Chapter 21 - The Immune System - Innate and Adaptive Body Defenses Flashcards
The immune system’s two intrinsic systems are:
- Innate (nonspecific) defense system 2. Adaptive (specific) defense system
The immune system is a ____ system rather than ____ system.
functional; organ
Innate and adaptive defenses of the immune system are ____.
intertwined
Both innate and adaptive defenses release and recognise many of the same
defensive molecules
How do innate defenses differ from adaptive?
- innate defenses have specific pathways for certain substances 2. innate responses release proteins that alert cells of adaptive system to foreign molecules
Innate defense system has two lines of defense–first and second. The first is composed of:
external body membranes (skin and mucosae)
Innate defense system has two lines of defense–first and second. The second is composed of:
antimicrobial proteins, phagocytes, and other cells
The second innate line of defense does what?
- inhibits the spread of invaders 2. has inflammation as its most important mechanism
The adaptive defense system’s third line of defense does what?
It attacks *particular* foreign substances.
How does the adaptive line of defense differ from the innate line of defense?
Takes longer to react than innate system.
Innate defenses have ____ to ward off invading pathogens.
surface barriers
The surface barriers of innate defenses are in the most general context:
skin, mucous membranes, and their secretions
What are the characteristics of surface barriers of the innate defense system?
- they are a physical barrier to most microorganisms 2. they are keratin resistant to weak acids and bases, bacterial enzymes, and toxins 3. mucosae provide similar mechanical barriers
Surface barriers of the innate defense system have protective chemicals that inhibit or destroy microorganisms. What are they?
- the acidity of skin and secretions–acid mantle 2. enzymes 3. defensins 4. other chemicals
The acidity of skin and secretions in the innate defense system does what to microorganisms?
inhibits growth
What are the enzymes that inhibit microorganisms in the innate defense system?
- lysozome of saliva 2. respiratory mucus 3. lacrimal fluid
What do the enzymes of the innate defense system do?
kill many microorganisms
Defensins of the innate defense system are what? What do they do to microorganisms?
antimicrobial peptides; inhibit growth
Other chemicals of the innate defense system are what? What effect do they have on microorganisms?
lipids in sebum, dermcidin in sweat; toxic
Respiratory system modifications (surface barriers) of the innate defense system are:
- mucus-coated hairs in nose 2. cilia of upper respiratory tract that sweep dust 3. bacteria-laden mucus toward mouth
Surface barriers of the innate immune system can be breached by nicks or cuts. What happens then?
second line of defense must protect deeper tissues
If microorganisms invade deeper tissues, internal defenses of cells and chemicals are necessary. What are they?
- phagocytes 2. natural killer (NK) cells 3. antimicrobial proteins 4. fever 5. inflammatory response
What is an example of antimicrobial proteins that protect deeper tissues upon invasion?
interferons and complement proteins
What partakes in the inflammatory response to protect deeper tissues upon invasion?
- macrophages 2. mast cells 3. WBCs 4. inflammatory chemicals
The phagocytes that participate in internal defenses are:
-neutrophils -macrophages
These are the most abundant phagocytes but die fighting.
neutrophils
_____ become phagocytic on exposure to infectious material.
neutrophils
____ develop from monocytes.
macrophages
The chief phagocytic cells are:
macrophages
____ macrophages wander through tissue spaces, e.g. alveolar macrophages.
free
___ macrophages are permanent residents of some organs, e.g. Kupffer cells (liver) and microglia (brain).
fixed
In order for phagocytosis to take place, the phagocyte must
adhere to particle
Some microorganisms evade phagocytic adherence with ____.
capsule
____ marks pathogens—coating by complement proteins or antibodies.
opsonisation
In phagocytosis, cytoplasmic extensions bind to and engulf the particle in a vesicle called ____.
phagosome
In phagocytosis, the phagosome fuses with lysosome, which creates ____.
phagolysosome
Pathogens are killed during phagocytosis due to acidifying and digesting with _____.
lysosomal enzymes
If lysosomal enzymes are unable to kill pathogens, helper T cells cause a release of enzymes of _____, which kill pathogens.
respiratory burst
What are the three ways that helper T cells kill pathogens that are resistant to lysosomal enzymes?
- release cell-killing free radicals 2. produce oxidising chemicals (e.g. H2O2) 3. increase pH and osmolarity of phagolysosome
In phagocytosis, defensins in neutrophils pierce ____.
membrane
nonphagocytic large granular lymphocytes
natural killer (NK) cells
NK cells attack cells that lack
“self” cell-surface receptors
NK cells induce ___ in cancer cells and virus-infected cells.
apoptosis
NK cells secrete potent chemicals that enhance:
inflammatory response
This is triggered whenever body tissues are injured.
inflammatory response
This prevents the spread of damaging agents.
inflammation
The cardinal signs of acute inflammation are:
-redness -swelling -heat -pain -sometimes impairment of function
When inflammation is triggered, it disposes of what?
cell debris and pathogens
When inflammation is triggered, it alerts which system?
adaptive immune system
When inflammation is triggered, it sets the stage for what?
repair
The inflammatory response begins with chemicals released into _____ by injured tissues, immune cells, blood proteins.
