Human Immune System

Question 1

Steps of inflammatory response:

Answer 1

1) Mast cells (leukocytes that sit in tissues) detect injury to nearby cells and release histamine
2) Histamine dilate nearby capillaries allowing for increased blood flow and make the capillary walls more permeable allowing fluid and immune cells to get to site of injury

Question 2

What are the five signs of inflammation?

Answer 2

(SLIPR)
1) Swelling: result of permeable capillaries causing blood vessels to become leaky which leads to fluid accumulating in nearby tissue
2) Loss of function: indirect outcome, swelling and pain causes part of body to become less usable
3) Iincreased heat: result of dilation of capillaries causing increased blood flow which results in higher temperature
4) Pain: slower, throbbing pain caused by swelling which exerts pressure on free nerve endings leading to continuous pain
5) Redness: result of dilation of capillaries causing redness of skin due to increased blood flow

Question 3

Neutrophils

Answer 3

• Most numerous/most common WBC (make up 40-70% of WBC)
• One of the first cells recruited to inflammation site
• Phagocytes in innate immunity: eat (phagocytosis) & destroy pathogens and engulf all kinds of pathogens
• drawn to infected/injured areas by chemicals via chemotaxis
• slip between endothelial cells of capillaries and into tissues via diapedesis

Question 4

Lymphocytes

Answer 4

Three types: B cells, T cells and natural killer cells
Originate from the bone marrow but end up concentrating in lymphatic organs (lymph nodes, spleen, thymus)

Question 5

Natural killer cells

Answer 5

Lymphocyte part of the innate immune response
Attack and kill virus-infected cells or cancerous body cells by:
1) perforin: perforates (pokes holes) in pathogenic cell membranes, causing cel lysis (breakdown)
2) granzymes: proteases which stimulate a target cell to undergo apoptosis (useful for killing cancer cells)

Question 6

Monocytes

Answer 6

• immature cells that circulate blood
• move into infected tissue (through diapedesis) and develop into macrophages (mature state)
• in its mature state, they are antigen-presenting cells that phagocytize pathogens nonspecifically for adaptive immunity
• monocytes can give rise to dendritic cells

Question 7

Eosinophils

Answer 7

Cytoplasm are filled with granules which contain proteins that are released to kill pathogens
Especially effective against multicellular parasites

Question 8

Basophils

Answer 8

Make up less than 1% of WBCs
Contains granules that can be released to nearby tissue
Granules contain histamine- vasodilation and make capillaries more permeable; and heparin- an anticoagulant (prevents blood from clotting too quickly)
Leave bone marrow as mature cells and circulate the blood

Question 9

Mast cells

Answer 9

Leave bond marrow and circulate in blood as immature cells
They mature once they enter tissue

Question 10

Innate immunity: complement system

Answer 10

A system of ~30 blood plasma proteins that help immune cells fight pathogens more effectively
The proteins turn each other on through activation of a complement cascade, producing a larger effect
Once a pathogen is recognize (or a pathogen bound antigen), a chain reaction of protease activity is triggered for the proteins to activate each other

Question 11

Effects of the complement system:

Answer 11

1) improves the eating ability of phagocytosing cells through a process called opsonization: binds complement protein C3b to antigens which tags them for phagocytosis
2) amplifies inflammatory response: proteins bind to mast cells which causes stronger histamine release
3) lysing pathogen membranes: Membrane Attack Complex (MAC) pokes holes in pathogen membrane

Question 12

How does Membrane Attack Complex (MAC) work?

Answer 12

1) MAC proteins group on the pathogen membrane
2) Salt and fluids enter the pathogen
3) Pathogen swells then bursts

Question 13

What is the adaptive immunity system?

Answer 13

Specific immune response that targets specific antigens

Question 14

Antigens

Answer 14

A marker or ID from a foreign molecule and triggers immune response
Cells with antigens = foreign cells; non-self

Question 15

Major Histocompatibility Complex (MHC) class I

Answer 15

Molecules on the cell surface of all nucleated cells that help the immune system recognize *self proteins * from non-self proteins
Every individual has their own unique MHC I molecules
Identical teens have the same MHC I expression
Made up of alpha 1, 2, 3 and beta-microglobulin protein chains

Question 16

MHC I molecules and organ transplant

Answer 16

During organ transplant, donor organ will have different MHC I molecule which will be viewed as antigen (foreign ID) by our immune system
Our immune system will attack foreign organ which can lead to organ failure and transplant rejection

Question 17

What should organ transplant patients take?

