Immune System Worksheets

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Name the two major functions of the immune system

destroy disease-causing organisms and detect and kill abnormal cells such as cancer cells

Pathogens are classified according to their

size and location in the body

What are the five types of pathogens (largest to smallest)

parasitic worms, fungi, protozoa, bacteria and viruses

Which type of pathogen is ALWAYS intracellular


Which type of pathogen is ALWAYS extracellular

parasitic worms

Name the three lines of defense

innate external defense (surface barriers), innate internal defense and adaptive defenses

Innate external defenses

skin and mucous membranes (moat & walls)

Innate internal defenses

cells and chemical in body fluids (guards of the castle)

Adaptive defenses

T-cells and B-cells (army of the king)

When the innate external defenses are penetrated, what is the next line of defense

innate internal defenses

Defense mechanisms identify enemies by recognizing markers unique to the pathogens and

when they are overwhelmed, they secrete chemical messengers to mobilize the adaptive defenses

What are the four key ways that adaptive defenses differ from innate defenses

they are specific, involve B and T lymphocytes, have memory and are systemic

B & T lymphocytes recognize

pathogens by binding to them

B & T lymphocytes recognize the

antigenic determinant found in the antigen

Specific B-cells called plasma cells secrete

antibodies which bind to antigens

Humoral immunity is directed against pathogens in the

extracellular fluid

Humoral immunity involves

B lymphocytes

Cellular immunity is directed against pathogens within the


Cellular immunity involves

T lymphocytes

Which type of immunity involves antibodies


List 3 circumstances where T-cells would be activated against body cells

cell becomes cancerous, is invaded by a virus or has been transplanted from another individual

Name two major anatomical parts of the immune system

specialized immune cells (i.e. leukocytes) and lymphoid organs and tissues (i.e. bone marrow)

Cells of the immune system originate

in the bone marrow and are called leukocytes

Leukocytes travel in the blood and are classified according to what

shape of the nucleus and the colors of the granules when stained

List the leukocytes in order of frequency (most common to least common)

NEVER LET MONKEYS EAT BANANAS (neutrophils, lymphocytes, monocytes, eosinophils and basophils)


multi-lobed nucleus with pale-staining granules


small leukocyte, round nucleus, no prominent granules


large leukocyte, U-shaped or kidney (S) shaped nucleus, no prominent granules


bilobed nucleus with granules and stains red


large granules hide lobed nucleus and stains blue/purple

List phagocytes and where they are found

neutrophils (blood) and macrophage (tissue)

List antigen-presenting cells (APC) and where they are found

dendritic (tissue), macrophage (tissue) and B-cells (blood)

List effector cells of adaptive immunity and where they are found

B-cells (blood) and T-cells (blood)

List the other specialized immune cells that aren't neutrophils, macrophage, dendritic or B-cells/T-cells

mast cells (tissue)

Primary lymph organs are where

B-cells and T-cells originate and mature

What are the primary lymph organs

bone marrow and thymus

Both B-cells and T-cells originate from

bone marrow

The B-cells mature in the

bone marrow

The T-cells mature in the


Secondary lymph organs are

LIKE A PLACE TO SPOON (lymph nodes, appendix, Peyer's patches, tonsils, spleen)

The lymphatic system consists of what three parts

lymph, lymph nodes and lymph vessels

The lymphatic vessels collect excess interstitial fluid that leaves the capillaries and returns it to

the cardiovascular system, at a rate of approximately 3L/day

If lymphatic vessels don't work right, there is a build up of fluid in the tissues know as


The lymphatic capillaries have one-way valves to

collect the excess interstitial fluid and any leaked proteins

The lymph is filtered through

the lymph nodes

The lymph nodes are where antigens and

pathogens are removed and the immune system is activated

Special lymphatic capillaries in intestines are called


What due lacteals transport

absorbed lipids (fats) from the intestines into the blood

Lymph node function

removal of antigens and other debris

Lymph node function

activation of the immune system (B & T cells)

