The migration of rat thoracic duct lymphocytes through spleen in vivo.

Rat thoracic duct lymphocytes have been labelled using [H]5-uridine. After injection intravenously into syngeneic recipients their fate has been followed by scintillation counting and autoradiography. During the first 24 hours the distribution of radioactivity between different organs changed greatly with time. Lungs and liver contained about 50% of the injected radioactivity within 0·5 hours and lost most of this within 4 hours. In the spleen the radioactivity increased for about 4-6 hours and then decreased, whereas that in mesenteric and peripheral lymph nodes increased almost linearly for 24 hours. Free [H]uridine and heat-killed cells failed to accumulate in lymphoid organs. When labelled lymphocytes were injected into splenectomized animals their lymph nodes accumulated more radioactivity earlier than the controls and remained more radioactive for at least 24 hours. It seems that one population of lymphocytes which accumulates in the rat spleen is released to accumulate subsequently in lymph nodes.