microbiology quiz chapter 14 and chapter 15 Flashcards
1
Q
what are activated complement proteins play a part in eliminating in eliminating microbial invaders from a host ?
A
Phagocytosis
Inflammation
Interferons
Fever
2
Q
the complement system comprises a group of blank in the bloodstream
A
proteins
3
Q
the complement system reacts
A
in a cascade
4
Q
complement proteins are found in
A
serum
5
Q
when is the classical complement pathway activated
A
when C1 binds to the antibody in an antigen body complex
6
Q
C3 convertase cleaves C3 into
A
C3a and C3b
7
Q
what role does C3b play
A
C3b binds to the surface of microorganisms and phagocyte receptors
8
Q
what do both the classical and alternative complement pathways create
A
C3 convertase
9
Q
the membrane attack complex kills cells by
A
creating holes in the cell membrane
10
Q
what are 3 primary functions of complement activation are
A
enhancing phagocytosis, causing inflammation, and killing target cells
11
Q
what are the following events that can occur after complement activation
A
cytolysis
opsonization
inflammation
enhanced phagocytosis
12
Q
what is opsonization?
A
when complement enhances phagocytosis of bacterium.
13
Q
What does the complement factors C5b+C6+C7+C8 make up a membrane attack complex result in
A
cytolysis
14
Q
true or false : Complement factors are named in the order in which they function.
A
false
15
Q
true or false : mitochondria contain hydrolytic enzymes
A
false
16
Q
what are the precursors to macrophages
A
monocytes
17
Q
what type of cell is capable of phagocytosis
A
neutrophils and macrophages
18
Q
true or false is phagocytosis apart of the body’s innate immune defense
A
true
19
Q
Is the complement system apart of the specific immune response
A
false
20
Q
phagocytes are not attracted to
A
enzymes released by lysozomes
21
Q
name the process by which phagocytes move toward microbial products?
A
chemotaxisis
22
Q
true or false: Complement factor C3b coats a bacterium and binds to C3b receptors on phagocytes, making the bacterium more susceptible to being phagocytized.
A
true
23
Q
what contains hydrolytic enzyme to digest foreign bacteria
A
lysosome
24
Q
how are microbes killed and digested in the phagolysosome
A
by hydrolytic enzymes
25
how can phagocytosis be enhanced using immunological medications
activated complemented proteins
26
after being engulfed a microbe is found within where
a phagosome
27
the microbe is digested within the phagocyte by enzymes delivered by
a lysozyme
28
true or false : If a bacterium could escape from a phagosome, it would be able to resist digestion by that phagocyte.
true
29
which of the following are antimicrobial substances are not part of our body first line defenses
antibodies
30
which of the following is part of the body's sensor systems ?
complement proteins
31
is it possible for one host to be resistant to infection by a pathogen that can normally cause disease in a different host
true
32
which of the following is part of the body's adaptive defensive
b cells
33
which event occurs in the early stages of inflammation
chemical medicators and cytokines are released from injured cells
34
what is the function of selectins
They promote sticking of neutrophils to the inner vessel wall
35
Which role does histamine play during inflammation?
It leads to vasodilation.
36
. Margination occurs when neutrophils stick to the lining of the endothelium.
true
37
tissue injury leading to inflammation can be due to
chemical injury
infection
mechanical energy
38
the four classic signs and symptoms of inflammation are
pain
redness
heat
swelling
not chills
39
what are the symptoms of inflammation due to
vasodilation
40
which of the following is not a function of inflammation
activate the complement system
41
describe these pattern recognition receptor functions
interferons
RLRs
TLRs
NLRs
Interferons these proteins are often secreted when viral RNA is detected which signals neighboring cells to express antiviral proteins.
RLRs These proteins are found in the cytoplasm and can detect viral RNA
TLRs These receptors are found anchored in sentinel cells like macrophages and dendritic cells.They can bind to foreign structures like dsRNA, ssRNA and some bacterial DNA fragments
NLRs These proteins are found in the cytoplasm and can detect bacterial components.
