Mortality of Radiation Chimeras in Relation to the Number of Transplanted Bone Marrow and Lymph Node Cells<xref ref-type="fn" rid="FN1">2</xref>

Abstract

Injection of lymph node cells along with therapeutic doses of bone marrow cells into irradiated animals can cause death if the lymphoid cells are capable of reacting against the host animal. The mortality and time of death are proportional to the number of lymphoid cells injected. Death can be as late as 70 days after irradiation. Injection of bone marrow cells alone can cause death but only when very large numbers of cells are given and only in certain donor-host combinations. Great numbers of bone marrow cells raise the death rate after injection of lymph node cells in certain donor-host combinations but counteract this killing effect in other combinations. The number of immunologically competent cells in bone marrow from both CBA and C57BL mice is small. In CBA mice an equivalent number of immunologically competent cells was estimated in 20 x 10(6) bone marrow and in 0.05 to 0.1 x 10(6) lymph node cells; for C57BL mice these figures were 50 x 10(6) bone marrow and 0.4 x 10(6) lymph node cells. To explain why bone marrow can apparently offset the killing effect of lymphoid cells, it is postulated that immunologically tolerant cells developing from pluripotent stem cells in bone marrow compete with immunologically competent lymphatic cells.