Immunology Chapter 5

Question 1

T cells and B cells are derived from

Answer 1

common lymphoid progenitors in the bone marrow

Question 2

Where do B cells develop and mature

Answer 2

the bone marrow

Question 3

What is the B cell receptor (BCR) also called

Answer 3

Membrane bound immunoglobulin (mIg)

Question 4

What determines the antigen specificity of a B cell

Answer 4

BCR

Question 5

B cells express (2)

Answer 5

BCR and Igα/Igβ co-stimulatory proteins

Question 6

What is the function of the Igα/Igβ co-stimulatory proteins

Answer 6

send signals to the inside of the B cell once an antigen has been bound

Question 7

What T cell complex is functionally analogous to the Igα/Igβ co-stimulatory proteins on B cells

Answer 7

CD3 complex

Question 8

What happens if the BCR of an immature B cell binds to an antigen in the bone marrow.

What is that process called?

Answer 8

The Igα/Igβ co-stimulatory proteins send a signal causing the cell to die.

Clonal deletion

Question 9

Clonal deletion in B cells is analogous to what process in T cells

Answer 9

Negative selection in the thymus

Question 10

Why don’t B cells undergo positive selection like T cells?

Answer 10

Because BCRs don’t need to interact with processed proteins or MHC molecules like TCRs do

Question 11

What happens to B cells that are not deleted during development

Answer 11

They become mature B cells, leave the bone marrow, circulate in the blood and to the spleen and lymph nodes

Question 12

What type of membrane bound immunoglobulins are found on mature, naive B cells?

Answer 12

mIgM and mIgD

Question 13

How many polypeptide chains make up a BCR molecule

Answer 13

4

– 2 identical heavy chains (H)
– 2 identical light chains (L)

Question 14

What regions are found on both the heavy and light chains of the BCR

Answer 14

Variable (V) region and Constant (C) region

Question 15

Which regions form the antigen binding pocket of the BCR

Answer 15

The VH (Variable region of the heavy chain) and VL (Variable region of the light chain)

Question 16

How many antigen binding sites does each BCR have

Answer 16

2

Question 17

How many BCRs are found on the membrane of a single mature B cell

Answer 17

100,000

Question 18

Do all BCRs on a single B cell have the same antigen specificity

Answer 18

Yes, because mIgM and mIgD on the same B cell have the same VH and VL regions

Question 19

What determines the antigen specificity of BCRs on a B cell

Answer 19

the VH and the VL

Question 20

How many types of epitopes can a single B cell recognize?

Answer 20

One or a few similar epitopes

Question 21

Why do different B cells have different antigen specificities

Answer 21

Because they rearrange different immunoglobulin gene segments to form unique VH and VL regions

Question 22

What are antibodies

Answer 22

they are a set of proteins made and secreted by B lymphocytes

Question 23

antibodies are also called

Answer 23

immunoglobulins (Igs)

Question 24

Humoral immunity is

Answer 24

immunity from antibodies

Question 25

Antibodies bind to macromolcules that are usually

Answer 25

foreign

Question 26

In antibodies, where are the heavy and light chain mRNA's translated

Answer 26

membrane-bound ribosomes

Question 27

Where are the H and L chains translocated during synthesis

Answer 27

into the ER

Question 28

How are H and L chains joined in the ER

Answer 28

By disulfie bonds

Question 29

How many chains form a complete antibody molecule

Answer 29

2 heavy chains and 2 light chains

Question 30

What is the pathway of completed antibodies after ER assembly

Answer 30

they move through golgi apparatus via vesicular transport

Question 31

How to antibodies exit the golgi and reach the plasma membrane

Answer 31

vesicles bud off from the Golgi and move to the plasma membrane

Question 32

The antibodies made can be two types, which are

Answer 32

membrane-bound immunoglobulines and secreted antibodies mIgs and sIgs

Question 33

what is the main difference between mIgs and sIgs

Answer 33

amino acid sequences at the carboxyl terminus of the H chain

Question 34

Why are mIgs molecules anchored in the membrane

Answer 34

because their carboxyl terminal amino acids are hydrophobic, allowing membrane anchoring

Question 35

Why are sIg molecules secreted into extracellular fluid

Answer 35

because their carboxyl-terminal acids are hydrophilic, allowing secretion when vesicles fuse with plasma membrane

Question 36

Where are secreted antibodies commonly found

Answer 36

blood, mothers milk, tears, saliva, gastrointestinal secretions and mucus of the respiratory and genitourinary tracts

Question 37

Do secreted antibodies associate with Igα/Igβ like membrane-bound ones?

Answer 37

No, sIg does not

Question 38

Do secreted antibodies have the same specificity as the B cell's BCR?

Answer 38

Yes, they have the same antigen specificity

Question 39

T or F. B cells react with antigens through TCR antigen receptors

Answer 39

False

Question 40

T or F There are secreted forms of both BCR and TCR after the B cell and T cell have been activated by antigen

Answer 40

False, TCR isn't secreted

Question 41

Explain the pathway of B cell maturation in the bone marrow

Answer 41

HSC --> CLP --> B cell precursor (Ig-) ---> Immature B cell (IgM+) ---> Mature B cell (Naive) (IgM+IgD+)

Question 42

How many B cells that commit actually nature into B cells

Answer 42

40%

Question 43

Why are B cells survival rate higher (when screened?)

Answer 43

Because 50% of thymocytes die because they failed positive selection, and B cells don't do positive selection

Question 44

What is the membrane bound form of B cell's antigen receptor

Answer 44

BCR / mIg

Question 45

What is the secreted form of B cell's antigen receptor

Answer 45

Antibody (Ab) / sIg or just Ig

Question 46

There are five classes of Ig

Answer 46

IgM, IgD, IgA, IgG, IgE

Question 47

All the different types of Ig can be membrane bound or secreted except

Answer 47

IgD, which is only found on the membrane of mature naive B cells

Question 48

How many binding sites does BCR and TCR have?

Answer 48

BCR: 2 TCR: 1

Question 49

What is the hypervariable (HV) region

Answer 49

parts of the Ig that contact the antigen

Question 50

Different antibodies have different roles in the immune system, this is determined by

Answer 50

the type of H chain of the antibody

Question 51

Do both antigen-binding sites of the BCR have the same specificity

Answer 51

Yes because the binding site is made of the combination of H and L chain, and both chains are identical

Question 52

What is an antigen

Answer 52

antibody generating structure