Failure of altered macrophage surface to lead to the formation of polykaryons.

Experiments have been performed which were designed to test the hypothesis of Mariano and Spector (1974), that the granulomatous environment leads to changes on the macrophage surface which result in fusion with normal incoming macrophages. Macrophages of different species were cultured together and it was observed that there was no apparent interaction between the xenogeneic cells, and no fusion resulted. Macrophages were cultured both in vivo and in vitro for varying periods of time before exposing them to a population of fresh macrophages. Again, no fusion was noted. Finally, an alternative hypothesis, which would account for the findings of Mariano and Spector was tested. Macrophages were cultured in inflammatory exudates, both in vitro and in diffusion chambers already containing exudate, in vivo. Inflammatory exudates were found to have no effect on macrophage fusion, either in vivo or in vitro. On the basis of previous work it is suggested that macrophage fusion depends on simultaneous endocytosis and that this in turn depends upon a supply of fresh macrophages.