All of the following are not false about cytokines, except:

Cytokines Definition Small, water-soluble, signaling proteins & glycoproteins secreted by hematopoietic & non-hematopoietic cells Also called Interleukins, because they mediate communication between leukocytes Functions Mediate specific cellular interactions and functions of leukocytes Site of action May act on: Cells that produce them (autocrine action) or On neighboring cells (paracrine) and rarely At a distance (endocrine)