Effect of age and sex on lung-colony-forming efficiency of injected mouse tumour cells.

The i.v. injection of a specified number of cells of either an Ehrlich ascites tumour (ELD) or spontaneous mouse mammary adenocarcinomas (MA) into C3H mice yielded a number of lung colonies which varied significantly with the age or sex of recipient mice. The yield was higher in mice of 71 weeks than in those of 15 weeks, except for MA cells injected into females, when the yield was higher in the younger mice. Sex did not influence very significantly the yield of colonies from ELD cells; in the case of MA cells the direction of sex differences depended on age. A difference in the effect of pre-immunization with age was not observed.