Induction of macrophage DNA synthesis in vitro by non-immunological inflammatory exudates: effect of irradiation and thymus or bone marrow cell reconstitution.

An acute inflammatory exudate possesses mitogenic activity in that it is able to induce both DNA synthesis and proliferation of macrophages in vitro. This activity is reduced however if the inflammatory exudate is obtained from irradiated rats (900 r). Transfer of bone marrow syngeneic cells into irradiated rats does not reverse this reduction. On the contrary the decrease of mitogenic activity is more pronounced. On the other hand transfer of thymic syngeneic cells not only restores the mitogenic activity of inflammatory exudate from irradiated rats but increases it. Transfer of both types of cell together fully restores the mitogenic activity of inflammatory exudate. It is postulated that the mitogenic activity of inflammatory exudate could be related to thymic cells and that T lymphocytes may be involved in non-specific inflammatory reactions.