Characterization of macrophages isolated from the maternal surface of human term placenta by a new method of urokinase treatment.

OBJECTIVES

This study was performed to establish a new method for isolating macrophages from the maternal surface of human term placenta by urokinase treatment and to characterize their immunological functions.

METHODS

Macrophages were recovered from the maternal surface of 6 human term placentas by urokinase treatment, adherence to plastic, and density gradient centrifugation using Percoll. The cells retrieved were tested for their surface markers by immunofluorescent staining. Their antigen-presenting capacity was examined by use of a mixed lymphocytes culture (MLC) test. In 2 cases, human leucocyte antigen (HLA) typing was performed.

RESULTS

An average of 4 x 10(6) macrophage-like cells were obtained per whole placenta. More than 90% of them were positive for CD14, HLA-DR, and DQ surface antigens. An MLC test revealed that they had antigen-presenting capacity. Of the 6 cases, 2 showed positive MLC test results with maternal peripheral-blood mononuclear cells. In 1 of the 2 cases, macrophages with paternal HLA phenotypes were identified.

CONCLUSION

The urokinase treatment is a new useful method for isolating macrophages from the maternal surface of human term placenta. Using this method, we obtained macrophages of paternal HLA phenotypes (fetal origin) that might have migrated to the maternal surface of human term placenta.