The invention relates to canine immunoglobulin G (IgG) and canine interleukin-13 receptors (IL-13R) as well as fusion proteins containing canine IgG and/or canine IL-13R. In particular, the present invention discloses nucleic acid molecules encoding canine IgG, including species-specific regions of the heavy chain of canine IgG, and canine IL-13R alpha chain (IL-13R.alpha.) proteins, particularly canine interleuken receptor alpha 1 (IL-13R.alpha.1) and canine interleuken receptor alpha 2 (IL-13R.alpha.2) proteins. Also included are canine IgG and IL-13R.alpha. proteins, antibodies having selectivity for such proteins, inhibitors of such proteins and/or nucleic acid molecules, cells transformed with said nucleic acid molecules, assays employing such cells, nucleic acids molecules, proteins, antibodies and/or inhibitors, and therapeutic compositions comprising said nucleic acids molecules, proteins, antibodies and/or inhibitors. Also included are kits containing said molecules or chimera thereof, including their use to evaluate and regulate an immune response in an animal.