Download The Body on Defense

The Body on Defense
Leukocytes



Leukocytes participate in the defense
against infection caused by foreign
invaders.
Fight infection and clear away damaged
tissue.
Move rapidly from blood stream and into
underlying tissue at sites of infection.
Types of Leukocytes



Neutrophils- release antibacterial pproteins
Monocytes- the precursors of
macrophages which engulf and destroy
foreign particles
Lymphocytes- The antigen recognizing
cells of eh immune system: Both T and B
types
Movement of Leukocytes


Movement of the leukocyte into the tissue
is called extravasation
Extravasation requires help from the cell
linings of the vessel and other cell-cell
interactions to allow the leukocyte to
move quickly through the tissues.
Movement- continued



The travel of leukocytes is aided by
selectins, specifically P-selectin for the
leukocyte-vascular interactions
P-selectins are located on the interior, the
blood facing surace, of endothelial cells.
All selectins contain a Ca2+ dependent
lectin domain on the end of the
extracellular region of the molecule.
Short presentation of the Leukocyte
Movement

http://bcs.whfreeman.com/lodish5e/
The “Works” of the Endothelial Cell
The P-selectin in resting state until cell is
inflamed by a bacteria or virus.
 Cell releases P-selectin to the surface of
cell and the leukocyte attaches and rolls
the length of the infection to the point of
the platelet-activating-factor PAF
 The PAF is released at the same time the
P-selectin is released from the cell

“Works” continued




The PAF is a phospholipid
Binding with leukocyte causes activation
the white blood cell
Integrins on leukocytes bind to each of
the two distinct IgCAMs on the surface of
the endothelial cells
The tight binding causes the movement
into the underlying tissue
Movement into Cell
Leukocytes


Leukocytes defend our bodies against
viruses and bacteria
Leukocytes are CAM specific to ensure the
destruction of only foreign or infected cells