Detection of early pregnancy factor (EPF) in pregnant and nonpregnant subjects with the rosette inhibition test.

We tested for early pregnancy factor (EPF) using a rosette inhibition test with polyclonal anti-lymphocyte serum from the horse and two monoclonal antibodies specific for the E-receptor of T-lymphocytes. When lymphocytes were preincubated with early human pregnancy sera, rosette inhibition titres were four or more dilutions higher (P less than 0.01) than when lymphocytes were preincubated with nonpregnant sera.