Macrophage cell lines are often used for phagocytosis studies. I want to know whether cells at different states of cell cycles have different manner/efficiency regarding phagocytosis..
I would say that the most important aspect of macrophage phagocytosis is their activation state. Are your macrophages pro-inflammatory M1-like or more tissue repair/anti-inflammatory M2-like? These elements are dependent upon which cell line you are using and culturing conditions. It might be useful to polarize them with LPS, IFNg, or IL4/IL10 prior to your phagocytosis assay. Also, these cell types will have very different cell proliferation signals, which would correlate with, but not cause changes in phagocytosis activity. For example, your LPS-stimulated macrophages get both proliferation and phagocytosis signals. I'm not sure about the other phenotypes, but it would be interesting to find out.
I am working with Raw 264.7 murine macrophage cell line, and some of my experiments are based on LPS stimulated phagocytic activity in these cells. That's why i was concerned about observed phagocytosis in LPS treated cells. It is likely that It may be affected by variation in cell cycles of LPS treated/untreated cells.
You can try fluorochrome labeled E.coli and then propidium iodide for cell cycle. There is just one problem about reading on FCM. Cell cycle process needs linear, the other uses log scale.