Engraftment of human lymphoid cells into newborn SCID mice leads to graft-versushost disease

Although there has been considerable progress in transplanting normal human hematopoietic cells into immune-deficient mice, the establishment of a functional human immune system has proved to be difficult. Current methods of introducing mature human lymphoid cells into adult SCID mice lead to oligoclonal engraftment with restricted dissemination to various organs. We have attempted to improve human lymphoid cell engraftment in mice, both qualitatively and quantitatively, by injecting human bone marrow cells and peripheral blood leukocytes intraperitoneally into newborn SCID mice. Newborn mice were used as recipients because certain immune functions such as natural killer cell activity do not develop until several weeks after birth and the numerous growth factors secreted in young mice may facilitate the engraftment and proliferation of transplanted human cells. At various times after transplantation, the presence of human cells in different organs was determined by Southern blot analysis using a human specific probe. Within 4 weeks, 70% of the mice were engrafted with human cells. Human cell engraftment of the bone marrow, spleen, lungs, kidneys, liver, and thymus exceeded 10% in at least 40% of the transplanted mice; most of these highly engrafted mice were sick. Flow cytometry and immunocytochemistry indicated these organs were heavily infiltrated with mature T and B lymphocytes. Histologic and molecular analysis showed massive human cell infiltrates within the liver, lung and spleen. The presence of human IgG and IgM antibodies against mouse red blood cells provided evidence that the engrafted human cells retained some immune function. Mice transplanted with peripheral blood leukocytes from donors that were allergic to mouse antigens engrafted to the same extent as normal cells but in addition developed the classical symptoms of acute allogeneic graft-versus-host disease (GVHD) including infiltrates of the skin, gut, and liver. The newborn SCID system provides a new in vivo model to study human xenoreactivity and GVHD.