Individual specificity of blocking antibodies in molar and normal term placenta-bound IgG.

In view of the protective and enhancing effect of blocking antibodies (BA) on the survival of trophoblastic cells, the presence or absence of individually specific BA against paternal HLA antigens in trophoblast-bound immunoglobulin G (IgG) of molar as well as normal term placentas were investigated using a mixed lymphocyte culture reaction (MLR) blocking assay and complement-dependent lymphocytotoxicity test. It was found in this study that IgG could be eluted from molar trophoblasts. Further, it was strongly suggested that each molar and normal placental eluate-IgG had individual, specific cytotoxic and blocking effects against paternal lymphocytes and on MLR between spouses, respectively. In conclusion, in molar as well as in normal term placenta-bound IgG, BA that are heterogeneous and partly contain IgG specific to the paternal HLA antigens, including HLA-D/DR antigens, are likely to exist. BA may also have a protective and enhancing effect on the survival of trophoblastic cells by binding with these cells.