What type of antigen are recognized by T Cells?

A) Free Antigens

B) Bacterial Antigens Only

C) Cancer Antigens only

D) Processed fragments of protein antigens displayed on surfaces of body cells

D) Processed fragments of protein antigens displayed on surfaces of body cells

What are B and T cells called that have not yet been exposed to an antigen?

A) Naive

B) Immunocompetent

C) Clone

D) Self-Tolerant

A) Naive

T cells achieve self-tolerance in the ___.

A) Lymph Node

B) Bone Marrow

C) Tonsils

D) Thymus

D) Thymus

**T cells learn and are screened for self-tolerance in the thymus.

Which letter represents the adhesion of the phagocyte to the pathogen? Select from letters A-D.

A

B

C

D

A

__________ immunity protects a baby who is fed breast milk.

A) Natural active

B) Artificial passive

C) Artificial active

D) Natural passive

D) Natural passive

**Natural immunity is achieved through natural, non-manmade means. Natural passive immunity occurs when an individual gets antibodies from another source--they are not self-made. In the case of a nursing infant, the process is natural and the baby is protected by antibodies received from the mother.

Neutrophils flatten and squeeze between the endothelial cells of the capillary walls during what process?

A) leukocytosis

B) margination

C) diapedesis

D) chemotaxis

C) diapedesis

Which of the following cells predominate at the sites of chronic infections?

A) Basophils

B) Macrophages

C) Eosinophils

D) B cells

B) Macrophages

B cells respond to the initial antigen challenge by ________.

A) reducing its size

B) forming of a large number of cells that are unlike the original B cell

C) producing progeny cells that include plasma cells and memory cells

D) immediately producing antigen-specific antibodies

C) producing progeny cells that include plasma cells and memory cells

Which of the following cells is the most critical cell in immunity?

A) B cell

B) APC

C) helper T cell

D) cytotoxic T cell

C) helper T cell

T/F: Fever is one of the cardinal signs of inflammation.

FALSE

Which of the following statements is a false or incorrect statement?

A) T cells and B cells become activated when they bind with recognized antigens.

B) It is our genes, not antigens, that determine what specific foreign substances our immune system will be able to recognize and resist.

C) The lymphoid organs where lymphocytes become immunocompetent are called primary lymph organs. All other lymphoid organs are referred to as secondary lymphoid organs.

D) After becoming immunocompetent, the naive T cells and B cells are exported to the bone marrow where the encounters with antigens occur.

D) After becoming immunocompetent, the naive T cells and B cells are exported to the bone marrow where the encounters with antigens occur.

Cellular immunity is attributed to the action of __________.

A) T cells

B) complement proteins

C) interferons

D) antibodies.

A) T cells

Which of the following is not an autoimmune disease?

A) multiple sclerosis

B) systemic lupus erythematosus

C) glomerulonephritis

D) type II diabetes

D) type II diabetes

Which of the following is characteristic of antibodies?

A) three binding sites per antibody monomer

B) composed of heavy and light polypeptide chains

C) incapable of being transferred from one person to another

D) carbohydrate structure

B) composed of heavy and light polypeptide chains

What mobilizes the adaptive defenses and provokes an immune response?

A) MHC proteins

B) pyrogens

C) interferons

D) antigens

D) antigens

**Antigens (anything the body recognizes as foreign) are substances that can mobilize the adaptive defenses and provoke an immune response. Antigens are the ultimate targets of all adaptive immune responses.

Treatment of an abscess often requires that it be surgically drained because ______.

A) the wall of the abscess prevents proper blood flow into the pus

B) the wall of the abscess prevents proper elimination of wastes from the enclosed pus

C) the wall of the abscess prevents neutrophils from entering the pus and attacking the pathogens

D) the wall of the abscess prevents macrophages from differentiating into monocytes in the pus

C) the wall of the abscess prevents neutrophils from entering the pus and attacking the pathogens

**Neutrophils are one of the first immune cells to respond to a site of pathogenic invasion. They can act as phagocytes and can kill bacteria using the respiratory burst.

Which cell of the immune system is absolutely required for an adaptive immune response in that it helps activate both humoral and cellular immune responses?

A) antigen-presenting cell

B) helper T cell

C) cytotoxic T cell

D) plasma cell

B) helper T cell

What protein can be released by infected cells to help protect cells that have not yet been infected?