ECF
Macrophages and epithelial cells of boundary tissues have ____ receptors.
Toll-like (TLR)
11 types of toll-like receptors (TLR) recognise specific classes of:
infecting microbes
Activated TLRs trigger release of _____ that promote inflammation.
cytokines
The three inflammatory mediators are:
-kinins -prostaglandins -complement
Inflammatory mediators dilate _____.
local arterioles
When inflammatory mediators dilate local arterioles, this is known as:
hyperemia
When inflammatory mediators dilate local arterioles, this causes:
redness and heat of inflamed region
Inflammatory mediators make capillaries ____.
leaky
Inflammatory mediators attract ____ to area.
leukocytes
Does edema increase capillary permeability or decrease it? What does this cause?
increase; exudate goes to tissues
Exudate is fluid containing ___ and ___.
clotting factors; antibodies
Exudate causes:
local swelling (edema)
When swelling occurs, it pushes on nerve endings which causes:
pain
Pain can also occur from:
-bacterial toxins -prostaglandins -kinins
Exudate moves foreign material into ____.
lymphatic vessels
Exudate delivers ____ and ____ to area of inflammation.
clotting proteins; complement
The clotting factors that exudate delivers to area of inflammation form _____.
fibrin mesh
The fibrin mesh formed by clotting factors at areas of inflammation is the scaffold for ____.
repair
The fibrin mesh formed by clotting factors at areas of inflammation isolates the injured area so that:
invaders can’t spread
In phagocyte mobilisation, ___ lead, and ___ follow.
neutrophils; macrophages
As phagocyte attack continues, ___ arrive.
monocytes
12 hours after leaving bloodstream, monocytes become ____. These are called ___.
macrophages; “late-arrivers”
“Late-arrivers” replace ____ and remain for ____.
dying neutrophils; clean up prior to repair
If inflammation is due to pathogens, ____ is activated and ____ arrive.
complement; adaptive immunity elements
The steps for phagocyte mobilisation are:
- leukocytosis 2. margination 3. diapedesis of neutropils 4. chemotaxis
the release of neutrophils from bone marrow in response to ____-inducing factors from injured cells
leukocytosis
neutrophils cling to walls of capillaries in inflamed area in response to CAMs
margination
inflammatory chemicals promote positive ___ of neutrophils
chemotaxis
inflammatory chemicals that promote chemotaxis are known as
chemotactic agents
Two different antimicrobial proteins are:
-interferons (IFNs) -complement proteins
Antimicrobial proteins attack microorganisms directly or indirectly?
directly
Antimicrobial proteins hinder the microorganisms’ ability to ____.
reproduce
The family of immune-modulating proteins are known as:
interferons
Viral-infected cells secrete interferons to:
warn neighbouring cells
After viral-infected cells secrete IFNs, they enter neighbouring cells and cause the cell to do what?
produce proteins that block viral reproduction and degrade viral RNA
IFN alpha and beta also activate ____.
NK cells
IFN ____ is secreted by lymphocytes.
gamma (immune interferon)
IFN gamma activates ____.
macrophages
IFN gamma has widespread ____ effects.
immune-mobilising
Since IFN activates NK cells and macrophages, it indirectly fights ____.
cancer
Artificial IFNs are used to treat:
-hepatitis C -genital warts -MS -hairy cell leukaemia
The complementary system is composed of ~20 blood proteins that circulate in ___ form.
inactive
The complement system includes which blood proteins?
-C1-C9 -factors B, D, and P -other regulatory proteins
Complement is the major mechanism for destroying:
foreign substances
Our cells contain complement activation ____.
inhibitors
Complement unleashes inflammatory chemicals that:
amplify all aspects of inflammatory response
Complement kills bacteria and certain other cell types by ____.
cell lysis
Complement enhances which defense?
both innate and adaptive
There are three pathways to complement activation, which are:
-classical pathway -lectin pathway -alternative pathway
In the classical pathway, antibodies bind to ____ and ____. This is called _____.
invading organisms; complement components; complement fixation
The classical pathway is the ___ step in complement activation.
first
____ are produced by the innate system to recognise foreign invaders.
lectins
When lectins are bound to foreign invaders they can also bind and activate ____.
complement
Complement pathway that is triggered when activated C3, B, D, and P interact on the surface of microorganisms.
alternative pathway
Each complement pathway involves activation of ___ and in an orderly sequence.
proteins
In complement activation, each step ___ the next.
catalyses
Each complement pathway converges on ___, which cleaves into __ and ___.
C3; C3a; C3b
In complement activation, there is a common terminal pathway initiated that does three things, which are:
-enhances inflammation -promotes phagocytosis -causes cell lysis
Cell lysis begins when:
C3b binds to target cell
After C3b binds to target cell, what happens?
insertion of complement proteins called [membrane attack complex (MAC)] into cell’s membrane
After MAC is inserted into cell’s membrane, what happens?
