Animal-free (AF) cytokines and growth factors are available that are produced in plants and are thus free of animal components, serum traces, endotoxins, and antibiotics. They are also free of human, animal, or bacterial infectious agents as well as other endogenous mammalian agents that might cause unwanted cell responses. The AF cytokines and growth factors show low proteolytic, pyrogenic, and inflammatory activity. Moreover, they retain eukaryotic folding and glycosylation, which can result in increased stability and biological activity.