Clinical applications of cytokines

Cytokines are multifunctional signaling peptide molecules which regulate a plethora of cellular activities in the immune system. Cytokines provide a means of communication between the immune system and its non-immune neighbours. Several clinical entities have been recognized as targets for clinical applications including interaction with malignant cell growth, host defence against infectious agents, negative regulation of autoagressive disorders and regulation of tissue and cell regeneration. Interferon-α (IFN-α) can effectively regulate maligant growth in hairy-cell leukaemia, the first example of a biological treatment modality which tames a malignant disease and normalizes life expectancy, although cure is not achieved. INF-α can also control myeloid hyperplasia in approximately two-thirds of the patients with chronic myelogenous leukaemia. In 30% of the patients, treatment is accompanied by partial or complete restoration of normal haematopoiesis. Such cytogenetic responses have not been observed with conventional chemotherapy. IFN-α is also effective in infectious viral hepatitis B, C and D. A long-term beneficial response is observed in 25-40% of the patients. Promising results have also been seen with IFN-γ and interleukin-2 for the treatment of chronic leishmania infection and lepromatous leprosy. Activation of monocytes or macrophages induces these cells to intracellularly destroy leishmania parasites. Growth factors have been identified which influence erythrocyte, granulocyte and macrophage production. Their clinical use has been studied in patients with bone marrow failure, chronic renal failure, acquired immunodeficiency syndrome and in patients with cancer undergoing chemotherapy or bone marrow transplantation. Additional work is needed to appreciate the immunomodulation effect of cytokines and their role in wound healing and tissue regulation.