innate immunity I

Question 1

what’s the relationship between innate and adaptive immunity?

Answer 1

they are different types of responses of the immune system

believed that innate immunity precedes adaptive immunity - in evolutionary history

Question 2

differentiate between innate and adaptive immunity

Answer 2

innate immunity
—— inherited! epigenetic imprinting (germ-line encoded) of past pathogen encounters
—— in the form of physical barriers, chemical defenses, cellular responses
—— present in all individuals at all times

adaptive immunity
—— non-inherited! relies on immunological memory, the survival of clones of cells expressing specific receptors to past antigens. these antigen-specific receptors are then generated via rapid gene recombination
—— in the form of cellular responses and antibody production
—— developed as antigens are encountered

Question 3

what is cellular immunity?

Answer 3

cell based
—– basically, processes mediated by a cell

cell-cell recognition
—– used to determine if cell kills, eats, etc. other cell

Question 4

what is humoral immunity?

Answer 4

humoral is defined as liquids and its soluble molecules

referring to antibodies

Question 5

describe Paul Ehrlich’s work – include his focus

Answer 5

credited for his research on adaptive immunity

took a chemistry perspective but also made discoveries regarding cells

coined “antibodies” and “antigens”

proposed the sidechain theory for how antibodies are generated - theory wasn’t correct but was influential in the field

discovered mast cell, basophil, and eosinophil

Question 6

who discovered the mast cell?

Answer 6

Paul Ehrlich

Question 7

who discovered the basophil and eosinophil?

Answer 7

Paul Ehrlich

Question 8

who proposed the sidechain theory?

Answer 8

Paul Ehrlich

Question 9

who coined the words “antibodies” and “antigens”?

Answer 9

Paul Ehrlich

Question 10

describe Metchnikoff’s work – include his focus

Answer 10

credited for his research on innate immunity

was trained as an embryologist

coined “cell-eating” aka phagocytosis and the term “macrophage” (big eaters)

he was trained as an embryologist

advocated for probiotics - known for pioneering the field of probiotics

discovered macrophages and neutrophils

Question 11

who discovered macrophages?

Answer 11

Metchnikoff

Question 12

who discovered neutrophils?

Answer 12

Metchnikoff

Question 13

immune cells make up how much of the blood’s composition?

Answer 13

those that are found in the blood make up less than 1% of the blood’s composition

Question 14

what are hematopoietic stem cells and where can you find them?

Answer 14

progenitor cell of all blood cells

found in bone marrow; are the reason bone marrow transplants work because they can replenish the recipient’s blood supply

Question 15

what’s myeloid origin? what immune cells stem from this?

Answer 15

“from bone marrow”

generally involved in innate immunity

neutrophils, monocytes (and as a result, macrophages), dendritic cells, and red blood cells stem from the myeloid progenitor

Question 16

what’s lymphoid origin? what immune cells stem from this?

Answer 16

“resident in lymphoid organ”

generally involved in adaptive immunity
—- exception: innate lymphoid cell AKA NK cell (natural killer cell)

B cells, T cells, and innate lymphoid cells stem from the lymphoid progenitor

T cells mature in the thymus

B cells develop in the bone marrow, but reside in spleen and lymph nodes

Question 17

where do B cells mature?

Answer 17

in the bone marrow and peripheral lymphoid organs such as the spleen and lymph nodes

Question 18

where do T cells mature?

Answer 18

in the thymus

Question 19

which cells form the basis of cellular and humoral adaptive immunity?

Answer 19

T cells forms the basis of cellular adaptive immunity

B cells forms the basis of humoral adaptive immunity
—– antibodies!

Question 20

how can you distinguish an innate lymphoid cell (ILCs) from other lymphocytes?

Answer 20

ILCs have a few more granules!!

Question 21

what are granules?

Answer 21

granules are not organelles but are found in organelles!

granules usually contains chemicals in crystallized form

Question 22

what are mast cells? and what do they do

Answer 22

innate cells stuffed with granules

in mast cells, the granules make histamine and in response to injury, release histamine to signal epithelial tissue to open up and blood vessels to dilate to allow blood flow to the wound
—— histamine is responsible for the symptoms associated with allergies, e.g. itching and swelling

Question 23

where are mast cells typically found?

