SUPPRESSED MULTIPLICATION OF TUBERCLE BACILLI WITHIN MACROPHAGES DERIVED FROM TRIIODOTHYRONINE-TREATED GUINEA PIGS

Abstract

A technique is presented which permits the intracellular multiplication of human tubercle bacilli in vitro to be followed in a quantitative manner. The intracellular growth characteristics of the 2 strains of H37RV tubercle bacilli used in this study were shown to be different. The H37RV-P strain exhibited a lag phase of 4 to 5 days before multiplication occurred. There was a 2 to 3-day growth phase, after which the intracellular population remained essentially constant. In monocytes derived from triiodothyronine-treated guinea pigs, the intracellular multiplication of the parasite appeared slightly suppressed. The H37RV-S strain, on the other hand, had the ability to multiply within normal monocytes at an almost constant rate throughout a 9-day period, with a generation time of 2 to 3 days. There was no appreciable lag phase. Multiplication of this strain in monocytes from treated animals was retarded, having a lag phase of about 2 days and a subsequent generation time of approximately 5 days. This study demonstrates the presence of "cellular resistance" which was induced in guinea pigs by a naturally occurring entity without previous infection or vaccination, and in which humoral factors did not appear to play a prominent role.