Differential modulation of the in vitro lymphocyte activation pathways by soluble and solubilized placental...

Soluble and detergent-solubilized placental extracts were studied for their modulatory effects upon the proliferation of lymphocytes stimulated by various activating agents. It was shown that soluble placental extract (SPE) exerted an inhibitory effect on the lymphoproliferation triggered by alloantigen or LPS but not by Con A or the combined action of PMA + calcium ionophore A 23187. This effect was also observed with SPE precipitated by 30% of ammonium sulfate (SPE30). On the other hand, a solubilized placental extract (SzPE) that was obtained by using octyl-beta-D-glucopyranoside inhibited the stimulation triggered by alloantigen, LPS, and Con A but did not affect the protein kinase C pathway. The modulatory effects were observed not only when SPE (or SPE30) and SzPE were added at the time of culture initiation but also at 24 h before or after the activating agents. Preincubation with SPE30 or SzPE immobilized on plastic surface, however, transduced an enhanced lymphoproliferative response to alloantigen and mitogen Con A but not to LPS. The above results suggest that placental substances exerted their modulatory effects by interfering mainly with the antigen or mitogen lymphoproliferation pathways.