Interleukin-6 (IL-6) is a cytokine with a wide variety of biological functions. IL-6 is a potent inducer of the acute phase response, and plays an essential role in the final differentiation of B-cells into Ig-secreting cells involved in lymphocyte and monocyte differentiation. IL-6 also induces myeloma and plasmacytoma growth and induces nerve cell differentiation. IL-6 is discharged into the bloodstream after muscle contraction and acts to increase the breakdown of fats and to improve insulin resistance.