Enhanced protein and IgM and IgG antibody synthesis following an early second injection of hemocyanin into the rabbit.

Rabbits were injected with 0.1 or 1 mg alum-precipitated keyhole limpet hemocyanin (KLH) into the hind footpads. One, 3, 8, 14 and 90 days later individual rabbits were reinjected with 1 mg of KLH. Three days later suspensions of popliteal lymph node cells were cultured and assayed for antibody and non-antibody protein synthesis by the incorporation of 14C-leucine. Reinjection of KLH at 1 and 3 days did not stimulate antibody or protein synthesis, but restimulation at 8 and 14 days did. Priming with 0.1 mg induced mainly IgM memory, whereas priming with 1 mg induced mainly IgG memory. Reinjection of KLH at 90 days stimulated a non-antibody-producing cell population to synthesize IgG antibody. There was only fair correlation between the type and extent of the primary antibody response and the type and extent of anamnestic response evoked. There was little correlation between the extent of stimulation of antibody and of non-antibody protein synthesis. Low levels of “natural” antibody to KLH were synthesized by lymph node cells from unimmunized rabbits.