Regional Lymph Node Irradiation: Effect on Local and Distant Generation of Antibody Forming Cells

After footpad injection of sheep erythrocytes into Fisher rats, the major site of appearance of direct and indirect antibody plaque forming cells (direct and indirect) is the regional lymph node. Indirect plaque forming cells are subsequently found in the spleen, but no other lymphoid tissues. Repeated irradiation (days 1, 3, 5, 7, and 9) to the draining lymph node region after antigenic stimulation prevents the appearance of plaque forming cells in the spleen by day 10. Selective irradiation of this node group on days 4 and 5 prevents splenic appearance of indirect plaque forming cells only, whereas contralateral node irradiation does not. Irradiation at a later time (days 7 and 8) did not significantly lower the level of splenic indirect plaque forming cells by day 10. We concluded from these experiments that the appearance of splenic indirect plaque forming cells was dependent on radiosensitive cell populations in the antigen draining lymph nodes, and not on the generation of these cells independently in the spleen.