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Host Defense Exam 1 > Cells of the Immune System > Flashcards

Cells of the Immune System Flashcards

1
Q

What two cell types comprise the HSC niche? What is the purpose of the niche?

A

The HSC niche consists of osteoblasts or sinusoidal endothelial cells. Even though HSCs have the ability to self-renew, they must be surrounded by this niche in order to do so.

The niche supplies growth factors and other regulatory molecules that support HSC-self-renewal.

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2
Q

Can HSCs be found in circulation?

A

Yes

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3
Q

What causes HSCs to home to their niche?

A

Chemical signals pull HSCs out of circulation and into their niches in the bone marrow so that they can grow

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4
Q

What are stromal cells?

A

Stromal cells are located within the niches and provide factors for HSC maintenance and differentiation.

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5
Q

What is the timing of return of HSCs to circulation?

A

HSC return to circulation is controlled in a circadian manner

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6
Q

How far along can stromal cells push HSCs towards differentiation?

A

Stromal factors can push HSCs to differentiate into progenitors (common myeloid or lymphoid) cells. Further differentiation is determined by stimulating factors and cytokine availability.

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7
Q

What cells are derived from common lymphoid progenitors?

A

NK cells, B-cells and T-cells.

All others are derived from the myeloid progenitor

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8
Q

What two cells can be derived from the monocyte?

A

macrophages and dendritic cells

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9
Q

What two factors are commonly involved in the HSC differentiation for common myeloid progenitors?

A

IL-3 and GM-CSF

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10
Q

What factor is commonly involved in HSC differentiation for common lymphoid progenitors?

A

IL-7

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11
Q

What factor stimulates differentiation into basophils?

A

IL-4

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12
Q

What factor stimulates differentiation into neutrophils?

A

G-CSF

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13
Q

What factor stimulates differentiation into eosinophils?

A

IL-5

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14
Q

What factors stimulate differentiation into monocytes and macrophages?

A

GM-CSF and/or M-CSF

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15
Q

What factors stimulate differentiation into dendritic cells?

A

Flt3L

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16
Q

What factors stimulate differentiation into T-cells?

A

IL-2 and IL-7

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17
Q

What factors stimulate differentiation into B-cells?

A

IL-3 and IL-7

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18
Q

How might a cytokine/differentiation factor be used clinically to help a patient?

A

Example: give patients G-CSF to help stimulate neutrophils to come out of the bone marrow and fight infection

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19
Q

Where are most immune cells in the body?

A

Most immune cells are constantly on the move, circulating through the blood, hoping for a chance encounter with a pathogen.

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20
Q

How do naive lymphocytes enter lymph nodes?

A

Through the blood (through HEVs)

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21
Q

How do antigens from sites of infection reach a lymph node?

A

Through lymphatics- they are taken from the site of infection by immune cells and travel through the lymphatics until they reach the lymph nodes

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22
Q

What happens to naive lymphocytes that don’t match their antigen in a lymph node?

A

After spending time in the lymphoid organ, the lymphocytes return to the blood circulation by traveling through the lymph system. They will then keep looking for their matching pathogen.

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23
Q

What happens to a lymphocyte that does find their match in a lymph node?

A

Naive T-cells will be activated and leave the and go to the site of infection via the bloodstream if they met their specific pathogen in the lymphoid organ.

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24
Q

Name 4 “lymphoid depots” where lymphoid cells may meet their specific antigen

A
  1. Lymph Nodes
  2. Spleen
  3. Peyer’s patches in the mucosal lymphoid tissue (like the intestine)
  4. Tonsils/adenoids
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25
Q

Do activated lymphocytes reach the site of infection via blood or lymphatics?

A

Blood- the lymphocytes will enter the systemic circulation via thoracic duct –> left subclavian vein

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26
Q

What is another name for neutrophils? Why?

A

polymorphonuclear cells (PMN’s). They are identified by their multi-lobed nucleus

27
Q

What is the appearance of neutrophils when stained with H&E?

A

Neutrophils are one of the granulocytic myeloid cells, so they have cytoplasmic granules that are neither basic nor very acidic. They appear light pink or “neutral” on H&E staining

28
Q

Which cells are the most abundant white blood cells?

A

Neutrophils. They are the most important front-line defense of the innate immune system.

29
Q

Discuss the ability to fight off infection with neutropenia.

A

Low neutrophils make it difficult to fight off basic infections. Without neutrophils or other antibiotics, you would die of an otherwise non-lethal infection

30
Q

What are neutrophils main job?

A

Phagocytosis and activation of bactericidal mechanisms

31
Q

What is the lifespan of a neutrophil?

A

Neutrophils are very short lived, and usually die after 1 round of phagocytosis.

32
Q

How do neutrophils kill microorganisms that are too large to ingest?

