Lymphocytes IV

Question 1

How do mature IgM and IgD B lymphocytes differentiate into other isotypes (IgE, IgA, IgG)?

Answer 1

By gene rearrangement mediated by cytokines and CD40 ligands (p.198)

Question 2

What is the function of IgG?

Answer 2

Serves as the main antibody in secondary (delayed) antigenic response; fixes compliment; opsonizes bacteria; provides infants with passive immunity; neutralizes bacterial toxins and viruses (p.198)

Question 3

What immunoglobulin type is the main responder in secondary, delayed antigenic response?

Answer 3

IgG (p.198)

Question 4

What is the most abundant immunoglobulin isotype?

Answer 4

IgG (p.198)

Question 5

What immunoglobulin isotype crosses the placenta?

Answer 5

IgG (p.198)

Question 6

What is the function of IgA?

Answer 6

To prevent attachment of bacteria and viruses to mucous membranes (p.198)

Question 7

In what form does IgA circulate?

Answer 7

As a monomer in circulation (p.198)

Question 8

What form is IgA in in secretions?

Answer 8

Dimeric form (p.198)

Question 9

How does IgA cross epithelial cells?

Answer 9

By transcytosis (p.198)

Question 10

Where is IgA found?

Answer 10

In secretions- tears, saliva, mucous, early breast milk (p.198)

Question 11

From where does IgA pick up secretory component before secretion?

Answer 11

From epithelial cells (p.198)

Question 12

What immunoglobulin type is the main responder in the primary, immediate antigenic response?

Answer 12

IgM (p.198)

Question 13

What is the function of IgM?

Answer 13

Serves as the primary immediate responder to an antigen; to fix complement; to serve as an antigen receptor on the surface of B cells (p.198)

Question 14

In what forms does IgM circulate?

Answer 14

As a monomer on B cells; as a pentamer otherwise (p.198)

Question 15

How does the shape of IgM contribute to antigen trapping?

Answer 15

Pentamer shape allows IgM to efficiently trap free antigens out of tissue while the humoral response evolves (p.198)

Question 16

Where is IgD found?

Answer 16

On the surface of many B cells and in serum (p.198)

Question 17

What is the function of IgE?

Answer 17

To bind mast cells and basophils. It cross links when exposed to antigen, mediating immediate (type I) hypersensitivity through release of inflammatory mediators such as histamine; Mediates immunity to worms (p.198)

Question 18

How does IgE contribute to the type I hypersensitivity response?

Answer 18

Through release of inflammatory mediators such as histamine (p.198)

Question 19

How does IgE mediate immunity to worms?

Answer 19

By activation of eosinophils (p.198)

Question 20

What type of immunoglobulin is in the lowest concentration in the serum?

Answer 20

IgE (p.198)

Question 21

What are thymus independent antigens?

Answer 21

Antigens lacking a peptide component that cannot be presented by MHC to T cells (p.198)

Question 22

Give two examples of thymus independent antigens.

Answer 22

Lipopolysaccharide from cell envelope of gram negative bacteria and polysaccharide capsular antigen (p.198)

Question 23

What is the function of thymus independent antigens?

Answer 23

To stimulate the release of antibodies without creating immunologic memory (p.198)

Question 24

What is a thymus dependent antigen?

Answer 24

An antigen containing a protein component (p.198)

Question 25

Give an example of a thymus dependent antigen.

Answer 25

Diptheria vaccine (p.198)