Microbiology 14
Match each receptor with the type of immune cell that carries it. Instructions
CD4 <-> T helper cell, CD8 <-> T cytotoxic cell
Mature T cells express ______.
CD4 coreceptors, CD8 coreceptors
Either _____ or _____ coreceptors are expressed on mature T cells.
CD4, CD8
Which is NOT a benefit of using attenuated vaccines?
Cannot cause infection
Which of the following would NOT be recognized by the immune system as foreign antigens?
Cells or substances from your own body
Which of the following is the region of an antibody in which the amino acid sequence does not vary greatly?
Constant region
What cell type searches for and destroys cancer cells through the detection of abnormal peptides displayed on the target cell surface?
Cytotoxic T
The CD8 coreceptor is found on the surface of which cell type?
Cytotoxic T cells
_____ is the ability of certain T cells to kill a specific target cell such as an infected cell or a cancer cell.
Cytotoxicity
Naive T helper cells upon encountering antigen and MHC differentiate into TH _____ or TH _____ cells depending on the cytokine environment.
1, 2
A molecule must have a molecular weight of _______ to elicit even a weak immune response.
1000
Molecules less than _____ MW are seldom good antigens since a substance must be large enough to attract the attention of immune system cells.
1000
How long does an injection of immune serum globulin (ISG) protect the patient?
2 to 3 months
An immunoglobulin molecule is made of _____ protein chains, which are _____ heavy chains and _____ light chains. (Use numbers)
4, 2, 2
How many protein chains are used to produce an immunoglobulin molecule?
4; two heavy chains and two light chains
Which of the following statements about vaccine use are true?
Does carry some risk, Is less risky than the deadly disease they prevent
HIV infects T helper cells and severely reduces their number. Which of the following do you expect as a result of this?
A reduced ability of cytotoxic T cells to be activated, A reduced ability of B cells to be activated
In most specific immune responses, antigen must be processed and presented by which of the following?
APCs
T-cell independent antigens trigger a response from B lymphocytes without the usual cooperation needed from ______.
APCs, T helper cells
Which of the following is NOT a serious complication associated with vaccines?
Acquired Immunodeficiency Syndrome
_____ immunity is the result of the body's response to antigen.
Active
_____ is the aggregation formed by antibodies binding cellular antigens or large particles.
Agglutination
Oral vaccines have which of the following advantages?
Easy to administer, More readily accepted, Well tolerated
A given host cell can express only one type of receptor.
False
Maternal antibodies are unable to cross the placental barrier.
False
The risks of vaccine use outweigh the risks associated with the diseases they are intended to prevent.
False
There is a vaccine for almost all known pathogenic microbes.
False
This fragment of the antibody molecule is exposed or made more accessible to phagocytes when antibodies opsonize an antigen.
Fc
_____ are foreign molecules that elicit a specific immune response.
Antigens
________ is the genetically programmed death of cells that is both a natural process of development and the body's means of destroying abnormal or infected cells.
Apoptosis
_____ immunity results when a person is given a vaccination or receives premade antibodies through medical intervention.
Artificial
_____ is a process, such as subculturing, that is used to reduce the virulence of a pathogen so it can be used in a live vaccine preparation.
Attenuation
The fraction of plasma proteins composed primarily of IgG is called ________ globulin.
gamma
The _____ _____ fraction of separated serum is composed primarily of IgG.
gamma, globulin
The CD4 coreceptor is expressed on T _____ cells.
helper
CD4 receptors are found on T _____ cells and CD8 receptors are found on T _____ cells.
helper, cytotoxic
Due to the property of _____ _____, nonvaccinated individuals are indirectly protected against a pathogen as a result of the collective immunity of vaccinated persons.
herd, immunity
The principle that states that when there is a large number of individuals in a population that are immune to a pathogen, it is less likely that an non-immunized member of the population will encounter the pathogen is called _____ _____.
herd, immunity
Sometimes several vaccines are given at the same time but experts have carefully balanced vaccines to prevent ________.
immune interference
The process of eliminating any lymphocytes with receptors that recognize self molecules during the development process is _____.
immune tolerance
Any clinical process that produces immunity in an individual is called a(n) ________.
immunization
The ability of the body to react to a myriad of foreign substances is termed ________.
immunocompetence
B cells recognize antigen via _____ receptors.
immunoglobulin
The class of proteins to which antibodies belong are ________.