A) complement

B) interferons (IFNs)

C) opsonins

D) pyrogens

B) interferons (IFNs)

Which of the following would be classified as a delayed hypersensitivity reaction?

A) anaphylaxis

B) cytotoxic hypersensitivity

C) allergic contact dermatitis

D) immune complex hypersensitivity

C) allergic contact dermatitis

Helper T cells ________.

A) often function to decrease the immune response

B) bind tightly to target cells and release a lymphotoxin called perforin

C) release B7 proteins

D) function in the adaptive immune system activation

D) function in the adaptive immune system activation

Why are children given vaccinations?

A) to develop a disease in a mild state rather than have it later on in a more serious state

B) to see whether the immune system is capable of defense against disease

C) to develop memory cells against various diseases

D) to activate the cell-mediated defense against pathogens

C) to develop memory cells against various diseases

Which of the following is not a mechanism for the development of autoimmune disorders?

A) cross-reaction of antibodies formed against foreign antigens with self-antigens

B) mutation followed by the appearance of membrane proteins not previously present

C) exposure of previously "hidden" self-antigens to the adaptive immune system

D) a second exposure to an allergen

D) a second exposure to an allergen

Proinflammatory signals include all of the following, EXCEPT __________.

A) antibodies

B) histamines

C) prostaglandins

D) leukotrienes

A) antibodies

**Antibodies are not proinflammatory signals. They are proteins that activated B cells produce to protect the body from specific foreign antigens.

T-cell activation requires ________.

A) antigen binding and co-stimulation

B) antibody production and co-stimulation

C) antigen binding, antibody production, and co-stimulation

D) antigen binding and antibody production

A) antigen binding and co-stimulation

Which of the following is a part of the second line of defense against microorganisms?

A) phagocytes

B) keratin

C) gastric juice

D) cilia

A) phagocytes

Select the correct statement about the prevention of immune attack on "self."

A) Neutrophils capable of binding to self-antigens are chemically inactivated.

B) Tolerance to self is due to the action of foreign antigens that inactivate the immune response to one's own tissues.

C) The development of tolerance is specific to B cells only.

D) Tolerance is developed during fetal life.

D) Tolerance is developed during fetal life.

Which mechanism of antibody action results in cell lysis?

A) precipitation

B) agglutination

C) complement fixation and activation

D) neutralization

C) complement fixation and activation

What activates CD8 cells?

A) peptides containing 14-17 amino acids

B) exogenous antigens

C) antigens on class II MHC proteins

D) antigen fragments on class I MHC proteins

D) antigen fragments on class I MHC proteins

Pyrogens induce __________.

A) cytolysis

B) inflammation

C) opsonization

D) fever

D) fever

Select the correct statement about the function of antibodies

A) The most potent agglutinating agent is IgG.

B) Antibodies may directly destroy "invaders."

C) Complement fixation is the main mechanism by which antibodies provide protection.

D) Neutralization is the process by which antibodies cause invading cells to clump together.

C) Complement fixation is the main mechanism by which antibodies provide protection.

The redness and heat of an inflamed area are due to a local hyperemia caused by ________.

A) complement production

B) phagocyte mobilization

C) vasoconstriction

D) vasodilation

D) vasodilation

What is the first antibody released in the primary response and usually indicates infection?

A) IgA

B) IgG

C) IgD

D) IgM

D) IgM

T/F: MHC I proteins (major histocompatibility class I proteins) are found on most cells of the body.

TRUE

Which cells mature in the thymus?

A) B cells

B) Memory Cells

C) Effector Cells

D) T Cells

D) T cells

Which of the following statements is incorrect or false?

A) MHC proteins are the cell's identity markers.

B) Class II MHC molecules appear only on the surface of antigen-presenting cells, thymic cells, and T cells that have been activated by exposure to antigens.

C) Class 1 MHC molecules are built into the plasma membranes of all body cells.

D) Haptens lack immunogenicity unless attached to protein carriers.

B) Class II MHC molecules appear only on the surface of antigen-presenting cells, thymic cells, and T cells that have been activated by exposure to antigens.

Which of the following is a role of interferons (IFNs)?

A) IFNs stimulate the release of histamine.

B) IFNs activate helper T cells by presenting antigens.

C) IFNs stimulate antibody production in response to a bacterial infection.

D) IFNs help the body combat viral infections.

D) IFNs help the body combat viral infections.

