GRAFT-VERSUS-HOST ACTIVITY OF RAT BONE MARROW, MARROW FRACTIONS, AND LYMPHOID TISSUES QUANTITATED BY A POPLITEAL LYMPH NODE WEIGHT ASSAY

Abstract

A sensitive popliteal lymph node weight assay and a bone marrow fractionation technique have been used to measure the weak graft-versus-host (GVH) activity of marrow and thymus cells as compared with that of other lymphoid tissues. After injection of spleen cells from Lewis rats into the hind footpads of (Lewis × Brown Norway)F1 hybrid rats, the weight of the draining popliteal lymph nodes increased exponentially for 6 days and plateaued from 8 to 12 days at values of up to 30 times normal. At 8 days, the node weight showed a linear relationship to the number of injected cells on a double logarithmic scale. The 8-day dose response curves of other Lewis lymphoid cell suspensions paralleled that of the spleen and indicated that their relative GVH activities were: thymus cells, 2.4%; bone marrow cells, 2.8%; spleen cells, 100%; mesenteric lymph node cells, 127%; blood leukocytes, 229%. No significant popliteal node enlargement was seen after control injections of heat-killed cells, nonlymphoid cells, or syngeneic lymphoid cells. Mixtures of cells from marrow and thymus showed no synergistic effect on popliteal node enlargement. Experiments using lymphocyte-rich fractions separated from Lewis bone marrow by sedimentation in sucrose-serum density gradients showed that GVH activity was a property of some lymphocytes normally situated in the marrow parenchyma and that the GVH activity of lymphocytes in bone marrow was at least 5 times greater than that of lymphocytes in the thymus.