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The Immune System Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is innate immunity? What is adaptive immunity?

A
  • Innate is nonspecific, defenses that are always active but can’t target specific invaders
  • Adaptive is specific, defenses that target a specific pathogen; slower but retain memory
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2
Q

Which cells make up the innate immune system? What do they do?

A
  • dendritic cells, phagocytes (macrophages, neutrophils), mast cells, granulocytes, natural killer cells
  • induce inflammatory response, secreting cytokines (trigger other immune cells)
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3
Q

Which cells make up the adaptive immune system?

A

B-cells and T-cells, both made in bone marrow

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4
Q

What is the humoral division of adaptive immunity?

A
  • Spleen stores blood and activates B-cells
  • B-cells are naive when they leave bone marrow until they encounter antigens
  • B-cells dissolve and act in blood, so humoral
  • B-cells produce antibodies (specific)
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5
Q

What is the cell-mediated division of adaptive immunity?

A
  • T-cells mature in thymus

- T-cells coordinate immune system and directly kill virally infected cells (specific)

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6
Q

What is the function of lymph nodes?

A
  • place for immune cells to communicate and mount an attack

- B-cells can be activated there as well

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7
Q

What are other immune tissues (near digestive system)?

A
  • gut-associated lymphoid tissue (GALT)
  • includes tonsils and adenoids in head
  • includes Peyer’s patches in small intestine
  • includes lymphoid aggregates in appendix
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8
Q

What do hematopoietic stem cells give rise to?

A
  • Leukocytes: granulocytes and agranulocytes
  • RBCs
  • Platelets
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9
Q

Which cells are granulocytes? Which cells are agranulocytes, and what do they do?

A
  1. Granulocytes:
    - neutrophils, eosinophils, basophils
    - contain granules of toxic chemicals
  2. Agranulocytes:
    - lymphocytes - antibody production, targeted killing of infected cells (B and T cells)
    - monocytes - phagocytic cells - become macrophages in tissues (many tissues have resident populations of macrophages with special names - osteoclasts, microglia, Langerhans cells)
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10
Q

What defense does the skin provide?

A
  • physical barrier
  • defensins - antibacterial enzymes
  • sweat - also has antimicrobial properties
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11
Q

What defense does the respiratory system provide?

A
  • mucous membranes are lined with cilia to trap matter or push it up
  • lysozyme secreted in tears and saliva - nonspecific bacterial enzyme
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12
Q

What defense does the GI tract provide?

A
  • stomach secretes acid

- gut colonized by bacteria, invaders have to compete for resources

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13
Q

What is the complement system? What are the 2 pathways for activation?

A
  • proteins in blood that act as nonspecific defense against bacteria
  • these proteins punch holes in bacterial walls, making them osmotically unstable
  • classical pathway: activated by binding of an antibody to a pathogen
  • alternative pathway: does not require antibodies
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14
Q

What are interferons?

A
  • produced by cells that have been infected with viruses
  • cause nearby cells to decrease production of viral and cellular proteins
  • also decrease permeability of these cells so it’s hard for viruses to infect them
  • also up-regulate MHC I and II molecules, releasing in increase antigen presentation and better detection of infected cells
  • responsible for many flu-like symptoms
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15
Q

How does a macrophage activate and act?

A
  1. activates when a bacterial invader enters tissue
  2. first, phagocytizes invader thru endocytosis
  3. then, digests invader with enzymes
  4. presents peptide pieces of invader to other cells using major histocompatibility complex (MHC), which binds to piece and carries it to cell surface where it can be recognized by immune cels
  5. in response, macrophages release cytokines
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16
Q

What is a cytokine?

A

chemical substance released by macrophage, stimulates inflammation and recruits additional immune cells

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17
Q

What is MHC class I?

A
  • all nucleated cells in the body display MHC class I molecules
  • any protein can be presented on cell surface; only those cells that are infected will present an unfamiliar, non-self protein on their surfaces
  • endogenous pathway: binds antigens that come from inside the cell
  • cells that have been invaded can then be killed by cytotoxic T-cells to prevent infection to others
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18
Q

What is MHC class II?

A
  • displayed by antigen-presenting cells like macrophages, dendritic cells in skin, some B-cells, certain activated epithelial cells
  • both innate and adaptive immune cells display antigens
  • exogenous pathway: antigens originate outside the cell
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19
Q

What do macrophages and dendritic cells have to recognize category of invader?

A
  • pattern recognition receptors (PRR), best described are toll-like receptors (TLR)
  • allows for production of appropriate cytokines to recruit the right immune cells
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20
Q

What are natural killer (NK) cells?

A
  • some viruses (and cancer) cause down-regulation of MHC, making it harder for T-cells to recognize infection
  • NK cells (nonspecific lymphocyte) can detect this down-reg and induce apoptosis in these infected cells
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21
Q

What do neutrophils do?

