Tuberculostatic Activity of Normal Human Sera

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Abstract
Summary: This study demonstrated that normal human sera possess an inhibitory activity for growth of tubercle bacilli. This tuberculostasis could not be shown upon dilution of the serum in various media devised for growth of tubercle bacilli. The analyses of the constitutents of these media with respect to their antituberculostatic activity showed that phosphate and citrate act as antagonists in the antimycobacterial activity. Investigation of the tuberculostatic factor showed the following: It is heat-stable at 56°C but loses its activity at 65°C or higher temperatures.It is composed of two parts, one which is heat-sensitive and nondialyzable and a second which is heat-stable and dialyzable; both parts are required for tuberculostatic activity.Both parts of the tuberculostatic factor are organic and their molecular weight may be higher than 30,000.The factor or its one part can be adsorbed from serum by heavy emulsions of tubercle bacilli. Study of the distribution of tuberculostatic factor showed that it is present in tuberculinnegative and tuberculin-positive people. The analysis of “racial sera,” as to the level of tuberculostatic activity suggested no difference among the races. Out of 92 sera investigated, 7 demonstrated low degree of tuberculostatic activity. Because of equal distribution of these “weak” sera among the racial groups, this might indicate an individual rather than a racial characteristic.