Chapter 3 Flashcards
how does leukocyte migration from blood into tissues occur?
through postcapillary venules and depends on
adhesion molecules expressed on the leukocytes
and vascular endothelial cells as well as
chemokines
what are selectins?
carbohydrate-binding adhesion molecules that mediate low-affinity interactions of
leukocytes with endothelial cells, as the first step
in leukocyte migration from blood into tissues
What are E-selectin and P-selectin?
expressed on activated endothelial cells and bind to selectin ligands
on leukocytes, and L-selectin is expressed on leukocytes and binds ligands on endothelial cells
What are integrins?
large family of adhesion molecules,
some of which mediate tight adhesion of leukocytes with activated endothelium, as a critical step
in leukocyte migration from blood into tissues
what are important leukocyte integrins?
e LFA-1
and VLA-4, which bind to ICAM-1 and VCAM-1,
respectively, on endothelial cells
What is the first setp to leukocyte migration from blood into tissues?
interactions
with endothelial cells, starting with low-affinity
leukocyte binding to and rolling along the endothelial surface (mediated by selectins and selectin
ligands).
What is the second step of leukocytes migration from blood into tissues?
leukocytes become firmly
bound to the endothelium, through interactions of
leukocyte integrins binding to Ig superfamily
ligands on the endothelium
What is the relationship between integrin binding and chemokines?
Integrin binding is
enhanced by chemokines, produced at the site
of infection, that bind to receptors on the
leukocytes
what is lymphocyte recirculation?
process by which
naive lymphocytes continuously migrate from
blood into secondary lymphoid organs through
HEVs, back into the blood through lymphatics,
and into other secondary lymphoid organs
what does lymphocyte recirculation maximize?
chance of naive T cell
encounter with the antigen it recognizes and is
critical for the initiation of immune responses.
how is the process of naive B and T cells migrating to the lymph nodes mediated?
by binding of
L-selectin on lymphocytes to peripheral lymph
node addressin on HEVs in lymph nodes and by
the CCR7 receptor on the lymphocytes that binds
to the chemokines CCL19 and CCL21, which are
produced in lymph nodes.
By what process do effector and memory lymphocytes that are generated by antigen stimulation of naive cells exiting the lymph nodes dependent on?
sphingosine-1 phosphate receptor on the lymphocytes and a gradient of sphingosine 1 phosphate
Effector T cells have decreased expression of what? What does it have increased expression of?
decreased L-selectin and
CCR7 expression but increased expression of integrins and E-selectin and P-selectin ligands