Answer 17

Immunosuppressants to lower/stop immune systems response to foreign organ
Causes patients to be more susceptible to general infections

Question 18

Autoimmune disease

Answer 18

When the immune system mistakenly attacks self cells (MHC I)

Question 19

Antigen-presenting cells (APCs)

Answer 19

Macrophages and dendritic cells
Have MHC I molecules and MHC II molecules on their cell surface
Used to present foreign antigens to activate immune cells

Question 20

How do APCs bridge innate and adaptive response?

Answer 20

1) APCs phagocytoses pathogen
2) APCs break off antigen from pathogen
3) APCs load that antigen onto their MHC molecule (either class of MHC molecules)
4) antigen is presented to adaptive immune cells

Question 21

Epitope

Answer 21

The section of the antigen that is recognizes by immune cells (B and T cells)

Question 22

B cells

Answer 22

Conduct antibody-mediated immunity (humoral immunity: antibodies found in blood and lymph)
Controls productions and release of antibodies
Can act as antigen-presenting cells

Question 23

Activation of B cells

Answer 23

1) **B cell receptors (BCR) bind to antigens epitope (either free-floating or APC presented antigens)
2) B cell becomes activated
3) B cell divides and makes copies of itself

Each B cell has a unique, uniform BCR that only binds one kind of antigen

Question 24

Clonal selection model

Answer 24

1 specific antigen selects 1 specific B cell to clone itself
Since each B cell has a unique BCR, the antigen selects which BCR to bind to (decides which B cell to activate)
This model shows the amplification of the B cell that is specific to the antigen from the pathogen present
Through clonal expansion, these B cells divide into either plasma cells (antibody-secreting cells) or memory B cells (to be activated later in case of another attack)

Question 25

Lysozymes

Answer 25

Antimicrobial proteins that are found in many types of body secretions, such as tears, saliva, and mucous
This type of enzyme nonspecifically breaks down bacterial cell walls

Question 26

Plasma B cells

Answer 26

• circulate the blood and produce/release free antibodies (immunoglobulins)
• part of the humoral immune system

Question 27

Functions of antibodies

Answer 27

• Tag the specific, corresponding antigen for removal (by phagocytosis)
• Coat the antigen in antibodies to neutralize it
• Activate the complement system
• Goal: destroy pathogen with specific antigen

Question 28

Memory B cells

Answer 28

Live for a long time in our bodies, sometimes even for decades
They do not release antibodies
They save the information about the antigen, and if the same antigen intrudes again within their lifespan, they will rapidly differentiate and proliferate into plasma cells to secrete corresponding antibodies
Responsible for the effectiveness of vaccines

Question 29

T cells

Answer 29

Responsible for cell-mediated immunity (they do the work themselves unlike B cells that send out antibodies to do it)
They have T cell receptors (TCRs) on their surface- every T cell has a unique, uniform TCR that binds to only 1 kind of antigen (clonal selection)
T cells cannot recognize free-floating antigens
Can only bind to antigens presented by APCs

Question 30

Cytotoxic T cells

Answer 30

T cells differentiate into cytotoxic T cells if an antigen is presented by MHC I
CD8 or CD8+ cell because co-receptor CD8 is formed in addition to TCR
CD8 cells will recognize every cell with presented antigen and kill it
Directly kill infected cells through perforin and granzymes
Different from natural killer cells because they are more specific and require antigen presentation

Question 31

Helper T cells

Answer 31

T cells differentiate into helper T cells if the antigen is presented by MHC II
CD4 because co-receptor CD4 is formed in addition to TCR
CD4 assist both innate and adaptive immunity by releasing interleukins (cytokines that boost both immunities)
Cytokines attract innate immunity cells (macrophages and dendritic cells) to location of identified antigen
Stimulate clonal selection and proliferation of B cells and T cells

Question 32

Memory T cells

Answer 32

Formed after clonal selection
Protect our body from future invasions of same pathogen
Memory T cells help adaptive immunity turn on quicker

Question 33

What results in blood clots?

Answer 33

The polymerization of fibrin (which results in the attraction of platelets) results in blood clots

Question 34

the role of skin in the innate immunity:

Answer 34

physical barrier covered in oily and acidic secretions (pH 3-5) released form sweat glands

Question 35

role of antimicrobial proteins in the innate immunity:

Answer 35

lysozome found in tears and saliva break down the cell wall of bacteria