The migration of lymphocytes across specialized vascular endothelium. III. Concanavalin A delays lymphocytes in normal traffic areas.

Radioactively labelled rat lymphocytes were treated in vitro with concanavalin A (con A) and injected intravenously into syngeneic recipients. By examining the blood and tissues at intervals from 30 min to 48 h after injection, it was confirmed that con A altered the distribution of lymphocytes. Comparison was made with the localization of alternatively labelled untreated lymphocytes injected into the same recipients and with untreated lymphocytes injected into other recipients. Within 1 h of injection there was a surplus of treated cells in the lungs and liver and deficits (of equal magnitude) in the blood, spleen and lymphonodes. By 24 h after injection there was a twofold surplus of treated cells in the spleen but a persisting deficit in lymphnodes. These perturbations can be ascribed to the prolonged retention of lymphocytes in normal sites of localization; there is no evidence that con A either hinders the migration of lymphocytes from the blood or diverts them to abnormal sites. It is not clear whether the delay in the recipients' tissues requires an active response to con A but, if so, then it does not proceed to blastic transformation.