IL-28A (also named interferon-A2, IFN-A2), IL-28B (IFN-A3) and IL-29 (IFN-A1) are type III interferons that are class II cytokine receptor ligands.1-4 They are distantly related to members of the IL-10 family and type I IFN family.1-4 Mouse IL-28A cDNA encodes a 193 amino acid (aa) protein with a 19 aa signal peptide and a 174 aa mature protein that lacks N-glycosylation sites. Mature mouse IL-28A shares 81% and 66% aa sequence identity with rat and human IL-28A, respectively, and functions across species.5 Mouse IL-28A and IL-28B share 97% aa identity, the mouse lacks a functional IL-29 gene.4 Type III interferons are widely expressed, but are mainly produced by antigen presenting cells in response to viruses and double-stranded RNA that interact with Toll-like receptors or RIG-1 family helicases.2-6 They signal through a widely expressed receptor that is a heterodimer of the IL-10 receptor b (IL-10 Rb) and IL-28 receptor a (IL-28 Ra, also called IFN-lambda R1).2, 3, 7, 9 Interaction of either type I or type III IFNs with their receptors activates similar pathways, including JAK tyrosine kinase activation, STAT phosphorylation and formation of the IFN-stimulated regulatory factor 3 (ISGF-3) transcription factor complex.1-3 Both type I and III IFNs induce antiviral activity and upregulate MHC class I antigen expression.2-6 Cell lines responsive to type III IFNs are also responsive to type I IFNs, but in general, higher concentrations of type III IFNs are needed for similar in vitro responses.8 In vivo, however, type III IFNs enhance levels of IFN-y in serum, suggesting that the robust antiviral activity of type III IFNs may stem in part from activation of the immune system.5, 7 Anti-proliferative and antitumor activity in vivo has also been shown for type III IFNs.9-11 A DNA sequence encoding mouse IL-28A (Met 1-Val 193, Accession Q4VK74) was fused with a six-histidine tag at the C-terminus. The protein was expressed in a mouse myeloma cell line, NS0. Calculated molecular mass of 20. kD. As a result of glycosylation, the recombinant mouse IL-28A migrates as an ~ 25-30kD protein in SDS-PAGE under reducing conditions. Activity: Measured in an anti-viral assay using human HepG2 cells infected with encephalomyocarditis virus. Storage and Stability: Lyophilized and reconstituted products are stable for 6 months after receipt at -20C. Reconstitute with sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