MAC forms and stabilises a hole in the membrane surface
After MAC forms a hole in the membrane surface, what happens?
Influx of water –> lysis of cell
C3b also causes ____.
opsonisation
C3a and other cleavage products amplify ___.
inflammation
C3a stimulates mast cells and basophils to release ___.
histamine
C3a attracts ___ and ____.
neutrophils; other inflammatory cells
Fever is a systemic response to:
invading microorganisms
Leukocytes and macrophages exposed to foreign substances secrete ___.
pyrogens
Pyrogens act on:
body’s thermostat in the hypothalamus, raising body temperature
The benefits of moderate fever are:
-causing the liver and spleen to sequester zinc and iron (needed by microorganisms) -increasing metabolic rate –> faster repair
this system must be primed by initial exposure to a specific foreign substance
adaptive (specific defense) immune system
The adaptive immune system activates ___.
complement
The adaptive immune system amplifies ____.
inflammatory response
The adaptive immune system protects against ___ and ___.
infectious agents; abnormal body cells
part of the adaptive immune system that recognises and targets specific antigens
specific
part of the adaptive immune system that is not restricted to initial site
systemic
the adaptive immune system has ____, which leads to stronger attacks to known anitgens
memory
The two separate, overlapping arms of adaptive immune system are:
-humoral (antibody-mediated) immunity -cellular (cell-mediated) immunity
humoral immunity is composed of ___, produced by lymphocytes, circulating freely in body fluids
antibodies
in humoral immunity, antibodies bind temporarily to the target cell and do two things:
-temporarily inactivate target cell -mark the target cell for destruction by phagocytes or complement
in cellular immunity ___ act against target cell.
lymphocytes
lymphocytes that act against target cell act directly by
killing infected cells
lymphocytes that act against target cell act indirectly by
releasing chemicals that enhance inflammatory response or activating other lymphocytes or macrophages
substances that can mobilise adaptive defenses and provoke an immune response
antigens
antigens are the targets of all ___ immune responses
adaptive
Most antigens are large, complex molecules not normally found in
body (nonself)
The two important functional properties of complete antigens are:
-immunogenicity -reactivity
Examples of complete antigens are:
-foreign protein -polysaccharides -lipids -nucleic acids
ability to stimulate proliferation of specific lymphocytes
immunogenicity
ability to react with activated lymphocytes and antibodies released by immunogenic reactions
reactivity
incomplete antigens are known as
haptens
incomplete antigens are not ___ by themselves
immunogenic
Example of haptens:
-peptides -nucleotides -some hormones
haptens may be immunogenic if attached to ____ and combination is marked foreign
body proteins
haptens cause the immune system to mount
harmful attack
Examples of mounted harmful attack as a result of haptens:
-poison ivy -animal dander -detergents -cosmetics
antigenic determinants are also known as
epitopes
Only certain parts (epitopes) of entire antigen are ___
immunogenic
Antibodies and lymphocyte receptors bind to epitopes as enzyme binds ___.
substrate
Most naturally occurring antigens have numerous antigenic determinants that
-mobilise several different lymphocyte populations -form different kinds of antibodies against it
Large, chemically simple molecules (e.g. plastics) have little or no ___.
immunogenicity
self-antigens are also known as
MHC proteins
self-antigens are
protein molecules on the surface of cells that are not antigenic to self but antigenic to others in transfusions or grafts
Example of self-antigens:
MHC glycoproteins
MHC glycoproteins are coded by genes of ____ and are unique to the individual.
major histocompatibility complex
MHC glycoproteins have a groove holding ___ or ___.
self-antigen; foreign antigen
Lymphocytes only bind ___ on MHC proteins.
antigens
The three types of cells of the adaptive immune system are:
-B lymphocytes -T lymphocytes -Antigen-presenting cells (APCs)
B lymphocytes participate in ___ immunity.
humoral
T lymphocytes participate in ___ immunity.
cell-mediated
these do not respond to specific antigens and play essential auxiliary roles in immunity
antigen-presenting cells (APCs)
The five steps of lymphocyte development, maturation, and activation are:
-origin (all originate in red bone marrow) -maturation -seeding secondary lymphoid organs and circulation -antigen encounter and activation -proliferation and differentiation
Lymphocytes are educated as they mature, and become B cells in ___ or T cells in ___.
bone marrow; thymus
a lymphocyte can recognise one specific antigen by binding to it is known as
immunocompetence
lymphocytes unresponsive to own antigens is known as
self-tolerance
Thanks to immunocompetence, B or T cells display a unique receptor on their surface when they achieve maturity, so they can bind
only one antigen
T cells mature in the thymus under ___ and ___ pressures.
