Antibody Synthesis in Relation to Levels of Humoral and Cell-Fixed Antibodies in Rabbits

Abstract

Summary The rate of antibody synthesis was measured in vitro in fragments of spleens taken from rabbits killed at different times following an intravenous injection of human serum albumin (HSA), using the method based on the incorporation of C14-amino acids. The values for synthesis were compared with the levels of “cell-fixed” antibodies, as expressed by uptake in vitro of I131-HSA, and also with the levels of precipitating antibodies in the sera, and with the capacity of the sera to confer on normal cells the ability to adsorb antigen (“cytophilic” antibody). The investigation was carried out using rabbits which had received a single dose of antigen, rabbits which had received two injections, and hyperimmunized rabbits which had received a booster injection of antigen. Antibody synthesis occurred in spleens taken 7–10 days after the first injection of antigen, or 3–5 days after a second or booster injection. The quantitative determination of “cell-fixed” antibody gave significant values only in the case of hyperimmune animals which had received a booster injection of antigen. Maximum adsorption of I131-HSA occurred in cells of spleens taken 3–6 days after the booster injection. Low precipitin titers were found in sera taken from animals 10 days or later, after a single injection of antigen, whereas sera of animals killed 3 days or later after a booster injection showed high precipitin titers. Significant levels of “cytophilic” antibody were found only in sera of rabbits killed 3 days or later after a booster injection.