Lymphocytes Identification, Tolerance, and Circulation

Question 1

What surface molecules distingush T and B cells apart?

Answer 1

B cells have a B cell receptor for binding to an antigen and t cells have a t-cell receptor that needs a CD3 molecule for signalling

Question 2

How are T and B cells identified (since you cannot distinquish normally with a microscope)?

Answer 2

flocytometry - the antibody molecules are coated with flourecent labels so once they bind to the T and B cells you are able to distinguish them

Question 3

What is the difference between the primary and secondary response?

Answer 3

the secondary response has a shorter lag time, stronger titer, and higher affinity for binding

Question 4

Define hybridoma.

Answer 4

a plasma cell tumor with a b cell that secretes a monoclonal antibody to recognize only 1 epitope

Question 5

What is central tolerance?

Answer 5

when an immature lymphocyte meets its antigen (self-antigen) in the generative lymphoid tissues

Question 6

What happens when an immature lymphocyte meets its antigen in primary lymphoid tissue?

Answer 6

die by apoptosis or follow a different route if it is a B cell or CD4 t cell

Question 7

If it is a B cell, what happens when an immature lymphocyte meets its antigen in primary lymphoid tissue?

Answer 7

it may edit its antigen receptor to recognize a different antigen

Question 8

If it is a CD4 T cell, what happens when an immature lymphocyte meets its antigen in primary lymphoid tissue?

Answer 8

it may become a regulatory T cell which supresses the T cell responses to the antigen

Question 9

What is peripheral tolerance?

Answer 9

when a mature naive lymphocyte recognizes its antigen in the absense of danger signals out in the tissues

Question 10

If a mature naive lymphocyte recognizes its antigen in the absence of danger what happens?

Answer 10

die by apoptosis, become anergic, or be supressed

Question 11

What is IgM’s role in B cell development?

Answer 11

in bone marrow, IgM is on the naive B cell surface, if it does not recognize its antigen it passes to the next test

Question 12

If the B cell does not recognize its self antigen, what happens?

Answer 12

it will mature, IgD will be put on its membrane and become a naive mature B-cell

Question 13

Where does T cell tolerance develop?

Answer 13

in the thymus

Question 14

What is positive selection of T cells?

Answer 14

if they recognize MHC I and MHC II they live, of not they die and are useless

Question 15

What is negative selection of T cells?

Answer 15

if they recognize their own peptide in the MHC groove they die, if not they live; recognition here is bad

Question 16

Through T-cell tolerance, what is the outcome if they pass the test?

Answer 16

they recognize self MHC I and MHC II, do not recognize their self peptide, and lose either CD4 or CD8 (whichever they do not need)

Question 17

What is the role of thymic epithelial cells and APCs in the thymus?

Answer 17

they present self peptides on MHC I and MHC II

Question 18

How does the thymus change as the individual ages and how does that effect immunity?

Answer 18

the thymus involutes (gets smaller) and there is an increase in infectious and autoimmune diseases, and cancers

Question 19

How do naďve lymphocytes and memory lymphocytes circulate in the blood stream and lymph system differently?

Answer 19

Memory lymphocytes can exit at interstitial space/tissues where infection is, where as immature lymphocytes have to go to the LNs

Question 20

What are high endothelial venules?

Answer 20

specialized venules that are the sites of lymphocyte migration from the blood into the stroma of secondary lymphoid tissues

Question 21

What is the structure of high endothelial venules?

Answer 21

lined with endothelial cells that produce into the vessel lumen

Question 22

What do the endothelial cells of high endothelial venules do?

Answer 22

express unique adhesion molecules for binding of naďve and central memory B and T cells

Question 23

What are the adhesion molecules that the endothelial cells of high endothelial venules express?

Answer 23

selectins and integrins

Question 24

How does the structure of lymphoid tissues maximize the opportunity for lymphocytes to meet their antigen and interact with one another?

Answer 24

the dendritic cells in the lymphoid tissues catch antigens so that when the lymphocytes circulate to the lymph tissue they have a higher chance of meeting their antigen in these areas due to the high concentration of antigen