Cytokines

Cytokines are low molecular weight extracellular signalling proteins secreted by specific cells. Their effect is generally paracrine: altering the behaviour of cells in their close proximity. However, they may also act in an endocrine or autocrine manner.

They are secreted by a vast range of cells; those secreted by lymphocytes are termed lymphokines; cytokines secreted by monocytes are termed monokines.

Cytokines have an ever-increasing array of functions: most are centred around immune and inflammatory responses. Their is frequent overlap and interaction of effects.

Examples include:

• tumour necrosis factor, cachectin
• interleukins 1 to 8
• transforming growth factor beta
• platelet-derived growth factor
• interferons
• colony stimulating factors

Therapeutic use of cytokines is becoming more common; examples include:

• GM-CSF in restoring normal neutrophil counts after bone marrow transplants or chemotherapy
• interferons in a range of malignancies and chronic granulomatous disease