Cytokines and Chemokines

Cytokines
These are small cell-signalling protein molecules that are secreted by a variety of cells and are a type of signalling molecule that is widely used in intercellular communication.

Cytokines are either proteins, peptides, or glycoproteins. The term "cytokine" refers to a broad and diverse family of regulators produced throughout the body by embryologically diverse cells. The word has also been applied to immunomodulating agents like interleukins and interferons.

Biochemists disagree over which molecules are cytokines and which are hormones. Anatomic and structural distinctions between the two are diminishing as we understand more about each. Classic protein hormones circulate in nanomolar (10-9) concentrations that rarely differ by more than one order of magnitude. Some cytokines, on the other hand, circulate in picomolar (10-12) concentrations that can rise up to 1,000-fold with trauma or infection.

Cytokines may be differentiated from hormones by their widespread dispersion of cellular sources. Endo/epithelial cells and resident macrophages (many of which are located at the interface with the external environment) are powerful makers of IL-1, IL-6, and TNF-alpha. Classical hormones, like as insulin, are produced by distinct glands (e.g., the pancreas).

Chemokines
This is a group of small cytokines (proteins secreted by cells). Chemotactic cytokines get their name from their ability to induce directed chemotaxis in nearby responsive cells.

Cytokines can take the form of proteins, peptides, or glycoproteins. The term "cytokine" refers to a broad and diverse family of regulators produced by embryologically diverse cells throughout the body. Immunomodulatory agents such as interleukins and interferons have also been given this name.

There is disagreement among biochemists over which molecules are cytokines and which are hormones. The anatomic and structural differences between the two are merging as we learn more about each. Traditional protein hormones circulate at nanomolar (10-9) quantities that rarely change by more than one order of magnitude. Some cytokines, on the other hand, circulate in picomolar (10-12) concentrations that can rise 1,000-fold in response to trauma or infection.

Cytokines can be differentiated from hormones by their widespread reach of cellular sources. Endo/epithelial cells and resident macrophages (many of which are located at the interface with the external environment) are potent pro-inflammatory cytokines. Traditional hormones, like as insulin, are produced by distinct glands (e.g., the pancreas).

Key terms:

• Cytokine: Any of various small regulatory proteins that regulate the cells of the immune system.
• Chemokine: Any of various cytokines, produced during inflammation, that organize the leukocytes.
• Chemotaxis: The movement of a cell or an organism in response to a chemical stimulant.

Key points:

• Cytokines and chemokines are important in the production and growth of lymphocytes, and in regulating responses to infection or injury, such as inflammation and wound healing.
• Cytokines are the general category of messenger molecules, while chemokines are a special type of cytokine that directs the migration of white blood cells to infected or damaged tissues.
• A cytokine and a chemokine both use chemical signals to induce changes in other cells, but the latter are specialized to cause cell movement.