Reconstruction of lymph follicles in the mouse popliteal lymph node after X-irradiation damage.

In order to suppress possible "de novo" formation of follicles in the node after irradiation, animals to be irradiated received surgical operations to block the afferent lymphatics to the popliteal node on one side, the corresponding node on the other side left intact. 600 R whole body X-irradiation severely destroyed lymph follicles in the nodes of both sides, but the number of follicles in the node on either side recovered toward normal by 3 weeks after irradiation, regardless of whether they contained germinal centers or not. In animals exposed to 1,000 R whole body X-irradiation and infused with bone marrow cells, no lymph follicles were observed in the nodes on day 9. If such treated animals were given 1.0 X 10(8) lymph node cells on day 5, lymph follicles were reconstructed in the nodes of both sides on day 9. In animals irradiated with 1,000 R to the lower half of the body, the number of follicles in the node on either side remained comparable to that of the unirradiated control node. The results favor the interpretation that although X-irradiation destroys the lymphoid elements of the follicles, the stromata of follicles persist and preserve the ability to collect small lymphocytes, and that lymph follicles are reconstructed at the sites of the stromata persisting from damaged follicles.