ADHESION OF LYMPHOCYTIC CELLS TO HUMAN TROPHOBLAST CELLS-INVITRO

The adherence of lymphocytic MOLT-4/clone 8 cells and normal human per ipheral blood mononuclear cells (PBMCs) to primary cultures of term hu man syncytiotrophoblast has been characterized. Adherence was measured using a fluorescence-based assay in which leukocytic cells were label led with calcein-AM. Adherence of MOLT cells to syncytiotrophoblast in creased in a time-dependent fashion up to about 4 h after which adhesi on decreased. Adhesion was detectable at 4-degrees-C but was greatly r educed compared to that seen at 37-degrees-C. Binding increased linear ly as the ratio of MOLT cells to trophoblast was increased. Scanning a nd transmission electron microscopy of MOLT cell-trophoblast coculture s revealed lymphocytes adherent to the free microvillous surface of th e syncytiotrophoblast masses. MOLT cells also adhered to cytotrophobla st but the extent of binding was lower than to syncytiotrophoblast. No rmal human peripheral blood mononuclear cells adhered to syncytiotroph oblast. Preincubation of trophoblast cells with trypsin in the presenc e of calcium had no effect on subsequent adhesion of MOLT cells. Howev er, preincubation of trophoblast cells with trypsin in the absence of divalent cations reduced subsequent adhesion. Adhesion of MOLT cells t o syncytiotrophoblast was dependent on magnesium and calcium. These re sults show for the first time that lymphocytic cells adhere to isolate d human syncytiotrophoblast and raise the possibility that this may be an important phenomenon in vivo.