Heterodimeric proteins comprising two helical bundle cytokines are disclosed. One of the polypeptides comprises zsig81 and a second polypeptide which comprises either p19 (aka IL-12A) or p35 (aka IL-12A). The proteins may be produced as fusion proteins or expressed as a single chain. The heterdimeric protein comprising zsig81 and p19 is designated zcyto33f2 and the heterodimeric protein comprising zsig81 and p35 is designated zcyto35f2. Zcyto33f2 and zcyto35f2 proteins are associated with epithelial cell types, including lung and gut epithelium, and may play a role in physiological conditions such as inflammation.