A LYMPH NODE WEIGHT ASSAY FOR THE GRAFTVERSUS- HOST ACTIVITY OF RAT LYMPHOID CELLS

SUMMARY When parental strain spleen cells or thoracic duct lymphocytes were injected into the feet of F1 hybrid recipients, the draining popliteal lymph nodes reached a weight which was up to 30 times greater than that of control lymph nodes. Seven days after injection, the mean lymph node weight was linearly related to the dose of cells injected on a double log scale. As a graft-versus-host assay, this method was found to be more sensitive as well as more convenient than other methods which have been used in the rat. The degree of lymph node enlargement produced by a given dose of cells was influenced by the volume in which they were injected, the precise site of injection, and the age of the recipient. On the other hand, the sex of the recipient and addition of F1 hybrid cells to the inoculum did not affect the lymph node weight. Graft-versus-host activity can be assayed in both Ag-B-disparate and Ag-B-identical strain combinations although, in the latter case, about 100 times as many cells are required to produce the same amount of lymph node enlargement.