immunoglobulins
The electrophoresis of serum results in bands of globulins that include antibodies. The term ________ is used to describe these antibodies.
immunoglobulins
Preventing or treating infectious diseases by administering substances such as premade antibodies that produce artificial immunity is called ________.
immunotherapy
After antigen stimulation, B cells produce antibodies to ______ antigens.
inactivate
T-cell ________ antigens trigger a response from B lymphocytes without the usual cooperation needed from antigen presenting cells or T helper cells.
independent
Due to herd immunity, nonvaccinated individuals are ______ protected from disease by the collective immunity of the immunized members of a population.
indirectly
The numerous antigen/epitopes found on a cell or complex molecule will each elicit a(n) _____ lymphocyte response.
individual
Because several vaccines are given at the same time, scientists must carefully balance vaccines to prevent immune _____.
interference
B cells are activated by chemical signals called ______ produced by macrophages and T cells.
interleukins
A _____ or _____ vaccine is one in which the entire pathogen is given but it has been treated in such a way that it can no longer multiply.
killed, inactivated
The CD8 coreceptor is expressed on _____ T cells.
killer
The most common complications associated with vaccines include ______.
local reactions at the injection site, fever, allergies
Methods used to achieve attenuation of microbes for vaccine production include ______.
long-term cultivation, selection of mutant strains that grow at colder temperatures
Antigen-presenting cells that both process and present antigenic determinants on their surfaces include B-cells, _____ and dendritic cells.
macrophages
Chemical signals produced by _____ and T cells called interleukins can activate B cells.
macrophages
One set of genes that codes for human cell receptors and plays a role in recognition of self by the immune system is the _____ _____ _____ (MHC).
major, histocompatibility, complex
Some specific immune cells can differentiate into _____ cells, which persist long after a pathogen has been cleared and can reactivate during re-infection.
memory
Pure antibodies produced from a cell line or hybridoma and they are specific for only one epitope are called _____ antibodies.
monoclonal
IgA circulates in the blood as a(n) ________.
monomer
In the blood, IgA circulates in the ______ form.
monomer
After receiving an ISG injection, the passive immunity protects for 2 to 3 _____.
months
A potential problem with the use of live attenuated viruses is that the bacteria or virus can _____ back to a virulent strain.
mutate
Any immunity that is acquired during the normal biological experiences of an individual, such as infection or through breast feeding is known as ________ immunity.
natural
After recovery from an infectious disease, the resistance to reinfection is called ________ immunity.
natural active
Recovery from infectious disease results in _____ _____ immunity.
natural, active
A severe infection due to "flesh eating bacteria" that results in local tissue death is called ______.
necrotizing fasciitis
Which of the following is LEAST likely to show a similar combination of class I MHC genes?
neighbors from unrelated families
In _____ reactions, antibodies bind to cells, viruses, or toxins thus blocking their ability to interact with host receptors.
neutralization
The binding of antibodies to cells, viruses, or toxins that results in the blocking of their ability to interact with host receptors is called ________.
neutralization
When an antibody binds to an exotoxin, the exotoxin is said to be ________.
neutralized
The binding of antibody to an exotoxin _____ it.
neutralizes
The objective of vaccines is to use modified microbes or their components to ______.
obtain the same protective memory immune response as a natural infection
The coating of nonself molecules with antibodies to increase their rate of phagocytosis is called _____.
opsonization
Rare but more serious complications associated with vaccines include ______.
panencephalitis, disease due to contaminating viruses, disease from mutation back to a virulent strain
Specific resistance that is acquired indirectly by donation of preformed immune substances (antibodies) produced in the body of another individual is called artificial ________ immunity.
passive
When the exact composition of an antigenic determinant is known, it is possible to develop a vaccine by artificially synthesizing the antigenic _____ or _____.
peptide, protein
When antibodies opsonize an antigen, the Fc fragment of the antibody molecule is exposed or made more accessible to ______.
phagocytes
For small, free antigen molecules, such as proteins, the process of _____ increases the speed of phagocytosis.
precipitation
The process that enhances phagocytosis of antigens much smaller than a cell, such as proteins, is ______.
precipitation
An antigen _______ cell is a cell that ingests and degrades an antigen and subsequently places the antigenic determinant molecules on its surface for recognition by CD4 T lymphocytes.
