Interleukin-1 family member 8 is a member of the interleukin 1 cytokine family. Protein structure modeling indicated that this cytokine may contain a 12-stranded beta-trefoil structure that is conserved between IL1A (IL-A alpha) and IL1B (IL-1 beta). This gene and eight other interleukin 1 family genes form a cytokine gene cluster on chromosome 2. Two alternatively spliced transcript variants encoding distinct isoforms have been reported.The deduced 157-amino acid protein, like FIL1-delta, contains neither a signal peptide nor a prodomain. It shares 46% sequence identity with FIL1-epsilon. PCR analyses detected expression in tonsil, bone marrow, heart, placenta, lung, testis, and colon but not in other tissues or in any hematopoietic cell lines. Modeling indicated that FIL1-eta has a conserved 12-stranded beta-trefoil structure.