Enclosed is an antagonist, which includes a peptide chain represented by an amino acid sequence. The amino acid sequence has a short sequence, C-X1X2X3X4X5-N, which is situated before and neighbored to the third cysteine (Cys, C) of the N-terminus, wherein X1 is an amino acid with aromatic ring, hydrophobic property or long chain, and X2, X3, X4 and X5 are glutamine (G), serine (S), alanine (A) and proline (P) respectively. In one embodiment, X1 is phenylalanine (F). The present antagonists can be used to inhibit or treat with the diseases caused by the activated cells expressing CXCR1 and/or CXCR2 receptor, for example, the acute or chronic inflammatory reaction induced with polymorphonuclear neutrophils (PMNs) expressing CXCR1 and/or CXCR2 receptor, and angiogenesis accompanied by tumor growth inhibition.
