Mycobacterium Leprae in Cultured Mouse Peritoneal Macrophages: In vivo Infection In vitro Cultivation

ABSTRACT

To grow Mycobacterium leprae in cultured mouse peritoneal macrophages, studies were made on 1) the purification of M. leprae from lepromatous nodules by trypsinization, 2) growth experiment of purified M. leprae in cu1tured macrophages by in vivo infection-in vitro cultivation technique and 3) the observation of pathological changes in sp1eens of mice induced by intraperitoneal inoculation of purified M. leprae. Results are summarized as follows. 1. A simple and effective procedure is described for purification of M. leprae from biopsied nodules of lepromatous leprosy patients by trypsinization and high speed centrifugation. The procedure resulted in a good yie1d of homogeneous preparation of M. leprae with a negligible contamination of tissue debris. 2. Significant decreases were observed in the numbers of acid-fast bacilli in cultured macrophages and of macrophages harboring acid-fast bacilli by the length of intervals between the time of intraperitoneal inoculation of purified M. leprae and the time of initiation of macrophage cultures. 3. Microscopic examination of stained preparations of macrophages cultured by in vivo infection-in vitro cultivation technique indicated that an apparent increase in the number of acid-fast bacilli in the macrophages occurred when the cultures made at 24 hours and 1 week after inoculation were maintained in vitro up to 2 months or more. 4. Pathological changes in the spleens of mice inoculated with purified M. leprae were of mainly degenerative nature in the red pulp. No multiplication of M. leprae was observed in the spleens of mice up to 5 months after inoculation.