**Interferons (IFNs) are a group of proteins that have antiviral effects. IFNs activate macrophages and mobilize natural killer cells (NK cells) as well. They also have an anticancer role.

Which of the following is not a role of activated complement?

A) insertion of MAC and cell lysis

B) prevention of immediate hypersensitivity reactions

C) enhancement of inflammation

D) opsonization

B) prevention of immediate hypersensitivity reactions

Which of the following is not a complement activation pathway?

A) alternative pathway

B) lactate pathway

C) classical pathway

D) lectin pathway

B) lactate pathway

How does a lymphocyte become immunocompetent?

A) Lymphocytes rapidly proliferate to form an army of cells exactly like themselves and bearing the same antigen-specific receptors.

B) Lymphocytes must be able to recognize their one specific antigen by binding to it.

C) An antigen binds to a particular lymphocyte that has a receptor for it.

D) Lymphocytes must be relatively unresponsive to self-antigens so that they do not attack the body's own cells.

B) Lymphocytes must be able to recognize their one specific antigen by binding to it.

Four (or five) cardinal signs indicate inflammation. What specific sign of inflammation is the result of exudate in the tissue spaces?

A) Heat

B) Impaired Function

C) Redness

D) Edema (swelling)

D) Edema (swelling)

Select the correct statement about immunodeficiency.

A) Severe combined immunodeficiency (SCID) disease is an acquired condition.

B) The causative agent in acquired immune deficiency syndrome (AIDS) is a virus that recognizes CD4 proteins.

C) The most common form of immunodeficiency is graft-versus-host (GVH) disease.

D) Hodgkin's disease is a hereditary immunodeficiency found in children.

B) The causative agent in acquired immune deficiency syndrome (AIDS) is a virus that recognizes CD4 proteins.

Which of the following cells engulf antigens and present fragments of them on their own surfaces, where they can be recognized by cells that will deal with them?

A) dendritic cells

B) CD8 cells

C) T lymphocytes

D) NK cells

A) dendritic cells

Which of the following does not respond to cell-mediated immunity?

A) pathogens in the lumen of the stomach

B) foreign tissue transplants

C) some cancer cells

D) intracellular pathogens that reside within host cells

A) pathogens in the lumen of the stomach

Which of the following exemplifies passive immunity?

A) Antitoxin

B) Infection

C) Vaccine

D) Vaccine Booster Shots

A) Antitoxin

Natural killer (NK) cells ________.

A) can kill cancer cells before the immune system is activated

B) are also called cytotoxic T cells

C) are a type of phagocyte

D) are cells of the adaptive immune system

A) can kill cancer cells before the immune system is activated

Activated T cells and macrophages release ________ to mobilize immune cells and attract other leukocytes into the area.

A) Interleukin 1 proteins

B) Cytokines

C) Perforins

D) Interleukin 2 proteins

B) Cytokines

Regulatory T cells ________.

A) may function in preventing autoimmune reactions

B) aid B cells in antibody production

C) release cytokines that increase the activity of cytotoxic T cells and activated B cells

D) decrease their activity as antigenic stimulus decreases

A) may function in preventing autoimmune reactions

Antibody functions include all of the following except ________.

A) binding and inactivating chemical toxins released by bacteria or other microorganisms

B) cross-linking cell-bound antigens on red blood cells when blood types are properly matched

C) targeting foreign cells so that complement proteins can cause cellular lysis

D) linking soluble antigens together so that they fall out of solution

B) cross-linking cell-bound antigens on red blood cells when blood types are properly matched

Select the correct statement about antigens.

A) The largest type of antigen is called a hapten.

B) "Self-antigens" is another name for incomplete antigens.

C) Only small antigens exhibit reactivity.

D) One antigen may have many different antigenic determinants and may therefore cause the formation of more than one antibody.

D) One antigen may have many different antigenic determinants and may therefore cause the formation of more than one antibody.

B lymphocytes develop immunocompetence in the ________.

A) thymus

B) spleen

C) lymph nodes

D) bone marrow

D) bone marrow

Innate immune system defenses include ________.

A) B cells

B) plasma cells

C) phagocytosis

D) T cells

C) phagocytosis

What type of T cell can directly attack and kill other cells, such as virus-infected cells?

