The invention provides compositions and methods for modulating the immunostimulatory properties and/or anti-inflammatory properties of IL-10. The present invention provides scIL-10 polypeptides of Formula 1. The polypeptides of the invention are optionally linked to a fusion partner. The polypeptides of Formula 1 are referred to herein as “scIL-10” polypeptides and comprise an amino acid sequence arrangement from N-terminus to C-terminus in accordance with Formula 1: (first monomer subunit)-LINKER-(second monomer subunit)   Formula 1 wherein the first monomer subunit, the second monomer subunit or both the first and second monomer subunits may be independently selected from: an unsubstituted IL-10 monomer subunit; or a substituted IL-10 monomer subunit comprising at least one amino acid substitution; and wherein LINKER is any amino acid linker of at least 1-100 amino acids in length.