-positive selection -negative selection
selects T cells capable of regonising self-MHC proteins; failures are destroyed by apoptosis
positive selection
T cells capable of recognising self-MHC proteins is known as
MHC restriction
prompts apoptosis of T cells that bind to self-antigens displayed by self-MHC; ensures self tolerance
negative selection
B cells are positively selected if they successfully make
antigen receptors
B cells that are self-reactive are handled by
elimination by apoptosis (clonal deletion)
Immunocompetent B and T cells that are not yet exposed to antigen are called
naive
Naive B/T cells are exported from ____ to ____.
primary lymphoid organs; “seed” secondary lymphoid organs
Exportation of naive B/T cells increases the chance of:
encounter with antigen
examples of primary lymphoid organs
-bone marrow -thymus
examples of secondary lymphoid organs
-lymph nodes -spleen
naive lymphocyte’s first encounter with antigen leads to selection for further development. this is known as
clonal selection
If the correct signals are present in clonal selection,
lymphocyte will complete its differentiation
An activated lymphocyte ____.
proliferates
Due to lymphocyte proliferation, this leads to
exact clones
Most lymphocyte clones become
effector cells that fight infections
Few lymphocyte clones remain as
memory cells
Memory cells are able to respond to the same antigen
more quickly the second time
B and T memory cells and effector T cells circulate ___.
continuously
____ determine which foreign substances the immune system will recognise.
genes (not antigens)
Immune cell receptors are the result of
acquired knowledge of microbes (likely in environment)
Lymphocytes make how many different types of antigen receptors?
up to a billion
Lymphocytes are coded for by ~____ genes.
25,000
Gene segments are shuffled by ____.
somatic recombination
these engulf antigens
antigen-presenting cells (APCs)
APCs present fragments of antigens to ___ for recognition.
T cells
The three major types of APCs are:
-dendritic cells -macrophages -B cells
dendritic cells are located in
connective tissues and epidermis
macrophages are located in
connective tissues and lymphoid organs
dendritic cells phagocytise ___
pathogens
dendritic cells enter ___ to present antigens to ___ in lymph node
lymphatics; T cells
the most effective antigen-presenter known is
dendritic cell
dendritic cells are the key link between
innate and adaptive immunity
macrophages are widespread in ___ and ___
lymphoid organs; connective tissues
macrophages can activate
naive T cells
macrophages present antigens to T cells to
activate themselves into voracious phagocytes that secrete bactericidal chemicals
these do not activate naive T cells
B cells
B cells present antigens to ___ to assist own activation
helper T cell
B cells are activated when
antigens bind to its surface receptors and cross-link them
After antigens cross-link surface receptors, what happens?
receptor-mediated endocytosis of cross-linked antigen-receptor complexes (clonal selection)
After receptor-mediated endocytosis of cross-linked antigen-receptor complexes takes place, what happens?
proliferation and differentiation into effector cells
Most clone cells become ____ cells.
plasma
Plasma cells secrete ___ at a rate of ___ for how long?
specific antibodies; 2000 molecules/sec; four to five days, then die
Antibodies circulate in ___ or ___.
blood; lymph
Antibodies bind to ___ and mark for
free antigens; destruction by innate or adaptive mechanisms
Clone cells that do not become plasma cells become ____.
memory cells
Memory cells provide ____ memory and mount ___ response to future exposures of same antigen.
immunological; immediate
In immunological memory—primary immune response, upon first antigen exposure, what takes place?
cell proliferation and differentiation
The lag period for cell proliferation and differentiation in the primary immune response is:
three to six days
In the primary immune response, peak levels of plasma antibody are reached in ___ days.
10
After peak level of plasma antibodies in primary immune response of immunological memory, what happens?
antibody levels decline
Re-exposure to the same antigen gives ____ response. (Part of secondary immune response)
faster, more prolonged, more effective
(part of secondary immune response) Sensitised memory cells respond within:
hours
(part of secondary immune response) Antibody levels peak in ___ days at much higher levels.
two to three
(part of secondary immune response) Antibodies bind with ___ affinity.
greater
(part of secondary immune response) Antibody level can remain high for
weeks to months
when B cells encounter antigens and produce specific antibodies against them, this is known as
active humoral immunity
The two types of active humoral immunity are
-naturally acquired -artificially acquired
response to bacterial or viral infection
naturally acquired humoral immunity
response to vaccine of dead or attenuated pathogens
artificially acquired humoral immunity
most of dead or attenuated pathogens are
vaccines
Vaccines spare us symptoms of
primary response
Vaccines provide
antigenic determinants that are immunogenic and reactive
Vaccines can cause
-illness trying to vaccine against -allergic responses
___ and ___ help prevent illness or allergic responses induced by vaccines.
-“naked DNA” -oral vaccines
In ____ immunity, readymade antibodies are introduced into body.
passive humoral
In passive humoral immunity, B cells are ___ by antigens.
not challenged
Does immunological memory occur in passive humoral immunity?
no
In passive humoral immunity, protection ends when
antibodies degrade
Two types of passive humoral immunity
-naturally acquired -artificially acquired
antibodies are delivered to fetus via placenta or to infant through milk. this is known as
naturally acquired passive humoral immunity
injection of serum, such as gamma globulin, is known as
artificially acquired passive humoral immunity
In artifically acquired passive humoral immunity, protection is immediate but ends when
antibodies naturally degrade in body
the gamma globulin portion of blood is known as
immunoglobulins
proteins secreted by plasma cells are
antibodies
Antibodies are capable of binding specifically with antigen detected by ___.
