NATURAL CELLULAR REACTIVITIES MEDIATED BY SPLENOCYTES FROM MICE BEARING THREE TYPES OF PRIMARY TUMOR

The ability of splenocytes from mice bearing three types of primary tumor to lyse YAC‐l target cells (NK activity) and to inhibit [¹²⁵l]dUrd incorporation ([¹²⁵l]dUrd l‐l = cytostasis) into B16‐F10 target cells was compared to the ability of normal splenocytes to perform such activities. The tumor systems used were urethane‐induced lung adenomas in BALB/c mice, di‐methylbenzanthracene (DMBA)‐induced tumors in hormonally‐stimulated BALB/c mice and mammary tumors in force‐bred C3HeB mice. The two types of natural cellular reactivity in lung adenoma‐bearing mice were unaffected. The NK activity of mice bearing DMBA and forced‐breeding‐induced tumors was suppressed. The cytostatic ability of splenocytes from mice bearing DMBA‐induced tumors was significantly elevated. The spleens of mice bearing primary DMBA‐induced tumors contained cells able to suppress NK activity or to compete against target cells for NK cells.