The Anti‐Rh₀(D) Responses of Immunized Volunteers following Repeated Antigenic Stimuli

Twenty‐nine Rh 0 (D) negative male volunteers previously immunized with D‐positive red cells have received series of antigenic stimuli repeated at intervals of 2 or 4 weeks. Although there is an individual variation in the magnitude of the anti‐D responses, the levels of anti‐D achieved are, in general, higher than those obtained after stimuli spaced at intervals of several months. Moreover, certain volunteers whose plasma was not suitable for inclusion into pools for the preparation of anti‐D immunoglobulin after spaced stimuli could donate regularly following the repeated stimuli. Whilst untoward clinical reactions did not occur as a result of the repeated stimuli five volunteers developed unwanted antibodies outside the Rh system and this may be related to the total dose of red cells injected.