Changes in Subcellular and Circulating Antibody Levels During the Hemolysin Response in Rabbits

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Abstract
Summary: Microsomal and cell-sap antibody titers in the spleen were compared with serum antibody levels for 18 days following the intravenous injection of sheep erythrocytes into rabbits. The microsomal fraction was isolated from individual spleens, sonicated and treated with DOC to release antibody. Both released and unreleased microsomal antibody was titrated. Titers were determined by a modification of the standard, 50% photometric assay for hemolytic antibody. As compared with the serum hemolysin response, the response measured on the subcellular level displayed a marked shortening of the interval between antigen injection and rise in titer. This interval was 4 days in the serum, 3 days in the microsomal fraction and 1 day in the cell-sap fraction. Subsequently, the subcellular antibody levels increased logarithmically, reached peak titers between days 6 and 12 and then declined. The data suggest an earlier peak titer in the cell sap and a more rapid titer decline in both the cell-sap and microsomal fractions than in the serum. The apparently earlier titer rise in the subcellular fractions than in the serum may be attributed to the masking effect of natural hemolysin levels in the serum, while the earlier appearance of antibody in the cell sap as compared with the microsomal fraction suggests the existence of an antibody pool in the soluble phase of the cytoplasm.