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 (FIL1delta, FIL1epsilon, FIL1zeta, and FIL1eta, with FIL1 standing for "Family of IL-1"). The novel genes demonstrate significant sequence similarity to IL-1alpha, IL-1beta, 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-1beta and IL-1ra. The novel genes form a cluster with the IL-1s on the long arm of human chromosome 2.