The present invention relates to canine and feline proteins. In particular, the present invention discloses feline interleukin-18, feline caspase-1, feline interleukin-12 single chain and canine interleukin-12 single chain proteins. The present invention also includes feline interleukin-18, feline caspase-1, feline interleukin-12 single chain and canine interleukin-12 single chain nucleic acid molecules encoding such proteins, antibodies raised against such proteins and/or inhibitors of such proteins or nucleic acid molecules. The present invention also includes therapeutic compositions comprising such nucleic acid molecules, proteins, antibodies and/or inhibitors, as well as their use to evaluate and regulate an immune response in an animal.