American Review of Respiratory Disease

We tested the hypothesis that enhanced cell division accounted for the augmented numbers of monocytic phagocytes with characteristics attributed to alveolar macrophages (AM) found in the lungs of habitual tobacco (T) and marijuana (M) smokers. The monocytic phagocytes, that is, alveolar macrophages, were obtained by bronchoalveolar lavage (BAL) from 12 nonsmoking subjects; 10 subjects who smoked T only (TS); 13 subjects who smoked M only (MS); and 6 smokers of both T and M (MTS). The replication of these cells was determined by measuring the incorporation of [3H]thymidine into the DNA of dividing cells and visually counting 2,000 cells on autoradiographically prepared cytocentrifuge cell preparations. This study demonstrated that the number of [3H]thymidine-labeled monocytic phagocytes with characteristics of alveolar macrophages from either TS or MS have a higher proliferative index compared to cells (macrophages) from nonsmokers, p < 0.05 by one-way ANOVA. The total number of BAL macrophages that are in mitosis in TS (17.90 ± 4.50 labeled AM × 103/ml) or MTS (10.50 ± 4.20 labeled AM × 103/ml) are 18- and 10-fold greater, respectively, than the number obtained from nonsmokers (1.01 ± 0.18 labeled AM × 103/ml). Interestingly, the number of [3H]thymidine-labeled macrophages from MS (2.90 ± 0.66 labeled AM × 103/ml) are also greater than the number obtained from nonsmokers, although this is not statistically significant. The stimulus augmenting alveolar macrophage replication is as yet unknown but may likely be found in the T or M smoke. These observations support the hypothesis that in situ monocytic phagocytes with characteristics associated with alveolar macrophages are capable of cell division and could account for the increased macrophage population found in BAL material obtained from either T or M smokers.

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