A description of the basic system of components in pregnant mice sera responsible for 'early pregnancy factor' activity.

Abstract

The supernatant and pellet retentate fractions obtained from sera from pregnant mice by ammonium sulfate fractionation and extensive dialysis cannot alone induce increased rosette inhibition titres in the rosette inhibition assay. In combination, however, the mixtures can induce increased rosette inhibition titres mimicking the activity of pregnancy sera previously ascribed to the early pregnancy factor. The studies described herein demonstrated that the supernatant retentate fractions derived from sera of pregnant mice were functionally equivalent to a platelet-activating factor (PAF) or a serum stimulus because they stimulated the spleen cells used in the assay to produce active moieties and cooperated with pure thioredoxin in allowing for expression of activity. Conversely, the pellet retentate fractions obtained from sera of pregnant mice were shown to be functionally equivalent to thioredoxin in that they cooperated with a PAF stimulus to allow for the expression of increased rosette inhibition titres. The supernatant retentate fractions obtained from sera from male mice were found to be functionally equivalent to the corresponding supernatant retentate fractions obtained from sera from pregnant mice in stimulating the production of active moieties and in cooperating with thioredoxin or the pellet fractions derived from sera from pregnant mice in allowing for increased rosette inhibition titres. The pellet retentate fractions obtained from male mouse sera, however, were not functionally equivalent to either thioredoxin or the corresponding pellet retentate fractions obtained from pregnancy sera. Consideration of these data led to a basic description of the system of components in pregnancy sera which is responsible for the expression of early pregnancy factor activity.