The present invention relates to polynucleotide and polypeptide molecules for zcyto20, zcyto21, zcyto22, zycto24, and zcyto25 proteins which are most closely related to interferon-.alpha. at the amino acid sequence level. The receptor for this protein family is a class II cytokine receptor. The present invention includes methods of reducing viral infections and increasing monocyte counts. The present invention also includes antibodies to the zcyto20 polypeptides, and methods of producing the polynucleotides and polypeptides.