A
  • most populous leukocyte
  • very short-lived
  • nonspecific
  • phagocytic and target bacteria using chemotaxis - senses products given off by bacteria - or once they have been opsonized (marked with antibody with B-cell)
  • pus = dead neutrophils collected
22
Q

What do eosinophils do?

A
  • contain bright red granules
  • allergic reactions and invasive parasitic infections
  • when activated, release lots of histamine - vasodilation and increased leakiness of blood vessels so more immune cells can move into tissue
  • inflammation useful against pathogens
23
Q

What do basophils do?

A
  • contain large purple granules
  • least populous leukocyte
  • allergic reactions, closely related to mast cells (in mucosa and epithelium)
  • release lots of histamine
24
Q

Which cells make up the innate immune system, and what do they do?

A
  1. Macrophages - consumes pathogens
  2. Mast cells - release histamine for inflammation
  3. Granulocytes - neutrophils, eosinophils, basophils - release toxic chemicals to kill pathogens
  4. Dendritic cells - presents antigens to adaptive immune cells
  5. Natural killer cell - destroys body’s own cells that have become infected with pathogens/cancer
25
Q

Which cells make up the adaptive immune system, and what do they do?

A
  1. B-cells: stimulated by antigens to divide and produce antibodies that tag invaders for killing
  2. T-cells: killer T-cells destroy infected cells using antigen presence; others coordinate immune response
26
Q

Where are B and T cells made, and where do they each mature?

A

Both are made in bone marrow. B mature in bone marrow, T mature in thymus.

27
Q

What response occurs when antigens bind to body fluid antibodies?

A
  1. once found to an antigen, antibodies may attract other leukocytes to phagocytize the antigen - opsonization
  2. antibodies can cause pathogens to agglutinate (clump), forming large insoluble complexes that can be phagocytized
  3. antibodies can block the ability of a pathogen to invade tissues, neutralizing it
28
Q

What response occurs when antigens bind to cell-surface antibodies?

A
  1. Antigen to B-cell: activates cell, causing it to proliferate and form plasma and memory cells
  2. Antigen to mast cell: causes degranulation (exocytosis of granule contents), releasing histamine and causing an inflammatory allergic reaction
29
Q

Describe the structure of antibodies.

A
  • Y-shaped molecules made of 2 identical heavy chains and two identical light chains
  • chains held together by disulfide linkages and noncovalent interactions
  • each antibody has an antigen-binding region at the end of which is called the variable region (domain) on tips of Y
  • within this region, there are specific polypeptide sequences that will bind 1 specific antigenic sequence
  • Rest of molecule is constant region (domain) - where cells like NKs, macrophages, monocytes, eosinophils have receptors and can initiate complement cascade
30
Q

What is part of the reason it takes so long to initiate the antibody response?

A
  • each B-cell goes thru hypermutation of its antigen-binding region, trying to find the best match for the antigen
  • only B-cells that have high affinity for antigen survive
  • called clonal selection - generates specificity
31
Q

What are the different antibody isotypes?

A
  • IgM, IgD, IgG, IgE, IgA
  • antibodies are also called immunoglobins (Ig)
  • cell can switch what they are producing when stimulated by diff cytokines - isotype switching
32
Q

What is the primary response?

A
  • naive B-cells wait in lymph nodes for their particular antigen to come along
  • upon exposure to the right antigen, B cell will proliferate and produce 2 daughter cells
  • Plasma cells: produce large amounts of antibodies; eventually die
  • Memory B-cells: stay in lymph node, awaiting re-exposure to the same antigen; live forever
  • takes 7-10 days
33
Q

What is the secondary response?

A
  • if the same microbe is encountered again, memory cells will produce specific antibodies
  • much faster and robust this time
  • how vaccines work
34
Q

What is positive and negative selection of T-cells?

A
  1. Positive: allowing only the maturation of cells that can respond to the presentation of antigen on MHC
  2. Negative: causing apoptosis in self-reactive cells (activated proteins made by organism itself)
35
Q

Where do T-cells mature, and what facilitates their maturation?

A
  • thymus
  • facilitated by thymosin, peptide hormone secreted by thymic cells
  • will leave thymus mature but naive
  • upon exposure, will undergo clonal selection so only those with highest affinity for antigen proliferate
36
Q

How many different T-cell types are there? What do helper T-cells do?

A
  • 3 types
  • Helper Ts (Th or CD4+ T) coordinate immune response by secreting lymphokines
  • these recruit other immune cells and increase their activity
  • respond to antigens presented on MHC II (exogenous antigens)
  • so most effective on parasitic, bacterial, fungal infections
  • two types: Th1 (release interferon that activates macrophages) and Th2 (activate B-cells, more in parasitic)
37
Q

What occurs in HIV? In AIDS?

A
  • loss of helper T-cells
  • prevents immune system from creating a good response to infection
  • in AIDS, even weak pathogens can cause big consequences
38
Q

What do cytotoxic T-cells do?

