Anti-IL-1 activity of peptide fragments of IL-1 family proteins.

A series of peptides containing retro-tuftsin- and tuftsin-like motifs from IL-1 proteins inhibits IL-1-induced IL-2 production and reduces the humoral immune response, thus supporting our hypothesis that tuftsin (Thr-Lys-Pro-Arg)-IL-1 competition depends on the presence of such motifs in IL-1 proteins. Some other peptides from regions of IL-1 responsible for receptor binding were also active, with peptide Ile-Thr-Gly-Ser-Glu (III) from IL-1alpha (residues 98-102), not only strongly affecting IL-2 production, but also suppressing the immune response; the analogue of hexapeptide Val-Thr-Lys-Phe-Tyr-Phe from the C-terminal part of IL-lra, with Lys replaced by Asp, was as efficient as Val-Thr-Lys-Phe-Tyr-Phe with respect to IL-1 competition.