presenting
The _____ immune response is the initial antibody response upon encountering antigen.
primary
The first response of the immune system when exposed to an antigen is called a ________ immune response.
primary
Requirements for an effective vaccine include ______.
produces a memory response, has a low level of toxicity or adverse side effects
A given host cell can express several different surface molecules called ________, each of which has a role in detection, recognition, and cell communication.
receptors
In ________ vaccines, a gene for the antigen of a pathogen is spliced into a plasmid, the antigen is expressed in a cloning host, and the expressed antigen is then harvested for use in a vaccine.
recombinant
Vaccine strategies include ______ vaccines made by isolating a gene for an antigen of a pathogen, splicing it into a plasmid for delivery to a cloning host, and then harvesting the produced antigen to be used in a vaccine.
recombinant
Requirements for most effective vaccines do NOT include ______.
regular booster dose schedule
Cells that prevent the immune system from overreacting by moderating inflammation, allergies, and autoimmunity are called _____ T cells.
regulatory
The most difficult task in vaccine production is finding antigens that are ______.
safe yet stimulate immunity
The _____ lymphoid tissues are continuously resupplied with B and T cells.
secondary
The _____ response, also called the anamnestic response, is the specific immune response generated upon subsequent exposure to a previously seen antigen and it is directed by memory cells.
secondary
The rapid rise in antibody titer following a repeat exposure to an antigen that has been recognized from a previous exposure is called a(n) ________ immune response.
secondary
Besides the J chain, secretory IgA possesses another accessory molecule called the _____ component which is involved in crossing the mucus membrane.
secretory
Dimeric IgA possesses a secretion piece and is called ________ IgA.
secretory
A given host cell can express ______.
several types of receptors
Activated T cells produce a spectrum of cytokines that ______.
stimulates other cells
Epitope based vaccines from viruses are not called acellular vaccines but instead are called _____ vaccines.
subunit
Vaccines based on viral epitopes are called ________ vaccines.
subunit
Bacterial proteins that are potent stimulators of T cells and can trigger massive release of cytokines leading to widespread cell death are called _____.
superantigens
Secretory IgA coats the surface of mucous membranes and is found in _____.
tears, mucus, colostrum, saliva
Which are NOT the most difficult tasks in vaccine production?
Finding antigens that are immunogenic, Finding antigens that are easy to isolate
Which of the following is NOT a common complications associated with vaccines?
Headaches or migraine headaches
________ is the principle that when there is a large number of individuals in a population that are immune to a pathogen, it is less likely that an non-immunized member of the population will encounter the pathogen.
Herd immunity
Which of the following is NOT a factor to be considered for vaccine preparation?
How long production of the vaccine takes
Which of the following is NOT a reason why IgA from mother's milk is critical for the protection of a nursing baby?
IgA is needed to stimulate the baby's immature B cells
The nursing baby receives IgA from the mother's milk which is critical for protection because ______.
IgA protects the gastrointestinal tract from enteric pathogens, natural intestinal barriers are not yet developed, the infant is not yet producing IgA
_____ is the antibody class that mediates anaphylaxis, asthma, and certain allergies.
IgE
At the beginning of an immune response most antibodies are IgM but as the response progresses you see production switch predominantly to which class of antibodies?
IgG
Which of the following is the most prevalent antibody in circulation and tissue fluids?
IgG
_____ is the most prevalent antibody in circulation and tissue fluids.
IgG
Match each antibody class with its biological function.
IgG <-> Long term immunity, opsonization, neutralizes toxins, IgA <-> Secretory antibody, IgM <-> Choice, First antibody produced in response to antigen First antibody produced in response to antigen, IgD <-> Serves as the B cell receptor, IgE <-> Allergies; worm infections
Early in the primary immune response, most antibodies are of which class?
IgM
Which is the first type of antibody produced by the body following exposure (first encounter) to a specific antigen?
IgM
_____ is the class of antibodies that comprise the majority of antibodies produced early in the primary immune response.
IgM
_____ is the first class of antibody produced by the body in the primary response, that is upon first encounter with antigen.
IgM
__________ contains immunoglobulins extracted from the pooled blood of many human donors.
Immune serum globulin
_____ _____ _____ (ISG) is used for passive immunization and contains immunoglobulin extracted from the pooled blood of at least 1000 human donors.
