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Immunology Exam 2 > L05 Phagocytosis > Flashcards

L05 Phagocytosis Flashcards

1
Q

Phagocytosis “Cell Eating”

A

The process by which cells bind, ingest or internalize foreign material or effete host cells and the subsequent destruction thereof

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2
Q

Is phagocytosis essential to life

A

Yes

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3
Q

All __________ cells are capable of this process to one extent or another

A

Nucleated

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4
Q

Professional Phagocytes

A

their main function is phagocytosis

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5
Q

Cells of Professional Phagocytes

A

Neutrophils
Monocytes
Dendritic Cells

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6
Q

Nonprofessional Phagocytes

A

can perform certain aspects of phagocytosis, but we recognize that they have other important functions

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7
Q

Cells of Nonprofessional Phagocytes

A

Basophils
Eosinophils

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8
Q

Quick acting phagocyte

A

Neutrophils

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9
Q

Comprises 60% of peripheral blood leukocytes

A

Neutrophils

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10
Q

Excellent at phagocytosing and killing bacteria

A

Neutrophils

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11
Q

Can kill intracellular or extracellularly

A

Neutrophils

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12
Q

Cannot renew their lysosome and die after digesting a few microbes

A

Neutrophils

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13
Q

Found in large amounts in the pus of wounds

A

Neutrophils (dead)

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14
Q

Multi-lobed Nucleus

A

Neutrophils

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15
Q

known as “large eaters”, make up 5-7% of the leukocytes in the blood

A

Monocytes/Macrophages

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16
Q

derived from monocytes and found in the tissues

A

Macrophages

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17
Q

Depending on the tissue their names can be different

A

Monocytes/Macrophages

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18
Q

Depending on their environment, can be activated as part of immune response

A

Monocytes/Macrophages

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19
Q

Can process and present antigen to T cells (adaptive immune system)

A

Monocytes/Macrophages

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20
Q

Act more slowly than neutrophils but have longer life span (2-4 months in tissue)

A

Monocytes/Macrophages

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21
Q

Can process and “present” antigens to T lymphocytes - can return to the secondary lymphoid organs to “show off” what was internalized

A

Monocytes/Macrophages

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22
Q

Examples of Tissue macrophages include:

A

Microglial cells (brain)
Kupffer cells (liver)
Alveolar macrophages (lungs)
Peritoneal macrophages (peritoneum)

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23
Q

Found throughout the body, but predominantly in potential sites of pathogen entry (skin, lungs, GI tract)

A

Dendritic Cells

24
Q

Named for the “dendrites” or branch like cytoplasmic projections

A

Dendritic Cells

25
Q

Use their projections to encircle and engulf fluid and extracellular pathogens

A

Dendritic Cells

26
Q

Important antigen-presenting cell to T cells

A

Dendritic Cells

27
Q

Important for phagocytosis, but do NOT actively induce generation of reactive oxygen species and/or other toxic products that induce local inflammation

A

Dendritic Cells

28
Q

Which 2 cells have these characteristics:
- arrive slowly
-activated slowly
- have longer life span
- live on to process and present antigen to T cells

A

Monocytes and Dendritic cells

29
Q

Which cell has these characteristics:
- arrive quickly
- quickly activated
- have a short half-life
-Ingest only a few microbes

A

Neutrophils

30
Q

Mechanism of internalization: Endocytosis (3 ways)

A

Pinocytosis
Receptor-mediated endocytosis
Phagocytosis

31
Q

Pinocytosis

A

nonspecific “cell drinking” of soluble molecules

32
Q

Receptor-Mediated Endocytosis

A

(soluble molecules) selective binding of macromolecules to membrane bound receptors triggers internalization

33
Q

Phagocytosis

A

Process whereby cells ingest and destroy insoluble particles (bacteria, viruses, fungi, cells, etc.)

34
Q

Pinocytosis “Cell Drinking”

A

Nonspecific invaginations in the cell membrane with coincidental internalization of accompanying extracellular molecules

35
Q

Steps of Phagocytosis (4 steps)

A

(R) Recognition and attachment of Microbes
(I) Ingestion of Microbes and other material
(D) Destruction of Ingested Microbes or other products
(S) Secretion of effector molecules

36
Q

Recognition and attachment of Microbes

A

Phagocytosis is initiated when several types of receptors are bound by pathogens

-Pathogen Recognition Receptors (PRR’s) (and/or Toll like receptors)

-Complement Receptors

-FC receptors (recognize the bottom 1/2 of Ab molecules)

  • receptors for defenses and/or other molecules
37
Q

Complement Receptors and Fc Receptors bind to ________ on the surface of microbes

