Cytokine Receptor Genes encode cell surface Cytokine Receptors that bind paracrine or autocrine cytokine growth factors that stimulate humoral and cellular immune responses, as well as activation of phagocytic cells. Cytokines are secreted by inflammatory leukocytes (lymphokines), by monocytes or macrophages (monokines), and by various other cells. Interleukin lymphokines, targeted to cells of hematopoietic origin, are not secreted by leukocytes but affect the cellular responses of leukocytes. (NCI) [ ]