A monoclonal antibody,EC-1, derived from a syngeneically multiparous mouse alters in vitro fertilization and development

A monoclonal antibody designated ‘EC-1’ was derived from a fusion of myeloma cells with lymphoid tissue from a syngeneically multiparous, but otherwise unimmunized, mouse and was selected by screening for reactivity with teratocarcinoma cells. The IgM antibody binds to the cell surface of ova, zygotes, and 2-cell embryos. Binding is not detected on the 4- or 8-cell embryo but reappears on the morula and blastocyst. EC-1 binds to the trophoblast but not to the inner cell mass of in vitro attached blastocysts and the ectoplacental cone of the peri-implantation embryo. In adult tissues, EC-1 binds to the follicular cells of the ovary, the lining epithelium of the pregnant uterus, the interstitial region of the testes and to epidydimal but not testicular sperm. In nongonadal tissues EC-1 binds to an epitope located in some, but not all, regions of connectives tissues associated with basement membrane. The antigen detected by EC-1, as expressed on teratocarcinoma-derived cell line PYS-2, is a large glycoprotein which is sensitive to reduction. EC-1 inhibits in vitro fertilization and partially inhibits in vitro development of in vitro fertilized ova. The possible implications of EC-1 binding and activity are discussed.