Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MCAT Biology > The Immune System > Flashcards

The Immune System Flashcards

You may prefer our related Brainscape-certified flashcards:
MCAT flashcards AP® Biology flashcards Biology 101 flashcards
1
Q

innate immunity

A
  • defences always active against infection
  • lacks ability to target specific invaders
  • nonspecific immunity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

adaptive or specific immunity

A
  • defences that target a specific pathogen

- slower to act but maintains immunological memory of an infection to mount a faster attack in subsequent infections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What constitutes the innate immune system?

A
  • antimicrobal molecules
  • phagocytes - cells that ingest and destroy pathogens
  • includes: macrophages, dendritic cells (trigger inflammatory response by secreting cytokines that trigger an influx of immune cells), monocytes and neutrophils
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What constitutes the adaptive immune system?

A
  • B-cells (activated B-cells secrete antibody molecules that bind to antigens that destroy invaders directly or mark them for attack)
  • T-cells (recognize antigens displayed on other cells and either help activate B-cells or other T-cells or directly attack infected cells)
  • T-cells and B-cells spawn memory cells that promptly eliminate invaders encountered before
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Bone marrow

A
  • produces all of the leukocytes that participate in the immune system
  • site of hematopoiesis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Spleen

A
  • location of blood storage
  • location of activation of B-cells
    (where B-cells turn into plasma cells that produce antibodies - dissolve and act in the blood in a form of adaptive immunity called humoral immunity)
  • when B-cells leave bone marrow, they are mature but naive (lack antigen exposure)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Thymus

A
  • small gland in front of the pericardium (sac that protects the heart)
  • site of T-cell maturation
  • agents of cell-mediated immunity because they coordinate the immune system and directly kill virally infected cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Lymph nodes

A
  • major component of the lymphatic system
  • place for immune cells to communicate and mount an attack
  • B-cells can also mature here
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Gut-associated lymphoid tissure (GALT)

A
  • close proximity to lymphatic system
  • include tonsil and adenoids in the head
  • Peyer’s patches in small intestine
  • lymphoid aggregates in appendix
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Skin

A
  • first line of defence
  • physical barrier between the outside world and our internal organs
  • antibacterial enzymes - defensins found on skin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

The Gastrointestinal Tract

A
  • stomach acid eliminates most pathogens

- large bacterial population makes it hard for potential invaders to compete

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

complement

A
  • number of proteins in the blood that act as nonspecific defense (cannot be modified to target a specific organism)
  • can be activated through classical pathway (with antibodies) or alternative pathway (without antibodies)
  • proteins punch holes in cell walls of bacteria –> makes them osmotically unstable
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

interferons

A
  • proteins prevent viral replication and dispersion
  • cause nearby cells to:
  • decrease viral and cellular protein production
  • decrease permeability of cells to make it harder for viruses to infect them
  • upregulate MHC class I and II molecules to increase antigen presentation and allow for better detection of infected cells by the immune system
  • responsible for many flu-like smptoms
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

macrophages

A
  • derive from blood-borne monocytes and can become a permanent resident population
  • activated when bacterial invader enters a tissure
  • phagocytizes invader through endocytosis then digests invader using enzymes and presents little pieces (peptides) of invader to other cells using a protein called the major histocompatibility complex (MHC)
  • MHC binds to pathogenic peptides (antigens) and carries them to the cell surface where they are recognized by cells of the adaptive immune system
  • release cytokines - chemical substances that stimulate inflammation and recruit other immune cells to the area
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

MHC class I molecules

A
  • all nucleated cells display MHC class I molecules
  • any protein produced within the cell can be loaded onto a MHC-I molecule and presented on the cell surface
  • allows the immune system to monitor cell health and determine if the cell has been ivaded
  • endogenous pathway - binds antigens from inside the cell
  • invaded cells can be killed by cytotoxic T-lymphocytes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

MHC class II molecules

A
  • displayed on antigen-presenting cells
  • include: macrophages, dendritic cells, some B-cells and certain activated epithelial cells
  • pick up pathogens from environment –> process them –> present them on MHC-II
  • exogenous pathway
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Pattern-recognition receptors

