Placenta-specific growth factor production by splenic cells during pregnancy.

Within the last 5 years strong evidence has correlated the successful outcome of pregnancy with various cytokines, which interfere with sperm mobility, fertilization, implantation, trophoblast outgrowth, as well as maternal immunoregulation. The newly arising antigens on the extra-embryonic membranes initiate many mechanisms protective to the fetus and not harmful to the mother, one of which is novel protein synthesis. These events are apparent in many different sites of the maternal organism including the decidual cap, uterine walls, draining lymph nodes, spleen etc. Working on a murine model, in the present study we concentrated on the growth factor production by spleen cells isolated from syngeneically pregnant mice on the 11th day of gestation. Focusing our interest on the proteins that have a stimulatory effect on placental cells, we fractionated 24 h spleen cell supernatants through a G-25 Sephadex followed by a Heparin-Sepharose affinity column and isolated pregnancy specific growth factors capable of inducing placental cell proliferation. In this study we focused on three growth factors, interleukin-3 (IL-3), granulocyte-macrophage colony stimulating factor (GM-CSF) and colony stimulating factor-1 (CSF-1), which have been previously shown to play an important role in placental growth. CSF-1 and IL-3 were detected in single Heparin-Sepharose fractions, whereas GM-CSF was found dispersed in essentially three fractions. Although we were able to detect these three growth factors in specific affinity column fractions, other proteins, which we have not yet characterized, showed significant biologic activity. Such biologic activity could not be detected from non-pregnant spleen cell supernatants similarly fractionated.(ABSTRACT TRUNCATED AT 250 WORDS)