What lymphatic vessels carry lymph from the tissues to the lymph nodes


What lymphatic vessels carry cleansed lymph away from the lymph nodes


B-cells are found in the

germinal centers of the lymphoid follicles

T-cells wander through the deep

cortex, searching for dendritic cells for their special antigen

What is the largest lymph organ

the spleen

What cleanses the blood like the lymph nodes cleanse the lymph

the spleen

Function of the spleen

removes pathogens, aged-erythrocytes and platelets

Function of the spleen

stores platelets and breakdown products of erythrocytes

Function of the spleen

site for activation of the immune system (B & T cells)

Collections of secondary lymphoid tissue called

MALT for short

Collections of secondary lymphoid tissue are distributed though out the mucosal surfaces of the

digestive, respiratory and genitourinary system

Aside from the diffuse cells in the respiratory and other mucosa, MALT includes the

tonsils, appendix and Peyer's patches

Protection of oral and nasal cavities are the


The first part of the large intestine is known as the


The distal portion of the small intestine is known as

Peyer's patches

The thymus is a primary

lymphoid organ

What organ is the site for differentiation of lymphocytes into mature T-cells

the thymus

What happens to the thymus when we age

decreases in activity and size (shrinks/atrophies)

Two major categories of the innate (nonspecific) defenses

innate external and innate internal

Surface barriers include

intact skin and mucous membranes of the respiratory, gastrointestinal and genitourinary tracts

Three properties of the skin that help it resist invasion are

keratin, intracellular junctions and skin secretions (i.e. lysozymes)

Mucous membranes provide a barrier as well as

produce a variety of protective chemicals

The stomach secretes digestive

enzymes and has a very low pH

Respiratory and digestive tracts are lined with

sticky mucous that traps pathogens

What are the five components of the innate internal defense system that attempt to limit the spread of pathogens

phagocytes, inflammation, natural killer cells, antimicrobial proteins and fever

What are the two types of phagocytes

neutrophils and monoctyes/macrophages

Which phagocyte is most abundant


Which phagocytizes more pahtogens


Which cell is NOT found in healthy tissue


A phagocyte recognizes and binds to molecules found on pathogens using special membrane receptors such as the

mannose receptor and the toll-like (TLR) receptor

How many different TLRs have been identified on human phagocytes


Name one reaction that is triggered when TLRs recognize a pathogen

they ingest the pathogen

Name one reaction that is triggered when TLRs recognize a pathogen

they release chemicals that mobilize other cells of the innate and adaptive immune system

A phagocyte engulfs a pathogen and brings it inside the phagocyte in a vesicle known as a


A phagosome fuses with a lysosome and is called a


Name one way a pathogen is destroyed

H+ is pumped in, making it acidic

Name one way a pathogen is destroyed

Respiratory burst (oxygen is converted into toxic reactive oxygen intermediates)

Name one way a pathogen is destroyed

hydrolytic enzymes from the lysosome digest pathogen, defensins poke holes in bacterial membranes and/or enzymes convert reactive oxygen intermediates to bleach-like chemicals

Many pathogens have evolved strategies to avoid

being killed by phagocytes

Some pathogens (bacteria) enclose themselves in capsules

to try and prevent being killed by phagocytes

A process of coating bacteria to enhance phagocytosis by a macrophage is known as


Phagocytes have receptors that can attach to

opsonins on the bacteria

What two factors act as opsonins

antibodies and complement proteins

Certain T-cells from the adaptive defense system can

enhance the killing process within a macrophage

An example of the interaction between the innate and adaptive defense systems is

when the macrophage presents antigens from bacteria to the T-cell

Natural killer cells are a type of lymphocyte that are

non-specific, unlike the B-cells and T-cells

Natural killer cells can still recognize

abnormal cells

T-cells look for the presence of abnormal antigens on the

cell surface

Natural killer cells look for the absence of

normally occurring self-proteins

Natural killer cells kill like

cytotoxic T-cells

Natural killer cells make direct contact with a

target cell and causes it to undergo apoptosis

A form of cellular death is known as


Name two types of antimicrobial proteins

interferons and complement proteins

Interferons are cytokines that

interfere with viral replication

Interferons are cytokines that

modulate inflammation

Interferons are cytokines that

activate immune cells

What causes a cell to secrete interferons

viral infection of the cell

Interferons secreted by an infected cell bind to receptors on nearby cells causing them to produce proteins that inhibit viral replication

by degrading viral RNA and preventing synthesis of viral proteins

The complement system is a cascade of

interdependent proteins that enhances both innate and adaptive defenses

When the complement system is activated, the proteins can

mark cells for phagocytosis, promote inflammation and kill some bacteria by themselves

