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