B cells
Antibodies are grouped into one of ___ Ig classes.
five
four looping polypeptide chains linked by disulfide bonds
antibody monomer
Antibodies have T- or Y- shaped ____.
antibody monomer
Overall antibody shape/structure:
-two identical heavy chains with hinge region at “middles” -two identical light chains -variable regions at one end of each arm -constant regions of stem
Variable regions at one end of each antibody arm combine to form two identical ____.
antigen-binding sites
Constant regions of antibody stem determine
antibody class
Constant regions of antibody stem serve common functions in all antibodies by dictating:
-cells and chemicals that antibody can bind -how antibody class functions to eliminate antigens
The different classes of antibodies are:
-IgM -IgA -IgD -IgG -IgE
Characteristics of IgM antibodies:
-pentamer (larger than others) -first antibody released -potent agglutinating agent -readily fixes and activates complement
Characteristics of IgA antibodies:
-monomer or dimer -in mucus and other secretions -helps prevent entry of pathogens
Characteristics of IgD antibodies:
-monomer attached to surface of B cells -functions as B cell receptor
Characteristics of IgG antibodies:
-monomer; 75-85% of antibodies in plasma -from secondary and late primary responses -crosses placental barrier
Characteristics of IgE antibodies:
-monomer active in some allergies and parasitic infections -causes mast cells and basophils to release histamine
B cells can switch antibody classes but retain ____.
antigen specificity
B cells can switch from ___ at first; then ___.
IgM; IgG
Almost all secondary antibody responses are ___.
IgG
How do antibodies affect antigens?
inactivate and tag antigens; do not destroy them
When antibodies interact with antigens, they form:
antigen-antibody (immune) complexes
The defensive mechanisms used by antibodies are
-neutralisation and agglutination (two most important) -precipitation and complement fixation
the simplest defense mechanism is
neutralisation
In neutralisation, antibodies block specific sites on ___ or ___.
viruses; bacterial exotoxins
In neutralisation, antibodies that block sites prevent antigens from
binding to receptors on tissue cells
In neutralisation ____ undergo phagocytosis.
antigen-antibody complexes
antibodies bind same determinant on more than one cell-bound antigen
agglutination
In agglutination, ____ agglutinate. An example is:
cross-linked antigen-antibody complexes; clumping of mismatched blood cells
soluble molecules are cross-linked
precipitation
When soluble molecules are cross-linked, what happens?
Complexes precipitate and are subject to phagocytosis.
The main antibody defense against cellular antigens is:
complement fixation and activation
In complement fixation, several antibodies bind close together on a cellular antigen. This leads to:
complement-binding sites on stem regions aligning
When complement-binding sites on stem regions align, this triggers:
complement fixation into cell’s surface —> cell lysis
Functions of activated complement are:
-amplifies inflammatory response -promotes phagocytosis via opsonisation - –>positive feedback cycle that enlists more and more defensive elements
A commercially prepared pure antibody (also known as ____) is specific for:
monoclonal antibody; single antigenic determinant
Monoclonal antibodies are produced by:
hybridomas
cell hybrids; fusion of tumor cell and B cell
hybridomas
Monoclonal antibodies proliferate indefinitely and have ability to produce:
single type of antibody
monoclonal antibodies are used in
-research -clinical testing -cancer treatment
What do antigen-antibody complexes do to antigens?
do not destroy; prepare them for destruction by innate defenses
Antibodies do not invade solid tissue unless:
there is a lesion present
Antibodies can act intracellularly if:
attached to virus before it enters cell –>activate mechanisms that destroy virus
In the cellular immune response, T cells provide defense against ____.
intracellular antigens
Some T cells ___ cells; others release chemicals that:
directly kill; regulate immune response
In cell-mediated immune response, there are two populations of T cells based on which glycoprotein surface receptors are displayed. These are:
-CD4 cells -CD8 cells
CD4 cells usually become ____ cells.
helper T
Helper T (CD4) cells activate:
-B cells -other T cells -macrophages -direct adaptive immune response
Some CD4 cells become ____.
regulatory T cells
Regulatory T cells moderate ____.
immune response
CD4 cells can also become ____.
memory T cells
CD8 cells become ____.
cytotoxic T cells
Cytotoxic T cells (CD8) destroy cells that are
harboring foreign antigens
CD8 cells can also become ___
memory T cells
Helper, cytotoxic, and regulatory T cells are ____ T cells.
activated
CD4 or CD8 cells are also known as
naive T cells
T cells only respond to processed fragments of antigens displayed on
surfaces of cells
Antigen presentation is vital for activation of ___ and normal functioning of ___.
naive T cells; effector T cells
The two types of MHC proteins important to T cell activation are:
-Class I MHC proteins -Class II MHC proteins
Both types of MHC proteins are synthesised at __ and bind to ____.
