ENDOGLIN (CD-105) EXPRESSION IN HUMAN LYMPHOID ORGANS AND PLACENTA

Endoglin (CD105) is a cell surface antigen widely expressed on vascula r endothelium, syncytiotrophoblast, some tissue macrophages, certain c ulture cells (including early leukemic B-lineage) and some endothelial cell lines. Though its relation to the transforming growth factor-bet a (TGF-beta) receptor system is well documented, its function and deta iled pattern of expression still remain to be clarified. We examined t he differential tissue distribution of endoglin in human lymphoid orga ns and placenta with several anti-CD 105 monoclonal antibodies (mAbs) using an indirect immunoperoxidase technique, and performed semi-quant itative measurements using an image-analyzing system for comparison. A rterial, venous and capillary endothelia in these organs were reactive with anti-CD 105 mAbs at varying intensities. Interestingly, a distin ctly stronger staining pattern was observed in the high endothelial ve nules (HEVs) which may indicate a special role for endoglin in lymphoc yte trafficking. Syncytiotrophoblast expressed endoglin strongly on th eir apical cell membrane. Extravillous trophoblasts at certain locatio ns selectively expressed endoglin on their cell membranes, suggesting a special role for this surface antigen during trophoblast differentia tion.