Visual observations of chemotaxis and chemotropism in mouse macrophages

Locomotion of mouse macrophages in relation to spores of Candida albicans in mouse serum was studied by time-lapse cinematography using thioglycollate-elicited peritoneal macrophages, resident peritoneal macrophages, and a murine macrophage line (J774 B10). Thioglycollate-elicited macrophages and the cell line responded well to the spores, but very few of the resident macrophages showed any response. The macrophages showed chemotactic responses with straight-line locomotion towards spores. Thioglycollate-elicited macrophages, which were frequently spread on glass, could also respond to spores 20-30 micrometers away by chemotropism, i.e. extension of a large hyaline veil to engulf the spore without prior displacement of the body of the cell. Engulfed spores were then pulled into the organelle-rich cell centre. In this population, there was no incompatibility between spread morphology and motile behaviour. In contrast, J774 B10 did not spread and moved with a rounded morphology and with a very small anterior hyaline veil towards the gradient source. Macrophages moved more slowly than peripheral blood neutrophils and monocytes. The mean speed of thioglycollate-elicited and cell line macrophages was 3-4 micrometers per minute. The few motile resident peritoneal macrophages moved even more slowly, i.e. ca 2 micrometers per minute.