Cytokines used for communication between leukocytic cells are called
interleukins. There are 17 known interleukins that are identified by numbers
assigned to them by an international committee. Table 14-1 lists important
interleukins.
Cytokines are used as therapeutic agents to combat disease. For example, Inter-
leukin-1 is used to stop blood flow to tumors in animals, thereby killing the tumor.
T Cells
T cellsdevelop from stem cells in bone marrow and migrate to the thymus gland
where they mature. They then migrate to the lymphatic system to begin their
fight against antigens. The âTâ stands for thymus gland. Once the organism
reaches late adulthood, the ability to create new T cells diminishes, resulting in
a weaker immune system as the organism ages.
ATcell attacks a specific antigen that is displayed on the surface of the cell.
These cells are called antigen-presenting cells (APCs), such as, macrophages
and dendritic cells. After the antigen is ingested by the APC, fragments of the
antigen are placed on the surface of the cell. These fragments must be near the
cell-surface self-molecules. Self-molecules are part of the histocompatibility
complex (MHC), which is a group of proteins that are unique to a person and
used to distinguish self from nonself.
When an antigen receptor encounters fragments of the complimentary anti-
gen, the T cell transforms into the effector T cellthat carries out the immune
response. An effector T cell is an antigen-stimulated cell. Some T cells attack
CHAPTER 14 Immunity^219
Interleukins Description
Interleukin-1 Stimulates T cells
Attracts phagocytes in an inflammatory response
Interleukin-2 Stimulates B cell production
Stimulates T cell production
Interleukin-8 Attracts phagocytes to the inflammation site
Interleukin-12 Stimulates the differentiation of CD4-type T cellsTable 14-1. Important Interleukins