Are Langhans giant cells precursors of foreign-body giant cells?

Granulomas were induced in rats by subcutaneous implantation of pieces of Melinex plastic into the dorsum. The pieces of Melinex were removed at intervals varying from 16h to 14 days, and the adherent cells were studied morphologically and quantitatively. Giant cell formation started about 32h after implantation. The first giant cells to appear were of the Langerhans type. Two days after implantation, most of the giant cells are still Langhans-type cells. A few giant cells of the foreign-body type and transition forms between the Langhans and foreign-body types are also present. From the third day on, the foreign-body type gradually becomes predominant. Independent of the duration of implantation, giant cells with 3, 4, or 5 nuclei are virtually without exception of the Langhans type. The higher the number of nuclei between 6 and 30, the more cells are of the foreign-body type. Giant cells with 30 or more nuclei are all foreign-body type. The findings are discussed in the light of current knowledge concerning giant cell formation. It is concluded that under the present experimental conditions, Langhans-type giant cells are the precursors of foreign-body-type giant cells.