Production of Plasma with High Anti‐D Concentration in Rh‐Negative Volunteers

. 63 Rh‐negative male volunteers were immunized with D‐positive red cells. 28 (44%) produced anti‐D. To provide sustained levels of high concentration of anti‐D, 18 of the 28 male volunteers have received repeated antigenic stimuli at individual intervals of 2–9 months. In all but 1 case the level of anti‐D rose to between 30 and 300 μg/ml and persisted at this level for several years. There was no evidence of a decrease in antibody response with an increase in the number of stimuli. 24 Rh‐negative women immunized by pregnancy were restimulated. 16 achieved anti‐D concentrations over 21 μg/ml. The levels achieved were not influenced by the different D‐positive cells injected, nor were larger antigenic doses of any benefit. No untoward clinical reactions occurred as a result of the repeated injections of antigenic material or of long‐term plasmapheresis. 2 volunteers developed unwanted antibodies outside the Rh‐system. Beginning in 1968, the programme to obtain anti‐D plasma has yielded more than 70,000 doses of 250 μg each, permitting the treatment of all Rh‐negative women at risk.