MORPHOLOGICAL EVIDENCE FOR MIGRATION OF PARTICLE-LADEN MACROPHAGES THROUGH THE INTERALVEOLAR PORES OF KOHN IN THE MURINE LUNG

We have investigated the topography of particle-laden macrophages in t he pulmonary tissue of CD-1 mice after intratracheal instillation of a suspension of 250 mug of calcium tungstate. The mice were sacrificed 1, 3, 7 and 14 days after the particle deposition. 1-ung fragments wer e,studied by scanning electron microscopy (SEM) coupled with X-rav mic roanalysis that allowed in situ elemental identification of tungsten i n the lungs. Tungsten-positive macrophages were distinctly located in the lungs of mice sacrificed at 1-3 days when compared with samples fr om mice killed 7- 14 days after the calcium tungstate instillation. At 1-3 days, the tungsten-carrying macrophages were accumulated near the terminal bronchioles whereas they were seen predominantly in the alve olar ducts and sacs in the 7- to 14-day groups of mice. This suggests that during pulmonary inflammation there is a redistribution of the pa rticle-containing macrophages throughout the deep lung tissue. In high -magnification SEM views, we observed that the tungsten-positive macro phages presented numerous surface microvilli. Tungsten-laden phagocyte s were detected in interalveolar fenestrae, at the so-called Kohn pore s. This finding documents that the Kohn pores may be used by inflammat ory cells as a pathway for the migration of phagocytes in between adja cent alveolar sacs.