Tumor immunity in mice, induced with lyophilized tissue, as influenced by tumor strain, host strain, source of tissue, and dosage.

When tumors originating in one inbred strain of mice are transplanted into a second inbred strain (homoiotransplants) they usually show either no growth, or temporary growth followed by complete regression. The maximum size attained varies greatly according to the tumor and host strain employed, but for any one combination of tumor and host strain it is often quite uniform. Particularly is this true within any one group of animals inoculated on the same day with tissue from the same tumor transplant generation. In previous experiments (2), mice of the recipient strain were given a series of injections of lyophilized (frozen-dried) tumor tissue, and inoculated with the living tumor about l0 days after the last injection. The results varied depending on the combination of tumor and host strain employed. Where the tumor was myeloid leukemia C1498 (C57 black origin) and the host strain the C57 leaden, the prior injections resulted in almost complete inhibition of tumor growth. In contrast to this, if the tumor was A strain carcinoma 15091a and the host strain the C57 brown, the prior injections changed the small, temporary growths that characterized the control into large tumors that killed 100 per cent of the brown hosts. Similar results were obtained with 15091a in C57 black and B alb C mice, though in the latter case the stimulation was less pronounced. In these and subsequent experiments there have proved to be at least four significant variables: (a) the tumor used as lyophilized tissue; (b) the tumor used as fresh tissue; (c) the host strain; (d) the dosage of lyophilized tissue. At this laboratory there are at least l0 readily available inbred strains of mice and more than 20 transplantable tumors. Thus an enormous number of