An animal model for hemolytic disease of the fetus and newborn. II. Fetal effects in New Zealand rabbits.

OBJECTIVE: The addition of ultrasonography and ultrasonographically directed fetal blood sampling was attempted in an effort to study the fetal effects of red blood cell alloimmunization in a rabbit model. STUDY DESIGN: Nineteen New Zealand does were alloimmunized to incompatible red blood cells. Sensitized does were bred twice, once with a homozygous buck of incompatible blood type and once with a homozygous buck of compatible blood type. Ultrasonographic examinations were performed on days 20 and 27 of gestation (term 28 to 31 days). Fetal blood sampling was undertaken on day 27 of gestation, and hematologic data were compared between compatible and incompatible litters. RESULTS: A total of 41 pregnancies occurred in 19 does. Fetal hemoglobin was higher in the compatible litters (9.7 gm/dl vs 5.8 gm/dl, p < 0.001), whereas no difference could be detected between the respective reticulocyte counts (31.9 vs 36.0/100 red blood cells, p = 0.2). Hydrops fetalis was noted in none of 18 compatible litters versus 12 of 19 incompatible litters (p < 0.01). CONCLUSION: A disease analogous to human hemolytic disease of the newborn can be induced in the rabbit fetus.

An animal model for hemolytic disease of the fetus and newborn. I. Alloimmunization techniques.

OBJECTIVE: Our purpose was to establish an animal model for hemolytic disease of the fetus and newborn by developing red blood cell alloimmunization techniques in the rabbit. STUDY DESIGN: Twenty-six nonpregnant New Zealand White or Red does underwent blood typing to identify them as homozygous at the HgA or HgF red blood cell antigen locus. Alloimmunization to incompatible red blood cells was attempted through a series of subcutaneous injections using complete then incomplete Freund's adjuvant. RESULTS: Successful induction of an antibody response occurred in 96% of cases. The median response in FF rabbits was 2560 (range 40 to 10,240), whereas the response in AA does was 2560 (range 320 to 20,480). These responses were not statistically different (p = 0.77). Responses were categorized as poor, moderate, or good. No difference was noted between FF and AA does in distribution of the categories of response (p = 0.53). CONCLUSION: Red blood cell alloantibodies of high titer can be induced successfully in the rabbit.