This invention identifies a monoclonal antibody (4G10) against the chemokine receptor CXCR4 and is a mouse IgG1 antibody. CXCR4 has been identified as a co-receptor mediating entry of HIV-1 into T cells. Subsequently, CXCR4 has been implicated in normal physiological functions, including activation of B cells and B cell progenitors and guiding their migration into the bone marrow (via its ligand SDF-1). CXCR4 also functions in T cell progenitor migration and neural progenitor stem cell activation. Since 4G10 is a monoclonal antibody raised against a synthetic peptide derived from the N- terminus of CXCR4 that may prove useful in the context of the above CXCR4 functions, 4G10 is an excellent reagent for detection and quantitation of CXCR4 by Western blot, immunoprecipitation, ELISA, and flow cytometry. It can also be used to purify CXCR4 by affinity chromatography. With these known characteristics, it would also function in immuno-histochemical assays as well. Thus, this invention is a good research tool and is available for licensing through a Biological Materials License Agreement as no patent application has been filed.