42
Which of the following are considered physical (versus chemical) factors that contribute to the skin and mucous membranes protective role against infection?
flushing of urinary tract
Mucociliary escalator
layers of cells
43
what are the true statements about fever induction and outcomes
fever is induced by cytoskines called pyrogens
fever inhibits bacteria from growing by inhibiting their metabolism
fever usually results when macrophages detect microbial invaders and release pro inflammatory cytoskines
pyrogens have an effect by acting on a certain part of the brain
44
what is not true about normal microbiota
Disruption of the normal microbiota has little effect on the host.
45
Which of the following statements about innate immunity are FALSE?
macrophages must become activated to function
mucous membrane are protected by keratin
lymphocytes form part of the first line of defense
fever inducing cytoskines are called pyroptosins
46
true or false:, IFN stands for interferon, molecules produced in response to a viral infection
true
47
how is the viral rna detected
RIG like receptors
RLRs
48
After producing IFN what happens to the cell
it is
is destroyed as a result of the virus infection.
49
when IFN made by one cell attaches to receptors on a second cell, what happens to that cell
makes antiviral proteins that when activated, degrade mRNA and prevent viral replication.
50
Once a cell detects viral RNA and produces IFNs, a sequence of events occurs. Place these steps in the correct order.
IFN diffuses out of the infected cell and attaches to receptors on healthy neighboring cells.
IFN stimulates healthy neighboring cells to express inactive antiviral proteins (iAVPs).
iAVPs become activated by the presence of viral dsRNA in the newly infected cell
Activated AVPs degrade mRNA, stopping protein synthesis and causing apoptosis of newly infected cell
51
How are apoptosis, pyroptosis and necroptosis the same?
They all lead to the death of the affected cell.
52
chapter 15 : what does the adaptive immune response involve
involves memory of antigens from previous exposure.
53
what is the responsibility of T cells
are responsible for cell-mediated immunity.
54
what are antigens
are molecules that can be recognized by B or T cells.
55
After repeated exposure to foreign material, innate immu
continues to react the same way.
56
what with antigen fragments displayed on their surfaces are known as antigen-presenting cells (APCs).
macrophages
57
When activated by antigen-presenting cells, helper T cells release what cytokine that activates B cells and cytotoxic T cells?
Interleukin-2
58
Cytotoxic T cells know that a cell is infected because
that cell has antigens from the disease-causing microbe on its surface.
59
B cells differentiate into ______, which make antibodies.
plasma cells
60
The immune system responds more quickly to second exposure to an antigen because
memory B cells are produced during the first response.
61
3. Cytotoxic T cells kill target cells by
exposing them to chemicals that induce apoptosis.
62
A child with a genetic disorder that does not allow immature B cells to develop would therefore not be able to make
antibodies.
63
. Antigen-presenting cells release what cytokine to activate helper T cells?
Interleukin-1
64
he antibody-producing progeny of an activated B cell are called
plasma cells
65
There are no antigens that can stimulate B cells without T cell help.
false
66
. T-dependent antigens
characteristically have a protein component
67
true or false : Antigen fragments are presented at the surface of macrophages along with self proteins.
true
68
how does a helper T cell activated
by an antigen presenting cell
69
An antigen-presenting cell presents antigen to a helper T cell on its surface using
a class 2 molecule on MHC molecule
70
After a B cell is activated to form plasma cells, those plasma cells each produce different antibodies
false
71
The process of antibody-dependent cellular cytotoxicity (ADCC) allows ______ cells to bind to antibody-coated host cells that may have viral proteins in their plasma membrane in order to kill them, inducing apoptosis and limiting viral spread.
natural killer
72
what is the difference between cytoxic T cells and helper T cells
Cytotoxic T cells recognizes antigens presented in mhc class 1 on molecules
cd8 T cells
not targeted by HIV
Realeses death packages
responds to endogenous antigens
helper T cells
CD4 T cells
targeted by HIV
Release cytoskines
Responds to exogenous antigens
recognizes antigens on MHC class 2 molecules
73
which is not a matching pair
peyer patchess and skin
74
how does negative selection occur in B and T lymphocytes
when cells binds to self antigens too strongly
75
Why is the process of gene rearrangement used in creating antibodies and T-cell receptors (TCRs) so important?
