IFN-αs are proteins secreted by leukocyte. They are mainly involved in innate immune response against viral infection. The IFN-α family has 13 subtypes and 23 different variants. The individual proteins have molecular masses between 19-26 kDa and consist of proteins with lengths of 156-166 and 172 amino acids. All IFN-α subtypes possess a common conserved sequence region between amino acid positions 115-151 while the amino-terminal ends are variable. Many IFN-alpha subtypes differ in their sequences at only one or two positions. IFN-α2b differs from IFN-α2a by a single amino acid (the substitution of arginine for lysine at position 23), which makes up a potentially and clinically relevant difference, involving its immunogenicity.