Amino Acid Incorporation into Precipitin at Different Stages in the Secondary Response to Bovine Serum Albumin

Abstract

A secondary response was induced in donor rabbits by a single reinjection of bovine serum albumin and at the same time the animals were started on a twice-daily dose of S35-labeled amino acids. Spleens from these labeled donors at various times during the induction period and during the rapid antibody rise were removed, minced, washed and injected into nonimmunized and unlabeled recipients. Bone marrows from labeled donors were also transferred at day 3.5, and spleens from unlabeled donors were transferred at day 1 and day 2. The precipitin-forming capacity of the spleen of the donors was nil on day 1, rose to a peak at day 2.5 and subsided rapidly during the following day and a half. The absolute time of the transfer after reinjection of the antigen was the important factor rather than the amount of antibody in the serum. A similar capacity was exerted by the red bone marrow at day 3.5. As precipitins increased in amount in the unlabeled recipients, their specific radioactivity decreased. This finding is interpreted as indicating that the transferred antibody-synthesizing mechanism produced initially a small amount of highly labeled antibody which was diluted by the subsequent synthesis of unlabeled antibody. Precipitins formed by the 3d day in the unlabeled recipients of 3.3-day spleen mince from S35-labeled donors, possessed very little S35 label (0.001 to 1.14% or a mean of 0.4 [plus or minus] 0.1% of the specific radioactivity of the donor). This finding confirms the work of Taliaferro and Talmage (1955) in demonstrating that there are no long-lived antibody intermediates formed during the induction period. A single intravenous injection of S35-labeled amino acids was given to rabbits during the rapid secondary response to bovine serum albumen (day 3.3 to 4) to determine the transit time. The S35-label did not appear in the precipitins at 20 minutes, was present in significant amounts at 40 minutes, reached a plateau at 4 to 5 hours and decreased slowly thereafter. The absence of the formation of long-lived antibody intermediates during the induction period, the short transit time for the S35-labeling of antibody and the more or less constant antibody-labeling following a single injection of S35-labeled amino acids at different times during the antibody rise, all indicate that, under the conditions of these experiments, there is no long storage of antibody either intra-or extracellularly.