chapter 26 - innate immunity

Question 1

What is immunity?

Answer 1

the ability of an organism to resist infection

Question 2

What are the two systems of immunity?

Answer 2

1. innate immunity: nonspecific immunity, built in capability of multicellular organisms to target pathogens that are seeking to colonize the host
2. adaptive immunity: acquired ability to recognize and destroy a particular pathogen or its product

Question 3

What is competitive exclusion?

Answer 3

pathogens do not easily infect tissues because the harmless microbes limit available nutrients and sites for infection

Question 4

What are the physical and chemical barriers to infection and why?

Answer 4

1- tight junction between epithelial cells that line body tissues inhibits invasion and infection
2- membranes are coated with a thick layer of mucous to trap microorgansims.
3- stomach acid inhibits bacterial growth
4- skin is salty and acidic, limiting bacterial growth

Question 5

How does blood travel in the body?

Answer 5

gets pumped through arteries and capillaries
returns from the body through veins

Question 6

What is the job of the lymph

Answer 6

It drains extravascular tissues into lymph capillaries and lymph ducts, then into lymph nodes throughout the lymphatic system

Question 7

What is the correlation between the blood and lymphatic systems?

Answer 7

1- leukocytes and solutes pass from blood int he lymphatic system
2- lymph contains antibodies and immune cells, and empties into the blood circulatory system

Question 8

What is plasma?

Answer 8

contains proteins and other solutes where blood cells are suspended

Question 9

What is serum?

Answer 9

portion of blood that is not cells or clotting proteins.

Question 10

What are the major cell types of blood?

Answer 10

1. erythrocytes (all red blood cells)
2. leukocytes (all nucleated cells - lymphocytes, granulocytes, monocytes)

Question 11

What are hematopoietic stem cells?

Answer 11

precursor blood cells found in bone marrow and the gut

Question 12

What is hematopoiesis?

Answer 12

differentiation of blood stem cells into different blood cells influenced by soluble cytokines and chemokines, proteins that direct immune cell production, function and movement

Question 13

What are myeloid cells?

Answer 13

the are derived from a myeloid precursor cells

Question 14

What are the two categories of myeloid cells?

Answer 14

1. antigen-presenting cells:
   engulf, process and present antigens to T-lymphocytes, which then initiates an adaptive immune response
   (monocytes, macrophages and dendritic cells)
2. granulocytes:
   contains toxins or enzymes that are released to kill target cells.
   (neutrophils, basophils and eosinophils)

Question 15

What is the function of natural killer cells?

Answer 15

function primarily in innate immunity, removing viruses and tumour cells by recognizing specific cell-surface molecules

Question 16

What are lymphocytes?

Answer 16

specialized leukocytes invovled exclusively in adaptive immune response

Question 17

What are the two types of lymphocytes?

Answer 17

1. B cells: originate and mature in bone marrow (antibodies)
2. T cells: originate in bone marrow but mature in thymus ((T cell receptors)

Question 18

What type of organs are bone marrow and thymus?

Answer 18

lymphoid organs

Question 19

What is microbial invasion?

Answer 19

the ability of a pathogen to enter host cells or tissues, multiply, spread and cause disease

Question 20

What are phagocyte-pathogen interactions?

Answer 20

result in activation of genes and translation of proteins that eventually lead to the destruction of the pathogen

Question 21

What is the mechanism of the recruitment of phagocytes?

Answer 21

1. wound or tissue damage leads to microorganisms entering
2. damaged cells release cytokines and chemokines
3. phagocytes in response to cytokine-chemokine gradient are recruited to the site of injury and squeezed out of the blood capillaries
4. the invading phagocytes are cleared by the phagocytes

Question 22

What is the pathogen-associated molecular pattern?

Answer 22

pathogens have structures and molecules not found in or on host cells

Question 23

What are patter recognition receptors?

Answer 23

leukocytes have membrane bound or soluble proteins that recognize pathogen-associated molecular pattern

Question 24

What are toll-like receptors?

Answer 24

a class of pattern recognition receptors
recognizes and interacts with a specific pathogen-associate molecular pattern

Question 25

What is the signal transduction in phagocytes?

Answer 25

upon activation of toll-like receptors, a leukocyte will start a phosphorylation cascade to transmit the activation signal to the nucleus activating transcription factors to turn on genes in response to the activation signal.

Question 26

What is a phagosome?

Answer 26

the membrane-bound vesicle that surrounds the bacterium
fusing a lysosome forms a phagolysosome

Question 27

What is inflammation?

Answer 27

a nonspecific reaction to noxious stimuli

Question 28

What is the mechanism for inflammation?

Answer 28

1. cytokines and chemokines released draw white blood cells to site of inflammation
2. leukocytes release proinflammatory cytokines (IL-1)
3. cytokines increase vascular permeability causing swelling
4. pressure force fluids away from blood vessels into lymphatic system

Question 29

What is systematic inflammation?

Answer 29

occurs when the inflammatory response fails to localize the pathogens and the reaction spreads throughout the body

Question 30

What are prostaglandins?

Answer 30

chemical signals that raise the body temperatureW

Question 31

What is the complement system?

Answer 31

a set of circulating, inactive proteins that are sequentially activated in response to a pathogen

Question 32

What are the three pathways?

Answer 32

1. sequence, orientation and activity of the components of the classical complement pathway
2. the manose-binding lectin pathway
3. the alternate pathway

Question 33

What are the three outcomes of complement activation

Answer 33

1. complement C3b coating the target making it easier for phagocytes to engulf it
2. complement C3a diffuses to the surrounding area serving as a chemoattractant
3. complement C5a binding to the target forming the membrane attack complex resulting in cell lysis.

Question 34

What do natural killer cells do to defend against viruses

Answer 34

1. nucleated cells have their surface MHC I proteins, virus-infected cells do not
2. when encountering a cell without MHC I, a natural killer cell will activate and destroy it by producing granzyme and perforin

Question 35

What is granzyme

Answer 35

an enzyme that induces apoptosis

Question 36

What is perforin?

Answer 36

pokes holes in the target membrane

Question 37

What are interferons?

Answer 37

small cytokine proteins produced by virally infected cells.