Immune, Serum, Globulin
_____ is the ability of the body to react to a myriad of foreign substances.
Immunocompetence
The term _____ was derived from the electrophoresis pattern of antiserum because four of the bands contained globulins of which most were antibodies.
Immunoglobulin
What type of receptors do B cells utilize to recognize their specific antigen?
Immunoglobulin
_____ are the chemical class of proteins to which antibodies belong.
Immunoglobulin
_____ is any clinical procedure that produces either passive or active immunity in a subject.
Immunotherapy
_____ is the medical procedure that may involve the transfer of premade antibodies to protect the individual.
Immunotherapy
Which of the following in NOT an advantage of oral vaccines?
Induce a faster response
The great majority of vaccines are administered by the following routes.
Intradermal injection, Subcutaneous injection, Intramuscular injection
Which method is NOT used to generate attenuated microbes for vaccine production?
Isolating microbe from recovering host
Artificial synthesis of a peptide or protein from a pathogen is used to produce a vaccine when ______.
the exact composition of the antigenic determinant is known
A(n) _____ exposes a person to a specific antigen preparation in order to trigger a protective specific immune response without the person suffering any effects associated with the pathogen.
vaccination
________ or ________ vaccines use a whole cell or intact virus preparation in which the microbes are dead or preserved and cannot multiply but are still capable of conferring immunity.
Killed, Inactivated
What is the set of genes that encodes human cell receptors that play a role in recognition of self by the immune system called?
MHC
Exposing a person to the antigenic components of a microbe without its pathogenic effects for the purpose of inducing a future protective response is called ________.
vaccination
_____ cells and _____ have receptors that bind to the Fc fragment of IgE and can detect antigen binding which then triggers the release of cytokines that increase the allergic response.
Mast, Basophils
_____ T or B cells remain for long periods to be ready to respond to the same antigen encountered at a later time.
Memory
These cells remain in circulation for long periods of time and are ready to respond to a specific antigen should it be encountered again.
Memory cells
Which of the following is a cell type that remains in the body long after a pathogen has been cleared, and can quickly respond if the body ever re-encounters the same pathogen?
Memory cells
After an initial exposure to antigen, which of the following is not a typical time period for the generation of a secondary immune response?
Minutes
______ antibodies are pure antibodies produced from a cell line or hybridoma and they are specific for only one epitope.
Monoclonal
Which of the following must be true if a newborn infant was found to have circulating antibodies against a pathogen it has never seen?
Mother's antibodies are able to cross the placenta
________ cells use the same killing mechanisms as cytotoxic T cells.
NK
_____ immunity is acquired from infection or through breastfeeding from the mother; this immunity is acquired through normal life experiences.
Natural
Which of the following lymphocytes is not antigen specific?
Natural killer
Although _____ _____ cells are not antigen specific, they have killing mechanisms similar to cytotoxic T cells and are able to destroy cancer cells and virus-infected cells.
Natural, Killer
_____ _____ cells are a type of lymphocyte with many similarities to T cells but the big difference is that they are NOT antigen specific.
Natural, Killer
_____ fasciitis is a condition in which a wound does not respond to antibiotic treatment and the surrounding tissue becomes damaged and dies.
Necrotizing
Biological functions associated with one or more of the different classes of antibodies include ______.
Neutralization, Complement fixation, Opsonization
Most materials that serve as good antigens include ______.
Nucleoproteins, Lipoproteins, Glycolipids, Proteins
______ enhances phagocyte recognition by coating the invader with antibodies so that they will be more readily recognized by phagocytes.
Opsonization
Which of the following is not a common route of vaccine administration?
Orally
_____ immunity is the acquisition of premade antibodies either from the mother or via injection of immune serum.
Passive
A larger dose and more boosters are required in order for killed vaccines to be effective because ______.
the microbe does not multiply
Which is not a characteristic shared by both the T and B cell antigen-specific receptors?
Possess two antigen recognition sites
The theory behind DNA vaccines is that human cells will take up the plasmid vectors and express ______.
the microbial DNA in the form of proteins that will stimulate immunity
Which type of T cell expresses both CD4 and CD25 receptors and acts to moderate inflammation, allergy, autoimmunity, and to reduce targeting of normal microbiota?
Regulatory T cells
When considering pathogenic microbes, ______.
there are many that lack a vaccine
Secretory IgA is NOT found in which of the following fluids?
