Reaction of macrophages to cigarette smoke. I. Recruitment of pulmonary macrophages.

Recruitment of pulmonary macrophages was studied in adult male mice which had been exposed 42 to 82 days to cigarette smoke. Scintillation counting procedures revealed that cigarette smoke induces increased DNA activity in pulmonary tissue. No such induction was noted in the liver or spleen--organs which, like the lungs, are also involved in clearance of foreign material. Autoradiographic analysis of lung samples taken at intervals up to 40 days following 3H-thymidine injection revealed an increase in DNA activity reflecting a marked increase in the number of labelled pulmonary macrophages. At times, more than 50% of the total pool of labelled cells were identifiable as macrophages. Therefore, cigarette smoke appears to elicit a recruitment of macrophages specifically to the lungs.