endoplasmic reticulum; peptide fragments
proteins that are displayed by all cells except RBCs
class I MHC proteins
proteins that are displayed by APCs (dendritic cells, macrophages, B cells)
class II MHC proteins
Class I MHC proteins bind with fragment of protein synthesised
in the cell
a fragment of protein synthesised in the cell is known as
endogenous antigen
In a normal cell, an endogenous antigen is ___. In an infected or abnormal cell it is ___.
self-antigen; nonself antigen
Class I MHC proteins are crucial for
CD8 cell activation
Class I MHC proteins inform cytotoxic T cells of
microorganisms hiding in cells (cytotoxic T cells ignore displayed self-antigens)
Class I MHC proteins act as
antigen holders; form “self” part that T cells recognise
Class II MHC proteins bind with fragments of ____ that have been engulfed and broken down in a phagolysosome.
exogenous antigens
Class II MHC proteins are recognised by ____.
helper T cells
Class II MHC proteins signal ___ cells that help is required.
CD4
CD4 and CD8 cells have different requirements for MHC protein that presents antigens to them. CD4 cells that become Th bind only:
class II MHC proteins typically on APC surfaces
CD4 and CD8 cells have different requirements for MHC protein that presents antigens to them. CD8 cells that become cytotoxic T cell bind only:
class I MHC proteins on APC surfaces
Once (CD8 cells that become) cytotoxic T cells are activated, they seek:
same antigen on class I MHC proteins on any cell
CD8 cells are activated by class __ MHC proteins.
I
How do APCs get endogenous antigens from another cell and display them on class I MHCs?
Dendritic cells engulf dying virus-infected or tumor cells, or import antigens via temporary gap junctions with infected cells–then display both class I and class II MHCs
The two-step process of T cell activation:
-Antigen binding -Co-stimulation
Both steps of T cell activation occur on surface of:
same APC
Both steps of T cell activation are required for ___.
clonal selection
T cell antigen receptors (TCRs) bind to ____ on APC surface.
antigen-MHC complex
TCR that recognises the nonself-self complex is linked to:
multiple intracellular signaling pathways
Other T cell surface proteins are involved in ____. (Ex. ___)
T cell activation; CD4 and CD8 help maintain coupling during antigen recognition
T cell activation–co-stimulation–requires T cell binding to:
other surface receptors on an APC (co-stimulatory signals)
Cytokines (interleukin 1 and 2 from APCs or T cells) trigger ___ and ___ of activated T cell.
proliferation; differentiation
Without co-stimulation of T cell activation, ___ occurs.
anergy
In anergy, T cells become:
tolerant to that antigen
In anergy, T cells are unable to:
divide
In anergy, T cells do not:
secrete cytokines
T cells that are activated do what?
-enlarge and proliferate in response to cytokines -differentiate and perform functions according to their T cell class
Primary T cell response peaks within:
a week
T cell apoptosis occurs between days:
7 and 30
The benefit of T cell apoptosis:
activated T cells are a hazard–produce large amount of inflammatory cytokines –>hyperplasia, cancer
Effector activity wanes as amount of:
antigen declines
Memory T cells remain and mediate:
secondary responses
chemical messengers of the immune system are:
cytokines
Cytokines mediate:
-cell development -differentiation -responses in immune system
Cytokines include ___ and ___.
interferons; interleukins
____ is released by macrophages which co-stimulates bound T cells.
Interleukin 1 (IL-1)
Interleukin 1 co-stimulates bound T cells to:
-release interleukin 2 (IL-2) -synthesise more IL-2 receptors
IL-2 is a key growth factor, acting on cells that:
release it and other T cells
IL-2 encourages activated ____ to divide rapidly.
T cells
Other cytokines amplify and regulate:
innate and adaptive responses
Examples of cytokines that amplify and regulate innate and adaptive responses:
-tumor necrosis factor – cell toxin -gamma interferon – enhances killing power of macrophages
Helper T (Th) cells play a central role in:
adaptive immune response
Helper T cells activate both:
humoral and cellular arms
Once primed by APC presentation of antigen, helper T cells do what?
-help activate T and B cells -induce T and B cell proliferation -their cytokines recruit other immune cells
Without helper T cells, there is no:
immune response
Helper T cells interact directly with B cells displaying:
antigen fragments bound to MHC II receptors
Helper T cells stimulate B cells to ___ and ___.
divide more rapidly; being antibody formation
B cells may be activated by helper T cells by binding to _____. Reponse is:
T cell-independent antigens; weak and short-lived
Most antigens require Th co-stimulation to activate B-cells, these are called:
T cell-dependent antigens
CD8 cells require helper T cell activation into:
destructive cytotoxic T cells
Helper T cell activation of CD8 cells cause dendritic cells to express ____ required for CD8 cell activation.
co-stimulatory molecules
Helper T cells amplify responses of:
innate immmune system
Helper T cells activate ___, which leads to:
macrophages; more potent killers
Helper T cells mobilise _____ and ____ and attract other types of ___.
