PHENOTYPIC AND FUNCTIONAL CELLULAR DIFFERENCES BETWEEN HUMAN CD3(-) DECIDUAL AND PERIPHERAL-BLOOD LEUKOCYTES

CD3(-) leukocyte clones derived from human decidualized endometrial ti ssue of first trimester pregnancy have been compared with CD3(-) PBL c lones. Most CD3(-) decidual granulated leukocyte (DGL) clones were CD1 6(-) CD56(+) whereas most CD3(-) PBL clones were CD16(+) CD56(+). CD3( -) DGL and PBL clones, whether CD16(+) or not, showed MHC-nonrestricte d NK cell activity. However, CD3(-) CD16(-) DGL clones had low cytotox ic activity against the NK-resistant cell line BSM, whereas CD3(-) CD1 6(+) DGL and CD3(-) PBL clones were strongly cytotoxic. Cytolytic acti vity has also been investigated in respect of target cell HLA-G expres sion, because this nonpolymorphic class I MHC molecule is expressed se lectively by invasive fetal cytotrophoblast. Class I HLA Ag loss cell mutants were killed efficiently by CD3(-) DGL clones. Expression of tr ansfected HLA-B8 increased their sensitivity to lysis by most CD3(-) D GL clones, whereas expression of transfected HLA-G commonly led to dec reased target cell killing. In addition, the effects of uncloned CD3(- ) DCL on the one-way MLR have been examined. These cells were very poo r responders and, unless cultured to induce expression of class II MHC molecules, were also very poor stimulators. When fresh CD3(-) DGLs we re added as third-party cells, either autologous or allogeneic to resp onder cells, [H-3]TdR incorporation was decreased in the MLR. Thus, CD 3(-) DGL clones express MHC-nonrestricted cytolytic activity, notably against HLA-negative cells, but expression of HLA-G offers protection to target cells. In addition, CD3(-) DGL may function to suppress allo geneic responses.