1 Hematology Laboratory (Tufts), Boston City Hospital, 818 Harrison Avenue, Boston, Massachusetts 02118
Complement titres were measured in three groups of newborn infants from group O mothers:
I. 31 group O infants.
II. 10 group A or B infants with probable ABO hemolytic disease of the newborn (ABO HDN).
III. 18 group A or B infants without ABO HDN.
Seven of the Group II infants had positive direct Coombs' test, and one of these required exchange transfusion; the three babies with negative direct Coombs' test had clinical course compatible with ABO HDN. There was no significant difference in the complement titres among these various groups.
Anti-serum to human C3 and C4 was used to detect complement components on the fetal red cells of 4 infants in Group I, 5 infants in Group II, and eight infants in Group III. The reaction was negative in all these cases.
These results suggest that complement does not participate in the in vivo destruction of red cells in cases of hemolytic disease of newborn infants due to ABO incompatibility.