lymphocytes; macropages; WBCs
Helper T cells are divided into these subsets of helper T cells:
-Th1 -Th2 -Th17
Subset helper T cells that mediate most aspects of cellular immunity:
Th1
Subset helper T cells that defend against parasitic worms; mobilise eosinophils, promote allergies:
Th2
Subset helper T cells that link adaptive and innate immunity by releasing IL-17; may play role in autoimmune disease:
Th17
these cells directly attack and kill other cells
cytotoxic T cells (Tc)
activated cytotoxic cells circulate in blood and lymph and lymphoid organs in search of:
body cells displaying antigen they recognise
Cytotoxic (Tc) cell targets are:
-virus-infected cells -cells with intracellular bacteria or parasites -cancer cells -foreign cells (transfusions or transplants)
Cytotoxic T cells bind to a ___ complex.
self-nonself
Cytotoxic T cells can destroy all:
infected or abnormal cells
Lethal hit of cytotoxic cells–two methods:
-Tc cell releases perforins and granzymes by exocytosis -Tc cell binds specific membrane receptor on target cell, and stimulates apoptosis
Perforins create pores through which:
granzymes can enter target cell
Granzymes stimulate ____.
apoptosis
Regulatory T cells dampen immune response by:
direct contact or by inhibitory cytokines such as IL-10 and TGF-beta
Regulatory T cells are important in preventing:
autoimmune reactions
By preventing autoimmune reactions, regulatory T cells do (two) things:
-suppress self-reactive lymphocytes in periphery (outside lymphoid organs) -research into using them to induce tolerance to transplanted tissue
Natural killer cells recognise other (3) signs of abnormality:
-lack of class I MHC -antibody coating target cell -different surface markers of stressed cells
NK cells use same key mechanisms as ___ cells for killing their target cells.
cytotoxic T cells
In ___, NK and cytotoxic T cells prowl for markers they recognise.
immune surveillance
The four varieties of organ transplants are:
-autografts -isografts -allografts -xenografts
graft from one body site to another in same person
autograft
graft between identical twins
isograft
graft between individuals who are not identical twins
allograft
graft from another animal species
xenograft
Sucess of graft depends on similarity of __.
tissues
Autografts and isografts have ideal donor tissues which are almost always successful if:
there is a good blood supply and no infection
There has been research into ___grafts from genetically engineered animals.
xenografts
The most common graft is:
allograft
In allograft, ___, ___, and ___ are mached as closely as possible.
ABO; other blood antigens; MHC antigens
In immunosuppressive therapy problems, the patient’s ___ is supressed.
immune system
After the immune system is suppressed, it cannot:
protect from foreign agents
After the immune system is suppressed, bacterial and viral infections lead to:
death
After the immune system is suppressed, it must balance drugs for ____ but no toxicity.
graft
After the immune system is suppressed, it uses ___ to control infections.
antibiotics
After the immune system is suppressed, undr best circumstances, rejection is after ____ in __% of patients.
10 years; 50%
congenital or acquired condition that impairs function or production of immune cells or molecules such as complement or antibodies
immunodeficiency
Severe combined immunodeficiency syndrome (SCID) is a ___ defect.
genetic
In SCID, there is a marked deficit in ___ and ___ cells.
B; T
In SCID, there is a defective ___ enzyme.
adenosine deaminase (ADA)
SCID is fatal if untreated; it is treated with ___ transplants.
bone marrow
Lymphoma is an acquired ____.
immunodeficiency
Lymphoma is cancer of ____.
lymphocytes
Lymphoma leads to immunodeficiency by depressing:
lymph node cells
Acquired immune deficiency syndrome (AIDS) cripples the immune system by:
interfering with activity of helper T cells
AIDS is characterised by:
-severe weight loss -night sweats -swollen lymph nodes
With AIDS, opportunistic infections occur, such as:
-pneumocystis pneumonia -Kaposi’s sarcoma
AIDS is caused by ____ transmitted by bodily fluids–blood, semen, and vaginal secretions
human immunodeficiency virus (HIV)
HIV enters body via:
-blood transfusions -blood-contaminated needles -sexual intercouse and oral sex -vaginal secretions
HIV destroys ___ cells, which leads to:
helper T cells; depression of cell-mediated immunity
HIV multiplies in lymph nodes throughout ___ period, ~10 years if untreated
asymptomatic
There are symptoms of HIV when ___ collapses:
immune system
HIV also invades brain, which leads to:
dementia
HIV-coated glycoprotein complex attaches to:
CD4 receptor
Acquired Immune Deficiency Synrome (AIDS) arises from:
HIV reverse transcriptase
HIV reverse transcriptase leads to:
frequent errors; high mutation rate and resistance to drugs
AIDS can be treated with these antiviral drugs:
-fusion inhibitors -integrase inhibitors -reverse transcriptase and protease inhibitors -antiretroviral vaginal gel
____ block HIV’s entry into cell.
fusion inhibitors
____ block viral RNA integration into host’s DNA.
integrase inhibitors
_____ inhibit viral replication enzymes.
reverse transcriptase and protease inhibitors
antiretroviral vaginal gel reduces AIDS risk by ___%.
