Simple estimation of macrophage activity in tumour-bearing animals treated with Corynebacterium parvum

The effects of Corynebacterium parvum on the reticuloendothelial system and on tumour growth have been known for many years. The causes of these effects have been the subject of many hypotheses and we here discuss a new method of evaluating macrophage activity and some of its components. These studies show that in macrophage activation the degree of enzymic activity and the cell size are more important than the number of cells present and that by giving silica concurrently it is macrophage enzyme activity and cell size that one affects and not cell number. Consequently, it is of no use simply to count macrophages in a section in studies of this system.