MIP-3β is a CC chemokine that is expressed in the thymus, lymph nodes and in activated bone marrow stromal cells and signals through the CCR7 receptor. MIP-3β is a chemoattractant for T and B lymphocytes and myeloid progenitor cells. Human MIP-3β is active on murine cells. Recombinant human MIP-3β is an 8.8 kDa protein containing 77 amino acid residues, including the four highly conserved cysteine residues present in CC chemokines.