Without it, we would need a single gene for every antibody and TCR required to mount all the possible responses needed during our lives
76
Clusters of differentiation (CD) molecules are important because they
allow us to differentiate between cells that may look identical by microscopy.
77
match each antibody class with each description
IgA
IgM
IgG
IgE
IgD
IgA Most abundant class overall, but mainly found in mucosal secretions. Generally found as a dimer.
igM First class produced in primary response. Forms a pentamer. Helps activate complement through the classical pathway.
IgG Main class found in blood. Only class that can cross the placenta. Found as a monomer.
igE Binds via Fc region to mast cells/basophils. Involved in allergic responses and responses to parasites
igd Involved in maturation of B lymphocytes and antibody responses, but function is largely uncharacterized.
78
Which of the following are secondary lymphoid organs (areas where mature lymphocytes become activated)?
Lymph nodes
Peyer's patches
Tonsils
Spleen
79
Which of the following is a primary lymphoid organ
bone marrow
80
Helper T cells secrete ______ to stimulate the proliferation of B cells.
cytokines
81
82
Helper T cells interact with target cells by recognizing
antigen-MHC protein complexes.
83
Which of the following are antigen-presenting cells?
Macrophages and B cells are both APCs.
84
Which of the following cells can be a target for cytotoxic T cells?
Transplanted cells.
Virus-infected cell.
Cancer cell
85
true or false:
Apoptosis occurs in infected host cells, as well as during positive and negative selection in lymphocyte development
true
86
In addition to perforins, what else is secreted by cytotoxic T cells?
proteases (e.g. granzymes)
87
true or false: A person deficient in cytotoxic T cells may be more susceptible to developing cancer.
true
88
Antigenic fragments are complexed with ______ and displayed on the surface of the infected cell.
mhc class 1 molecules
89
Cytotoxic T cells cause death of infected cells by
releasing cytotoxins, perforins, and enzymes that destroy the cell.
90
Cytotoxic T cells recognize
viral antigens and class I MHC molecules
91
what are molecules that stimulate response in T and B cells
antigens
92
surface receptors on immune system cells function in
cell development
communication
identification of self/non-self molecules
93
what is the role of helpwer T cells
stimulate B cells and other T cells
94
function of helper T cells
function in both cell-mediated and humoral immunity.
95
All of the following cells have class II MHC receptors on their surface EXCEPT
red blood cells
96
Antigen-presenting cell
may be dendritic cells.
may be macrophages.
All of the answer choices are correct.
present antigen fragments on their surface.
may be B cell
97
true or false;A helper T cell must be activated before it can stimulate a B cell to produce antibody.
TRUE
98
Both antigen-presenting cells and B cells have class II MHC receptors on their surface
true
99
B cells differentiate into plasma cells and
memory cells
100
After a B cell is activated to form plasma cells, those plasma cells each produce different antibodies.
false
101
toll like receptors are only capable of recognizing
they are capable of recognizing antigen epitopes presented on major histocompability MHC moecuoes
102
how are macrophages and neutrophills different ?
macrophages and neutrophills are both phagyotic cells but macrophages reside in the tissues and neutrophills typically in the blood.
103
how does toll like receptors binding to macrophages help the immune response
These secreted molecules help bind pathogens and then direct them to receptors on the immune system cells that can eliminate them from our systems.
104
the voices of the cell that carry messages are called what
cytokines
105
what are the two functions that phagocytes serve
Engulfment/destruction of foreign cells AND alerting the other cells of the immune system to an invader.
106
what is the definition of neutralization
Antibodies fill the surface receptors on microbe to prevent attachment to the host
107
what is the definiton of complement system activation
Immune complexes activate complement proteins, leading to inflammation and production of MACs
108
what is the definition of immobilization and prevention of adherence
Antibodies bind to flagella preventing movement or to pili preventing attachment of bacteria
109
what is cross linking ?
