The detection of early pregnancy factor (EPF) is a controversial subject. The findings of independent groups attempting to confirm the phenomenon of EPF have been quite variable. The present article gives details of an improved rosette inhibition assay using a monoclonal antibody (anti-human-Lyt-3), instead of an anti-lymphocyte serum (ALS), in order to increase reproducibility. Results are calculated for the first time in terms of absolute monoclonal anti-Lyt-3 concentrations. It is suggested that results be expressed as the Rosette Inhibition Antibody Concentration (RIAC) or the more accurate extrapolated 25% Rosette Inhibition Antibody Concentration (25% RIAC), in place of the previously used Rosette Inhibition Titer (RIT), when monoclonal antibodies are used. Following a 1.5 h incubation period the mean 25% RIAC for pregnant serum was 15.9 +/- 4.0 ng/ml and for control serum 48.0 +/- 12.7 ng anti-Lyt-3/ml. The improved method described should enable different groups to establish the test and compare results.

Sununary: Dipeptidyl peptidase IV (CD 26 leukocyte differentiation antigen) is an enzymic surface marker of a human T lymphocyte subpopulation which has been shown to be associated with their capacity to produce large amounts of interleukin 2 and proliferate strongly in response to mitogenic Stimulation. The peptidase activity on the surface of purified human peripheral mononuclear cells was determined spectrophotometrically with the Substrate glycyl-L-proline-4-nitranilide. The peripheral mononuclear cells of pregnant women exhibited depressed mean dipeptidyl peptidase IV activity when compared with the activity of peripheral mononuclear cells from non-pregnant or male individuals. The gestational age (7 to 20 weeks) of the pregnant collective had no effects on peptidase levels. Women taking oral contraceptives had a slightly lower mean activity than the non-pregnant group not using contraceptives. Thus, reduced dipeptidyl peptidase IV activity of peripheral mononuclear cells might reflect impairement of cellülar immunity during pregnancy.

Human pregnancy can be recognized as early as 48 hours after conception using the rosette inhibition test (RIT) to detect early pregnancy factor (EPF). A modification of the test as originally described by Morton et al. is demonstrated using a monoclonal pan T-cell antibody. Studies were performed to investigate the relationship between EPF levels during normal first trimester intact pregnancies and therapeutic abortions. The change in EPF levels is compared with those of hormones after interrupted pregnancy.

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