and granular proteins do NETs release extracellular

A

DNA, histones, granular proteins

49
Q

What does the extracellular degranulation in NETs creat

A

mesh that traps bacteria and the antimicrobial proteins kill the bacteria

50
Q

NET is NOT a result of neutrophil death but an active response to _____

A

inflammatory stimuli called as NETosis

51
Q

What is the fate of neutrophils after extended phagocytosis, killing, and digestion of baterial cells AND what does this form

A

die and lyse; forms pus

52
Q

What is the fate of macrophages

A

egest digested debris and allow insertion of microbial antigenic components into the plasma membrane for presentation to lymphocytes in the immunological response

53
Q

What are the major surface receptors of macrophages

A
  1. complement receptors
  2. antibody receptors
54
Q

How are macrophages innately activated

A

TLRs and related receptors

55
Q

What does IL-4, IL-13, and IL-10 do to macrophages

A

alternate activation- M2 cells (tissue repair and less microbial killing)

56
Q

What does IFN-y do to macrohages

A

classical activation-M1 cells

57
Q

How does arginine cells activate macrophages

A
  1. converted to ornithine, activates M2 cells
  2. NOS2 activates M1 cells
58
Q

What is the role of macrophages in chronic infections

A

prolonged tissue irritation->M2 macrophages accumulate->IL-1, TGFB, fibroblast GF, angiogenic factors->fibrosis->granuloma formation

59
Q

how do macophages remove dying neutrophils

A

when CD31 fails to reply, neutrophil is phagocytosed

60
Q

What cells begin the healing process in damaged tissues?

A

macrophages

Veterinary Immunology (20 decks)

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