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MCAT Biology Review > The Immune System > Flashcards

The Immune System Flashcards

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1
Q

Innate (nonspecific) immunity

A

Composed of defenses that are always active against infection, but lack the ability to target specific invaders
This system includes antimicrobial molecules and phagocytes (such as dendritic cells and macrophages) that can cause an inflammatory response to trigger influx of immune cells from blood such as monocytes and neutrophils

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2
Q

Adaptive (specific) immunity

A

Defenses that target a specific pathogen, slower to act but can maintain immunological memory of an infection to mount a faster attack in subsequent infections
Features activated B-cells, which secrete antibody molecules that bind to antigens and destroy the invader directly or mark it for attack by others, and T-cells that recognize antigens displayed on cells with some helping to activate B-cells and other T-cells and others directly attacking infected cells

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3
Q

B-cells

A

Located and activated in spleen, turn into plasma cell to produce antibodies agents of humoral immunity division, considered mature but naive when they leave bone marrow due to not yet being exposed to antigen

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4
Q

T-cells

A

Mature in the thymus, agents of cell-mediated immunity due to coordinating immune system and directly killing virally infected cells

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5
Q

Lymph nodes

A

Part of the lymphatic system, provide a place for immune cells to communicate and mount an attack, can activate B-cells too, filters blood and lymph, contain a lymphatic channel as well as an artery and vein

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6
Q

Gut-associated lymphoid tissue (GALT)

A

Immune tissue found in close proximity to the digestive system, includes the tonsils and adenoids in the head, Peyer’s patches in the small intestine and lymphoid aggregates in the appendix

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7
Q

Lymphadenopathy

A

Swelling of the lymph nodes that occurs with activation of immune system

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8
Q

Skin (integument)

A

First line of defense, provides physical barrier between outside world and internal organs

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9
Q

Defensins

A

Antibacterial enzymes that can be found on the skin

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10
Q

Complement system

A

Consists of a number of proteins in blood that act as a nonspecific defense against bacteria, can be activated through classical or alternative pathway, these proteins punch holes in cell walls of bacteria to make them osmotically unstable

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11
Q

Classical pathway

A

One way to activate complement system, requires binding of an antibody to a pathogen

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12
Q

Alternative pathway

A

One way to activate complement system, does not require antibodies

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13
Q

Interferons

A 
Proteins that prevent viral replication and dispersion, produced by cells that have been infected with viruses
Cause nearby cells to decrease production of viral and cellular proteins, decrease permeability of these cells, upregulate MHC class I and II molecules, and are responsible for many flu-like symptoms
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14
Q

Resident population

A

Becoming a permanent, rather than transient, cell group in the tissue (as can happen with macrophages derived from monocytes)

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15
Q

Action of macrophages

A

Phagocytizes invader through endocytosis, then digests the invader using enzymes, and then presents little pieces of the invader to other cells using major histocompatibility complex (MHC) to be recognized by cells of the adaptive immune system, can also release cytokines

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16
Q

Cytokines

A

Chemical substances that stimulate inflammation and recruit additional immune cells to the area

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17
Q

Major histocompatibility complex (MHC)

A

Binds to pathogenic peptide (antigen) and carries it to the cell surface to be recognized by cells of adaptive immune system

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18
Q

MHC class I

A

Displayed by nucleated cells in the body, can present any protein produced within a cell allowing immune system to monitor health of these cells
Often known as endogenous pathway because it binds antigens that come from inside the cell

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19
Q

MHC class II

A

Mainly displayed by professional antigen-presenting cells like macrophages, which pick up pathogens from the environment and presents these antigens
Often called exogenous pathway as antigens presented come from outside the cell

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20
Q

Pattern recognition receptors (PRR)

A

Special receptors on macrophages and dendritic cells that are able to recognize the category of the invader (bacterium, virus, fungus, parasite), allowing for production of appropriate cytokines
Best known PRRs are toll-like receptors (TLR)

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21
Q

Natural killer (NK) cells

A

Nonspecific lymphocyte that is able to detect downregulation of MHC and induce apoptosis in these virally infected cells

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22
Q

Neutrophils

A

Most populous leukocyte in the blood, very short-lived, phagocytic and target bacteria using chemotaxis (movement of an organism according to chemical stimuli), can also detect bacteria once they have been opsonized

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23
Q

Pus

A

Formed as a result of dead neutrophil collections during an infection

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24
Q

Opsonization

A

Being marked with an antibody from a B-cell for phagocytization

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25
Q

Eosinophils

A

Contain bright red-orange granules and are involved in allergic reactions and invasive parasitic infections, release large amounts of histamine when activated to start inflammation process

26
Q

Inflammation

A

Mediated by histamine which, when activated, leads to vasodilation and increased leakiness of blood vessels to allow additional immune cells to move into tissue from bloodstream

27
Q

Basophils

A

Contain large purple granules and are involved in allergic responses, least populous leukocyte in bloodstream under normal conditions, release large amounts of histamine in response to allergens

28
Q

Mast cells

A

Closely related to basophils but have smaller granules and exist in tissues, mucosa, and epithelium, release large amounts of histamine in response to allergens

29
Q

Humoral immunity

A

Involves production of antibodies (or immunoglobulins) that are specific to the antigens of the invading molecule and are produced by B-cells

