Bone marrow transplantation in the rat. I. Histologic correlations and quantitation of cellular infiltrates in acute graft-versus-host disease.

In an attempt to define which cytologic manifestations of inflammation are characteristic of acute graft-versus-host disease (aGVHD), the authors have analyzed hematologic reconstitution in the bone marrow, spleen, and blood of bone marrow transplant recipients and correlated these events to concomitant cytologic changes in the parenchymal target organs. After bone marrow transplantation from Lewis to BN strain, the strongest inflammatory changes were observed in the liver, a "model" parenchymal target organ for aGVHD in this strain combination. The inflammatory episode of the aGVHD in the liver was characterized by an early lymphoid blastogenesis, the presence of large granular lymphocytes (LGLs), lymphocytosis, and some monocytosis, lacking or significantly less prominent in the liver of syngeneic BN to BN recipients. Concomitantly with the infiltration of the liver with LGLs and lymphocytes, these cells were depleted from blood; and with their disappearance from the liver, they appeared in the recipient spleen. Lack of lymphoid blastogenesis in the bone marrow of allograft recipients and similar though less prominent cytologic changes in the syngeneic graft recipients, make it difficult to differentiate aGVHD-associated changes from normal reconstitution in the lymphoid tissue paper; the minimal changes in the blood make this organ the least suitable site for the monitoring of the aGVHD in the rat.