Adaptive and innate defense systems can activate the complement system via

classical pathway and lectin pathway and alternative pathway

Antibodies on cells activate the complement system (cascade) via

the classical pathway

Lectins bind to sugars on the surface of bacteria which is the

lectin pathway

A lack of inhibitory proteins on body cells activates the

alternative pathway

What pathways cause activation of the C3 protein

classical, lectin and alternative

C3 protein splits into what two fragments

C3a and C3b

C3a causes


C3b causes


C3b cleaves C5 into what two parts

C5a and C5b

C5a causes


C5b combines with other complement proteins to form

MAC (membrane attack complex) which causes the cell to lyse

What are the four cardinal signs of inflammation

heat, redness, swelling and pain

What is the purpose of inflammation

to bring WBCs and proteins into an injured area

What is accomplished when WBCs and proteins are brought to an injured area

it prevents the spread of injurious agents

What is accomplished when WBCs and proteins are brought to an injured area

it disposes of pathogens and dead cells

What is accomplished when WBCs and proteins are brought to an injured area

it sets the stage for repair

When tissues are inured, macrophages release chemical mediators known as

inflammatory mediators

Inflammatory mediators cause

vasodilation, which causes redness and heat

Inflammatory mediators cause

increased vascular permeability, which causes swelling and therefore pain

Inflammatory mediators activate cell adhesion molecules on

endothelial cells

Margination is the process by which neutrophils and monocytes

bind to cell adhesion molecules

When neutrophils bind to cell adhesion molecules

they are activated and leave blood vessels by the process known as diapedesis

Once in the tissue, neutrophils follow

a chemical trail to the site of infection which is known as chemotaxis

The leakiness of the capillaries allows

plasma and proteins to leak into the injured areas of a cell

What three important classes of proteins enter the effected area of a cell

antibodies, complement proteins and clotting factors

In addition to the complement system, what other chemicals act as inflammatory mediators

histamine, prostaglandins & kinins and cytokins

Bacterial components and cytokines act as pyrogens

which cause the body's thermostat to set its temperature higher, creating a fever

Why is a fever advantageous to our defense system

most pathogens don't grow as well at higher temperatures

Why is a fever advantageous to our defense system

fever causes the liver and spleen to sequester iron and zinc

Why is a fever advantageous to our defense system

higher temperatures enhance phagocytosis and enzymatic activity

Shared features of B & T lymphocyte functions

specificity of receptors, diversity of receptors, regulation of activation (clonal expansion) and memory

Lymphocytes must distinguish between normally occurring internal antigens called "self" antigens and those external to the body; the ability to distinguish between pathogens depends

on the specificity of the lymphocyte antigen receptors

Specificity of B & T cells depends on their ability to recognize

antigenic determinants, they have the ability to do this because their surface is covered with 10,000 to 100,000 lymphatic receptors

All the receptors on a specific B-cell are identical, thus

the cells bind optimally with only one antigenic determinant

The antigen receptor on a B-cell is an

immunoglobulin, which is Y-shaped and basically a membrane-bound antibody

The T-cell receptor recognizes antigen fragments housed in cell membrane proteins called

major histo-compatiblity complex proteins (MHC)

The immune system can develop receptors for a

specific antigen before the antigen enters the body

Lymphocytes make a wide variety of receptors and when an antigen

binds and activates one of these receptors, the cell divides, making many clones, which is known as clonal selection

We only have 25,000 different genes in our body, so the body is able to make over

100 million different types of lymphocyte antigen receptors by random recombining of gene segments

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