Antibodies, Antibody Diversity, and T cell Development

Question 1

What is an antigen?

Answer 1

Anything that can be SPECIFICALLY bound by cells of the adaptive immune system

• B cell receptor
• T cell receptor

Question 2

Which cells bind in a specific manner to antigen?

Answer 2

B and T Cells

Question 3

T/F. B cells are involved in humoral immunity whereas T cells are involved in cell-mediated immunity.

Answer 3

True.

Question 4

What happens when B cells recognize antigen?

Answer 4

1. antibody secretion by plasma cells (effector B cells)

2. development of immunologic memory (memory B cells)

Question 5

Recognition of antigen by T cells results in what?

Answer 5

1. T cell activation

2. Development of immunologic memory (memory T cells)

Question 6

What is another name for antibody?

Answer 6

immunoglobulin (Ig)

Question 7

What are the two forms that an antibody can be found?

Answer 7

membrane bound (B cell receptor) or secreted

Question 8

What are the functions of antibodies?

Answer 8

1. Antigen recognition
2. Direct antigen neutralization
3. Opsonization (enhances phagocytosis by phagocytes)
4. Activation of the complement cascade

Question 9

Which cells recognize antigen? Antigen fragment (peptide) + MHC?

Answer 9

B cells; T cells

Question 10

What is hematopoiesis?

Answer 10

The generation of blood cells

Question 11

___ selection involving either deletion or receptor editing mediated by ___-avidity interactions with ___ antigen.

Answer 11

Negative; high; self

Question 12

___ selection and lineage commitment is ___-avidity interaction with ___ antigen.

Answer 12

Positive; low; self

Question 13

B cell’s hematopoietic stem cells originate in the ___ ___ and immature B cells migrate to the ___ and eventually become ___ B-2 B cells or ___ ___ B-2 B cells.

Answer 13

bone marrow; spleen; follicular; marginal zone

Question 14

T/F. Antibody binding alone is not sufficient to neutralize antigen.

Answer 14

False, it is.

Question 15

How do antibodies trigger the elimination of foreign antigen?

Answer 15

1. activation of complement leads to cell lysis
2. opsonization leads to phagocytosis
3. ADCC causes NK mediated cytotoxicity

Question 16

What are the two fragments of an antibody?

Answer 16

Fab and Fc portion

Question 17

Which fragment binds antigen?

Answer 17

Fab

Question 18

Four chain structure contains 2 ___ heavy chains that spans ___ and ___. There are also 2 ___ light chains that span ___ only.

Answer 18

identical; Fab; Fc; identical; Fab

Question 19

Match the immunoglobulin with its heavy chain:

1. IgG
2. IgM
3. IgA
4. IgD
5. IgE

A. mu
B. gamma
C. delta
D. epsilon
E. alpha

Answer 19

1. IgG – B. heavy chain gamma
2. IgM – A. heavy chain mu
3. IgA – E. heavy chain alpha
4. IgD – C. heavy chain delta
5. IgE – D. heavy chain epislon

Question 20

Which immunoglobulin isotype is found in mucosal areas, saliva, tears, and breast milk to prevent colonization by pathogens?

Answer 20

IgA

Question 21

What form is IgA found?

Answer 21

dimer

Question 22

Which antibody functions mainly as an antigen receptor on B cells that have not been exposed to antigens?

Answer 22

IgD

Question 23

Which Ig binds allergens and triggers histamine release from mast cells and basophils?

Answer 23

IgE

Question 24

T/F. IgG provides the majority of antibody-based immunity against invading pathogens. It is the only antibody capable of crossing the placenta to give passive immunity to the fetus.

Answer 24

True.

Question 25

Which Ig is expressed on the surface of B cells and in a secreted form with very high avidity?

Answer 25

IgM

Question 26

what structure is IgM found?

Answer 26

pentamer

Question 27

In IgG, the Fab arms are linked to the Fc by an extended region of polypeptide chain known as the ___.

Answer 27

hinge

Question 28

What two forms do the light chains of IgG have?

Answer 28

kappa and lambda

Question 29

How many subclasses of IgG heavy chains are there?

Answer 29

4 (gamma 1-4)

Question 30

The hypervariable regions of the antibody are known as the ___ ___ ___.

Answer 30

complementary determining regions (CDR)

Question 31

Where is the CDR located?

Answer 31

on the tip of the Fab and Fc regions of the light chain of the antibody. This is where antigen binding occurs.

Question 32

There are an estimated ___ human protein-coding genes. How could our body make so many different antibodies?

Answer 32

20,000-25,000; VDJ rearrangement

Question 33

The human ___ chain variable region is constructed from the joining of three gene segments, V (variable), D (diversity), and J (joining). The ___ chain variable gene is constructed by the joining of two gene segments, ___ and ___.

Answer 33

heavy; light; V; J

Question 34

___ ___ is the creation of antibody diversity in the Ig repertoire through the joining of various gene segments.

Answer 34

combinatorial diversity

Question 35

After antigen stimulation, the V, D,J genes in B cells can make ___ base changes (often at the region of ___). This is called ___ ___, which occurs to increase the ___ of antibody (affinity maturation).

Answer 35

single; CDR; somatic mutation; affinity

Question 36

What are the two BCRs you find on a naive B cells?

Answer 36

IgM or IgD

Question 37

T/F. Plasma cells can secrete ALL of the Ab isotypes but they can only secrete ONE form of Ab.

Answer 37

True.

Question 38

What allows for the generation of multiple antibody isotypes with the same Ag specificity?

Answer 38

Class switching (isotope switching)

Question 39

T/F. In class switching, some genes of the constant region are looped then cut to produce a primary RNA transcript that only expresses one form of antibody.

Answer 39

True.

Question 40

Where do T cell mature?

Answer 40

thymus

Question 41

Those lymphocytes that do not bind ___ through their TCR are destined to die by apoptosis. This ___ selection takes place in the ___ region of the thymus.

Answer 41

MHC; positive; cortical

Question 42

___ selection mediated by ___-avidity interactions with self antigen takes place in the ___ region of the thymus.

Answer 42

negative; high; medullary

Question 43

T/F. If the thymocyte TCR engages in a low-affinity interaction with a self MHC molecule on the thymic epithelial cell, it is rescued from programmed cell death and continues to mature.

Answer 43

True. This is known as positive selection.

Question 44

T/F. If the thymocyte TCR does not engage in any interactions with peptide-MHC molecule complexes on thymic epithelial cells, it will die by apoptosis.

Answer 44

True. This is known as lack of positive selection.

Question 45

T/F. If the thymocye TCR binds peptide-MHC complexes on a thymic antigen-presenting cell with high affinity or avidity, it is induced to undergo apoptosis.

Answer 45

True. This is known as negative selection.

Question 46

Eater cells are also known as what?

Answer 46

phagocytes. This antibody marking is the process of opsonization.