50
immune system loses ability to distinguish self from foreign
autoimmune disease
in autoimmune disease, there is production of ____ and ____ that destroy body tissues.
autoantibodies; sensitised Tc cells
Examples of autoimmune diseases:
-MS -myasthenia gravis -Graves’ disease -type I diabetes mellitus -systemic lupus erythmatosus -glomerulonephritis -rheumatoid arthritis
Autoimmune diseases are treated by suppressing the entire immune system by:
-anti-inflammatory drugs (e.g. corticosteroids) -blocking cytokine action -blocking co-stimulatory molecules
Research into autoimmune disease treatment includes:
-activating regulatory T cells -inducing self-tolerance using vaccines -directing antiboies against self-reactive immune cells
In autoimmune disease, weakly self-reactive lymphocytes may be activated by:
-foreign antigens that may resemble self-antigens -new self-antigens may appear
When foreign antigens that may resemble self-antigens appear, antibodies against foreign antigen may:
cross-react with self-antigen
In autoimmune disease, new self-antigens may appear, generated by:
-gene mutations -changes in self-antigens by hapten attachment or infectious damage -release of novel self-antigens by trauma to barrier
immune responses to perceived (otherwise harmless) threat cause tissue damage
hypersensitivities
different types of hypersensitivities are distinguished by:
- their time course 2. whether antibodies or T cells are involved
Antibodies cause ___ and ___ hypersensitivities.
immediate; subacute
T cells cause ___ hypersensitivity.
delayed
_____ hypersensitivities begin in seconds after contact with allergen.
acute (type I) [allergies]
Initial contact with allergen is ____ but sensitises person.
asymptomatic
Allergy reaction may be ___ or ___.
local; systemic
Allergy reaction involves ___ secrete by ___ cells.
IL-4; Th2
Secreted IL-4 stimulates ____ to produce ___.
B cells; IgE
Produce IgE binds to ___ and ___, which leads to:
mast cells; basophils; flood of histamine release and induced inflammatory response
A later encounter with same allergen leads to:
allergic reaction
mast cells of skin and respiratory and gastrointestinal mucosa react to allergen
local reaction
allergic systemic response is ____.
anaphylactic shock
in allergic reaction, histamine release leads to
blood vessels dilated and leaky –> runny nose, hives, watery eyes -asthma if allergen is inhaled
allergic reaction histamine release is controlle by
antihistamines
systemic response to allergen that directly enters blood and circulates rapidly
anaphylactic shock
in anaphylactic shock, ___ and ___ are enliste throughout the body
basophils; mast cells
Systemic histamine release may cause:
-constriction of bronchioles; tongue may swell -sudden vasodilation and fluid loss from bloodstream that may cause ->circulatory collapse (hypotensive shock) and death
anaphylactic shock is treate by
epinephrine
subacute hypersensitivities are caused by ___ and ___ transferred via blood plasma or serum
IgM and IgG
subacute hypersensitivities have a ___ onset and ___ duration
slow; long
two subacute hypersensitivities are:
-cytotoxic (type II reactions) -immune complex (type III) hypersensitivity
an example of cytotoxic (type II) reaction
mismatched blood transfusion reaction
an example of immune complex (type III) hypersensitivity
systemic lupus erythematosus
antibodies bind to antigens on specific body cells, stimulate phagocytosis and complement-mediated lysis of cellular antigens
cytotoxic (type II) reactions
in immune complex (type III) hypersensitivity, ___ are widely distributed in body or blood
antigens
in immune complex (type III) hypersensitivity, once antigens are distributed in the body, ____ form.
insoluble antigen-antibody complexes
in immune complex (type III) hypersensitivity, complexes cannot be cleared from:
particular area of body
in immune complex (type III) hypersensitivity, complex buildup leads to:
-intense inflammation -local cell lysis -cell killing by neutrophils
delayed hypersensitivities (type IV) have a ___ onset.
slow
delayed hypersensitivities (type IV) mechanism depends on _____ cells.
helper T
in delayed hypersensitivities (type IV), ____ and ___ cause damage.
cytokine-activated macrophages; cytotoxic T cells
an example of delayed hypersensitivity (type IV) is
allergic contact dermatitis (e.g. poison ivy)
type IV hypersensitivity agents act as ____.
haptens
___ test depends on type IV hypersensitivity reaction.
TB skin
immune system stem cells develop in liver and spleen in weeks ____.
1-9
bone marrow becomes primary source of stem cells when?
later and through adult life
lymphocyte development continues in ___ and ___.
bone marrow; thymus
___ lymphocytes preominate in newborn; ___ system educated as person encounters antigens
Th2; Th1
depression, emotional stress, and grief do what do the immune response?
impair
vitamin ____ is required for activation of CD8 cells to produce Tc cells
D
vitamin D supplements reduce _____.
influenza
vitamin D deficiency is linked to ____.
MS
with age, immune system begins to ___.
wane
as a person ages, there is greater susceptibility to:
immunodeficiency and autoimmune diseases
as a person ages, there is greater incidence of:
cancer