A
  • macrophages and dendritic cells can also have special receptors called pattern-recognition receptors (PRR) or toll-like receptors (TLR)
  • recognize category of pathogen and production of proper cytokine to recruit the right type of immune cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

natural killer cells

A
  • nonspecific lymphocytes detect downregulation of MHC by viruses and cancer and induce apoptosis in these virally infected cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

neutrophils

A
  • most populous leukocyte in the blood
  • short-lived (about 5 days)
  • phagocytic and target bacteria
  • follow bacteria by chemotaxis (sensing certain products given off by bacteria and following products back to their source)
  • opsonized bacteria - marked with antibodies- can be detected
  • dead neutrophils form pus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

eosinophils

A
  • contain bright red-orange granules
  • involved in allergic reactions and invasive parasitic infections
  • upon activation, release large amounts of histamines (inflammatory mediator - vasodilation and increases leakiness to allow macrophages and neutrophils into tissues)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

inflammation

A

particularly useful against extracellular pathogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

basophils

A
  • contain large purple granules and are involved in allergic responses
  • least populous
  • mast cells are similar but they have smaller granules and are present in tissues, mucosa and epithelium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Where do B-cells mature?

A
  • bone marrow
24
Q

Where do T-cells mature?

A
  • thymus
25
Q

humoral immunity

A
  • production of antibodies by B-cells
  • may take up to a week to become fully effective after initial infection
  • antibodies specific to antigens of invading microbe
26
Q

immunoglobulins

A
  • can be present in body fluids or the surfaces of cells
27
Q

How do antibodies in body fluid act?

A
  • can bind to specific antigens and attract other leukocytes to phagocytize these antigens immediately
  • can cause pathogens to agglutinate and form large insoluble complexes that can be phagocytized
  • can block ability of pathogen to invade tissues - neutralization
28
Q

How do antibodies at the cell surface act?

A
  • antigen binds to B-cell –> activation –> proliferation and formation of plasma and memory cells
  • binding to mast cell –> degranulation - exocytosis of granule contents (release of histamine –> inflammatory allergic reaction)
29
Q

antibody

A
  • Y-shaped molecule
  • has a constant region and variable region
  • has two heavy chains (inner) and two light chains (outer) held together by disulphide bonds or noncovalent interactions
  • B-cell undergoes hypermutation of its antigen-binding region until best match is found –> high affinity binding cells survive –> clonal selection
30
Q

constant region

A

natural killer cells, macrophages and eosinophils have receptors for this
- can initiate complement cascade

31
Q

How many types of antibodies does each B-cell make?

A

1

32
Q

What are the different isotypes of antibodies?

A

IgM, IgA, IgG, IgE, IgD

- different types are used at different times,/ for different pathogens/ different locations

33
Q

isotype switching

A

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

34
Q

How does B-cell maturation occur?

A
  • naive B-cells wait in the lymph nodes until the particular antigen arrives
  • after, B-cells proliferate to produce plasma cells - produce large amounts of antibodies and memory cells - stay in the lymph nodes, awaiting rexposure
35
Q

primary response

A
  • initial activation
  • takes 7 to 10 days to become fully effective against antigen
  • plasma cells eventually die
  • memory cells may last a lifetime
36
Q

secondary response

A
  • rapid and robust
  • memory cells jump into action and produce antibodies specific to pathogen
  • basis of vaccination
37
Q

positive selection

A
  • maturing only cells that can respond to the presentation of antigens on MHC
38
Q

negative selection

A
  • causing apoptosis in cells that are self-reactive
39
Q

How are T-cells activated?

A
  • once T-cells leave the thymus, they are mature but naive until exposure to antigens
  • clonal selection - only those with a high affinity for a given antigen proliferate
40
Q

helper T-cells

A
  • also called CD4+ T-cells
  • coordinate immune response by secreting lymphokines
  • recruit other immune cells (plasma cells, cytotoxic T-cells, macrophages) and increase their activity
41
Q

autoimmune deficiency syndrome

A
  • advanced HIV infection
42
Q

What is HIV?