A) APC

B) regulatory T (T_Reg) cells

C) cytotoxic T (T_C) cells

D) helper T (T_H) cells

C) cytotoxic T (T_C) cells

Involved in allergies

IgE

Protects mucosal barriers

IgA

First to peak during a primary immune response

IgM

Along with IgM, this is a B cell receptor

IgD

Main antibody of both primary and secondary immune response

IgG

Which defense mechanism results in redness, heat, pain, and swelling?

A) cell-mediated immunity

B) phagocytosis

C) inflammation

D) antibody production

C) inflammation

**The cardinal signs of an inflammatory reaction are redness and heat (due to increased blood flow to the area), pain (due to increased blood flow and chemical mediators), and swelling (due to leakage of blood plasma into the injured area).

Fever ________.

A) is a higher-than-normal body temperature that is always dangerous

B) causes the liver to release large amounts of iron, which seems to inhibit bacterial replication

C) production is regulated by chemicals that reset the body's thermostat to a higher setting

D) decreases the metabolic rate of the body to conserve energy

C) production is regulated by chemicals that reset the body's thermostat to a higher setting

Which of the following is not a method by which antibodies work?

A) neutralizing antigen

B) direct cell lysis

C) enhancing phagocytosis

D) agglutinating and precipitating antigen

B) direct cell lysis

Which immunoglobulin class can cross the placenta to provide naturally acquired passive immunity to the fetus?

A) IgG

B) IgM

C) IgA

D) IgD

A) IgG

Which of the following determine(s) what specific foreign substances our adaptive immune system will be able to recognize and resist?

A) Our genes

B) The type of antigen

C) Enzymes present at the time of the invasion

D) Memory cell production

A) Our genes

Select the correct statement about active and passive immunity.

A) Active and passive humoral immunity are both mechanisms of adaptive immunity that use antibodies.

B) Immunological memory is established by passive immunization.

C) A vaccination is an example of the introduction of passive immunity into the body.

D) The antibodies utilized in active immunity are acquired from another organism.

A) Active and passive humoral immunity are both mechanisms of adaptive immunity that use antibodies.

What is the specific target of interferons?

A) specific viruses

B) infected cells

C) nearby healthy cells

D) antibodies

C) nearby healthy cells

What part of the antibody's structure determines its class?

A) heavy (H) chain

B) light (L) chain

C) constant (C) region

D) variable (V) region

C) constant (C) region

Which of the following do NOT serve as antigen-presenting cells (APC)?

A) dendritic cells

B) macrophages

C) natural killer cells

D) B cells

C) natural killer cells

How do interferons protect against infection in healthy cells?

A) Interferons block viral reproduction in healthy cells through the production of antiviral proteins.

B) Interferons promote fever, or an abnormally high body temperature.

C) Interferons perform opsonization to coat microorganisms.

D) Interferons perform complement activation.

A) Interferons block viral reproduction in healthy cells through the production of antiviral proteins.

Which of the following is NOT a nonspecific internal defense against disease?

A) NK cells

B) inflammation

C) phagocytes

D) T cells

D) T cells

Cancer cells and virus-infected body cells can be killed before activation of adaptive immunity by ________.

A) natural killer cells

B) T lymphocytes

C) pinocytosis

D) B lymphocytes

A) natural killer cells

Which of the statements below does not describe antigens?

A) The parts of antigen molecules that initiate immune responses are called epitopes or antigenic determinants.

B) Antigens exhibit immunogenicity and reactivity.

C) Antigens can include proteins, nucleic acids, lipoproteins, glycoproteins, and certain large polysaccharides.

D) Antigens only come from microbes.

D) Antigens only come from microbes.

Which letter represents the formation of a phagolysosome resulting from the fusion of a lysosome with the phagocytic vesicle? Select from letters A-D

Answer: C

Which of the following is not characteristic of the adaptive immune system?

A) It is antigen-specific.

B) It is systemic.

C) It is specific for a given organ.

D) It has memory.

C) It is specific for a given organ.

Which of the following is an effect of complement activation?

A) T cell activation

B) opsonization

C) tissue repair

D) fever

B) opsonization

__________ are lymphocytes that directly kill virus- infected cells.

A) Macrophages

B) B cells

C) Helper T cells

D) Cytotoxic T cells

D) Cytotoxic T cells

Which of the following mechanisms of antibody action occur when red blood cells clump due to a transfusion of mismatched blood?

