# Target cell tension regulates macrophage trogocytosis

## TL;DR

This study shows that the tension of a target cell's membrane influences whether macrophages trogocytose or phagocytose it.

## Contribution

The paper reveals that target cell cortical tension, not the macrophage, regulates trogocytosis versus phagocytosis.

## Key findings

- Low target cell tension promotes trogocytosis, while high tension favors phagocytosis.
- Macrophages can switch from trogocytosis to phagocytosis when membrane tension increases.
- A mechanical model explains how antibody density and cell stiffness affect this process.

## Abstract

Macrophages are known to engulf small membrane fragments, or trogocytose, target cells and pathogens, rather than fully phagocytose them. However, little is known about what causes macrophages to choose trogocytosis versus phagocytosis. Here, we report that cortical tension of target cells is a key regulator of macrophage trogocytosis. At low tension, macrophages will preferentially trogocytose antibody-opsonized cells, while at high tension they tend towards phagocytosis. Using model vesicles, we demonstrate that macrophages will rapidly switch from trogocytosis to phagocytosis when membrane tension is increased. Stiffening the cortex of target cells also biases macrophages to phagocytose them, a trend that can be countered by increasing antibody surface density and is captured in a mechanical model of trogocytosis. This work suggests that the target cell, rather than the macrophage, determines phagocytosis versus trogocytosis, and that macrophages do not require a distinct molecular pathway for trogocytosis.