Modern biotechnology has led to increase of interest in producing pharmaceutically important and commercially valuable proteins in plants. Plants can efficiently produce recombinant proteins in large quantities and plant-derived proteins are free of human disease factors. In general, plant systems can now be used to produce a variety of proteins, including antibodies, cytokines, blood substitutes, vaccines and others. Cytokines are small proteins secreted by animal cells. They mediate and regulate immunity, inflammation, and hematopoiesis. Due to their properties many cytokines have medical application, mostly in treatment of virus infections, cancer symptoms and diseases affecting the immune system. However clinical deployment of cytokines is limited by the high production costs. Recently, several research groups reported using various plant-based expression systems for the production of biologically active mammalian cytokines.