A) agglutination

B) precipitation

C) complement fixation and activation

D) neutralization

A) agglutination

Small molecules that bind with self-proteins to produce antigenic substances are called ________.

A) haptens

B) reagins

C) antibodies

D) ions

A) haptens

Which of the following is not a function of the inflammatory response?

A) disposes of cellular debris and pathogens

B) prevents the spread of the injurious agent to nearby tissue

C) replaces injured tissues with connective tissue

D) sets the stage for repair processes

C) replaces injured tissues with connective tissue

Cytotoxic T (T_C) cells check cells of the body for identity flags to see if they look they way they are supposed to. What is this process called?

A) opsonization

B) anergy

C) immune surveillance

D) complement fixation

C) immune surveillance

Which of the following is NOT a property of interferons (IFNs)?

A) IFNs activate macrophages.

B) IFNs have an anticancer role.

C) IFNs stimulate B cells to produce antibodies.

D) IFNs have antiviral activity.

C) IFNs stimulate B cells to produce antibodies.

All of the following are functions of interferons, EXCEPT that __________.

A) they are not virus-specific

B) they mobilize natural killer cells

C) they interfere with viral replication in affected cells

D) they only occur naturally

D) they only occur naturally

Interferons can be used to treat all of the following, EXCEPT __________.

A) muscular dystrophy

B) cancer

C) hepatitis C

D) viral infections

A) muscular dystrophy

Tears and mucus membranes would be a part of which defense system?

Innate external defenses

Phagocytotic cells such as macrophages identify a variety of enemies by recognizing markers unique to pathogens. They would be classified as which type of defense system?

Innate internal defenses

What cells make antibodies?

plasma B cells

What is the name of the unique area (specific region) that a lymphocyte recognizes and binds to?

An antigenic determinant

What type of immunity can be transferred by bodily fluids from one person to another, thus conferring immunity to the recipient?

Humoral Immunity

If a virus attacks a cell, which type of immunity would be activated?

cell-mediated immunity (cellular immunity)

Cancer cells would be attacked by which type of cells?

Cytotoxic T Cells

When do neutrophils enter the blood from the red bone marrow, in response to leukocytosis-inducing factors?

Leukocytosis

Which of the following is NOT a sign of inflammation?

A) Pain

B) Fever

C) Swelling

D) Redness

B) Fever

Which of the following is NOT a characteristic of Natural Killer (NK) cells?

A) NK cells recognize abnormal or cancer cells by a specific antigen on their cell membrane.

B) NK cells induce the target cell to undergo “apoptosis” (cell suicide).

C) NK cells attack infected or cancerous cells.

D) NK cells attack transplanted organs.

A) NK cells recognize abnormal or cancer cells by a specific antigen on their cell membrane.

Which of the following innate internal defenses work by interfering with viral replication?

A) interferons

B) complement proteins

C) phagocytes

D) T lymphocytes

A) interferons

How do phagocytes recognize foreign cells or bacteria?

A) The phagocytes recognize molecules on pathogens not normally found on body cells.

B) The phagocytes look for the absence of “self” proteins.

C) All the foreign cells or bacteria are marked with opsonins that the phagocytes recognize.

D) Phagocytes recognize a specific antigen on the cell surface.

A) The phagocytes recognize molecules on pathogens not normally found on body cells.

Which of the innate defense mechanisms can lyse bacteria and mark cells for phagocytosis?

Complement Proteins

Which of the following can act as opsonins on bacteria, thus enhancing phagocytosis?

A) interferons

B) natural killer (NK) cells

C) antibodies and complement proteins

D) T cells

C) antibodies and complement proteins

T/F: A moderate fever is a protective adaptive response.

TRUE

Which of the following does NOT protect the skin from bacteria?

A) the temperature of the skin

B) defensins

C) cathelicidins

D) the low pH of the skin

E) dermcidin

A) the temperature of the skin

Choose the FALSE statement.

A) Skin acts as a biological barrier.

B) Skin does not have a role in regulating body temperature.

C) Low pH protects the skin.

D) There are substances in sweat that can kill bacteria.

B) Skin does not have a role in regulating body temperature.

The skin is permeable to organic solvents, such as acetone or turpentine, because they ________.

can dissolve the lipid bilayers of epidermal and dermal cell plasma membranes

MHC II proteins are found on __________.

