Week 13.2 Adaptive Immunity

Question 1

How can blood serum from an infected person help another infected patient fight the infection?

Answer 1

Serum contains a high concentration of antibodies of that specific infection produced from plasma cells

Question 2

Antigen

Answer 2

A molecule that is not normally found in the body that stimulates the production of antibodies

Question 3

Epitope

Answer 3

Region of an antigen that antibodies interact with (pathogens can have multiple antigens with multiple epitopes)

Question 4

Dendritic cells

Answer 4

phagocytic cells of innate immune response that function to activate the adaptive immune response

Question 5

Steps of dendritic cell phagocytosis

Answer 5

1. Bacterium is engulfed into dendritic cell and is encased in a phagosome
2. Lysosomes fuse with the phagosome and digest bacterium
3. Immunodominant epitopes are associated w/ MHC II and presented on cell surface

Question 6

Two types of MHC found on our cells

Answer 6

1. MHC I
2. MHC II

Question 7

MHC I

Answer 7

found on all nucleated body cells

Question 8

MHC II

Answer 8

found only one macrophages, dendritic cells, and B cells

Question 9

What happens after dendritic cell is activated?

Answer 9

The dendritic cell brings the antigen to the lymph nodes and presents them to MHC II receptors on T cells

Question 10

What are T cells?

Answer 10

white blood cells involved in the regulation of other immune cells and the destruction of infected/tumor cells

Question 11

T-cell receptor?

Answer 11

-a membrane-bound protein that binds to antigens similar to an antibody
-have variable regions that are produced through genetic recombination
-binds to antigen on MHC

Question 12

CD4/CD8 on T cells

Answer 12

coreceptors that bind to the MHC protein on the antigen-presenting cell (dendritic cells)

Question 13

CD28 on T cells and B7 on antigen-presenting cell

Answer 13

checks to make sure TCR binding is real

Question 14

CD8 naive T cell

Answer 14

recognizes antigens on MHC I complex and develops into cytotoxic T cells and T-memory cells

Question 15

Cytotoxic T cells?

Answer 15

Will travel to infected tissue and kill infected cells using perforin and granzymes to induce apoptosis (same as NK cells)

Question 16

Difference between NK cells and Cytotoxic T cells?

Answer 16

What they’re asking about host cell

Question 17

What do cytotoxic T cells ask host cell?

Answer 17

Is this cell expressing an antigen that my TCR binds to (are you sick with this specific illness?)
-Yes: Kill
-No: DON’T kill

Question 18

CD4 naive T cell

Answer 18

recognizes antigens on MHC II and develops into helper T cells (TH0, TH1, TH2, THreg, TH17)

Question 19

What helper T cells activate B cells?

Answer 19

TFH, TH1, and TH2

Question 20

What two homogenous antibodies on naive B cells serve as antigen receptors (or B cell receptors)?

Answer 20

IgM and IgD

Question 21

What is an antibody?

Answer 21

A Y-shaped protein produced by B cells with variable and non-variable regions

Question 22

Fragment of antigen binding (antibody)

Answer 22

variable proteins that will interact w/ antigen
-top part of antibody (light chain and top part of heavy chain)

Question 23

Fragment of crystallization (antibody)

Answer 23

constant region that is structural and will interact w/ immune cells
-bottom part of heavy chain of antibody

Question 24

Sequence variation in the antigen binding site will…

Answer 24

create a pocket with different chemical properties

Question 25

Four major forces that help create pockets in antigen binding sites

Answer 25

1. Hydrogen bonding 2. Electrostatic forces (charges) 3. Van der waals 4. Hydrophobic/hydrophilic interactions

Question 26

How are unique antibodies produced?

Answer 26

By inducing point mutations in hypervariable regions of the heavy and light chain genes

Question 27

What happens when an antigen bind to a BCR?

Answer 27

1. The B cell internalizes the BCR and antigen 2. The antigen is degraded and parts are expressed on the MHC II 3. A helper T cell that has been exposed to the same antigen binds to the antigen on the B cell's MHC II w/ its TCR

Question 28

What happens after the B cell is activated by the T cell?

Answer 28

The B cell proliferates quickly and introduces new mutations to the daughter cells to improve antibody affinity -More T helper cells will present the antigen to the new B-cells -If antibody doesn't match = apoptosis -If affinity improves = proliferate

Question 29

What two cells do B cells differentiate into?

Answer 29

Plasma cells and memory B cells

Question 30

Plasma cells (effector B cell)

Answer 30

produce 2000 unbound antibodies per second for 4-5 days before they die

Question 31

Five mechanisms that antibodies use to destroy pathogens

Answer 31

1. Agglutination 2. Neutralization 3. Opsonization 4. Antibody-dependent cellular cytotoxicity 5. Complement activation

Question 32

Agglutination

Answer 32

Clumps of agglutinated cells are easier to fight because a phagocyte can kill many pathogens at one time

Question 33

Neutralization

Answer 33

Antibodies block a pathogen's ability to infect Ex: an antibody might bind to a surface protein on a virus; if that protein is required to infect a cell, the virus can no longer infect the cell bc the protein is blocked

Question 34

Opsonization

Answer 34

Phagocytic cells can use Fc receptors to bind to IgG-opsonized pathogens and initiate attachment

Question 35

Antibody-dependent cellular cytotoxicity

Answer 35

If a pathogen is too large to phagocytize, antibodies can bring NK cells into close proximity where it will release extracellular cytotoxins

Question 36

Complement activation

Answer 36

Antibodies help INITIATE the classical pathway of the complement system

Question 37

T-cell-dependent B cell activation steps summarized

Answer 37

1. Antibody on naive B cell BCR contacts a matching antigen 2. B cell internalizes BCR and antigen 3. B cell presents antigen pieces on MHC II 4. Matching T-helper cell activates B cell 5. Hypermutations improve antibody affinity 6. B cell proliferates into plasma cells and memory B cells 7. Class switching 8. Response

Question 38

T-cell-independent activation

Answer 38

PAMP and TLR interactions can also activate B cells

Question 39

If plasma cells produce antibodies, what are memory B cells' function?

Answer 39

Memory B cells retain the antibody sequence (hence "memory") to produce a faster and more effective response to future infections w/ the same antigens

Question 40

Long-lived plasma cells

Answer 40

After initial infection, some plasma cells become long-lived plasma cells (and don't die after 4-5 days)

Question 41

Where are long-lived plasma cells found?

Answer 41

In the bone marrow; they secrete circulating antibodies for months to years

Question 42

What if circulating antibodies isn't enough to fight off infection?

Answer 42

Then memory B cells in the spleen and lymph nodes (secondary lymphoid organs) come into contact w/ the antigen and proliferate into plasma cells

Question 43

What happens to memory B cells during second exposure to an infection?

Answer 43

Some memory B cells will go through a second round of somatic hypermutations to try and improve antibody affinity

Question 44

How can memory T cells be reactivated?

Answer 44

By antigen presenting cells in the lymph nodes