A cytogenetic study of subcutaneous murine macrophages and multinucleate giant cells.

Macrophages and multinucleate giant cells (MGC), collected by subcutaneous implantation of melinex discs into the dorsum of mice for 7 days, were examined cytogenetically. Two per cent of the metaphases seen were polyploid and were considered to represent dividing MGC. Twenty-two per cent of the diploid metaphases showed chromosomal damage. Seventy per cent of damage consisted of chromosomal gaps, but the remaining 30% consisted of breaks and chromosomal fragments which would lead to unbalanced karyotypes in the next generation. More than 50% of the polyploid metaphases analysed had chromosomal damage, including 16.6% which displayed premature chromatin condensation, the damage being more severe in polyploid than in diploid metaphases. The chromosomal damage parallels that previously reported in resident peritoneal macrophages and in cultured exudate macrophages. The cause of such damage is unclear, but it was concluded that, because of the extent of damage, mitosis is unlikely to play a major part in the maintenance of macrophages or MGC at inflammatory sites.