A) red blood cells

B) cytotoxic T cells

C) helper T cells

D) antigen-presenting cells

D) antigen-presenting cells

Which of the following is a nonspecific barrier defense?

A) natural killer cells

B) complements

C) antibodies

D) mucous membranes

E) macrophages

D) mucous membranes

Toll-like receptors are found on __________.

A) lymphocytes

B) macrophages

C) neutrophils

D) mast cells

B) macrophages

Which of the following is a metabolic function of skin?

A) elimination of nitrogenous wastes

B) synthesis of a vitamin D precursor

C) cutaneous sensation

D) body temperature regulation

B) synthesis of a vitamin D precursor

Which class of tissue graft is the least likely to be accepted by a patient's body?

A) autograft

B) isograft

C) allograft

D) xenograft

D) xenograft

__________ are substances that can trigger the adaptive defenses and provoke an immune response.

Antigens

Saliva and lacrimal fluids contain this enzyme that destroys bacteria.

Lysozyme

When a localized area exhibits increased capillary filtration, hyperemia, and swelling, it is an indication that __________.

inflammation is occuring

The process that begins when a helper T cell binds to a class II MHC protein on a displaying cell is known as __________.

Costimulation

Which of the following is NOT one of the cardinal signs of inflammation?

A) opsonization

B) swelling

C) pain

D) redness

E) heat

A) opsonization

Cytotoxic T cells kill target cells __________.

A) through injection of tumor necrosis factor

B) through insertion of perforins into the target's membrane

C) by releasing oxidizing agents

D) by phagocytosis by secreting antibodies

B) through insertion of perforins into the target's membrane

Which of the following are mismatched?

A) immediate hypersensitivity: allergic contact dermatitis

B) severe combined immunodeficiency syndrome (SCID): genetic defect resulting in a shortage of B and/or T cells

C) multiple sclerosis: autoimmune disorder

D) AIDS (acquired immune deficiency syndrome): helper T cells are destroyed by a virus

A) immediate hypersensitivity: allergic contact dermatitis

What is the second step of T cell activation?

A) chemotaxis

B) anergy

C) antigen binding

D) co-stimulation

D) co-stimulation

A "nonself" substance that can provoke an immune response is called a(n) __________.

A) interferon

B) colony-stimulating factor

C) antigen

D) immunoglobulin

E) antibody

C) antigen

Which of the following minerals needed for bacterial reproduction do both the liver and spleen sequester during a fever?

A) Copper

B) Magnesium

C) Phosphorous

D) Zinc

D) Zinc

Without __________ there is no adaptive immune response.

T Lymphocytes

Self-reactive B cells are eliminated in the __________.

Bone Marrow

These molecules are secreted by leukocytes and macrophages and result in a fever.

Pyrogens

**Pyrogens target the hypothalamus and raise the body's temperature above normal.

Which is correctly matched?

A) helper T cells: recognize virus-infected cells

B) cytotoxic T cells: activated by antigens bound to MHC I

C) B cells: suppress the immune response once the foreign antigen has been cleared from the body

D) regulatory T cells: make antibodies

B) cytotoxic T cells: activated by antigens bound to MHC I

The first step in inflammation is __________.

the release of inflammatory chemicals

All of the following are examples of autoimmune disorders, EXCEPT __________.

A) systemic lupus erythematosus (SLE)

B) myasthenia gravis

C) sickle-cell anemia

D) Graves disease

E) rheumatoid arthritis

C) sickle-cell anemia

Leukotrienes cause __________.

dilation of the small blood vessels in an injured area

Which of the following steps is the first step in an inflammatory response?

A) release of leukocytosis-inducing factor

B) adhesion of the neutrophil's cell-adhesion molecules to antigen

C) positive chemotaxis

D) diapedesis

A) release of leukocytosis-inducing factor

Which of the following is mismatched?

A) B cells: can be activated to produce antibodies

B) cytotoxic T cells: carry out cellular immune responses regulatory

C) T cells: release inhibitory cytokines to dampen the immune response

D) helper T cells: directly target and kill cancer cells

D) helper T cells: directly target and kill cancer cells

Lymphocytes that develop immunocompetence in the thymus are __________.

T Lymphocytes

Active artificially acquired immunity is a result of __________.

A) antibodies passed on from mother to baby through breast milk

B) contact with a pathogen

C) injection of an immune serum

D) antibodies passed on from mother to fetus through the placenta

E) vaccination

E) vaccination