A
  • loss of Th cells (human immunodeficiency virus) prevents immune system from mounting an adequate response to infection
43
Q

What type of molecules do CD4+ cells respond to?

A
  • CD4+ T-cells respond to antigens presented on MHC-II molecules
  • most effective against bacterial, fungal and parasitic infections
44
Q

cytotoxic T-cells or CTL

A
  • CD8+ T-cell
  • capable of directly killing virally infected cells by injecting toxic chemicals that promote apoptosis into the infected cell
  • respond to antigens presented on MHC-I molecules
  • most effective against viral (an intracellular bacterial or fungal infections)
45
Q

suppressor or regulatory T-cells

A
  • express CD4
  • can be differentiated from CD4+ by protein Foxp3 - tones down the immune system when the infection has been contained and turns off self-reactive lymphocytes to prevent autoimmune disease
46
Q

memory T-cells

A
  • similar to memory B-cells
47
Q

What happens during a bacterial (extracellular) infection?

A
  • macrophages (and other antigen-presenting cells) engulf the bacteria, digest it and present antigens via MHC-II and release inflammatory mediators
  • cytokines attract inflammatory cells (neutrophils and macrophages)
  • mast cells activated by inflammation degranulate - release histamines that increase capillary leakiness
  • immune cells travel to affected tissue
  • dendritic cell leave affected tissue and travels to nearest lymph node -> presents antigen to B-cell
  • B-cells that produce correct antibody proliferate through clonal selection –> plasma and memory B-cells
  • antibodies travel through bloodstream to affected tissue and tag bacteria for destruction
  • dendritic cells present to T-cells –> activate T-cell response (particularly CD4+)
  • Th1 - release interferon gamma which activates macrophages and increases their ability to kill bacteria
  • Th2 - activates B-cells
48
Q

What happens during a viral (intracellular pathogen) infection?

A
  • virally-infected cell will release interferons
  • infected cells will present intracellular proteins (some are viral) on MHC-I
  • CD8+ T-cells recognize MHC and antigens as foreign and inject toxins -> apoptosis
  • viruses downregulate production and presentation of MHC-I –> natural killer cells cause apoptosis
  • memory T-cells will be generated after pathogen elimination
49
Q

self-antigens

A
  • proteins and carbohydrates that are present on every body cell
  • signal to the immune system that cell is non-threatening
50
Q

autoimmunity

A
  • immune system attacks cells expressing self-antigens
51
Q

hypersensitivity

A

allergies and autoimmunity

52
Q

active immunity

A
  • immune system stimulated to produce antibodies against a specific pathogen
  • natural exposure - antibodies generated by B-cells after infection
  • artificial exposure - vaccines without infection
53
Q

passive immunity

A
  • transfer of antibodies to an individual
  • includes: transfer across the placenta or through breast milk or transfer of IV immunoglobulins when exposed to rabies virus or tetanus
54
Q

What is the structure of the lymphatic system?

A
  • one-way vessels that become larger as they move towards the body’s center
  • vessels carry lymphatic fluid - lymph- and join to comprise a large thoracic duct in the posterior chest to deliver fluid to the left subclavian vein
55
Q

lymph nodes

A
  • small bean-shaped structures along the lymphatic vessels
  • contain a lymphatic channel, artery and vein
  • allow immune cells to be exposed to possible pathogens
56
Q

What are the functions of the lymphatic system?

A
  • fluid leaves bloodstream –> tissues
  • quantity of fluid leaving depends on Starling forces
  • lymphatic vessels drain tissues and then return it to the bloodstream- only when lymphatics are overwhelmed does edema occur
  • transports fat from digestive system into bloodstream via lacteals
  • fats are packaged into chylomicrons by intestinal mucosal cells and enter lacteals
  • lymphatic fluid with many chylomicrons takes on a milky white appearance - chyle
  • lymph nodes are places for the lymphocytes and antigen-presenting cells to interact
  • B-cells proliferate and mature in the lymph nodes in collections called germinal centers

MCAT Biology (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions