An animal model for hemolytic disease of the fetus or newborn in New Zealand white and New Zealand red rabbits: Newborn effects

OBJECTIVE: Our purpose was to study the neonatal effects of red blood cell alloimmunization in a rabbit model. STUDY DESIGN: Eighteen does were alloimmunized to incompatible red blood cells. Does were bred twice, once with a homozygous buck of incompatible blood type and once with a homozygous buck of compatible blood type. Fetal blood sampling was undertaken on day 27 of gestation (term 28 to 31 days). Does were delivered on day 30 and the neonatal pups were anesthetized. Direct cardiac samplings were performed for hemoglobin, reticulocyte count, and direct Coombs' test. Hepatic, splenic, and renal wet weights were measured. RESULTS: Twenty-two pregnancies (12 compatible and 10 incompatible) were studied. Neonatal hemoglobin was higher in the compatible litters (11.1 gm/dL [7.7 to 12.6 gm/dL] vs 4.9 gm/dL [2.1 to 9.1 gm/dL], P < .001), whereas no difference could be detected between the respective reticulocyte counts (34.0/100 red blood cells [27.3 to 36.1/100 red blood cells] vs 32.6/100 red blood cells [26.8 to 43.5/100 red blood cells], P = .55). The direct Coombs' assay was negative in 23 pups from 8 compatible litters and false positive (weakly positive result) in 2 pups of a ninth compatible litter. The Coombs' assay was positive in all 22 incompatible pups tested. Hepatosplenomegaly was noted in affected pups but not in controls. CONCLUSIONS: A disease analogous to human hemolytic disease of the newborn can be induced in the rabbit neonate.