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MCAT Essentials > BIOL 8: Immune System > Flashcards

BIOL 8: Immune System Flashcards

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1
Q

Innate vs Adaptive immunity

A
  • innate aka nonspecific immunity: immune defenses that are always active against infection but lack the ability to target specific invaders
  • adaptive aka specific immunity: defenses that target a specific pathogen
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2
Q

Components of innate/nonspecific immunity

A

antimicrobial molecules, phagocytes (neutrophils, monocytes, macrophages), cytokines

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3
Q

Components of adaptive/specific immunity

A

dendritic cells, lymphocytes (B-cells, T-cells)

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4
Q

What is the role of the bone marrow in the immune system?

A

It is where blood cells are produced, including leukocytes. It is where B-cells mature.

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5
Q

What is the role of the spleen in the immune system?

A

It is where majority of B-cells are stored and activated (B-cells mature in the bone marrow but naïve and inactive).

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6
Q

What is meant by humoral immunity?

A
  • humoral immunity: immune defense with the use of antibodies; immune pathway of B-cells
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7
Q

What is the role of the thymus in the immune system?

A

It is where T-cells mature (but not necessarily activate)

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8
Q

What is meant by cell-mediate immunity?

A
  • cell-mediated aka cytotoxic immunity: immune pathway of T-cells
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9
Q

Lymph nodes

A

Provide a place for immune cells to communicate and mount an attack on foreign pathogens; also where some B-cells are activated

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10
Q

Gut-associated lymphoid tissues

A

Other immune sites found close to the digestive tract; e.g. tonsils, adenoids, appendix, Peyer’s patches

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11
Q

Peyer’s patches

A

Groupings of lymphoid follicles found in the mucous membrane lining of the small intestine

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12
Q

List the different types of leukocytes.

A
  • granulocytes: neutrophils, eosinophils, basophils

- agranulocytes: lymphocytes (B-cell, T-cells), monocytes

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13
Q

Monocytes

A

Agranulocytes that can be incorporated into specific tissues to become macrophages; e.g. microglia (in CNS), Langerhans cells (in skin), osteoclasts (in bone)

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14
Q

B-cells

A
  • develop and mature in the bone marrow but activated in the spleen and/or lymph nodes
  • function: to produce antibodies
  • immune pathway: humoral immunity
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15
Q

T-cells

A
  • develop in the bone marrow but mature in the thymus and activated in thymus and/or lymph nodes
  • function: to directly attack pathogen-infected cells
  • immune pathway: cell-mediated immunity
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16
Q

Differentiate granulocytes from agranulocytes.

A
  • granulocytes contain granules that have toxic enzymes and chemicals that can be released through exocytosis to fight against bacteria, fungi, and parasitic pathogens
  • agranulocytes do not contain such granules
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17
Q

Lymphocytes

A

Responsible for antibody production, immune system modulation, and targeted killing of infected cells

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18
Q

List some non-cellular non-specific immune defenses.

A
  • skin: provides barrier between inner and outside environment; also contains defensins, which are enzymes with antibacterial properties
  • respiratory tract: mucous membranes are lined with cilia to trap particulate matter
  • gastrointestinal tract: stomach acid has low pH that can kill some pathogens; gut is colonised by bacteria that keep pathogenic bacteria away
  • perspiration: sweat has antimicrobial properties
  • lysozymes: nonspecific antibacterial enzymes found in tears and saliva
  • the complement system: consists of proteins in the blood that can punch holes in bacterial cell walls to enhance antibody and phagocytic activity, promote inflammation, and attack the pathogen’s cell membrane
  • interferons: proteins produced by viral-infected cells to prevent replication and dispersion of viral pathogens and infections
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19
Q

Complement System

A

consists of proteins in the blood that can punch holes in bacterial cell walls to enhance antibody and phagocytic activity, promote inflammation, and attack the pathogen’s cell membrane

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20
Q

Differentiate between the classical and alternative pathways of the complement system.

A

In the classical pathway, activation is through the binding of antibodies to pathogens; whereas antibodies are not required in the alternative pathway.

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21
Q

What are some functions of interferons?

A
  • upregulates MHC I & II to increase antigen presentation and detection of infected cells
  • to prevent replication and dispersion of viral infection by decreasing viral and cellular protein production in neighboring cells and decreasing permeability of neighboring cells
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22
Q

What are some functions of macrophages?

