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 16 h to 14 days, and the adherent cells were studied morphologically and quantitatively. Giant cell formation started about 32 h after implantation. The first giant cells to appear were of the Langhans 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.