innate immunity I Flashcards
what’s the relationship between innate and adaptive immunity?
they are different types of responses of the immune system
believed that innate immunity precedes adaptive immunity - in evolutionary history
differentiate between innate and adaptive immunity
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
what is cellular immunity?
cell based
—– basically, processes mediated by a cell
cell-cell recognition
—– used to determine if cell kills, eats, etc. other cell
what is humoral immunity?
humoral is defined as liquids and its soluble molecules
referring to antibodies
describe Paul Ehrlich’s work – include his focus
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
who discovered the mast cell?
Paul Ehrlich
who discovered the basophil and eosinophil?
Paul Ehrlich
who proposed the sidechain theory?
Paul Ehrlich
who coined the words “antibodies” and “antigens”?
Paul Ehrlich
describe Metchnikoff’s work – include his focus
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
who discovered macrophages?
Metchnikoff
who discovered neutrophils?
Metchnikoff
immune cells make up how much of the blood’s composition?
those that are found in the blood make up less than 1% of the blood’s composition
what are hematopoietic stem cells and where can you find them?
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
what’s myeloid origin? what immune cells stem from this?
“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
what’s lymphoid origin? what immune cells stem from this?
“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
where do B cells mature?
in the bone marrow and peripheral lymphoid organs such as the spleen and lymph nodes
where do T cells mature?
in the thymus
which cells form the basis of cellular and humoral adaptive immunity?
T cells forms the basis of cellular adaptive immunity
B cells forms the basis of humoral adaptive immunity
—– antibodies!
how can you distinguish an innate lymphoid cell (ILCs) from other lymphocytes?
ILCs have a few more granules!!
what are granules?
granules are not organelles but are found in organelles!
granules usually contains chemicals in crystallized form
what are mast cells? and what do they do
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
where are mast cells typically found?
typically found in tissues, specifically epithelial tissue (skin, linings of lungs and digestive tract, etc.)
why do people take anti-histamines for allergies?
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
what innate cells play major roles in allergies?
mast cells, eosinophils, and basophils play roles in allergies and parasitic infections
what innate cells plays a major role in parasitic infections?
mast cells, eosinophils, and basophils play roles in allergies and parasitic infections
why are neutrophils segments?
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
how do you distinguish neutrophils from other cells?
can be distinguished due to its segmented/multilobed nucleus
what cell has been termed “first responders”
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!
describe the role of neutrophils in wound healing
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
what are neutrophil extracellular traps?
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
where are dendritic cells usually found?
usually present in tissues – not the blood
describe dendritic cells
can undergo phagocytosis
—- they are constantly “eating”
they are the most important cell in initiating an immune response
what are monocytes? where are they typically found?
progenitor for macrophages
—- with the right stimulation, they can differentiate into macrophages
typically found in the blood
describe macrophages. where are they typically found?
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
describe the process of phagocytosis aka cell eating
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
what are the antimicrobial properties of the phagolysosome that allows it to break down pathogens
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
some bacteria can survive phagocytosis – how? (list methods)
inhibition of phagosome-lysosome fusion
inducing degradation of phagolysosome
some sort of survival mechanism inside the phagolysosome
what are some bacteria that can survive phagocytosis?
salmonella
mycobacterium
listeria monocytogenes
s. aureus
they’re called professional intracellular pathogens