Formation of large Ab-Ag complexes as a result of the Ab binding two separate antigens
110
what is Antibody-dependent cellular cytotoxicity (ADCC)
IgG molecules attach to a cell targeting it for attack by a NK cell
111
if a pathagen avoid binding by the complement C3B what would protect itsef from
opsonization
112
A physician is attempting new therapies for HIV patients who are suffering from an impaired immune response. He decides to try using a recombinant form of colony-stimulating factor cytokine (CSF). Why?
CSF will help to stimulate the production of new lymphocytes, the very cells that are affected by HIV. This may help to keep the patients' immune responses "normal" for a period of time.
113
what is the main phagocytes in circulation
neutrophils
114
what is involved in inflammation and allergic reactions
basophills
115
what Displays no antigen specificity but are active against tumor and virally infected cell
natural killer cells
116
what are Phagocytic cells that leave circulation and differentiate into macrophages
monocytes
117
what is the accumulation oif dead cells and neutrophils
pus formation
118
what does vasodilation and incrreased blood flow cause
heat and redness
119
what causes leaky blood cells and phagocyte cells migration
swelling and pain
120
what is the effect of chemical nerves
pain
121
what is the difference between innate and adaptive immunity?
Innate immunity is routine protection present at birth
Adaptive immunity develops throughout life as body is exposed to microbes or foreign material
122
describe how innate factors destroy invadors
Interferon (IFN) secreted with viral infection
Phagocytes engulf microbes or cell debris by phagocytosis
Inflammatory response is coordinated
Fever interferes with pathogen growth and enhances other immune responses
123
describe the overview of the innate immune defenses
Sentinel cells use pattern recognition receptors (PRRs) to identify unique microbial components
Complement system found in blood and tissue fluid
124
dexcribe the antimicorbial substances peroxidases lysozyme AMP and lactoferrin
Lysozyme degrades peptidoglycan
Peroxidases form antimicrobials; break down hydrogen peroxide
Lactoferrin and transferrin bind iron
Antimicrobial peptides (AMPs)
Defensins form pores in microbial membranes
125
what are the roles of the granulocytes neutrophils basophils and eosinphils
Neutrophils engulf and destroy bacteria; granules contain enzymes
, antimicrobials; also called PMNs, increase in number during infection
Basophils involved in allergic reactions, inflammation; granules contain histamine
Mast cells similar; found in tissues
Eosinophils fight parasitic worms; involved in allergic reactions; granules contain antimicrobials and histaminase
126
what is the mononuclear phagocyte system compose dof
Includes monocytes (circulate in blood) and cell types that develop as they leave bloodstream
Macrophages differentiate from monocytes
Sentinel cells found in nearly all tissues
127
what is the responsibility of dendritic cells
Sentinel cells, function as “scouts”
Engulf material in tissues, bring it to cells of adaptive immune system for
“inspection”
Usually develop from monocytes
128
what is the main responsibility of lymphocytes
Responsible for adaptive immunity
B cells, T cells highly specific in recognition of antigen
Generally reside in lymph nodes, lymphatic tissues
Innate lymphoid cells (ILCs) lack specificity
Can promote inflammatory response
Natural killer (NK) cells destroy certain types of cells
129
what is the defintion of chemokines colony stimulating factors and interferons and interleukins,and tumor necrosis factor
Chemokines: chemotaxis of immune cells
Colony-stimulating factors (
CSFs): multiplication and differentiation of leukocytes
Interferons (IFNs): control of viral infections, regulation of immune responses
Interleukins (ILs): produced by leukocytes; important in innate and adaptive immunity
Tumor necrosis factor (TNF): inflammation, apoptosis
130
what is a cytoskine storm
is a potentially deadly overproduction of cytokines that can occur during an immune response to certain pathogens, including COVID-19
131
describe the pattern recognition receptors DAMP
PAMP and MAMPs
Microbe-associated molecular patterns (MAMPs) detected by PRRs
Include cell wall components (peptidoglycan,
PAMPs are pathogen-associated, but not exclusive to pathogens
Damage-associated molecular patterns (DAMPs) indicate cell damage
132
