Natural agglutinis in rat sera against cells of mouse tumors differing in their transplantability to pretreated rats.

A previous study (15) has shown tha t transplantable mouse tumors differ in their capacity to grow progressively in rats pretreated with lyophilized mouse tumor tissue. An inverse correlation was found between the degree of strain specificity of tumors in mice and their transplantability to Pretreated rats. The present study deals with the correlation found between the transplantability of mouse tumors to pretreated rats and the difference in the titers of natural agglutinins found in sera of normal rats against the cells of mouse tumors. Davidsohn and Stern (4, 5) found that sera of normal mice of different strains varied in the titer of natural agglutinins against sheep erythrocytes. Especially high titers were found in sera of mice of the C57BL strain. This study was later extended to thirteen strains of mice. Differences in the titer of agglutinins were found in these strains against sheep and chicken erythrocytes, though they were independent of each other (21). Natural agglutinins against human erythrocytes, mainly of Groups A and AB, were found by Aptekman and Bogden (2, 3) in various titers, in sera of normal rats of several strains. We could confirm these findings on our two inbred strains of rats? An indication of a possible relationship between the presence of natural agglutinins and the growth of heterologous tumors was found by Green and Lorincz (8), who showed tha t the Krebs-2 ascites cells injected into chick embryo proliferated and produced nodules in viscera up to the 17th day of incubation, when the nodules usually began to degenerate so that, with few exceptions, when the chicken hatched, neither tumor nodules nor live tumor cells were present in the viscera. The death of the tumor cells occurred at the period when the