Cytokines are proteins, peptides or glycoproteins secreted by lymphocytes and monocytes that regulate immune responses, haematopoiesis and lymphocyte development. Cytokines include interleukins, chemokines and other signalling molecules. Each cytokine acts through its own receptor on target cells, and these receptors include members of the immunoglobulin (Ig) superfamily and tumour necrosis factor (TNF).

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Growth Factors are naturally occurring substance capable of stimulating cellular growth, proliferation, healing, and cellular differentiation. Usually it is a protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes.

Growth factors typically act as signaling molecules between cells. They often promote cell differentiation and maturation, which varies between growth factors. For example, epidermal growth factor (EGF) enhances osteogenic differentiation, while fibroblast growth factors and vascular endothelial growth factors stimulate blood vessel differentiation (angiogenesis).