describe the three types of cell death apoptosis pyroptosis and necrosis
Necrosis: traumatic cell death due to damage
Self-destruction of host cells
Apoptosis: programmed cell death; does not trigger inflammatory response
Pyroptosis and necroptosis: types of cell death that triggers an inflammatory response that sacrifices infected cells
133
describe acute inflammation and what happens when acute inflammation fails
acute inflammation is short term mostly neutrophils and macrophages that kill dead cells by ingesting dead cells and debris
If acute fails, chronic inflammation results; macrophages, giant cells accumulate, and granulomas form
134
describe the definition of cellular changes
a process called diapedesis
absceses
and what makes pus
Cellular changes - Cytokines cause endothelial cells of blood vessels to “grab” phagocytes in the bloodstream
Phagocytes squeeze between the cells of the dilated vessel, and move into tissues in a process called diapedesis
Dead neutrophils accumulate; along with tissue debris, make up pus
A localized collection of pus within a tissue is called an abscess
135
describe vascular changes
Vascular changes - The diameter of local blood vessels increases due to the action of histamine and other inflammatory mediators
Results in greater blood flow to the area, causing the heat and redness associated with inflammation
136
describe the process of exudate
Changes in the endothelial cells of capillaries allow fluid, called exudate, to leak from the blood vessels and into the tissue
Exudate is a protein-rich fluid that contains transferrin, complement system proteins, antibodies, and other substances to counteract invading microbes
Accumulation of exudate causes swelling and pain associated with inflammation
137
what is inflammation the purpose of inflammation and the conclusion of inflammation?
Infection or tissue damage results in inflammation
Purpose is to contain site of damage, localize response, eliminate invader, and restore tissue function
Results in swelling, redness, heat, pain, sometimes loss of function
138
what does pattern recognition receptors trigger
Pattern recognition receptors (PRRs) trigger
Detect MAMPs, DAMPs
Host cells release inflammatory mediators (cytokines, histamine)
139
what are the characteristics of neutrophils
Neutrophils act as “SWAT team”
Rapid response; move into area and eliminate invaders
More powerful than macrophages, but short life span of 1 to 2 days in tissues
Die once granules used
Kill microbes via phagocytosis and release of granule content
allowing enzymes and peptides from granules to destroy them
140
characteristics of macrophages
Macrophages are everyday “beat cops”
Phagocytize dead cells, debris, destroy invaders
Live weeks or months; regenerate lysosomes
Activated macrophages - response to cytokines
M1 macrophages have greater killing power
M2 macrophages lessen inflammation
Macrophages, giant cells, T cells form granulomas
Wall off organisms or material resistant to destruction
Important sentinel cells; alerts other immune cells
141
describe phagocytosis and exocytosis
Phagocytes engulf and digest material, pathogens
Chemotaxis: phagocytes recruited by chemoattractants
Recognition and attachment: direct (receptors bind mannose) and indirect (binding to opsonins)
Engulfment: pseudopods surround, form phagosome
Phagosome maturation and phagolysosome formation: directed by TLRs; fuse with lysosomes containing enzymes
Exocytosis: vesicle fuses with cytoplasmic membrane, expels remains
142
describe the complement system
Regulation prevents host cells from activating complement system
Molecules in host cell membranes bind regulatory proteins that inactivate C3b, preventing opsonization or triggering of alternative pathway
143
describe the pattern recognition receptors
Allow body to “see” signs of microbial invasion; lead to cytokine secretion
Microbe-associated molecular patterns (MAMPs) detected by PRRs
PAMPs are pathogen-associated, but not exclusive to pathogens
Damage-associated molecular patterns (DAMPs) indicate cell damage
144
describe toll like receptors
Anchored in membranes of sentinel cells
Surface TLRs monitor extracellular environment
TLRs in phagosomal or endosomal membranes of organelles characterize ingested material
Specific for distinct MAMPs
Dendritic cells have both TLRs and CLRs (C-type lectin receptors)
145
describe rig and nod like receptors
RIG-like receptors (RLRs) in cytoplasm detect viral RNA
