Studies on serum‐mediated inhibition of cellular immunity to spontaneous mouse mammary tumors

Abstract Sera from mice which have either spontaneously developed a mammary tumor, or which have been immunized against such a tumor, have been shown capable of abrogating the ability of lymph‐node cells from these mice to specifically inhibit colony formation by mammary tumor cells in vitro . Sera from mice sensitized to another, independently arising, syngeneic mammary tumor or to a syngeneic Moloney sarcoma virus‐induced tumor are less active in this respect, indicating that this reaction is specific. It is suggested that these observations are related to the in vivo phenomenon called immunological enhancement.