Adaptive Immunity-08

Question 1

what are the hallmark features of adaptive responses?

Answer 1

memory and specificity

Question 2

somatic recombination

Answer 2

DNA segments shuffled and form new combinations of base sequences to produce antibody genes; can generate BCRs and TCRs

Question 3

BCRs and TCRs

Answer 3

2 Types of antigen receptors that recognize specific antigenic determinants

Question 4

how quick-acting is the adaptive response?

Answer 4

slow; 3-5 days

Question 5

in which is the adaptive immune response present?

Answer 5

only in jawed vertebrates

Question 6

adaptive response and specificity

Answer 6

narrow specificity and huge specificity repertoire

Question 7

what happens when a vaccine is administered?

Answer 7

a dendritic cell picks it up and takes it to the lymph node; B-cell that recognizes it will make multiple copies of itself and become plasma cells producing antibodies against that vaccine

Question 8

transition from innate to adaptive response

Answer 8

performed when APCs interact with a T-cell that is specific for a given antigen; they are capable of taking something from outside the cell, bringing it into the cell and presenting it up on the surface w/ MHCII to show to other immune cells (make antibodies)

Question 9

what is an antigen?

Answer 9

any molecule to which an antibody can specifically bind; proteins, carbohydrates, nucleic acids, etc

Question 10

antibody (Ab)

Answer 10

a globular protein produced by B cells that can bind to a specific antigen; when an Ab binds to its antigen, it tags toe pathogen for destruction by phagocytes like macrophages and neutrophils; antibodies = immunoglobulins

Question 11

MHC I

Answer 11

is expressed on almost all nucleated cells

Question 12

MHC II

Answer 12

only expressed on professional APCs

Question 13

what can T cells recognize?

Answer 13

T cells only recognize fragments of antigenic proteins that are processed and presented in a certain way - they can’t recognize “native” antigen

Question 14

role of antigen-presenting cells

Answer 14

pick up the antigen, process it and present it on MHC proteins

Question 15

what are the antigen processing pathways?

Answer 15

MHCI & MHCII

Question 16

MHC I pathway

Answer 16

for stuff you already make inside your cells

1. pathogen goes through ER and is put to MHC and inserted onto plasma membrane
2. passing T cells detect infection by unfamiliar virus
3. excites CD8+ or cytotoxic T cell

Question 17

MHC II pathway

Answer 17

extracellular pathogens

1. professional APC takes something from outside into it and processes it through a lysosome
2. engulfed from outside, break down of pathogen
3. small chunks of antigen loaded on MHC II and travels to surface
4. Talks to CD4+ T helper cell (provides help to get B cells to make antibodies)

Question 18

where do the MHC processing pathways happen?

Answer 18

APCs begin processing antigen right after they have engulfed a pathogen; they will then travel through lymphatic vessels to a lymph node (or through blood to spleen) where they will present the antigens to naive T cells and B cells

Question 19

t-cell activation in the lymph node

Answer 19

T cells are very particular and each only has one specificity of T-cell receptor
- a TCR will only react to one antigen

Question 20

generation of diversity

Answer 20

the generation of a diverse repertoire of antigen-binding receptors on B or T lymphocytes that occurs in the bone marrow or thymus, respectively; germline and somatic diversification theory

Question 21

germline theory

Answer 21

separate gene for each distinct receptor

Question 22

somatic diversification theory

Answer 22

recombination of a limited # of gene sequences leading to a large # of distinct receptors

Question 23

T and B cell development

Answer 23

some will be autoreactive and target “self” molecules, so therefore need to undergo negative selection to eliminate such cells; T cells may further undergo positive selection

Question 24

negative selection

Answer 24

central tolerance; causing apoptosis in cells that are self-reactive

Question 25

positive selection of T cells

Answer 25

MHC restriction; maturing only cells that can respond to the presentation of antigen on MHC

Question 26

where does T cell development occur?

Answer 26

thymus; precursors travel from bone marrow to thymus and once matured travel to secondary lymphoid tissues

Question 27

where does B cell development occur?

Answer 27

bone marrow; migrate to secondary lymphoid tissues once matured

Question 28

clonal selection postulates

Answer 28

1. each lymphocyte bears a single type of receptor w/ unique specificity
2. interaction b/w a foreign molecule and lymphocyte receptor capable of binding that molecule w/ high affinity leads to lymphocyte activation
3. the differentiated effector cells derived from an activated lymphocyte will bear receptors of identical specificity to those of the parental cell from which that lymphocyte was derived
4. lymphocytes bearing receptors specific for ubiquitous self molecule are deleted at an early stage in lymphoid cell development and are therefore absent from the repertoire of mature lymphocytes

Question 29

how does clonal selection occur?

Answer 29

APCs present antigen to T cell, only T cells with TCRs specific for the antigen will undergo clonal selection; antigen-specific T cells will proliferate and differentiate (in secondary tissues, results in swelling)

Question 30

cellular immunity

Answer 30

immune response that relies on T cells to destroy infected body cells

Question 31

humoral immunity

Answer 31

specific immunity produced by B cells that produce antibodies that circulate in body fluids

Question 32

CD4+ T cells

Answer 32

helper T cells that carry the CD4+ protein antigen on their surface

Question 33

CD8+ T cells

Answer 33

T cells whose role is cytotoxicity - “killer”

Question 34

activation of B-cells (T cell dependent)

Answer 34

1. B-cell must first encounter antigen, unprocessed antigen binds to BCR to activate B cell (weak), B cell presents processed antigen in the context of MHCII
2. Interaction w/ helper T cell, binding of TCR to MHCII represents the first signal; release of interleukins by the T cell provide second signal for strong activation of B cell

Question 35

costimulation

Answer 35

done by several interleukins; helper T cell recognizes the B cell is displaying processed antigen and releases costimulators for a second stronger activation of B cells

Question 36

activation of B-cells (T cell independent)

Answer 36

if a pathogen expresses a large antigen w/ repeating subunits, it can bind several BCRs at once resulting in BCR cross-linking; this results in a signal being prod. in the B cell leading to B cell activation (this process results in weak B cell activation and develops poor immunologic memory)

Question 37

what are the functions of antibodies?

Answer 37

complement activation, antibody-dependent cellular cytotoxicity, opsonization, neutralization immobilization

Question 38

what are the 4 classes of antibodies?

Answer 38

IgG, IgA, IgE, IgM

Question 39

IgG

Answer 39

most abundant throughout body, secondary responses, neutralize/opsonize/activate complement system, placental transfer

Question 40

IgA

Answer 40

secreted dimer, mucosal surfaces (tube-like structures in body)

Question 41

IgE

Answer 41

binds mast cells, responsible for allergies, protects against worms (in GI tract)

Question 42

IgM

Answer 42

pentameter, primary responses, only present in circulation (too big), fixes complement