Often double-stranded; no cap
NOD-like receptors (NLRs) in cytoplasm detect microbial components or cell damage
146
describe the interferon process
PRRs detect viral RNA; cell produces interferon (IFN)
Interferon causes neighboring cells to express inactive antiviral proteins (iAVPs)
iAVPs activated by viral dsRNA
Degrade mRNA, stop protein synthesis, infected cells undergo apoptosis
147
what are the three pathways for activation
Alternative pathway triggered when C3b binds to foreign cell surfaces (C3 unstable, so some C3b always present)
Lectin pathway: pattern recognition molecules (mannose-binding lectins, or MBLs) bind to mannose of microbial cells, interact with complement system components
Classical pathway: activated by antibodies bound to antigen, which interact with complement system
148
what are the outcomes of activation of the complement system
Opsonization: C3b binds to bacterial cells and foreign particles, promotes engulfment by phagocytes that attach to opsonins (like C3b)
Inflammatory Response: C5a attracts phagocytes to area; C3a and C5a increase permeability of blood vessels, induce mast cells to release cytokines
Lysis of Foreign Cells: membrane attack complexes (MACs) formed by proteins C5b, C6, C7, C8, and C9 molecules assembling in cell membranes of Gram-negatives
149
describe natural killer cells
Lysis of Foreign Cells: membrane attack complexes (MACs) formed by proteins
C5b, C6, C7, C8, and C9 molecules assembling in cell membranes of Gram-negatives
NK cells bind, deliver perforin- and protease-containing granules to cell, initiating apoptosis
Also recognize host cells lacking MHC class I
150
describe lymphocyte development
Negative Selection of Self-Reactive B Cells
B cells are exposed to “self” in bone marrow; if bind, induced to undergo apoptosis
This negative selection removes most B cells; critical for preventing immune system from attacking body
Positive and Negative Selection of T Cells
Positive selection: T cells must recognize MHC
Eliminated if unable to recognize
Negative selection: T cells also eliminated if recognize “self” peptides presented on MHC molecules
151
describe lymphocyte development
B cells mature in bone marrow, T cells mature in thymus
Gene rearrangement generates diversity
Process similar for B cells and T cells
152
describe t independent antigens
can activate cells without aid TH cells
Molecules with numerous identical evenly spaced epitopes (for example, polysaccharide capsules) are bound by clusters of B-cell receptors
Lipopolysaccharide (LPS), a component of the outer membrane of Gram negative bacteria, is also a T-independent antigen
153
describe the characteristics of the secondary immune response
Receptors already fine-tuned through affinity maturation
Antibodies coded by these cells bind antigen effectively
When activated, some quickly become plasma cells, producing IgG or IgA due to class switching
Proliferating cells again undergo affinity maturation, generating even more effective antibodies
Mediated by memory cells
Significantly faster, more effective than primary
Pathogens usually eliminated before causing harm
Vaccination exploits this natural phenomenon
154
describe the primary response
Plasma cells undergo apoptosis after several days, but are replaced as long as antigen is present
Antibody produced by those plasma cells
Some of the B cell clones become memory B cells, which are long-lived even in the absence of antigen
retains some of the antigens, maintaining memory of the response
Once the antigen is cleared, the antibody response decreases
activated lymphocytes undergo apoptosis
155
describe class switching
B cells are originally programmed to produce plasma cells that secrete IgM
As cells multiply some are induced to differentiate into plasma cells that secrete other antibody classes
B cells in lymph nodes usually switch to IgG
B cells in MALT switch to IgA
156
describe affinity maturation
Form of natural selection among proliferating B cells
Spontaneous mutations occur in multiplying B cells resulting in slight changes in B-cell receptor
B cells that bind antigen longest are most likely to proliferate
157
describe the eveloution of the primary response
When the few naive B cells that recognize a particular antigen are activated, they multiply to generate a population of clones
Some form antibody-secreting plasma cells; produce IgM
Others form a region the secondary lymphoid organ called a germinal center (GC) TH cells direct activated B cells to optimize their response
