Effectivity of living and non-living BCG vaccine on experimental metastatic spread in mice and the stimulation of the reticulohistiocytic system (RHS).

Heat-killed or formalin-killed BCG vaccine caused statistically significant increases in weight of lungs, spleen and liver, which were in the same range as after administration of equal doses of viable BCG vaccine. Similarly, there was no quantitative or temporal difference in the phosphatase-positive proliferations of the RHS in liver spleen and lungs when using identical doses of viable or heat- or formalin-killed BCG vaccines. The metastasis-prophylactic effect demonstrated for viable BCG was present also after administration of the killed vaccines to a statistically significant degree. The increases in organ weight, extent of phosphatase-positive proliferation foci in liver, spleen and lungs as well as the metastasis-prophylactic effect were entirely identical; they seem to be in a close relationship with each other.