Factors in Resistance to Tuberculosis *

The investigations of Sabin and her co-workerse9 demonstrated that the tubercie phosphatide was the biologically most active fraction of the various split-products of the tubercle bacillus as separated by Anderson.2 It produced epithelioid cell response and tubercle formation. Sabin also observed that, after intraperitoneal injection, the rabbit monocytes phagocytized the phosphatide, but were not able to destroy it. Similar results were published later by Roulet."8 Thomas and Dessau,40 however, demonstrated that mice reacted only slightly to the injection of the tubercle phosphatide and were able to eliminate it without the development of a long-continued cellular reaction. These observations suggested that the mouse cells or a group of them were able to break down the tubercle phosphatide rapidly and to change it into a biologically inactive substance, while those of the rabbit phagocytized the phosphatide but eliminated it at a slower pace, if at all. These differences in response gain interest when correlated with the pathology of tuberculosis in both species. Previous investigations"5 have demonstrated that the innate high resistance of mice to tuberculous infection is not based purely on cellular response or on hypersensitivity. The mouse appeared to have additional means of resistance. Among these, the ability of the cells to break down the complicated lipoid fractions of the tubercle bacillus may be one of the factors. If this assumption were correct, a difference in the amount or rate of splitting of the tubercle phosphatide effected by the cells of various species should be detectable and, if any splitting took place, one or several cleavage products of the tubercle phosphatide should be demonstrable. A qualitative determination of the enzymes responsible for the splitting seemed essential before beginning a quantitative comparison between various species.