The origin of monocyte-macrophage heterogeneity: possible alternatives

The heterogeneity of the monocyte-macrophage population may be explained by several alternatives. In the present study we summarize our data and other studies concerning the variability and instability in the expression of markers and functions by monocytes and macrophages as well as the analysis of cloned populations of macrophages. We suggest the hypothesis that most macrophage heterogeneity may be due to reversible changes in a multifunctional population.