A
  • phagocytization of invaders through endocytosis
  • digestion of invaders through enzymes
  • release of cytokines
  • presenting small invader peptide fragments in its cell surface attached to an MHC molecule for MHC recognition
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23
Q

Cytokines

A

chemical substances that stimulate inflammation and recruit additional immune cells to area

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24
Q

Major Histocompatibility Complex molecules

A

proteins that “tag” antigens by binding to pathogenic peptides (antigens) and carrying them to the cell surface for recognition and attack by the adaptive immune system

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25
Q

What are the different types of phagocytes?

A

Neutrophils (a granulocyte), monocytes (a granulocyte), macrophages (migrated monocytes), and dendritic cells

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26
Q

Differentiate MHC I and MHC II pathways.

A

1) MHC I: endogenous pathway, binding with antigens that come from inside the cell
2) MHC II: exogenous pathway, binding with antigens that come from outside the cell

27
Q

MHC class I molecules

A

Displayed by all nucleated cells in the body and loaded with proteins produced within the cell - these molecules are seen as “self” when not invaded and seen as “other” when invaded by endogenous antigens (viruses, intracellular bacteria, intracellular fungi)

28
Q

MHC class II molecules

A

Mainly displayed by professional antigen-presenting cells, including macrophages, dendritic cells, some B-cells, to indicate “other” when exogenous antigens invade

29
Q

Pattern recognition receptors (PRR)

A

are able to recognize the category of the invader to allow for the production of appropriate cytokines; e.g. toll-like receptors (TLR)

30
Q

Natural killer cells (NK cells)

A
  • non-specific lymphocytes (same family as B and T cells) that can induce apoptosis in pathogen-infected cells; are also able to detect the downregulation of MHC in cells and attack these infected cells
31
Q

T or F: viruses alone can alter MHC in cells

A

F: aside from viruses, cancer can also downregulate MHC

32
Q

Differentiate among the 3 types of granulocytes.

A

1) Neutrophils: short-lived phagocytic leukocytes that target bacteria (classically part of innate immunity but there is recent evidence of role in adaptive immunity as well)
2) Eosinophils: contain bright red-orange granules, primarily involved in allergic reactions as well as responses to invasive extracellular/parasitic infections; release histamines upon activation
3) Basophils: contain large purple granules; involved in allergic response, releasing large amounts of histamines in response to allergens

33
Q

What are the most and least populous leukocytes in the blood?

A
  • most populous: neutrophils (ones that form pus)

- least populous: basophils

34
Q

Mast cells

A

Closely related to basophils, but have smaller granules and exist in tissues, mucosa, epithelia; releases histamine and other chemicals that promote inflammation

35
Q

T or F: humoral immune response is a quick response

A

F, humoral immune response is slow and can take up to a week before becoming fully effective due to the production of antibodies, which takes time

36
Q

Immunoglobulins

A

Also called antibodies; are the main components of humorous immunity

37
Q

List the functions of immunoglobulins (3).

A

1) opsonization: attracting other leukocytes to phagocytize the antigen
2) agglutination: forming large insoluble clumps or complexes which can be phagocytized
3) neutralization: blocking the ability of pathogens in invading tissues

38
Q

T or F: the binding of an immunoglobulin with an antigen activates B-cells to create plasma cells and memory cells

A

T

39
Q

What happens when antibodies on the surface of mast cells bind to antigens?

A

Degranulation of the mast cell, an immune response (releases histamines)

40
Q

Describe the structure of an antibody.

A
  • Y-shaped: 2 boomerang shaped legs attached by a disulfide bond (between the heavy-chain segments) to form a Y + a light-chain segment attached to each of the heavy-chain legs at each the forks by a disulfide bond;
  • V-domain: antigen-binding site is at the tip of the forks; forks are called V-domains (as they are the variable part of antibody specific to antigen identity)
  • C-domain: the non-fork part of the antibody is constant, and contains the receptors for NK cells, macrophages, monocytes, eosinophils
41
Q

List the 5 isotypes of immunoglobulins.

A

IgA, IgD, IgE, IgG, IgM
*The body uses among these isotypes the appropriate antibodies depending on the location and specific purpose it is meant for.

