Immunologic Reactivity in Canine Marrow Graft Recipients

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Abstract
Immune reactivity was studied in 55 dogs between 20 days and 8 years after lethal total body irradiation (TBI) or cyclophosphamide (CY) and grafting of autologous or allogeneic marrow. This was compared to findings in 50 normal dogs. Cytogenetic and other blood genetic markers showed that the hemopoietic and lymphoid systems in allogeneic chimeras conditioned by TBI were repopulated only by cells of donor type. In contrast CY chimeras showed persisting mixtures of host and donor cells. Recovery of granulocyte counts and return of granulocyte function as determined by iodination tests were complete by day 25 after grafting. Blood lymphocyte counts did not reach the normal range until day 200. Lymph node histology showed lymphoid hypoplasia for 100 to 200 days and returned to normal thereafter. Short-term chimeras (<200 days postgrafting) had slightly lower and long-term chimeras (τ;200 days postgrafting) had significantly higher serum IgG level than did normal dogs. Antibody formation to chicken red blood cells and sheep red blood cells and bacteriophage φX174 (phage) was lower than normal in the first 200 days and within the normal range thereafter. The class of antibody after repeated immunization was predominantly IgM in short-term and predominantly IgG in long-term chimeras and in normal dogs. Phage clearance was normal in all chimeras. Transfer of immunity to distemper and phage was studied with equivocal results. Cellular immunity (first and second set skin grafts, stimulation of lymphocytes in mixed leukocyte culture and by phytohemagglutinin) was impaired in short-term chimeras and normal in long-term chimeras. An exception was the tuberculin conversion after Bacille Calmette-Guerin immunization which occurred as early as day 29. As a clinical correlate to these studies on immune function, long-term chimeras regained their health and are able to live in an unprotected environment without increased susceptibility to infections or other diseases.

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