Mixed hematopoietic chimerism for preventing graft-versus-host disease in mice receiving rat bone marrow transplantation.

OBJECTIVE: To find a method for preventing graft-versus-host disease (GVHD) in BALB/c mice receiving rat bone marrow transplantation. METHODS: Firstly 12 SD rats were conditioned with 5.0 Gy sublethal total body irradiation(TBI), followed by infusion of 8 x 10(7) bone marrow cells from 28 BALB/c mice within 4 h and intraperitoneal administration of 100 mg/kg cyclophosphamide (Cy) 2 d later, for the purpose of inducing chimeric SD rats with specific immunological tolerance. Secondly, 24 BALB/c mice were exposed to 9.0 Gy lethal TBI and divided randomly into 3 equal groups designated respectively as groups A, B and C. Mice in group A were injected with 4 x 10(7) bone marrow cells from 4 normal rats, and mice in group B were injected with 4 x 10(7) bone marrow cells and 2 x 10(7) spleen cells from 4 normal rats, while those in group C were given 4 x 10(7) bone marrow cells and 2 x 10(7) spleen cells from 6 chimeric rats. The mice were then observed for 150 d for GVHD. RESULTS: In the second procedure, 2 mice in group A failed to survive due to infection and radiation injury respectively, and none of the rest mice presented signs of GVHD. The mice in group B all developed GVHD of varied degrees with symptoms as wasting, diarrhea, fur loss, arched body posture, and even bloody stool, and all died within 5 to 15 d with an average survival of 10.0 d (95% confidence interval 8,12). Pathological examination of the liver and intestinal tissues revealed inflammatory lymphocyte infiltration and necrosis. The majority of the mice in group C, in contrast, survived for more than 150 d with only two died on the postoperative days 18 and 31 respectively. The survival time of group B was significantly shorter than that of the other two groups. CONCLUSION: Donor/recipient chimerism may help prevent GVHD in xenogeneic bone marrow transplantation.