Lecture 6

Question 1

What sort of cells participate in humoral immunity?

Answer 1

B cells

produce antibodies

Question 2

What sort of cells participate in cell mediated immunity?

Answer 2

T cells

Question 3

Where do B cells mature?

Answer 3

bone marrow

Question 4

Where do T cells mature?

Answer 4

thymus

Question 5

What is positive selection in regards to t cell maturation?

Answer 5

a t cell that binds with low affinity to MHC is sent to secondary lymphoid organ (aka it passes the test)

Question 6

What is negative selection in regards to t cell maturation?

Answer 6

a t cell that binds with high affinity to MHC (aka is aggressive towards self) gets signal to die

Question 7

What are the two primary functions of antibodies?

Answer 7

recognize and bind to antigen

trigger elimination of foreign antigen (opsonization, complement activation etc)

Question 8

What are the components of an antibody?

Answer 8

2 fragments: Fab and Fc

4 chains: 2 heavy, 2 light

Question 9

What is the difference between Fab and Fc on Ab?

Answer 9

Fab: antigen binding fragment, highly variable

Fc: crystalline fragment, constant

Question 10

Where are the light chains found on ab?

Answer 10

only on Fab

Question 11

Where are the heavy chains found on ab?

Answer 11

Fab and Fc

Question 12

IgG

Answer 12

• main source of ab immunity
• 4 different forms
• light chains have kappa, lambda forms
• capable of crossing placenta

Question 13

IgM

Answer 13

• pentomer
• on surface of B cells
• eliminates pathogens in early stages before IgG is sufficient

Question 14

IgA

Answer 14

• dimer
• found in mucosal areas, saliva, tears, milk
• prevents colonization by bacteria

Question 15

IgD

Answer 15

• Ag receptor on naive B cell

- activates basophils/mast cells to produce antimicrobial factors

Question 16

IgE

Answer 16

• binds to allergens, triggers histamine release from mast cells
• protection agains parasitic worms

Question 17

What are the components of the heavy chain?

Answer 17

Variable V segment
Diversity D segment
Joining J segment

Question 18

What are the components of the light chain?

Answer 18

V segment

J segment

Question 19

Where does positive selection of T cells take place?

Answer 19

cortex of thymus

Question 20

Where does negative selection of t cells take place?

Answer 20

medulla of thymus

Question 21

Does Ag covalently bind to Ab?

Answer 21

No, a strong bond like that would reduce the specificity of binding

Question 22

Instructive theory of Ab production

Answer 22

cells respond to ag by imprinting shapes of ag and making ab accordingly

doesn’t make sense and is stupid

Question 23

Selective theory of Ab prduction

Answer 23

ab specificity is randomly generated, need 10^7 dif types of ab premade.

(we don’t have enough genes for this, but we do kind of use this method)

Question 24

How many genes make the light chain?

Answer 24

2 (gamma and kappa)

Question 25

How many genes make the heavy chain?

Answer 25

just one

Question 26

What are the two types of Ig initially produced by immature B cells?

Answer 26

IgM and IgD

Question 27

What happens after a mature B cell is exposed to ag?

Answer 27

becomes plasma cell or memory B cell, produces Ig

Question 28

Why does a progenitor B cell not produce ab?

Answer 28

because it still has all of the segments of its Ig gene too many stop codons are present

Question 29

What must happen to the Ig gene before a b cell can produce ab?

Answer 29

deletion and recombination of different segments

Question 30

What is germ line DNA?

Answer 30

DNA which is passed down through gametes before it is modified by somatic recombination or maturation

Question 31

Do mature B cells have germ line DNA?

Answer 31

no, their Dna has been modified

Question 32

What cells contain germ line DNA?

Answer 32

pro-B cells in bone marrow

Question 33

How is the kappa chain protein (i believe this for the light chain) produced?

Answer 33

A V segment variation and a J segment variation are randomly combined this is also the same process for the gamma chain

Question 34

How are segments deleted from Ig gene?

Answer 34

homologous recombination forms a hairpin loop and the ends are cut off and deleted

Question 35

Are promoters located closer to the genes they influence in germ DNA or recombinant DNA?

Answer 35

recombinant

Question 36

What are the gene units for kappa chain production?

Answer 36

Vk, Jk, Ck Vk and Jk are variable

Question 37

How many segments are in Vk, Jk, and Ck?

Answer 37

Vk: 30 Jk: 5 Ck: 1 (constant)

Question 38

How many recombinant possibilities are there for the kappa chain?

Answer 38

30 x 5 = 150 total

Question 39

What are the gene units for the gamma chain?

Answer 39

Vg, Jg, Cg | same as kappa

Question 40

How many segments are in Vg, Jg and Cg?

Answer 40

Vg: 30 Jg: 7 Cg: 7

Question 41

How many recombinant possibilities are there for the gamma chain?

Answer 41

30 x 7 x 7 = 210

Question 42

How many recombinant possibilities are there for the heavy chain?

Answer 42

51 V variations x 30 D variations x 6 J variations = 9180

Question 43

What is the recombinational inaccuracy mechanism?

Answer 43

when combining V or J segments of gene units, instead of end to end joining a few nucleotides are cut out during recombination on purpose to create variability. not precise process.

Question 44

What is the n-nucleotide addition mechanism?

Answer 44

a few nucleotides may be inserted between D and JH and between VH and D to create further diversity basically just stick a few more nucleotides in randomly when recombining segments

Question 45

What is the somatic mutation mechanism?

Answer 45

after ag stimulation, the V, D and J genes in B cells can make single base mutations so that the ag sticks better into binding site (affinity maturation)

Question 46

What is the class switching mechanism?

Answer 46

Fc region can switch from IgM, D, G etc. but once IgG is expressed, you cannot go back to another class

Question 47

What are the mechanisms used for antibody diversity? (7)

Answer 47

1. multiple germ line V genes 2. V-J and V-D-J recombinations 3. Recombination inaccuracies 4. N-nucleotide addition 5. Somatic mutation 6. Assorted heavy and light chain combination 7. Class switching

Question 48

Can a t-cell express CD4 and CD8?

Answer 48

nope

Question 49

If a immature t cell is presented with MHC in the thymus and it has a weak reaction to it, what is its fate?

Answer 49

gets signal to survive (positive selection)

Question 50

if an immature t cell is presented with MHC in the thymus and it has no interaction with it, what is its fate?

Answer 50

DEATH (lack of positive selection)

Question 51

if an immature t cell is presented with MHC in the thymus and it has a very strong interaction with it, what is its fate?

Answer 51

DEATh (negative selection)

Question 52

how many t cells actually make it out of the thtymus

Answer 52

only 2% of those made