WITH THE TECHNICAL ASSISTANCE OF
N THE preceding paper6 it was shown that I injection of the mitochondria1 fraction of rat lymphosarcoma into rabbits produces relatively high titered antisera reacting with a lipid fraction extractable from the whole tissue with chloroform-methanol. There were two features of that study that distinguished it from previous investigations of alcohol-soluble lipid haptens. The first of these was the homogenization of the whole tissue, under very mild conditions, in an organic solvent, chloroform-methanol, which extracts the lipids almost completely and therefore reproducibly. The second was that the QUANTITY of active substance in the tissue was measured (in units defined by a standard antigen preparation) and found to be 7000 to 9000 units per gram.
Taken together, these two features appear to permit a quantitative evaluation of the specificity of the antiserum, which, in turn, would increase enormously its value as a sensitive reagent for the measurement of antigens in various tissues. Since serological inquiry into the component parts of the animal body has shown that antisera against tissues display organ specificity to various degrees,3 a quantitative evaluation is necessary for any precise understanding of these organ differences and their eventual exploitation.