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MICB 202 > Introduction to the Immune System > Flashcards

Introduction to the Immune System Flashcards

1
Q

Give examples of microorganisms humans encounter on a daily basis.

A

Bacteria

Viruses

Fungi

Parasites

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2
Q

List the three levels of defense the human body has to protect against infection?

A

Anatomical and physiological barriers

Innate immune responses form internal barriers

  • (innate immunity)

Adaptive immune responses as a last line of defense

  • (adaptive immunity)
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3
Q

What are examples of anatomical/physical barriers?

A
  • intact skin provides a physical barrier,
  • mucosal surfaces of the gut, respiratory, urogenital and conjunctivae surfaces,
  • stomach acid, lysozyme and other antimicrobial body secretions.
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4
Q

Describe innate immune responses.

A
  • quick and non-specific,
  • involves phagocytosis and activation of the complement proteins,
  • limits the spread of infection,
  • often resolves the infection.
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5
Q

What is the body’s last line of defense against infection?

A
  • The adaptive immune responses are the last line of defense:
    • slower to respond but specific to the particular pathogen,
    • involve antibody-mediated responses and cell-mediated responses.
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6
Q

What are the two major cell populations in blood?

A
  • erythrocytes (also called red blood cells or RBCs) carry oxygen to the tissues,
  • leukocytes (also called white blood cells or WBCs) are the cells of the immune system.
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7
Q

What are erythrocytes?

A

Red blood cells: carry oxygen to the tissues.

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8
Q

What are leukocytes?

A

White blood cells: the cells of the immune system.

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9
Q

Where do blood cells originate?

A

All blood cells, including RBCs, arise from hematopoietic stem cells (HSC, hemato = blood; poiesis = formation).

  • HSCs are self-renewing stem cells!
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10
Q

What are the two groups of leukocytes?

A

Leukocytes can be further separated into myeloid cells and lymphoid cells. (Also dendritic cells are leukocytes)

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11
Q

Where are HSCs found?

A

In the bone marrow, umbilical cord blood and in the blood (a very small number).

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12
Q

What are myeloid cells?

A
  • monocytes (that mature into macrophages),
  • mast cells, and
  • granulocytes (neutrophils, basophils, and eosinophils).
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13
Q

Which cells participate in the innate immune responses?

A

Myeloid cells

NOTE: Natural killer cells (NK cells) are a type of lymphoid cell that participates in innate responses as well.

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14
Q

What are the three granulocytes?

A

Neutrophils

Basophils

Eosinophils

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15
Q

What do monocytes mature into?

A

Macrophages

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16
Q

Which cells participate in the adaptive immune responses?

A

Most types of lymphoid cells (also called lymphocytes).

NOTE: Natural killer cells (NK cells) are a type of lymphoid cell that participates in innate responses instead.

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17
Q

Give examples of lymphoid cells.

A
  • cytotoxic T cells (CTLs),
  • T helper (Th) cells,
  • T regulatory (Treg) cells,
  • B cells,
  • Natural Killer (NK) cells.
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18
Q

Why are dendritic cells important to the immune system?

A

Dendritic cells are an integral link between the innate and adaptive responses. They are important cells for activating T cells and initiating the adaptive immune response.

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19
Q

Where are dendritic cells derived?

A

Some types of dendritic cells are derived from the lymphoid cells whereas others are derived from the myeloid cells.

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20
Q

Where is the immune system located?

A

The immune system is distributed throughout the body. The cells of the immune system are found in the blood circulatory system, lymphatic circulatory system, and the lymphoid organs.

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21
Q

What are the primary lymphoid organs?

A

The primary lymphoid organs are the sites where developing lymphocytes mature. The primary lymphoid organs include:

  • the bone marrow (the center part of the long bones), and
  • the thymus (a flat, bi-lobed organ that is situated above your heart).
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22
Q

What are the secondary lymphoid organs?