A

Extracellular killing mechanisms: they can spill the contents of their antimicrobial granules into the extracellular milieu, which, in addition to being microbial, can also cause local tissue damage

33
Q

What are “NETs”?

A

neutrophil extracellular traps- full of granular enzymes and killing molecules + DNA elements which act to immobilize pathogens to decrease spreading and help with phagocytosis

34
Q

What is the main component of pus?

A

Dead neutrophils

35
Q

What is the primary role of macrophages?

A

Phagocytosis and intracellular killing

36
Q

Differentiate primary vs secondary neutrophil granules

A

Primary: direct toxic/enzymatic activity
Secondary: Free radical formation

37
Q

What are the three ways neutrophils kill invaders?

A

Nets, phagocytosis, extracellular killing

38
Q

What organelle is overly represented in macrophages and why?

A

Lysosomes- macrophages phagocytose pathogens and kill them through formation of a phagolysosome

39
Q

How do macrophages involve the adaptive immune system in a response to an invader?

A

Macrophages present antigens to T-cells in the lymphoid tissues

40
Q

Which cells are important for the release of inflammatory cytokines?

A

Macrophages

41
Q

Briefly, how to macrophages recognize foreign invaders?

A

Through pattern recognition receptors (e.g. TLRs, mannose receptors, LPS receptors, and glucan receptors)

42
Q

Name three pro-inflammatory cytokines released by macrophages at the site of an infection

A

IL-1 beta
TNF-alpha
IL-6

43
Q

What is the primary focus of a dendritic cell?

A

Antigen presentation. Dendritic cells degrade pathogens, but for the purpose of presentation (not killing)

44
Q

Which cells provide the crucial link between the innate and adaptive immune system?

A

DCs: without them, a robust T cell response toward new microbes probably wouldn’t exist and we would never form life-long memory towards infections that we have previously encountered

45
Q

What two ways can dendritic cells pick up antigen?

A

phagocytosis and macropinocytosis

46
Q

Why is it so important that dendritic cells can recognize an incredible diverse set of antigens?

A

Because of dendritic cell versatility in the antigens they can present, there is very little that can escape recognition by immune system

47
Q

What is the appearance of eosinophils upon H&E staining?

A

Bright pink due to their highly basic granules. They usually have a bilobed nucleus

Eosinophils are granulocytes

48
Q

What is the main role of eosinophils?

A

Eosinophils are charged with the job of neutralizing and destroying large parasitic invaders

49
Q

Why is it important that eosinophils are tightly regulated?

A

In order to kill a parasite, eosinophils release many enzymes and molecules that cause tissue destruction to not only the pathogens, but the surrounding tissue.

50
Q

In what type of tissue are eosinophils normally found?

A

subepithelial connective tissue

51
Q

What is the role of eosinophils in an allergic reaction?

A

The granules release by eosinophils can augment and help sustain allergic responses causing them to be chronic. The damage down to surrounding tissue can be significant and permanent

52
Q

.Describe the appearance of mast cells

A

Mast cells are large, mononuclear cells that are filled with dark, basophilic granules containing mainly acidic histamine.

53
Q

What is the main job of mast cells?

A

Open the vascular doors. This allows the recruited white blood cells to enter the site of infection.

This is accomplished through release of vasoactive substances upon activation

54
Q

What are some of problems associated with non-pathogen mast cell activation?

A

Locally: local damage

Systemically: vasodilation and vascular permeability leads to loss of blood pressure, airway constriction and swelling of the epiglottis.

55
Q

What is allergic urticaria?

A

Hives: caused by slowly absorbed ingested allergens that reach the skin, which then activate mast cells and cause large, itchy,, red swellings (hives)

56
Q

Which cells are known as “the accomplice to mast cells and eosinophils”?

A

basophils

57
Q

What is the role of basophils?

A

anti-parasitic and allergic responses

58
Q

What is the appearance of natural killer cells?

A

NK cells are easily identifiable as large cells that are mononuclear and have a very distinctive granular cytoplasm compared to the previous granulocytes

59
Q

What is the primary role of nk cells?

A

NK cells primarily attack virus infected cells or tumor cells and release their granules that cause their target cell to undergo apoptosis

60
Q

How are NK cell surface receptors different from B and T cells surface receptors?

A

They are invariant- they do not rearrange and become specific for one type of antigen

61
Q

What is the role of activated B cells?

A

Production of antibodies

62
Q

What are plasma cells?

A

Soluble antibody-making machines (effector B-cells)

63
Q

Which cells are the “commander and chief” of the immune system, and why?

A

T-cells; they help to orchestrate the antibody and macrophage response appropriate for the specific type of infection/pathogen.

Host Defense Exam 1 (12 decks)

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