Biological activity of the suppressor cells inducer factor secreted by theJeg-3 choriocarcinoma cell line

PROBLEM: We wanted to further study the mechanisms of immune suppression an d suppression inducing capacities by choriocarcinoma products, e.g. both cr ude human choriocarcinoma supernatant (HCS) and especially an active fracti on obtained by high performance liquid chromatography (HPLC) from the cultu re supernatant of the Jeg-3 human choriocarcinoma cell line. since it appea red by weight and charge criteria to be a different molecular species than the low molecular weight fraction previously isolated from mouse and human term placenta. It was important to know whether the purified material was a ctive in giro as it was in vitro. Therefore. we tested the effects of HCS i n giro in three systems: prevention of fetal demise in the CBA/J x DBA/2 ab ortion prone murine mating combination, where the effects of the HPLC purif ied fraction were also monitored as well as by a cell transfer system, wher e the suppression is revealed by a local GVH/HVG assay, and finally enhance ment the survival of a mildly immunogenic tumor allograft. METHODS: An active fraction was isolated from HCS by ion exchange HPLC. Fem ale CBA/J were mated with DBA/2 and the influence of 3 intraperitoneal inje ctions of both crude HCS and the active fraction was evaluated by monitorin g the percentage of fetal resorptions. Simultaneously, on the day when reso rptions were counted. maternal splenocytes from these females were harveste d and were injected by the subcutaneous way in C3H/HEJ hind feet. The lymph node reactivity (HVG+ GVH) was assessed by [H-3]thymidine intake by cells harvested from the draining popliteal lymph nodes. For assessment of influe nce of HCS on allograft rejection, BALB/b (H-2(b)) mice received a subcutan eous injection of allogeneic P815 tumor cells (H-2'(d)). The influence of H CS injections on tumor survival was analyzed by regular measurements of the mean tumor diameter. RESULTS: Intraperitoneal injection of HCS reduced fetal resorptions from 24 .7 to 13%. Injection of the in vitro active fraction induced the same rate of reduction. The mean intensity of HvG/GvH reaction was 13400 cpm per lymp h node when splenocytes from the control group were injected compared to 29 00 cpm when splenocytes from treated mice were used. P815 tumor allografts were completely rejected in all cases after 21 days. Weekly subcutaneous in jections of HCS prolonged tumor survival in all cases up to at least 30 day s. CONCLUSION: The fraction isolated from HCS increased very efficiently the s urvival of allografts as well as those of allogeneic fetuses in a resorptio n prone murine mating. The choriocarcinoma cell line might prove to be a us eful source of immunosuppressive materials, which could otherwise be import ant for the fetal-maternal tolerance and a successful pregnancy.