EFFECT OF MYCOBACTERIUM BOVIS (BCG) INFECTION ON THE KINETICS OF THE MONONUCLEAR CELL RESPONSE WITHIN THE LUNG

Specific pathogen-free LBN rats were parabiotically linked and the monocyte donor animal was labeled with multiple pulses of tritiated thymidine (1 .mu.Ci/g body weight). The right-hand (recipient) rat lungs were infected with 105 viable Mycobacterium bovis (BCG) Pasteur by the i.v., aerogenic, or intratracheal routes. Control animals received heat-killed BCG or saline only, given intratracheally. The BCG infection resulted in a 10-fold increase in the number of heavily labeled, blood-derived monocytes recovered 24 h later in the lung lavage fluid. The percentage of labeled cells peaked on day 3 and then declined slowly. Introduction of heat-killed BCG into the lung produced a smaller mononuclear cell influx but a marked polymorphonuclear phagocyte response that persisted for several days. The labeled monocyte counts for the infected recipient rat lung washouts were 5 to 10 times those for the uninfected donor parabiont, except when the aerogenic infection route was used, when both donor and recipient rats were equally infected and both showed substantial increases in labeled monocytes in the lung washouts.