Answer 23

typically found in tissues, specifically epithelial tissue (skin, linings of lungs and digestive tract, etc.)

Question 24

why do people take anti-histamines for allergies?

Answer 24

for allergies, people take anti-histamines to prevent that over-exaggerated allergic response as mast cells and its histamine are essential to the allergic reaction

histamine is responsible for the symptoms associated with allergies, e.g. itching and swelling

Question 25

what innate cells play major roles in allergies?

Answer 25

mast cells, eosinophils, and basophils play roles in allergies and parasitic infections

Question 26

what innate cells plays a major role in parasitic infections?

Answer 26

mast cells, eosinophils, and basophils play roles in allergies and parasitic infections

Question 27

why are neutrophils segments?

Answer 27

used to exit blood and rapidly enter infected tissues

they can squeeze thru tight spaces (e.g. between epithelial cells to reach wounds)

they even have receptors to recognized, sense, and follow the bacteria – allows for efficient movement

Question 28

how do you distinguish neutrophils from other cells?

Answer 28

can be distinguished due to its segmented/multilobed nucleus

Question 29

what cell has been termed “first responders”

Answer 29

neutrophils

they swarm in large numbers to the site of injury or infection in response to inflammatory signals

– macrophages also form the first line of defence!

Question 30

describe the role of neutrophils in wound healing

Answer 30

in response to injury, alarm signals (e.g. histamine) are released which is then sensed by neutrophils

neutrophils swarm from the blood and enter the tissues, where they’ll phagocyte bacteria and they will release their own mediators to recruit more white blood cells to the tissues

Question 31

what are neutrophil extracellular traps?

Answer 31

neutrophils can explode and release their DNA to trap pathogens in a process called NETosis

their DNA or nets are decorated with covalently attached antimicrobial proteins - that will kill bacteria if they come in contact with it

Question 32

where are dendritic cells usually found?

Answer 32

usually present in tissues – not the blood

Question 33

describe dendritic cells

Answer 33

can undergo phagocytosis
—- they are constantly “eating”

they are the most important cell in initiating an immune response

Question 34

what are monocytes? where are they typically found?

Answer 34

progenitor for macrophages
—- with the right stimulation, they can differentiate into macrophages

typically found in the blood

Question 35

describe macrophages. where are they typically found?

Answer 35

highly phagocytic; constantly eating as well, they don’t require stimulation
—- they even eat other cells and material
—- they’re very important for remodelling. e.g. they remove webbing during embryonic development

they have pseudopodia smaller than dendritic cells

typically found in the tissues throughout the body and in high concentration in the skin

Question 36

describe the process of phagocytosis aka cell eating

Answer 36

after breaking down pathogens into parts, cells can present the material to adaptive cells!

1) bacterium binds to PRRs (pattern recognition receptors) on membrane evaginations called pseudopodia (or dendrites)

2) bacterium is ingested form phagosome aka vacuole

3) phagosome fuses with lysosome with very low pH (which activated the lysosomal enzymes)
—– most ingested pathogens can be killed in the phagolysosome, as the low pH is also toxic for bacteria

4) bacterium is killed and then digested by low pH-activated lysosomal enzymes
—– they’re broken down into peptides, lipids, small carbohydrate molecules

5) digestion products are released from the cell and can also be recycled

Question 37

what are the antimicrobial properties of the phagolysosome that allows it to break down pathogens

Answer 37

low pH
—- most organisms can’t survive

the NADPH oxidase in phagolysosomes (more specifically lysosomes) produces reactive oxygen species
—- e.g. H2O2, hydrogen peroxide (antimicrobial)

myeloperoxidase (MPO) can transform H2O2 into hydrochlorous acid (bleach)

lactoferrin captures Fe2+ that is essential for bacterial growth - so bacteria can’t survive
—- part of nutritional immunity

defensins form pores in pathogens, causing their content to leak out

lysozymes degrade peptidoglycan found in bacterial cell wall

Question 38

some bacteria can survive phagocytosis – how? (list methods)

Answer 38

inhibition of phagosome-lysosome fusion

inducing degradation of phagolysosome

some sort of survival mechanism inside the phagolysosome

Question 39

what are some bacteria that can survive phagocytosis?

Answer 39

salmonella

mycobacterium

listeria monocytogenes

s. aureus

they’re called professional intracellular pathogens