A MONOCLONAL-ANTIBODY, HCL-2, RAISED AGAINST HUMAN LUTEAL CELLS REACTS WITH APOLIPOPROTEIN-B AND DETECTS THE UPTAKE OF LOW-DENSITY-LIPOPROTEIN BY LUTEINIZING GRANULOSA-CELLS

A monoclonal antibody, HCL-2, was raised by immunizing mice against hu man luteal cells. HCL-2 reacted with luteal cells and villous trophobl asts, The sodium dodecyl sulphate-polyacrylamide gel electrophoresis p rofile of immunopurified antigens from corpus luteum, chorionic villi, and placenta showed the same main protein band, the molecular mass of which is >200 kDa. The sequence of a portion of the N-terminal region of the antigenic protein purified from placenta was identical to that of apolipoprotein-B, The antigen purified from human serum and low de nsity lipoprotein (LDL) using HCL-2 showed the same protein band as th at from corpus luteum, Furthermore, the amino acid sequence (20 amino acids) of the protein purified from serum was also identical to that o f apolipoprotein-B. Thus, we concluded that HCL-2 antigen is apolipopr otein-B, Human luteinizing granulosa cells isolated from the patients undergoing in-vitro fertilization treatment were cultured in the mediu m containing lipoprotein-deficient serum with or without supplementati on of LDL, Using HCL-2, apolipoprotein-B was immunocytochemically dete cted on granulosa cells only in the presence of LDL, These findings sh owed that the uptake of LDL by granulosa cells was detected by immunoc ytochemical staining of apolipoprotein-B, indicating that HCL-2 is use ful for analysing dynamic utilization of LDL by ovarian cells.