EXPRESSION OF INTERCELLULAR-ADHESION MOLECULE-1 (ICAM-1) ON CULTURED HUMAN ENDOMETRIAL STROMAL CELLS AND ITS ROLE IN THE INTERACTION WITH NATURAL KILLERS

PROBLEM: Recent evidence emphasizes the role of natural killer cells ( NKs) as potential effecters of peritoneal immune surveillance directed against the outgrowth of endometrial cells, refluxed with menstrual d ebris, in ectopic sites. This NK-mediated cytotoxicity toward autologo us endometrial antigens seems to be significantly decreased in endomet riosis patients. METHOD: We set up experiments to clarify which molecu les are involved in NK-endometrial cell interaction. In particular, we evaluated the surface expression and functional activity of intercell ular adhesion molecule-1 (ICAM-1), a cell surface glycoprotein that ha s been identified as one of the ligands for lymphocyte function-associ ated antigen-1 (LFA-1), present on almost all leucocyte cell types. Im munofluorescence flow cytometry was used to assess ICAM-1 expression o n resting and IL 1 beta-activated endometrial stromal cells in culture . Dermal fibroblasts were used as control cells. Cytotoxicity and bind ing assays by Cr-51 release in presence and absence of a specific mono clonal antibody (mAb) against ICAM-1 were then performed in order to d etermine the effect of this molecule on NK-mediated cytotoxic and bind ing activity toward endometrial stromal cells. RESULTS: The results of this study indicated that ICAM-1 expression on endometrial stromal ce lls seems to be constitutively higher than on dermal fibroblasts and c an be up-regulated upon exposure to IL 1 beta. Furthermore, a mAb agai nst ICAM-1 strongly inhibits the binding but not the cytotoxicity of N Ks toward endometrial cells. No difference in the expression of this m olecule was observed throughout the cycle. CONCLUSIONS: The presence o f ICAM-1 on human endometrium might relate to the action of the immuno competent cells in human specific reproductive events.