Immunosuppression by human placenta lactogen (HPL) and the pregnancy-specific beta 1-glycoprotein (SP-1). Inhibition of mitogen-induced lymphocyte transformation.

The in vitro effect of human placental lactogen (HPL) and the gravidity-specific beta1-Glycoprotein (SP-1) on the lymphocyte transformation was investigated in 20 healthy women. It was shown that simultaneous incubation of the lymphocytes with HPL or SP-1 together with PHA has no influence on the incorporation rate of H3-Thymidine. When the fetal calf serum (FCS) in the lymphocyte cultures was substituted by a 3% human albumin-solution, there was a reduction of the incorporation rate of the radioactive nucleic acid precursors to 20%, as compared to the controls with FCS. After addition of HPL and SP-1 to the cultures there was a further dosis dependent decrease of the incorporation rate. When lymphocytes were preincubated with the proteins for 24 h, there was a marked reduction of the blastogenesis after additon of PHA, HPL and SP-1 under these conditions had a immunosuppressive effect on the lymphocyte transformation.