Response of peripheral blood leucocytes to mitogenic factor(s) in porcine seminal plasma

Porcine seminal plasma (PSP) contains a potent mitogenic substance capable of causing proliferation and extensive agglutination in cultured porcine peripheral blood leucocytes (PBL). In order to determine the specific leucocyte cell population affected by this mitogen, lymphocyte, monocyte and polymorphonuclear (PMN)-enriched cell fractions were separated from PBL and treated with increasing concentrations of PSP (1-8%, v/v). For monocyte cell populations enriched through elutriation and adherence to plastic, cell proliferation in response to PSP treatment was consistently higher than PSP-treated unfractionated PBL. Monocyte-depleted PBL and lymphocyte populations enriched through elutriation demonstrated a decrease in proliferation compared to PSP-treated unfractionated PBL. PMN populations separated from PBL by discontinuous Percoll gradient centrifugation were unresponsive to PSP. Agglutination was observed for the unfractionated PBL and each enriched cell population. These results demonstrate that PSP contains a potent mitogen which induces proliferation in monocyte-enriched cell populations and may reflect the potential of PSP to act as an immune regulator in the uterine environment during early embryo development and implantation.