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 microgram/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 microgram/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 microgram each, permitting the treatment of all Rh-negative women at risk.