Objective To investigate the distribution and the role of macrophage inflammatory protein-la (MIP- 1α) in human endometrium during cyclic changes.

Setting Department of Obstetrics and Gynaecology, Shiga University of Medical Science and University Hospital.

Materials Eighteen endometrial tissue specimens surgically resected or biopsied from women with normal menstrual cycles, without hormonal disorder or endometrial diseases.

Methods By immunohistochemistry, using monoclonalantibodies (lambda delta 78 for MIP-la and CR3/43 for human leukocyte antigen-DR (HLA-DR)).

Results Immunoreactivity for anti-MIP-lα was distributed diffusely in epithelial cells throughout the proliferative and secretory phases but was absent during menstruation due to degenerative or necrotic changes. HLA-DR was expressed in epithelial cells only in the late secretory phase and was not expressed in stromal cells.

Conclusion Immunohistochemicalanalysis showed the presence of MIP- lα in the endometrial epithelium. Expression of HLA-DR in epithelial cells was observed only in the late secretory phase, suggesting that accumulation of MIP-lα in epithelium occurred by self production and not via a receptor mediated pathway. MIP-lα was released from the denuded epithelium during menstruation and appeared to contribute to the accumulation of monocytes/macrophages into the endometrial cavity. MIP-la has a number of biological effects other than monocytic chemotaxis, and some of these effects may be exerted in the endometrial tissue.