Lymphocytes Identification, Tolerance, and Circulation Flashcards
What surface molecules distingush T and B cells apart?
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
How are T and B cells identified (since you cannot distinquish normally with a microscope)?
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
What is the difference between the primary and secondary response?
the secondary response has a shorter lag time, stronger titer, and higher affinity for binding
Define hybridoma.
a plasma cell tumor with a b cell that secretes a monoclonal antibody to recognize only 1 epitope
What is central tolerance?
when an immature lymphocyte meets its antigen (self-antigen) in the generative lymphoid tissues
What happens when an immature lymphocyte meets its antigen in primary lymphoid tissue?
die by apoptosis or follow a different route if it is a B cell or CD4 t cell
If it is a B cell, what happens when an immature lymphocyte meets its antigen in primary lymphoid tissue?
it may edit its antigen receptor to recognize a different antigen
If it is a CD4 T cell, what happens when an immature lymphocyte meets its antigen in primary lymphoid tissue?
it may become a regulatory T cell which supresses the T cell responses to the antigen
What is peripheral tolerance?
when a mature naive lymphocyte recognizes its antigen in the absense of danger signals out in the tissues
If a mature naive lymphocyte recognizes its antigen in the absence of danger what happens?
die by apoptosis, become anergic, or be supressed
What is IgM’s role in B cell development?
in bone marrow, IgM is on the naive B cell surface, if it does not recognize its antigen it passes to the next test
If the B cell does not recognize its self antigen, what happens?
it will mature, IgD will be put on its membrane and become a naive mature B-cell
Where does T cell tolerance develop?
in the thymus
What is positive selection of T cells?
if they recognize MHC I and MHC II they live, of not they die and are useless
What is negative selection of T cells?
if they recognize their own peptide in the MHC groove they die, if not they live; recognition here is bad
Through T-cell tolerance, what is the outcome if they pass the test?
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)
What is the role of thymic epithelial cells and APCs in the thymus?
they present self peptides on MHC I and MHC II
How does the thymus change as the individual ages and how does that effect immunity?
the thymus involutes (gets smaller) and there is an increase in infectious and autoimmune diseases, and cancers
How do naďve lymphocytes and memory lymphocytes circulate in the blood stream and lymph system differently?
Memory lymphocytes can exit at interstitial space/tissues where infection is, where as immature lymphocytes have to go to the LNs
What are high endothelial venules?
specialized venules that are the sites of lymphocyte migration from the blood into the stroma of secondary lymphoid tissues
What is the structure of high endothelial venules?
lined with endothelial cells that produce into the vessel lumen
What do the endothelial cells of high endothelial venules do?
express unique adhesion molecules for binding of naďve and central memory B and T cells
What are the adhesion molecules that the endothelial cells of high endothelial venules express?
selectins and integrins
How does the structure of lymphoid tissues maximize the opportunity for lymphocytes to meet their antigen and interact with one another?
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