A

Opsonins

38
Q

Opsonins are defined as

A

molecules that, when bound to the surface of microbes, make them more attractive to phagocytic cells

39
Q

Examples of opsonins are (2)

A

C3b - from complement pathway and IgG

40
Q

When a microbe is covered with either C3b or IgG, receptors of these opsonins can

A

tightly grab onto the microbe and ingest it

41
Q

Some organisms produce a __________ __________ that makes it challenging for phagocytes to surround and phagocytose these organisms

A

HydroPHILLIC capsule

42
Q

Production of capsules that do not allow phagocytosis is

A

a major determinant of many pathogens’ ability to cause diseases (i.e. a virulence factor or a factor that enables a pathogenic organism to cause disease)

43
Q

in the cases of capsules, opsonins become paramount in

A

the ability of a phagocyte to engulf and destroy these microorganisms

44
Q

Ingest of Microbes and other materials

A

For Phagocytosis:
after attachment, the microorganism is engulfed by extensions of the cytoplasm and cell membrane
once internalized, a vesicle is formed called a Phagocytic Vesicle or Phagosome

45
Q

The formation of the phagosome activates the phagocyte to:

A
  • Increase in cell size
  • Become more phagocytic
    -initiate production of molecules that destroy the engulfed microorganism
46
Q

Destruction of Ingested Microbes or other Products - the phagosome fuses…

A

the phagosome fuses with lysosomal in the cytoplasm to form the phagolysosome

47
Q

Destruction of Ingested Microbes or other Products

A

Within the phagolysosome, multiple products are produced that attack and destroy the ingested pathogen
- the oxidative burst chemical reaction creates superoxide (O2-) hydroxyl radicals and hypochlorite (e.g bleach)

48
Q

Individuals with mutations in enzymes in this pathway (destruction of ingested microbes) have

A

significant immunological deficiencies

49
Q

Oxidative Burst

A

Oxygen dependent reaction in the phagolysosome
- generates molecules that have very potent anti-microbial activities (superoxide, hydrogen peroxide, hydroxyl radicals, hypochlorite ‘bleach’
- enzyme in the last step- Myleoperoxidase (deficiency in this enzyme can cause diseases)

50
Q

Chronic Granulomatous Disease

A

X-linked disease, deficient in Myleoperoxidase and other enzymes
- body uses neutrophils instead which can phagocytose pathogen, but not kill it
- defect of intracellular killing
- Neutrophils become “trojan horse”
-Manifests within first 2 years of life
-Granulomatous lesions found in various organs

51
Q

Destruction of Ingested Microbes or other Products: Toxic Nitrogen Oxides:

A

-Inducible Nitric Oxide synthase (iNOS) is induced by cytokines such as IFN-gamma and TNF-alpha
iNOS - modifies arginine and ultimately makes NO
Nitrous oxide (NO-) - inhibits iron/sulfur-dependent enzymes; damages DNA and oxidizes membrane lipids

52
Q

Within the phagolysosome, other microbial products that contribute to killing:

A

Lysozyme - attacks bacterial cell walls

Lactoferrin - chelates iron, which is necessary for normal microbial metabolism

Defensins - small antimicrobial peptides that distrupt membrane function and can induce osmotic lysis

53
Q

Secretion of effector molecules

A

Not only are molecules produced in the phagolysosome to kill ingested organisms, activated phagocytes produced secreted molecules to alert and activate the rest of the immune response:
Chemokines - recruit additional cell types
Cytokines - to activate infiltrating cells
Nitrous oxide - can be secreted
Degradative enzymes

54
Q

Mechanism to increase phagocytosis and killing neutrophils

A

Neutrophils inherently don’t require significant stimulus to phagocytose and kill
However, certain stimuli have been shown to enhance neutrophil activation, phagocytosis and killing
- stimulation of PRR’s on neutrophils
-complement can increase oxidative burst in neutrophils
-cytokines can also help

55
Q

Monocyte/Macrophages and Dendritic cells require activation of phagocytose

A

-Stimulation of PRR’s
- engagement of complement receptors and Fc receptors on the surface
-Cytokines, such as IFN-gamma, can signficantly impact monocyte differentiation into macrophages and activation to kill; IFN-gamma can also increase the ability of both macrophages and dendritic cells to present antigen

56
Q

What happens after the pathogen is phagocytose and destroyed?

A
  • Nucleic acids and amino acids are re-used
  • Proteins are broken down into peptide fragments that are “presented” to T lymphocytes to activate T cells (only macrophages and dendritic cells) in a process called Antigen Presenting

Immunology Exam 2 (4 decks)

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