42
Q

Hypermutation

A

Occurs in the V-domain of antibodies when B-cells are looking for the best antibody match the antigen and bind with it with high affinity

43
Q

Clonal selection

A

Describes the mechanism for generating immunoglobulin specificity - only those Ig that can bind with high affinity to antigens survive

44
Q

Isotype switching

A

~ Cells can change which isotype of antibody the produce when stimulated by specific cytokines

45
Q

Differentiate the different daughter cells of B-cells (2).

A

1) Plasma cells: create large amounts of immunoglobulins
2) Memory B-cells: stay in the lymph node and await re-exposure to the same antigen, upon which memory cells can differentiate into plasma cells for specific antibody production

46
Q

Primary vs secondary responses (humoral immunity)

A

1) primary: slow response as B-cells learn about novel invader (~7-10 days)
2) secondary: faster more robust response where memory cells are able to contribute to immune response

47
Q

T or F: T-cells can also undergo clonal selection

A

T

48
Q

T or F: There exist memory T-cells which are analogous to memory B-cells

A

T: memory T-cells also lie in wait until the next exposure to the same antigen to activate a more rapid and robust response

49
Q

Differentiate between positive and negative selections in T-cell maturation.

A

1) positive selection: only T-cells that can respond to MHC antibody presentation are allowed to mature
2) negative selection: cells that cannot respond to MHC tagging properly (either do not respond to MHC antibody presentation or respond to “self”-presented MHC) undergo apoptosis

50
Q

Thymosin

A

A peptide hormone secreted by thymic cells to help T-cell maturation

51
Q

Differentiate the types of T-cells (4).

A

1) Helper T-cells (Th or CD4+ T-cells): respond to MHC-II, coordinate immune response by secreting lymphokines (cytokines secreted by lymphocytes)
2) Cytotoxic T-cells (Tc or CTL or CD8+ T-cells): respond to MHC-I, capable of directly killing virally-infected cells
3) Suppressor T-cells (Treg): regulate immune response by toning down activity of other lymphocytes when infection is adequately contained to prevent overactivity of immunity
4) Memory T-cells: wait for re-exposure to same antigens for faster and more robust response

52
Q

CD4+ T-cells

A

Helper T-cells: respond to MHC-II molecules, secrete lymphokines

53
Q

CD8+ T-cells

A

Cytotoxic T-cells: respond to MHC-I molecules, directly kill virally-infected cells

54
Q

Self-tolerance

A

Suppressor T-cells turn off self-reactive lymphocytes (those responding to self-presenting MHC) to prevent autoimmune diseases

55
Q

What are considered extracellular pathogens? Intracellular?

A

1) Extracellular pathogens: bacteria, fungi, parasite
2) Intracellular pathogens: viruses, intracellular bacteria, intracellular fungi
* with some exceptions

56
Q

Dendritic cells

A

Present antigens from pathogens and cancer cells to adaptive immune cells

57
Q

cells die after pathogenic infection is cleared while can survive to a lifetime.

A

Plasma B- and T-cells die; memory B- and T-cells survive

58
Q

A common method for treating autoimmune diseases is the use of glucocorticoids. What is the idea behind this treatment?

A

Glucocorticoids have potent immunosuppressive qualities, downregulating the immune response including the response against self-cells (autoimmunity).

59
Q

What are examples of hypersensitive immune reactions?

A

Autoimmunity and allergic reactions as there is no real pathogenic threat, but an immune response is elicited.

60
Q

Differentiate between active and passive immunity.

A

1) Active: immune system is stimulated (either directly by pathogen invaders when getting sick or artificially through vaccines) to produce antibodies.
2) Passive: immunity results from the transfer of antibodies to an individual (and only antibodies, rather than plasma cells that can make them); e.g. placental transfer during pregnancy, transfer through breastfeeding, artificial through intravenous Ig transfer

61
Q

Thoracic duct

A

Largest lymphatic vessel where most lymphatic channels join

62
Q

Lymph nodes

A

Small bean-shaped structures along the lymphatic vessels; contain a lymphatic channel, an artery, and a vein

63
Q

What are the functions of the lymphatic system?

A
  • immunity
  • equalization of fluid distribution: interacts with the circulatory system and tissues
  • transfer of biomolecules: such as that transfer of fats from the digestive system (small intestine) into the bloodstream

MCAT Essentials (15 decks)

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