We have isolated a novel human C-C chemokine, MIP-1 delta from a human fetal spleen cDNA library. The human MIP-1 delta cDNA has an unusually long 400-bp 5-prime untranslated region and a predicted 113-amino acid protein of 10 kDa. The coding sequence contains a signal peptide of 21 amino acids, indicating that the mature protein has 92 amino acids (8 kDa). Recombinant human MIP-1 delta produced by transfected human embryonic kidney 293 cells produced an 8-kDa protein, which confirmed the presence of a signal peptide. Compared with other human C-C chemokines, human MIP-1 delta shows the highest homology with human HCC-1, CK beta-8, murine C10, and CCF18 (MIP-1 gamma). The human MIP-1 delta gene is localized on chromosome 17 where most of the C-C chemokine superfamily is located. Human MIP-1 delta is expressed in T and B lymphocytes, NK cells, monocytes, and monocyte-derived dendritic cells, but not in bone marrow-derived dendritic cells. Its expression can be induced by other proinflammatory cytokines in monocytes and dendritic cells. Human MIP-1 delta is chemotactic for T cells and monocytes, but not for neutrophils, eosinophils, or B cells. Human MIP-1 delta induced calcium flux in human CCR1-transfected cells.