Immunology Exam 1

CHAPTER 1

CHAPTER 1

what is the immune system?

how the body protects and fights dangerous pathogens or foreign invaders

what are pathogens?

organisms that cause disease, such as bacteria, viruses, fungi, and parasites.

is there a situation where someone doesnt have an immune system?

AIDS. you develop HIV which destroys T helper cells, leaving the person unable to mount an effective adaptive response

what are you suffering from when you dont have an immune system?

immunodeficiency

how can immunodeficiencies arise?

from birth (genetic) or you can acquire it later in life through an infection (HIV → AIDS)

what is another benefit of the immune system apart from fighting pathogens?

it protects us from cancers/ malignancies

what are some cells of the immune system?

• B cells

• T cells

• basophils

• macrophages

• neutrophils

• NK cells

• eosinophils

• dendritic cells

• monocytes

• mast cells

what are the cells of the immune system?

white blood cells

is there a situation where the immune system is actually your enemy? why?

lupus, which is an autoimmune disease where the immune system stops telling self from non-self and starts attacking the body’s own healthy tissue as if it were a foreign invader

why are diseases autoimmune?

the immune system attacks the body’s own tissues/proteins, rather than foreign pathogens. immune response against your own body

what happens if your immune system is attacking its own joints?

you get rheumatoid arthritis

what happens if your immune system is attacking the pancreas?

you have type 1 diabetes

what happens if your immune system is attacking your nervous system?

you get multiple sclerosis

what type of autoimmune disease is lupus?

systemic, meaning your immune system attacks different parts of the body

if you have an autoimmune disease, what do you have to take and why?

immunosuppressants to calm the overactive immune system attacking the body’s own tissues. also autoimmune diseases are chronic

what is the trade-off with taking immunosuppressants?

suppressing the immune system to stop it from attacking itself also makes the person more vulnerable to infections since you’re dialing down the whole system

a healthy immune system need to tell the difference between what?

self and non-self (foreign)

how is the immune system able to know what is foreign and self?

through their immune receptors

is receptor generation random or controlled?

receptor generation itself is random (DNA rearrangement/"generation of diversity" creates a huge variety of unique receptors by chance), especially the the process that generates specificity for the receptors since they’re highly specific

what are autoreactive cells?

B or T lymphocytes whose receptors bind to self-antigens instead of foreign ones

what happens when too many autoreactive cells recognize self?

they activated, attack your own body and then you end up with an autoimmune disease

what happens when self-antigens are detected?

they are eliminated and inactivated during development

how does your body make sure that you dont have that many autoreactive cell floating around?

your lymphocytes are developed in primary lymphoid organs

what are the primary lymphoid organs?

thymus and bone marrow

where are B cells made?

bone marrow

where do T cells fully develop?

thymus

when lymphocytes develop in the primary lymphoid organs, what do they need to be in contact with?

the tissues of the lymphoid organs theyre growing in

what allows the lymphocytes to be in contact with the various tissues of the primary lymphoid organs

receptors

what fundamental question are developing lymphocytes "asked" before leaving the primary lymphoid organs?

do your receptors recognize self antigens?

What should the lymphocyte "answer" to pass the test? why?

no because only lymphocytes that recognize non self are allowed o survive and leave the primary lymphoid organ

what happens if a lymphocyte answers that it recognizes self?

it is killed, deleted, or inactivated during development. it dies by apoptosis

what is negative selection?

the process during lymphocyte development where cells with receptors that strongly binds self-antigens are eliminated (deleted) in the primary lymphoid organisms

what latin terms is the source of the english word immunity?

immunis

what does immunis mean?

exempt

what ancient greek historian first wrote about immunity?

thucydides. he wrote about the plague in athens that was caused by the black death. he observed that if youre sick and i want to get close to you, im also going to get sick within days. then he realized that if you had the disease and were lucky to recover and go help someone that is sick, you likely wouldnt get sick again

what are the two ways to build immunity?

• natural (getting sick and getting better)

• artificial (vaccines)

what important skill does the immune system have?

immunological memory

what is immunological memory?

the ability of the adaptive immune system to respond faster and stronger upon re-exposure to an antigen it has already encountered due to long-lived lymphocytes left over from the first primary response

in order for a cell to recognize something foreign, it needs to have the right specific….

receptor

if the cell has a receptor that binds to something its supposed to recognize, what happens to that cell?

it signals

what happens after a cell signals?

it gets activated and divides/expand through mitosis

if we only have a few cells to combat an infection on their own, what do these few cells need to do?

they need to divide and expand

what is clonal expansion?

after a B or a T cell’s receptor binds to its specific antigen, it proliferates, producing many identical copies all with the same antigen specificity

should activated lymphocytes stay activated long-term after clearing an infection?

no once the pathogen is cleared, most effector lymphocytes should die off to prevent unnecessary/chronic inflammation and tissue damage

how does the immune system get rid of the activated lymphocyte once it has fought off the invasion?

once you activate the lymphocyte it becomes a ticking bomb, meaning it has enough time to do its job (effector function) but slowly it starts the process of apoptosis

what happens to a very small percentage of activated lymphocytes?

they survive as memory cells for future protection

what is immunological memory driven by?

memory cells

what are memory cell and what are they important?

lymphocytes that have survived the initial activation stage and let the body respond faster, stronger, and more specifically if the same pathogen ever comes back, often stopping it before you even feel sick. this is exactly why vaccines work, and why we usually don't get certain diseases twice.

what are mechanisms of the immune system that they harness to fight pathogens?

