Suppression of Memory by Passive Immunization Late in the Primary Response

The acquisition of a capacity to respond well to sheep erythrocytes in the presence of anti-SRBC antibody was taken as an indication of the presence of immunological memory. By the use of passive immunization, both the primary IgG plaque-forming cell response and the establishment of memory were abolished, despite occurrence of a full peak IgM PFC response. Evidence for regarding the aquisition of memory and the IgM PFC and IgG PFC responses as three separate processes was presented. Antibody on day 3 of the response to 1.5 x 10(8) SRBC abolished formation of memory; this effect was less if passive immunization was further delayed and absent by day 10.