Four New Members Expand the Interleukin-1 Superfamily*

We report here the cloning and characterization of four new members of the interleukin-1 (IL-1) family (FIL1δ, FIL1ε, FIL1ζ, and FIL1η, with FIL1 standing for “Family of IL-1”). The novel genes demonstrate significant sequence similarity to IL-1α, IL-1β, IL-1ra, and IL-18, and in addition maintain a conserved exon-intron arrangement that is shared with the previously known members of the family. Protein structure modeling also suggests that the FIL1 genes are related to IL-1β and IL-1ra. The novel genes form a cluster with the IL-1s on the long arm of human chromosome 2.