Objective      To establish a new method for the separation of sperms from the mixture of sperms and vaginal epithelial cells by applying a sperm-specific antibodiy against sperm-associated antigen 8 (SPAG8) and immunomagnetic bead sorting.       Methods      Cell mixture suspensions containing vaginal epithelial cells (10

4

/mL) and sperms at 3 different concentrations (10

3

/mL

10

4

/mL and 10

5

/mL separately) were prepared

10 samples for each suspens

ion. Biotin-labeled anti-SPAG8 monoclonal antibody and avidin-coated immunomagnetic beads were incubated with the mixed cell systems and the sperm cells were connected with the magnetic beads by the antibody-biotin-avidin system. The DNA of sperm cells was extracted and amplified by PCR. PCR products were separated and analyzed. Differential lysis was also conducted for the mixed samples to evaluate the effectiveness of immunomagnetic bead sorting.       Results      Sperm cells were separated by the immunomagnetic beads from the mixtures successfully. The antibody-biotin-avidin-magnetic bead system was stable for the separation. The sperm DNA was extracted and the DNA typing of 13 STR loci and 16 STR loci was acquired in 90% suspension samples when the sperm cell number was larger than 10

3

/mL and 10

4

/mL

respectively. DNA typing of 13 STR loci was acquired in 80% mixed stain samples when the sperm cells number was larger than 10

4

/mL. The detection rate of immunomagnetic bead sorting for mixed samples was higher than that of the differential lysis method.       Conclusion      Immunomagnetic bead sorting is a simple and quick method for the separation of sperms from sperm and vaginal epithelial cell mixture

and can be utilized as a supplementary means in forensic practice.