Quantitative factors which determine the effect of the immune response on the growth rate of the Cloudman melanoma in the DBA/2 mice

Abstract

We compared the growth rate of Cloudman melanoma in DBA/2 mice produced by injections of tumor cells taken from tissue culture (TC cells) to that of tumor cells prepared from tumor nodules already growing in DBA/2 mice (An cells). We found that small numbers of An cells grew better than TC cells. In contrast larger numbers of An cells grew less well than TC cells. We could make the growth rate of TC cells comparable to that of AN cells by (a) immunosuppressing recipient mice and/or (b) injecting the host with the proper dose of tumor cell proteins, debris and antigens extracted from the tumors with potassium chloride. The immunologic basis for both the tumor-retarding and tumor-promoting effects of the KC1 extracts was established by adoptive transfer experiments. Thus, some tumor cell products which have the potential to stimulate the immune response do so in a distinctive fashion depending in part on whether they are associated with viable tumor cells. The effects that nonviable cell-associated tumor products have on the immune response to viable tumor cells varies with their dose; they increase the magnitude of the immune response against the tumor at moderate doses but decrease it at higher or lower doses. The latter point may help explain the phenomenon of “sneaking through.”