Mechanism of antitumor activity of bone marrow natural suppressor cells.

Co-culturing of P-815 tumor cell strain and intact mouse bone marrow cells nonadherent to plastic resulted in the appearance of soluble mediators with antitumor activity. Bone marrow cells start releasing these antiproliferative factors only after signal exchange with the target tumor cells. The cell-cell contact is an important factor for the induction of antitumor activity. Antitumor activity of bone marrow cells (similarly as immunosuppressive activity) is realized through suppressor factors; the appearance of these factors is induced by target tumor cells.