resulta in class switching including affinity maturation
158
describe the immuglobiin reesponses
IgE barely detectable in serum; most is tightly bound via Fc region to basophils and mast cells
igD Involved with development and maturation of antibody response
IgM
First class produced during primary response
Principal class produced in response to some T-independent antigens
IgG
Maternal IgG protects fetus and newborn
Degrade gradually over 6 month period
Infant begins producing its own antibodies
IgG found in colostrum (first breast milk); absorbed by newborn’s intestinal tract
159
what are the characterisitcs of antibodies
Antibodies (immunoglobulins) have Y-shaped structure called an antibody monomer
Variable region at the end of each arm gives the antibody its antigen-binding specificity
The remaining part is the constant region
The two identical arms are called the Fab region
Stem is the Fc region
160
descrine b cel activation
Activated B cell proliferates and gives rise to antibody-secreting plasma cells as well as memory cells
161
describe b cell receptors
Composed of four polypeptide chains—two duplicate copies of a heavy chain and two duplicate copies of a light chain
Disulfide bonds link together these chains
Forms a Y-shaped structure with two identical arms and a stem
The part farthest from the cell surface is a variable region that binds to the antigen
The part closest to the cell surface is the constant region
162
the role of macrophages activation in TH cells
Activated macrophages can fuse together to form giant cells; form granulomas that wall off the invader, preventing its escape
if a TH cell recognizes one of the peptides, it delivers cytokines that activate the macrophage
macrophages engulf and degrade invading microbes TH cells activate macrophages to make them more potent
163
effector function of TC cells
TC cells can induce apoptosis in cancerous cells because they make abnormal proteins however, peripheral tolerance mechanisms referred to as immune checkpoints often stops that from happening
TC cell binds to a presented peptide it releases proteases and perforin; forms pores in the target cell membrane
The proteases enter the target cell through the pores and induce apoptosis
tc cells can survive and go into other targets
164
activation of T cells
Dendritic cells activate T cells
Reside in peripheral tissues (skin, mucosa)
Gather materials via phagocytosis, pinocytosis
Can send extensions between epithelial cells of mucosal barriers and sample material in respiratory tract and lumen of intestine
Toll-like receptors (TLRs) and others recognize pathogens
If pathogens detected, cell takes up more material
Travels to secondary lymphoid organs; matures
Produces co-stimulatory molecules signaling “danger”
Presents antigens on both MHC class I and class II
T cell is activated by dendritic cell with co-stimulatory molecules
T cell becomes anergic or develops into T reg cells if no co-stimulatory molecules
Mechanisms of tolerance
165
what are two types of mhc molecules
Two types of MHC molecules can present antigen
MHC class I and MHC class II
Cytotoxic T cells have CD8 marker and only recognize antigens presented on MHC class I
Helper T cells have CD4 marker and only recognize antigens presented on MHC class II
166
describe the types of lymphocytes
Immature lymphocytes lack fully developed antigen-specific receptors
Naïve lymphocytes have receptors; have not yet encountered appropriate antigen
Activated lymphocytes have bound antigen and received confirmation, are able to proliferate
Effector lymphocytes are descendants of activated TH cells and Tc cells
Memory lymphocytes are long-lived descendants of activated lymphocytes; responsible for rapid secondary response if antigen encountered again
167
what are secondary lymphoid organs
Lymph nodes, spleen, tonsils
Mucosal immunity prevents microbial invasion via mucous membranes
Lymphoid tissues under skin are skin-associated lymphoid tissue (SALT)
168
characteristics of adaptive immunuty
Develops most effective means to eliminate invader
Lymphocytes recognize foreign material (antigen) and proliferate, leading to adaptive immunity
Characteristics of adaptive immunity
Molecular specificity
Immunological Memory
Stronger response to re-exposure
Vaccination relies upon this ability
Immune Tolerance
Must distinguish between “healthy self” and “dangerous”
169
cell meditated vs hummoral immunity
