Extracts of pregnancy urine contain a mitogen for human peripheral blood lymphocytes (PBL).

A mitogen for human peripheral blood lymphocytes (PBL) has been found in commercial batches of crude human chorionic gonadotropin (hCG), which is obtained from pregnancy urine. These crude hCG preparations, as well as column eluates free of hCG and a previously noted immunosuppressive factor, are mitogen for normal human PBL cultured in fetal calf serum. This mitogen is designated pregnancy-associated growth factor (PAGF) because of its source. PAGF induces 3H-thymidine incorporation of mixed Ia+ non-T cells and T cells, probably confined to the helper subclass; proliferation is abolished by complement-mediated lysis using monoclonal antisera to Ia, mature T cells (OKT3), and the Th (OKT4) subset, but not by antisera to the Ts (OKT8) subset. The proliferating cell is a T cell because irradiation of these cells, but not the non-T cells, abolished PAGF mitogenicity. In addition, PAGF augments the autologus mixed lymphocyte reaction. Preliminary experiments indicate that its m.w., in the range of 18,000 to 22,000, is different from epidermal growth factor, the only previously described growth factor found in crude hCG preparations. In addition epidermal growth factor failed to stimulate PBL under similar conditions.