A
  • Tc or CTL or CD8+
  • can kill virally infected cells by injecting toxic chemicals that promote apoptosis in infected cells
  • respond to antigens on MHC-I (endogenous)
  • so most effective on viral (and intracellular bacterial or fungal) infections
39
Q

What do suppressor/regulatory T-cells do?

A
  • Treg
  • also express CD4, but also a protein called Foxp3
  • tone down immune response once infection has been contained
  • turn off self-reactive lymphocytes to prevent autoimmune problems - called self-tolerance
40
Q

What do memory T cells do?

A
  • lie in wait until exposure to the same antigen

- carry more robust and rapid response the second time

41
Q

Describe the steps of the immune system if bacteria enters through a cut.

A
  1. Macrophages engulf bacteria and release inflammatory mediators
  2. Present antigens on their surfaces with MHC-II
  3. Cytokines attract inflammatory cells (more macrophages, neutrophils)
  4. Mast cells activated by inflammation and degranulate, resulting in histamine release and capillary leakiness
  5. Dendritic cell leaves affected cell and travels to nearest lymph node, where it presents antigen to B-cel
  6. B-cell that makes the right antibody proliferates thru clonal selection to create plasma and memory cells
  7. Antibodies travel thru the bloodstream to the affected tissue, where they tag bacteria for destruction
  8. At the same time, dendritic cells present the antigen to T-cells, specifically CD4+ T-cells, type Th1 activates
  9. Plasma cells die, but memory B and T remain
42
Q

Describe the steps of the immune system if one has a virus.

A
  1. Virally infected cell will produce interferons, which will reduce permeability of nearby cells (decreased ability to get infected), reduce rate of transcription and translation of nearby cells (virus can’t multiply as well), and cause systemic symptoms (fever, muscle aching, etc)
  2. Infected cells present antigen (like viral proteins) with MHC-I
  3. CD8+ T-cells will recognize MHC-I complex and will inject toxins in the cell for apoptosis
  4. If virus down-regulates production of MHC-I, NKs will recognize the absence of MHC and will cause apoptosis
43
Q

What are self-antigens, autoimmunity, and hypersensitivity reactions?

A
  • self-antigens: carbs and proteins present on the surface of every cell of the body
  • signal to immune cells that they are not foreign and shouldn’t be attacked
  • autoimmunity: when immune system stops making the distinction between self and foreign and attacks cells with self-antigens
  • hypersensitivity reactions: autoimmunity + when body misidentifies a foreign antigen as dangerous (pollen)
44
Q

How does the body try to prevent autoimmune diseases?

A
  • T-cells are educated in the thymus; those that respond to self-antigens are eliminated (negative selection)
  • Immature Bs that respond to self-antigen are eliminated before they leave marrow
  • But not perfect process
45
Q

How are autoimmune diseases treated?

A

One example is glucocorticoids (cortisol) - potent immunosuppressive qualities

46
Q

How is immunity achieved actively?

A
  • immune system stimulated to produce antibodies, natural or artificial
  • antigen in vaccine can be weak or dead form of microbe, or part of microbe’s protein structure
  • takes weeks to build
47
Q

How is immunity achieved passively?

A
  • transfer of antibodies to a individual
  • only antibodies, not plasma cells that produce them, are given to individual, so it’s transient immunity
  • like across placenta and thru birth milk
  • immediate immunity
48
Q

Describe the structure of the lymphatic system.

A
  • one-way vessels that become larger as they move toward the center of the body
  • carry lymph
  • join to form a large thoracic duct in the posterior chest that delivers fluid into left subclavian vein
  • lymph nodes: small structures along vessels that contain a lymphatic channel, artery, and vein
  • nodes provide space for immune system cells to be exposed to pathogens
49
Q

How do lymphatic vessels help equalize fluid distribution?

A
  • at capillaries, fluid leaves bloodstream for tissues
  • depends on Starling forces: oncotic pressure draws water back into vessel at venule end, once hydrostatic pressure has decreased
  • because net pressure drawing fluid in at the venule end is a bit less than net pressure pushing fluid out at arterial end, a small amount of fluid remains in tissues
  • lymphatic vessels drain these tissues and return it to bloodstream
  • edema occurs if lymph vessels overwhelmed
50
Q

How do lymphatic vessels help transport biomolecules?

A
  • transports fats from digestive system to bloodstream
  • lacteals (small lymph vessels) are located at the center of each villus in the small intestine
  • fats enter lacteal; lymphatic fluid carrying lots of these (chylomicrons) looks white and is called chyle
51
Q

How do lymphatic vessels help immunity?

A
  • nodes are a place for antigen-presenting cels and lymphocytes to interact
  • B-cells proliferate and mature in lymph nodes in collections called germinal centers

Biology (14 decks)

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