30
Q

Antibody function (in body fluids)

A

When an antibody is bound to a specific antigen, it may attract other leukocytes to phagocytize those antigens immediately (opsonization), antibodies may also cause pathogens to clump together (agglutinate) to form large insoluble complexes that can be phagocytized, and they can also block the ability of a pathogen to invade tissues by neutralizing it (antibodies on cell surface act in proliferation and formation of plasma and memory cells)

31
Q

Degranulation

A

Exocytosis of granule contents, releasing histamine and causing an inflammatory allergic reaction, when antigen binds to antibodies on the surface of a mast cell

32
Q

Structure of antibody

A

Y-shaped molecule that is made of 2 identical heavy chains and 2 identical light chains, held together by disulfide linkages and noncovalent interactions

33
Q

Antigen-binding region

A

Segment of each antibody at the end of which is called the variable region (domain) at the tips of the Y

34
Q

Hypermutation

A

Process in B-cells at their antigen-binding region to find the best match for the antigen, contributes for long time for initiation of the antibody response

35
Q

Clonal selection

A

Only the B-cells that can bind their antigen with affinity survive, producing specificity

36
Q

Constant region

A

Region of antibody that cells (NK cells, macrophages, monocytes, eosinophils) have receptors for and that can initiate the complement cascade

37
Q

Five isotypes of antibodies

A

IgA, IgD, IgE, IgG, IgM

38
Q

Isotype switching

A

Process in which cells can change which isotype of antibody they produce when stimulated by specific cytokines

39
Q

Naive B-cells

A

B-cells not yet exposed to an antigen, wait in the lymph nodes for their particular antigen to come along, after which it can produce 2 types of daughter cells (plasma cells and memory B-cells)

40
Q

Plasma cells

A

Produces large amount of antibodies in response to antigen binding to parent B-cell

41
Q

Memory B-cells

A

Stay in the lymph node awaiting reexposure to the same antigen, may last the lifetime of the organism

42
Q

Primary response

A

Initial activation of naive B-cell with its appropriate antigen, producing plasma cells and memory B-cells, takes approximately 7-10 days

43
Q

Secondary response

A

Memory cells jump into action if same microbe is encountered again, producing the antibodies specific to that pathogen in a more rapid and robust response

44
Q

Positive selection

A

Allowing only the maturation of cells that can respond to the presentation of antigen on MHC

45
Q

Negative selection

A

Causing apoptosis in cells that are self-reactive (activated by proteins produced by the organism itself)

46
Q

Two types of B-cells

A

Plasma and memory

47
Q

Three types of T-cells

A

Helper (CD4+), cytotoxic (CD8+), and suppressor

48
Q

Helper (CD4+) T-cells

A

Coordinate the immune response by secreting lymphokines, which are capable of recruiting other immune cells (plasma B cells, cytotoxic T cells, macrophages) and increasing their activity, respond to antigens presented on MHC-II molecules and are thus more effective against bacterial, fungal and parasitic infections

49
Q

Cytotoxic (CD8+) T-cells

A

Capable of directly killing virally infected cells by injecting toxic chemicals that promote apoptosis into infected cell, respond to antigens presented on MHC-I molecules and are thus most effective against viral (and intracellular bacterial or fungal) infections

50
Q

Suppressor (regulatory) T-cells

A

Express CD4 but they also express a protein called Foxp3, helping tone down the immune response once infection has been adequately contained
Can also turn off self-reactive lymphocytes to prevent autoimmune diseases (self-tolerance)

51
Q

Memory T-cells

A

T-cells that lie in wait until the next exposure to the same antigen to carry out more robust and rapid response

52
Q

Self-antigens

A

Proteins and carbohydrates present on the surface of every cell of the body that normally signal to immune cells that the cell is not foreign and should not be attacked

53
Q

Autoimmunity

A

Condition in which the immune system fails to make the distinction between self and foreign, attacking cells expressing particular self-antigens

54
Q

Allergic reaction

A

When the immune system misidentifies a foreign antigen as dangerous when it actually is not, such as pet dander, pollen and peanuts

55
Q

Hypersensitivity reactions

A

Where people’s immune systems are hypersensitive to self-antigens or misidentified antigens and become overactivated when these antigens are encountered, include allergies and autoimmunity

56
Q

Active immunity

A

The immune system is stimulated to produce antibodies against a specific pathogen, either through natural exposure or artificial exposure (through vaccines)

57
Q

Passive immunity

A

Results from the transfer of antibodies to an individual without the plasma cells that produce them, such as transfer of antibodies across placenta during pregnancy and transfer of antibodies from mother to her nursing infant through breast milk

58
Q

Lymphatic system

A

Circulatory system made up of one-way vessels that become larger as they move toward center of the body, carrying lymphatic fluid (lymph), with most of the vessels joining to form a large thoracic duct in posterior chest that delivers fluid into left subclavian vein

59
Q

Lacteals

A

Small lymphatic vessels located at the center of each villus in the small intestine, which is the starting point for transport of fats from digestive system into the bloodstream

60
Q

Chyle

A

Lymphatic fluid carrying many chylomicrons that takes on a milky white appearance

61
Q

Germinal centers

A

Collections in the lymph nodes where B-cells proliferate and mature

MCAT Biology Review (10 decks)

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