IFN-alpha is a pharmaceutical drug composed of natural interferon alpha (IFN-α). Interferon alfa is used in a variety of treatments, including certain forms of leukemia, malignant melanoma, non-Hodgkin's lymphoma, hepatitis B, and hepatitis C. It is typically administered as an injection under the skin. Interferon alfa contains a mixture of several proteins, all with structural, serological, and functional properties typical for natural interferon alpha (IFN-α). IFN-α8 enhances the proliferation of human B cells, as well as being able to activate NK cells. The subtypes α10 and α2, along with α8, are the most efficient and powerful NK cell activators. Subtypes α21 and α2 enhance the expression of IFN-gamma-inducible protein-10 (IP-10) in dendritic cells. Activated dendritic cells initiate immune responses and induce the expression of IP-10, a chemokine which promotes a Th1 inflammatory response. IFN-α1 causes increased HLA-II expression, and can directly inhibit tumor cell growth in vitro. However, it is a poor activator of NK cells, has relatively little antiviral activity, does not induce B cell proliferation, and does not enhance HLA-I or tumor antigen expression. Despite its apparent inactivity, it is still used clinically in the treatment of metastatic renal cell carcinoma, with a reported lower toxicity than the recombinant IFN-α2. Overall, IFN-α has a general inflammatory action which skews the immune response towards a Th1 profile.