Should anti‐Rh immunoglobulin be given to D variant women?

Summary. D variant women occasionally form anti‐D during or following pregnancy with a D‐positive fetus. It is not known whether Rh immunization could be suppressed by using anti‐Rh immunoglobulin (Rh Ig), or whether the injected antibodies would be absorbed by the woman's D variant cells. In order to predict the likely outcome, three anti‐Rh Ig preparations were absorbed independently with five examples of D variant red cells: R 1 VI r (n = 3), R 1 B r( n = 2), and with cells of common Rh‐positive and Rh‐negative phenotypes: R 0 , r′r, r″r or rr cells ( n = 1 each). The titres of the Ig preparations against all these cells were compared after three, six, nine and 12 absorptions. The titres of the unabsorbed anti‐Rh Igs against R 0 cells ranged from 2 15 to 2 18 . Anti‐D activities were hardly affected by absorption with r′r, r″r or rr cells, but were completely exhausted after three to six absorptions with R 0 cells. Most of the D variant cells were as ineffective as rr cells in reducing anti‐D activity against R 0 cells, but one R 1 VI r variant produced a fall in titre against R 0 cells, equivalent to four or five doubling dilutions after three to six absorptions, which could not be reduced further by subsequent absorptions. Therefore, a substantial proportion of the anti‐D in the immunoglobulin preparation does not bind to D variant red cells. The component of the anti‐D that does not bind to D variant cells would be expected to be present in the circulation of D variant individuals injected with anti‐Rh immunoglobulin, and should be effective in suppressing Rh immunization. An increased dose of the anti‐Rh Ig might have to be administered in order to allow for the fraction that can bind to D variant red cells and which would not be available for immunosuppression.