Stomach acid
Which of the following types of molecules does NOT typically serve as a good antigen?
Sugars
______, such as some bacterial toxins, are potent stimulators of T cells and are responsible for diseases such as toxic shock.
Superantigens
Cytotoxicity is the ability for this type of lymphocyte to kill specific target cells.
T
____ cells are the "mediators" of cell-mediated immunity.
T
_____ cells are responsible for cell-mediated immunity.
T
CD4 T cells can differentiate into which cell types when stimulated by antigen displayed on MHC?
T helper 1, T helper 2
Assisting in the recognition steps of the T-cell response, which type of cell has a receptor that binds with the class II MHC receptor on the APC and with the antigen?
T helper cell
Which immune system cell assists in activating both B cells and T cells?
T helper cell
The CD4 coreceptor is found on the surface of which cell type?
T helper cells
Which cell types are needed to activate B cells in the absence of B cells activating independently?
T helper cells
Which are benefits of using attenuated vaccines?
They confer longer lasting immunity, The pathogen is most "real" to the immune system
What term is used to describe a vaccine which is constructed by placing a specific DNA sequence encoding a pathogenic antigen into a non-pathogenic organism that is later used as a vaccine?
Trojan horse
_____ _____ vaccines are constructed by placing DNA encoding a pathogenic antigen into a non-pathogenic organism, which is then introduced into the body to stimulate an immune response.
Trojan, Horse
At the beginning of an immune response, most antibodies produced are IgM but as the response progresses, you see mainly IgG antibodies or some other class being produced.
True
Circulating naive B lymphocytes eventually adhere to secondary lymphoid tissues by attaching to specific binding molecules in the tissues.
True
The objective of vaccines is to obtain the same protective memory immune response as a natural infection.
True
A measure of antibody level in a patient's serum is called ________.
titer
The concentration of antibodies in serum is expressed as the _____.
titer
In a mature lymphocyte, which immunoglobulin gene segments would be active?
V and D gene segments selected during gene rearrangement
During the proliferative stage of lymphocyte development, the process of eliminating any lymphocytes with receptors that recognize self molecules is called immune _____.
tolerance
B and T lymphocytes provide protection against specific antigens as part of _____ immunity.
acquired
The third line of defense, also known as ________ immunity provides long-term protection against foreign antigens encountered through infection or vaccination.
acquired, adaptive
The result of the body's response to exposure to antigen is called ________ immunity.
active
A(n) _____ is a chemical vehicle that is mixed with an antigen preparation to enhance its immunogenicity which is usually due to increased persistence of the antigen.
adjuvant
In immunology, a chemical vehicle that enhances antigenicity, presumably by prolonging antigen retention at the injection site, is called a(n) ________.
adjuvant
The aggregation (or clumping) by antibodies of whole cells or similar-sized particles is called ________.
agglutination
In a mature lymphocyte, which immunoglobulin gene segments would be deleted?
all V and D gene segments for heavy chains not involved in gene rearrangement, all V gene segments for light chains not involved in gene rearrangement
A(n) _____ is a type of antigen that provokes an allergic response.
allergen
An antigen that provokes an allergic reaction is called a(n) ________.
allergen
The presence of IgE on mast cells and basophils can lead to some destructive responses, including ______.
allergies, asthma, anaphylaxis
A(n) _____ is an antigen that is present in some but not all members of a species.
alloantigen
An antigen that is present in some but not all members of the same species is called a(n) ________.
alloantigen
A latent period occurs at the beginning of the primary immune response and it is marked by a lack of ______ to the activating antigen.
antibodies
Activated B cells (plasma cells) secrete immunoglobulins otherwise known as _____.
antibodies
Plasma B cells produce _____.
antibodies
Plasma cells produce copious amounts of ________.
antibodies
Plasma cells secrete immunoglobulins called ________.
antibodies
The latent period that occurs during the initial phase of a primary immune is marked by a lack of _____ to the activating antigen.
antibodies
Following stimulation by antigen, B cells differentiate either into plasma cells, which produce and secrete _____, or into _____ cells, which will react rapidly if the antigen is encountered at some point in the future.
antibodies, memory
A molecule that induces a specific immune response is known as a(n) __________.
antigen
A(n) _____ is also called an immunogen and induces a specific immune response.
antigen
According to the clonal selection theory, each distinct lymphocyte has an ability to recognize only one specific _____.