Humoral Immunity
Eliminates microbial invaders and toxins in the blood or tissue fluids
Involves B lymphocytes (B cells);
Programmed to produce Y-shaped proteins called antibodies
These bind to specific antigens, marking them as an invader to be eliminated
Cell-Mediated Immunity (CMI)
Deals with invaders residing in a “self” cell
Invaders include viruses and bacteria
Relies on T lymphocytes (T cells ); T indicates they mature in the thymus
Two types of T cells help eliminate antigens; differ in surface proteins, called CD markers
170
describe the three types of receptors
T-cell receptors (TCRs) only bind an antigen “presented” by one of the body’s own cell
Binding is guided by a surface molecule called a CD marker
Cytotoxic T cells have CD8 marker
Helper T cells have a CD4 marker
B-cell receptors (BCRs) are membrane-anchored antibodies
A region of the receptor called an antigen-binding site is responsible for that recognition
The antigen receptors on a single lymphocyte are identical; all recognize the same antigen
171
describe the types of tolerance
Immune tolerance, prevents inappropriate adaptive immune responses from damaging the body’s own tissues
Provided by two sequential processes:
Central tolerance - as lymphocytes mature (T cells in the thymus and B cells in the bone marrow), immature T and B cells that recognize “self” molecules are eliminated
Peripheral tolerance - prevents mature T and B cells that were not eliminated during central tolerance from reacting against self or other harmless molecules
172
describe peripheral tolerance
Naïve lymphocyte: never encountered antigen; cannot react until it receives confirming signals
Activated lymphocyte: has received confirming signals, proliferates, differentiates
Effector lymphocytes: short-lived, primary response
Memory lymphocytes: long-lived, activated more quickly to provide a secondary response
The first adaptive immune response to a particular antigen is called the primary response
Additional encounters with the same antigen result in a faster and more effective reaction called the secondary response
Memory lymphocytes are responsible for the secondary response
173
descrobe cell meditated t cell actovation
Immune response cannot begin until a lymphocyte becomes activated
Dendritic cells help activate the naive T cells
Present pieces of the antigen
Producing surface proteins, called co-stimulatory molecules if the antigen being presented is microbial or otherwise represents “danger”
If a T cell TCR binds an antigen presented by a dendritic cell that also has co-stimulatory molecules, T-cell activation may result
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t cell activation
a cytotoxic t cell proliferates
tc cell can induce the self cell to undergo aptosis
can become th cells deliver cytokines to macrophages and B cells, thus activating them
and also produce ctyokines
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describe primary lymphoid organs
Include bone marrow, thymus
Organs where lymphocytes develop
Hematopoietic stem cells reside in bone marrow; give rise to all blood cells including lymphocytes
B cells mature in bone marrow
T cells migrate to the thymus
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t independant vs t dependant antigens
An antigen that elicits immune response is immunogenic
T-dependent antigens - B cells that recognize them cannot be activated without TH cell help
T-independent antigens - activate B cells without TH cell help
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what are the protetivr outcomes of antigen body building
Neutralization: prevents toxins, viruses from binding
Opsonization: enhancement of phagocytosis
Complement system activation: classical pathway
Immobilization and prevention of adherence: binding to bacterial flagella or pili interferes
Cross-linking: two arms of antigen bind separate antigens
Antibody-dependent cellular cytotoxicity (ADCC): targets cell for destruction by natural killer (NK) cells
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hummoral immunity b cell activatiobn
Once a B cell becomes activated and proliferates many of the clones differentiate to become plasma cells
Plasma cells make antibodies, which are secreted versions of the BCR
If antibodies bind to antigens of microbial cells, toxins, and viruses, they protect the body against the effects of those antigens
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