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MCAT - Biology > Chapter 8 - The Immune System > Flashcards

Chapter 8 - The Immune System Flashcards

1
Q

Describe Innate Immunity

A

Composed of defences that are always active, but that cannot target a specific invader and cannot maintain immunological memory; also called Nonspecific Immunity

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2
Q

Describe Adaptive Immunity

A

Composed of defences that take time to activate but that target a specific invader, and can maintain immunological memory; also called Specific Immunity.

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3
Q

Where do immune cells come from?

A

The bone marrow (b and t)

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4
Q

How do the Spleen and Lymph Nodes assist the immune system?

A

They are sites where immune responses can be mounted, and in which B-cells are activated/matured.

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5
Q

Where are T-cells matured?

A

The thymus

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6
Q

What does Gut-Associated Lymphoid Tissue (GALT) include?

A

The tonsils and adenoids

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7
Q

What is the Spleen’s function in terms of mood cells?

A

The spleen also acts as a storage area for white blood cells and platelets, a recycling centre for red blood cells, and a filter of blood and lymph for the immune systems.

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8
Q

What are the different types of leukocytes involved in immune defence?

A

Granulocytes and agranulocytes. Both come from a common precursor: hematopoietic stem cells

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9
Q

What is the major function of B-cells? Are they Specific or Nonspecific? Humoral or Cell-Mediated?

A

Produce antibodies; Specific; Humoral

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10
Q

What is the major function of T-cells? Are they Specific or Nonspecific? Humoral or Cell-Mediated?

A

Coordinate immune system and directly kill infected cells; Specific; Cell-Mediated.

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11
Q

Which cells are considered Granulocytes?

A

Neutrophils, eosinophils and basophils.

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12
Q

Which cells are considered Agranulocytes?

A

B-cells, T-cells (lymphocytes), and monocytes (macrophages).

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13
Q

What are some examples of noncellular nonspecific defence mechanisms?

A

Skin, mucus, saliva, stomach, tears etc.

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14
Q

How does the skin contribute to immune defence?

A

Acts as a physical barrier and secretes antimicrobial compounds, like defensins.

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15
Q

How does mucus contribute to immune defence?

A

Mucus on Mucous membranes traps pathogens; in the respiratory system, the mucous is propelled upward by cilia and can be swallowed or expelled.

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16
Q

How do tears and saliva contribute to immune defence?

A

Both contain lysozyme; and antibacterial compound.

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17
Q

How does the stomach contribute to immune defence?

A

Produces acid, killing most pathogens. Colonization of the gut helps prevent overgrowth by pathogenic bacteria through competition.

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18
Q

What is the Complement System’s role in immune defense?

A

Can punch holes in the cell walls of bacteria, making them osmotically ustable.

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19
Q

How do Interferons contribute to immune response?

A

Given off by virally infected cells and help prevent viral replication and dispersion to nearby cells.

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20
Q

How does the Normal Gastrointestinal Flora contribute to immune response?

A

Provides competition, making it hard for pathogenic bacteria to grow in the gut.

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21
Q

Which cells are professional antigen-presenting cells?

A

Macrophages, dendritic cells in the skin, some B-cells, and certain activated epithelial cells.

22
Q

What do Macrophages do?

A

Ingest pathogens and present them on major histocompatibility complex (MHC) molecules. They also secrete cytokines.

23
Q

What is MHC Class 1 (MHC-1)?

A

Present in all nucleated cells and displays endogenous antigen (proteins from within the cell) to cytotoxic T-cells (CD8+ cells).

24
Q

What is MHC Class II (MHC-II)?

A

Present in professional antigen-presenting cells (macrophages, dendritic cells, some B-cells, and certain advanced epithelial cells) and displays exogenous antigens to helper T-cells (CD4+ cells)

25
Q

What are Exogenous Antigens?

A

Proteins from outside the cell.

26
Q

What are Mast Cells?

A

This cell releases histamine and other chemicals that promote inflammation.

27
Q

What are Dendritic Cells?

A

Present antigens - fragments of protein or other molecules from pathogens or cancer cells - to adaptive immune cells, inducing them to attack bearers of the displayed antigens. In the skin

28
Q

What are Natural Killer Cells?

A

Destroy the body’s own cells that have become infected with pathogens; they also go after cancer cells: (Activated by cells that do not present MHC).

29
Q

What are Neutrophils?

A

Activated by bacteria presence. They ingest bacteria, particularly opsonized bacteria (those marked with antibodies). They can follow bacteria using chemotaxis.

30
Q

What are Eosinophils?

A

Used in allergic reactions and activated by invasive parasitic infections. They release histamine causing an inflammatory response.

31
Q

Other than Eosinophils, what other cells are used to combat allergic reactions?

A

Basophils

32
Q

What is the function of Histamine?

A

Causes inflammation by inducing vasodilation and the movement of fluid and cells from the bloodstream into tissues.

33
Q

What is Humoral Immunity?

A

Centered on antibody production by plasma cells, which are activated B-cells.

34
Q

What is the main function of Memory B-cells?

A

Also form from B-cells exposed to antigens and lie in wait for second exposure to a given antigen to mount a rapid, robust response.

35
Q

What is the main function of Helper T-cells?

A

Coordinate the immune system through lymphokines and respond to antigens bound to MHC-II.

36
Q

What is the main function of Cytotoxic T-cells?

A

Directly kill virally infected cells and respond to antigens bound to MHC-1.

37
Q

What is the main function of Suppressor (Regulatory) T-cells?

A

Quell the immune response after a pathogen has been cleared and promote self-tolerance.

38
Q

What is the main function of Memory T-cells?

A

Like memory-B cells, lie in wait until a second exposure to a pathogen to mount a rapid, robust response.

39
Q

What are the three main effects that Circulating Antibodies have on a pathogen?

A
  1. Can mark a pathogen for destruction by phagocytic cells (opsonization)
  2. Cause agglutination of the pathogen into insoluble complexes that can be taken up by phagocytic cells
  3. Can neutralize a pathogen by preventing it from invading tissues.
40
Q

Why do antigen-binding regions of activated cells undergo Hypermutation?

A

To improve the specificity of the antibody produced. Cells may be given signals to switch isotopes of antibodies (IgM, IgD, IgE, IdG, IgA).

41
Q

What does Cytotoxic (cell-mediated) Immunity focus on?

A

T-cells; they undergo maturation in the thymus through positive selection negative selection.

42
Q

What’s the difference between Positive and Negative Selection of T-cells?

A

Positive: only selects T-cells that can react to antigen presented on MHC.
Negative: causes apoptosis in self-reactive T-cells.

43
Q

What peptide hormone promotes T-cell development?

A

Thymosin

44
Q

What’s the difference between Th1 cells and Th2 cells?

A

Th1: secrete interferon gamma, which activates macrophages.
Th2: activate B-cells, primarily in parasitic infections.

45
Q

What does Active Immunity refer to?

A

The stimulation of the immune system to produce antibodies against a pathogen.

46
Q

What does Passive Immunity refer to?

A

The transfer of antibodies to prevent infection, without stimulation of the plasma cells that produce these antibodies.

47
Q

How does the body respond in Autoimmune conditions?

A

A self-antigen is identified as foreign, and the immune system attacks the body’s own cells.

48
Q

How does the body respond in Allergic Reactions?

A

Nonthreatening exposures incite an inflammatory response.

49
Q

What are Immunizations meant to do?

A

A method of inducing active immunity (activation of B-cells that produce antibodies to an antigen) prior to exposure to a particular pathogen.

50
Q

What is the structure of Lymphatic System?

A

A circulatory system that consists of one-way vessels and intermittent lymph nodes. It connects to the Cardiovascular System via the thoracic duct in the posterior chest.

51
Q

What is the function of the Lymphatic System?

A

Equalizes fluid distribution, transports fats and fat-soluble compounds in chylomicrons, and provides sites for mounting immune responses.

52
Q

W. bancrofti is a parasite that resides in the lymph nodes and causes blockage of flow. If an individual contracted a W. bancrofti infection in the lymph nods of their thigh, what would likely happen?

A

Fluid would be unable to return from the lower leg, and edema would result. This infection leads to Elephantiasis; severe swelling of the limb with thickening of the skin.

MCAT - Biology (12 decks)

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