Produced by macrophages, IFN-alpha have antiviral activities. Interferon stimulates the production of two enzymes: a protein kinase and an oligoadenylate synthetase. Two forms exist; alpha-1a (shown here) and alpha-1b (PubMed:11032395). Interferons alpha-1 and alpha-13 have identical protein sequences. Belongs to the alpha/beta interferon family.