Some characteristics of the participation of lymphocytes in non-immune inflammation.

Leucopenic rats were injected i.v. with either allogeneic or syngeneic lymphocyte suspensions and their capacity to respond to carrageenin tested at various intervals after the injection of the cells. The carrageenin-induced inflammatory response, which is characteristically attenuated in leucopenic animals, was partially but none the less definitely restored when allogeneic cells were transfused 20 min before the irritant, and less so when they were given 1 or 2 h before. Syngeneic cells were effective in restoring this response up to 2 h after injection. Only a small fraction of the exogenous cells, either allogeneic or syngeneic, remained in the blood, and this for short intervals. One hour after administration of cell suspensions blood leucocyte counts again attained previous values. The same rate of disappearance of the cells from blood was observed in splenectomized rats. Removal of the cells from circulation was thought to reflect "homing" into lymphoid tissues and other tissues, but not selectively in the spleen. Lymphocyte constituents, obtained by cell disintegration and injected i.v. into leucopenic rats, did not cause any change in blood leucocyte counts and yet restored the previously inhibited inflammatory response to carrageenin, as much as the viable cells. It is suggested that inflammation-producing materials, either deposited in tissues or formed or transformed at a site of injury, might gain access to the lymphatics during the early stages of a non-immune, inflammatory response, and "stimulate" lymphoid cells in adjacent lymphoid tissues either to release pro-inflammatory factors or to migrate to the site of injury, where they would exert pro-inflammatory activities. Apparently, only a small number of these cells in involved in the response.