A

The secondary lymphoid organs are places where mature lymphocytes encounter pathogens or foreign molecules and where adaptive immune responses begin. The secondary lymphoid organs include:

  • the spleen (located in the left side of the abdominal cavity), and
  • the lymph nodes (~600 located throughout the body).
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23
Q

Where do HSCs complete the process of differentiation and maturation?

A

All hematopoietic cells complete the process of differentiation and maturation in the bone marrow with the exception of T cells (cells destined to become T cells begin this process in the bone marrow and complete it in the thymus).

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24
Q

What is the lymphatic system?

A

The lymphatic circulatory system is a circulatory system that enables lymphocytes and proteins to move around the body. The lymphatic system lacks a pump.

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25
Q

How do lymph and blood compare?

A

Lymph fluid is similar to the blood, but it lacks red blood cells and platelets.

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26
Q

How are the lymphatic and blood circulatory systems connected?

A

Fluids in tissues drain into lymphatic capillaries and then into the lymph nodes.

The lymphatic circulation connects the different lymph nodes.

Lymphatic fluid returns to the blood circulatory system via the thoracic duct located near the heart.

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27
Q

Where are immune responses mediated by lymphocytes activated?

A

Secondary lymphoid tissues (e.g., spleen, lymph nodes).

28
Q

What are the differences between the primary and secondary lymphoid organs?

A
  • The bone marrow and thymus are primary lymphoid organs.
  • The primary lymphoid organs are the sites where developing lymphocytes mature.
  • Immune responses mediated by lymphocytes are activated in the secondary lymphoid tissues (e.g., spleen, lymph nodes).
  • The secondary lymphoid organs are places where mature lymphocytes encounter pathogens or foreign molecules and where adaptive immune responses begin.
29
Q

Compare the three main defenses against infection.

A

Anatomical defenses are always present.

Innate immunity is rapid, non-specific, and effective at controlling infections and eliminating most infections.

Adaptive immunity is slower but specific.

30
Q

What network of cells comprise the immune system and where are they derived?

A

The immune system comprises a network of cells including neutrophils, macrophages, dendritic cells, T cells, and B cells. They are all derived from hematopoietic stem cells.

31
Q

What are the primary and secondary lymphoid organs?

A

The primary lymphoid organs are the bone marrow and the thymus.

The secondary lymphoid organs are the spleen and the lymph nodes.

32
Q

Which leukocytes are derived from myeloid precursors?

A
  • monocytes (that mature into macrophages),
  • mast cells, and
  • granulocytes (neutrophils, basophils, and eosinophils).
33
Q

What problems would a person have if they didn’t have HSCs?

A

Compromised immune system due to no leukocyte replenishment

34
Q

Explain the consequences of removal of the thymus as a newborn versus as an adult.

A

“Removal of the organ in the adult has little effect, but when the thymus is removed in the newborn, T-cells in the blood and lymphoid tissue are depleted, and failure of the immune system causes a gradual, fatal wasting disease,” according to Encyclopedia Britannica.

35
Q

What’s in blood?

A

Liquid portion is called plasma – contains many types of proteins.

Red and white blood cells suspended in the plasma. (Erythrocytes and leukocytes suspended in the plasma.)

36
Q

What are the three major groups of cells in blood?

A

Erythrocytes

Leukocytes

Platelets

37
Q

What is the main role of a neutrophil?

A

phagocytose and kill bacteria.

38
Q

What is the main role of a macrophage?

A
  • phagocytose and kill bacteria, alert the immune system of the presence of an infection, tissue repair and wound healing.
39
Q

What is the main role of a dendritic cell?

A

Phagocytose and kill bacteria/viruses, migrate to lymph node and activate adaptive immune responses.

Dendritic cells are especially important in the immune system - they bridge the innate and adaptive responses!

40
Q

Which lymphoid cells are important to know for MICB202?

