Direct Antiglobulin Reaction in ABO-Haemolytic Disease of the Newborn

Abstract

The minimum number of IgG anti-A (or anti-B) molecule detectable on A or B red cells by the antiglobulin reaction wsu found to be the same—that is, about 150 molecules per red cell—with newborn as with adult cells. Furthermore, the ratio of and IgG bound to IgG and-A (or and-B) molecules was the same whether the and-A (or and-B) molecules were present on newborn or on adult cells and was similar to that found for and IgG bound to IgG anti-Rh. In 15 infants (11 group A, 4 group B) with haemolydc dis ease of the newborn due to ABO-incompatibility the amount of anti-A or anti-B on the red cells ranged from 0.25 to 3.5 µg and body per ml red cells, corresponding to 90-1,320 antibod] molecules per cell; only five infants had more than 0.55µg and body per ml of red cells. These amounts are far smallei than those found in most moderate or severe cases of Rh haemolytic disease. It is concluded that the weak direct antiglobulin reaction: observed in ABO-haemolydc disease are due simply to the fact that the number of and-A (or and-B) molecules on the infant's red cells is at the lower limit of sensitivity of the test Since ABO-haemolytic disease can be quite a severe process it seems probable that IgG anti-A and anti-B molecules are more effective than anti-Rh molecules in bringing about red cell destruction. © 1973, British Medical Journal Publishing Group. All rights reserved.