the present invention relates to a process to isolate genetic material containing the nucleotide sequence coding for interferon in human fibroblastic cells which comprises cultivating cells producing interferon when exposed to an inducer of interferon , exposing same to such inducer , extracting messenger rna from said induced cells , purifying the interferon messenger rna , transcribing the messenger rna into dna and cloning the dna in a suitable vector . preferred cells are human diploid foreskin cells . the invention further relates to a process for engineering a bacterial strain to produce interferon polypeptide which comprises introducing a cloned interferon dna into a suitable vector - carrier . a preferred vector - carrier is e . coli . the invention also relates to the mrna of human interferon in highly purified form , to the mrna of human interferon in β1 highly purified form , to the mrna of human interferon in β2 highly purified form , to the dna coding for a polypeptide having interferon activity , insertable in a vector , such as plasmid pbr322 , and also to human interferon β1 in highly purified form , and human interferon β2 in highly purified form .