[5][6] TGF-β is a multifunctional set of peptides that controls proliferation, differentiation, and other functions in many cell types.

[7] TGF-β1 was first identified in human platelets as a protein with a molecular mass of 25 kilodaltons with a potential role in wound healing.

[14][15] Similarly, TGF-β1 can inhibit the secretion and activity of many other cytokines including interferon-γ, tumor necrosis factor-alpha (TNF-α), and various interleukins.

[11][17] The effects of TGF-β1 on macrophages and monocytes are predominantly suppressive; this cytokine can inhibit the proliferation of these cells and prevent their production of reactive oxygen (e.g. superoxide (O2−)) and nitrogen (e.g. nitric oxide (NO)) intermediates.

Furthermore, the expression of monocytic cytokines (such as interleukin(IL)-1α, IL-1β, and TNF-α),[15] and macrophage's phagocytic can be increased by the action of TGF-β1.