antigen
Each genetically distinct lymphocyte has the ability recognize one specific ________.
antigen
Visualizing the Y shaped antibody structure, the _____ binding sites are found at the ends of the arms.
antigen
In most specific immune responses, antigen must be processed and presented by _____-_____ cells.
antigen, presenting
In DNA vaccines, human cells will take up the plasmid vectors and express the microbial DNA in the form of _____ that will stimulate immunity.
antigens
T cytotoxic cells initiate _____ or programmed cell death in their target cells.
apoptosis
Immunity that is induced as a medical intervention, either by exposing an individual to an antigen or by administering an immune substance such as antiserum is called ________ immunity.
artificial
Looking at a Y shaped antibody structure, the antigen binding sites are found ______.
at the end of each of the forks
Naive B cells in circulation are able to adhere to secondary lymphoid tissues by ______.
attaching to specific binding molecules
Different host cell surface receptors can be involved in a wide range of significant roles such as ______.
attachment to foreign antigens, aiding in cellular development, receiving and transmitting chemical messages, promoting recognition of self antigens
To reduce the virulence of a pathogenic bacterium or virus by passing it through a non-native host or by long-term subculture is to _________ the organism.
attenuate
When comparing the T and B cell antigen-specific receptors they both ______.
belong to the same protein family, are inserted into the lymphocyte cell membrane, are formed by genetic rearrangements
The activation of B cells involves ______.
binding of antigen, clonal selection.
The disadvantages associated with using live attenuated vaccines include ______.
can be transmitted to others, requiring special storage facilities, possibility of mutating back to a virulent strain
Cytotoxic T cells can destroy ______ cells.
cancer, foreign, virally infected
A hapten which is too small to elicit an immune response on its own becomes immunogenic when linked to a _____ molecule.
carrier
When a hapten molecule is linked to a larger ________ molecule, it develops immunogenicity.
carrier
Foreign antigens recognized by the immune response include ______.
cells or substances from animals, substances such as proteins from other humans, cells from other humans, whole microbes or their parts
A conceptual explanation for the development of lymphocyte specificity and variety during immune system maturation is known as the _________ theory.
clonal selection
The activation of B cells by antigen involves the ______ ______ of a B cell bearing the complementary antigen-specific receptor.
clonal selection
The _____ _____ theory is a conceptual explanation for the development of lymphocyte specificity and variety during immune system maturation.
clonal, selection
The multiplication of lymphocytes upon encountering antigen results in production of a _____, or group of genetically identical cells.
clone
Upon encountering antigen, lymphocytes undergo differentiation and proliferation resulting in production of a group of genetically identical cells called ________.
clones
The entire _____ region of an antibody has an amino acid content that does not vary greatly.
constant
The secondary lymphoid tissues are ______ with new B and T cells.
continuously supplied
The ________ fragment is the portion of an antibody that does not bind to antigen.
crystallizable
The segment of the antibody that does not bind antigen is called the _____ _____ or the Fc fragment.
crystallizable, fragment
Activated T cells produce a spectrum of _____ which stimulates other cells.
cytokines
Mast cells and basophils have receptors that bind to the Fc fragment of IgE and, upon allergen binding by the surface bound IgE, the cell releases ________ that increase the allergic response.
cytokines
Killed vaccines often require a larger _____ and more _____ to be effective because the microbe does not multiply and is cleared quickly from the host.
dosage, boosters
Foreign cells and molecules are antigenically complex with multiple epitopes which are capable of ______.
each eliciting a separate lymphocyte response
The principles of vaccine preparation include ______.
effectiveness of vaccine against the disease, safety and cost of vaccine, ease in administration of vaccine, immunogen selection for vaccine
A(n) _____ is the molecular fragment of an antigen that defines its specificity and triggers an immune response.
epitope
The precise molecular group of an antigen that defines its specificity and triggers an immune response is called a(n) _____.
epitope
An important characteristic of an antigen is that it be perceived to be ________.
foreign
Antigens are ________ molecules that stimulate a specific immune response.
foreign
Due to individual differences in the inheritance of class I MHC genes, the cells of each individual express molecules that are _____ to other humans.
foreign
One important characteristic of an antigen is that it be perceived as _____ meaning that it is not a normal constituent of the body.
foreign
A secondary immune response can occur ______ after exposure to antigen.
weeks, months, years
