The Presence of Forssman Antigen in Inbred Mice

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Abstract
Summary: Subcellular fractions were prepared from spleen, kidney, liver, 3 types of malignant tumors of the mouse, and from guinea pig kidney. Fresh and boiled portions of the homogenates and the cell fractions of these tissues were tested for their capacity of absorbing heterophilic and isophilic hemolysin for sheep red cells. By means of these absorption experiments, kidney, spleen, and tumors of the mouse were found to contain Forssman antigen in quantities increasing in the order of enumeration. No qualitative difference was found between the antigen in mouse tissues and the prototype Forssman antigen in guinea pig kidney. The mitochondrial and microsome fractions contained larger amounts of Forssman antigen than the nuclear fraction in all tissue examined. None of the normal mouse tissues showed qualitative or quantitative differences depending on the strain of derivation. Hence, there is no reason to assume that differences observed by us in presence and titer of natural antisheep agglutinins in various inbred strains, including C57BL and C3H, are caused by, or related to, differences in tissue antigens in these strains. In contrast to the thermostability of Forssman antigen commonly observed in tissue suspensions, boiled subcellular fractions, particularly those consisting of “small particles,” showed a reduction of absorptive potency for heterophilic antibody as compared with their fresh counterparts. In vivo experiments demonstrated inability of mice of 3 inbred strains to produce antibodies for sheep red cells after active immunization with heterophilic antigen (guinea pig kidney). Passively introduced heterophilic antibody, in contrast to isophilic antibody, disappeared in mice so rapidly that its absorption by tissue antigen is the most likely explanation. The findings in vivo confirm those in vitro with regard to the presence of Forssman antigen in the mouse. Of 3 mouse tumors (1 sarcoma, 2 carcinomas) a transplantable carcinoma of DBA mice had the highest content of Forssman antigen.
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