Data from: Efferocytosis perpetuates substance accumulation inside macrophage populations

In both cells and animals, cannibalism can transfer harmful substances
from the consumed to the consumer. Macrophages are immune cells that
consume their own dead via a process called cannibalistic efferocytosis.
Macrophages that contain harmful substances are found at sites of chronic
inflammation, yet the role of cannibalism in this context remains
unexplored. Here we take mathematical and experimental approaches to study
the relationship between cannibalistic efferocytosis and substance
accumulation in macrophages. Through mathematical modelling, we deduce
that substances which transfer between individuals through cannibalism
will concentrate inside the population via a coalescence process. This
prediction was confirmed for macrophage populations inside a closed
system. We used image analysis of whole slide photomicrographs to measure
both latex microbead and neutral lipid accumulation inside murine bone
marrow-derived macrophages (104-105 cells) following their stimulation
into an inflammatory state ex vivo. While the total number of phagocytosed
beads remained constant, cell death reduced cell numbers and efferocytosis
concentrated the beads among the surviving macrophages. % from small to
large numbers per cell. Since lipids are also conserved during
efferocytosis, these cells accumulated lipid derived from the membranes of
dead and consumed macrophages (becoming macrophage foam cells).
Consequently, enhanced macrophage cell death increased the rate and extent
foam cell formation. Our results demonstrate that cannibalistic
efferocytosis perpetuates exogenous (e.g. beads) and endogenous (e.g.
lipids) substance accumulation inside macrophage populations. As such,
cannibalism has similar detrimental consequences in both cells and
animals.