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 murine MIP-3β is a 9.2 kDa protein containing 83 amino acid residues, including the four highly conserved cysteine residues present in CC chemokines.