• recognizing self from non-self

• clonal expansion

• immunological memory

can we generate immunity without inducing disease? how?

yes through vaccination

what do vaccinations do?

prepares the immune system to eradicate an infectious agent before it causes disease

what is an example of a vaccine that has eradicated an infectious agent?

rabies vaccine and the eradication of smallpox

who is the father of vaccination?

Edward Jenner

how did edward jenner discover vaccinations?

he made the observation that milk maids who were getting cowpox, were then immune to smallpox

how were people who obtained cowpox, then immune to smallpox?

cowpox is similar enough to smallpox that the immune system's memory cells formed against cowpox could also recognize and fight off smallpox

what is immunological cross-protection?

when memory cells built against one pathogen also protects against a different but closely related pathogen because they share similar antigens (example cowpox exposure → protection against smallpox)

what mediates an immune response?

antibodies or cells

who makes antibodies?

B cells

what are the two branches of adaptive immunity?

• cell-mediated immunity

• humoral immunity

what is cell-mediated immunity driven by?

t cells that directly kill infected cells/help other immune cells

what is humoral immunity driven by?

b cells that secrete antibodies into body fluids to neutralize/tag pathogens

what are antibodies produced by?

B cells

what do humoral and cell-meditated immunity rely on?

surface receptors- B-cell receptors and T-cell receptors

how are the receptors on B cells and T cells generated?

randomly through gene segment rearrangements in B and T cells

what happens when a B cell encounters its antigen?

it produces antibodies— soluble versions of the same specificity as its membrane-bound immunoglobulin (B-cell receptor)

what do T cell receptors bind to?

specific peptides presented by MHC molecules (not free-floating antigen like B cells)

what does each individual B or T cell have specificity for?

a single antigen because each cell expresses many copies of one receptor that binds only one antigen type

what happens when a B or T cell interacts with its specific antigen?

it is selected and becomes activated?

what does activation of a B or T cell lead to?

proliferation, producing a large number of identical clones

what are these clones reactive against?

the same antigen that originally activated the parent lymphocyte

what does tolerance ensure?

that the immune system doesnt attack self

why is tolerance necessary, given how B- and T-cell receptors are made?

since receptors are generated randomly, many of the random rearrangements could accidentally create anti-self receptors

which mechanism is the one that ensures tolerance?

negative selection

how does tolerance protect the body?

it keeps anti-self cells/receptors or in other words cells that react to self from circulating in the bloodstream (by eliminating or inactivating them during development)

what 2 components if the immune system itself divided into?

adaptive and innate

is the adaptive or innate more specific?

adaptive

what immune system component is the largest organ in our body part of?

innate

what enzyme do we have in salvia and tears?

lysozyme

what does lysozyme do?

break down the cell wall

what bacteria primarily does lysozyme break down?

gram positive

is the process of lysozyme breaking down the cell wall of gram positive bacteria innate or adaptive?

innate (not specific because it doesnt matter what gram positive bacteria it is, its breaking down the cell wall)

what cells are part of the innate system?

everything apart from B cells and T cells

• basophils

• mast cells

• monocytes

• macrophages

• dendritic cells

• NK cells

• neutrophils

what is the difference between adaptive and innate cell receptors

innate receptors dont have the kind of specificity that B cells or T cells have. adaptive receptors recognize patterns

what immune system component has the most diversity?

adaptive because theyre highly specific. the more specific you are, the more diversity you need to have to cover all the specificities out there

tolerance and the ability to recognize self from non-self is a trait of what immune system component?

adaptive (B cells and T cells)

why are tolerance and negative selection features of the adaptive immune system?

only adaptive cells make random, unique receptors and random receptors can accidentally recognize self. tolerance and negative selection are the safety check that remove those self-reactive cells.

why dont innate cells need to be negatively selected?

their receptors are not randomly generated, theyre inherited, fixed genes passed down that specifically evolved to recognize common pathogen patterns, not self. since theres no randomness, theres no risk of accidentally creating a self-reactive receptor so no screening process is needed

immunological memory is a characteristic of which immune system component?

adaptive

When you get infected with the same pathogen repeatedly, how does the innate immune system respond each time?

the same way every time — with the same speed and strength. Innate immunity has no memory, so it doesn't improve or respond faster/stronger on repeat exposures

how does the innate response time compare to the adaptive?

innate is much faster (minutes to hours). Adaptive is slower (takes 5-6) days to fully develop

how does the innate specificity compare to the adaptive?

innate immunity has limited, fixed specificity. it recognizes broad, shared pathogen patterns but cant distinguish fine differences. adaptive immunity is highly specific. it cant distinguish tiny molecular differences and generates new, tailored receptors

how does the innate response to repeat infection compare to the adaptive?

Innate immunity responds the same way every time (no memory). Adaptive immunity responds faster and more effectively with each repeat exposure, due to memory cells left over from the first encounter

what are pattern recognition molecules (PRRs)?

receptors on innate immune cells that recognize common, shared structures found on many pathogens (PAMPs- pathogen associated molecular patterns). they are inherited fixed genes, always expressed, allowing fast but non specific detection of invaders

what are the physical and chemical barriers of the innate immune system?

• skin

• mucosal membranes

• stomach acidity

• lysozyme in tears

What do many innate immune cells do to pathogens? how do they destroy them?

using phagocytosis

which cells are involved in innate immune responses?

• neutrophils

• eosinophils

• macrophages

• dendritic cells

• NK cells

what are interferons?

a type of cytokine (alpha and beta) released by virus-infected cells to warn nearby cells of infection, triggering an antiviral state that blocks viral replications

what are cytokines?

molecules that WBC make soluble to either talk to each other or cause damage to foreign things. a way that cells talk to each other

what are complement proteins?

group of inactive serum proteins able to destroy membranes of pathogens or facilitate their clearance