To search for genes which encode human interferon receptor molecules, we applied the technique of exon trapping to human chromosome 21 yeast artificial chromosomes (YACs). A full length cDNA encoding human CRF2-4 was identified which is shown here to be widely expressed in human tissues. The human CRF2-4 cDNA was used as a probe to screen a mouse macrophage cDNA library. A mouse CRF2-4 cDNA was isolated which encodes a 349-amino-acid (aa) polypeptide that is 69% identical at the aa level with its human counterpart. Mouse CRF2-4 is predicted to be another member of the interferon receptor-class II cytokine receptor family.