A

T helper cells, the CTLs (cytotoxic or killer T cells) and the B cells.

41
Q

What is the main role of B cells?

A

secrete antibodies into body fluids.

42
Q

What do antibodies do?

A
  1. kill bacteria (in the presence of complement)
  2. opsonsize pathogens (makes phagocytosis more efficient)
  3. neutralize pathogens (prevent pathogens from binding/infecting cells)
43
Q

What is the role of the lymphocyte CTL?

A
  • kill viral infected cells (helps to prevent spread of viral infection)
44
Q

What is the role of the T helper cells?

A
  • provide cytokines and other stimulatory signals to B cells, CTLs and macrophages.
45
Q

Which cells play an important role in our adaptive immune response?

A

Lymphoid cells

46
Q

Where are immune cells derived?

A

All cells of the immune system are derived from a common hematopoietic stem cell (HSC).

HSCs divide to replenish the HSC pool and to provide progenitor cell types.

47
Q

How do HSCs know what type of immune cell to develop into?

A

Various chemical and “environmental” signals - soluble chemicals, receptor/ ligand binding interactions.

48
Q

How did the atomic bombings of Japan reveal that HSCs, CMPs, CLPs are very sensi\ve to radiation?

A

Some victims that were exposed to “lower Doses” of radiation (but still lethal doses) had compromised hematopoietic systems.

These people could not regenerate sufficient white blood cells to protect against otherwise nonpathogenic infections or not enough platelets to clot their blood.

49
Q

Where are lymphocytes found?

A

Most lymphocytes are present in specialized lymphoid tissues.

50
Q

Where do lymphocytes develop and mature?

A

Lymphocytes develop and mature in the primary lymphoid organs.

For B cells, the entire process of B cell development occurs in the bone marrow.

For T cells, the process begins in the bone marrow. T cell precursors leave the bone marrow and migrate to the thymus to continue the process of development and maturation.

51
Q

Where do lymphocytes respond to antigens?

A

Lymphocytes encounter and respond to antigen (pathogens) in the secondary (peripheral) lymphoid organs. The antigen is physically trapped by the secondary lymphoid organs or brought there by the dendritic cells.

52
Q

What are the secondary lymphoid organs?

A

The secondary lymphoid organs are specialized structures that allow lymphocytes to “scan” for antigens:

  • spleen and lymph nodes,
  • gut-associated lymphoid tissues (GALT) that include the tonsils, adenoids, appendix and Peyer’s patches,
  • bronchial-associated lymphoid tissues (BALT),
  • other mucosal surfaces.

Given that the gut has the largest exposure to microorganisms, it might not be surprising to find that secondary lymphoid tissues are associated with the gut!

53
Q

Could you live without a spleen?

A

Yes, the liver will take over some of the workload.

54
Q

Could you live without a thymus or bone marrow?

A

No.

55
Q

Can you live without a lymph node?

A

Yes. (eg - tonsil removal)

56
Q

What are the two circulatory systems in the body?

A

Blood & lymph

57
Q

How do the spleen and lymph nodes help to develop immune responses?

A

The spleen and lymph nodes act as filters – traps pathogens so immune responses can develop.

58
Q

Where is lymph fluid returned to the blood?

A

Via the thoracic duct.

59
Q

Immature T cells are found in the lymph nodes and spleen.

True or False?

A

False.

60
Q

The hematopoietic stem cell is one of the most abundant cell types in the bone marrow.

True or false?

A

False

61
Q

There are no hematopoietic stem cells in blood.

True or false?

A

False

62
Q

B cells develop in the thymus.

True or False?

A

False

63
Q

Leukocyte is another name for blood cells.

True or false?

A

True

64
Q
A
65
Q

All blood cells, with the exception of red blood cells, are derived from the hematopoietic stem cell.

True or false?

A

False

66
Q

B cells mature in the bone marrow.

True or false?

A

True

MICB 202 (25 decks)

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