The inflammatory responses of rats depleted of lymphocytes or with an artificial obstruction of the thoracic duct.

Rats selectively depleted of lymphocytes by chronic drainage from the thoracic duct during a 3-day period presented a marked lymphopenia, and decreased responses to carrageenin injected into one of the hind paws. The intensity of the inflammatory responses in thse animals was restored by the i.v. administration of suspensions of viable or lysed lymphocytes, collected from the spleen or lymph of normal animals. A spontaneous reversal of the depressed responses to carrageenin was observed 40 days after the period of lymph drainage, when lymphocyte counts were again normal in blood. If highly inbred rats were used, the i.v. injection of syngeneic lymphoid cells was equally effective in restoring the inhibityed inflammatory responses resulting from lymphocyte depletion. Artificial obstruction of the thoracic duct, with interruption of lymphocyte recirculation, was followed by decreased lymphocyte counts in blood and severely depressed inflammatory responses to carrageenin. This unresponsive state was corrected as the animals recuperated, probably coincidentally with the development of collateral lymph channels and as the temporarily disturbed blood picture returned to normal. It is concluded that lymphocytes can participate in the development of non-immune inflammation through the release of pro-inflammatory factors. This release is independent of previous sensitization of the cells.