Cytokines are small secreted proteins released by cells have a selected effect on the interactions and communications between cells. Cytokine may be a general name; other names include lymphokine (cytokines made by lymphocytes), monokine (cytokines made by monocytes), chemokine (cytokines with chemotactic activities), and interleukin (cytokines made by one leukocyte and acting on other leukocytes).