Macrophages are essential to the immune system because they combat infections and help heal damaged tissue. It's critical to comprehend how these cells are triggered in various contexts to design novel medical interventions.

The complexity of cells and their reactions has made it difficult to identify and research macrophage activation.

The protein known as colony-stimulating factor 1 receptor (CSF1R) was discovered by the study team to be a dependable marker for macrophages in tissues and monocytes and dendritic cells in blood, enabling the distinct identification and separation of various sample types. People of all ages and genders can dependably use the new method.

Dr Fernando Martinez Estrada, who led the research project and is a Senior Lecturer in Innate Immunology at the School of Biosciences at the University of Surrey, said, "We have developed a method using CSF1R that can identify all types of Mononuclear phagocyte system cells in the body. This marker is incredibly useful for studying these cells in both health and disease, and it unlocks exciting new possibilities for cell isolation and quantification for diagnosing and monitoring various conditions with a single cell marker."

The study developed a set of tools to understand and check how these immune cells respond when they are activated.

These tools focus on signals in the body, including IL-4 (involved in healing and fibrosis), steroids (deactivation), IFNg (fights infections), and LPS (a bacterial product that causes inflammation).

The research team also described a novel concept that they call Macrophage Activation Mosaicism. This means that macrophages do not simply switch between the canonical two states previously described; instead, they can exhibit a mix of activation characteristics, reflecting the complexity of real tissue environments.

Dr Federica Orsenigo, co-author of the study, explains further, "This discovery is significant because it changes how we perceive macrophage activation.

"Recognising that macrophages can have mixed activation status helps us better understand their roles in different diseases and could lead to more targeted and effective treatments."

Emeritus Professor Siamon Gordon, co-author of the study from the University of Oxford, said:
"Therapies that seek to re-educate macrophages are widely sought. However, the tools to measure activation are underdeveloped. Having a robust multi-gene tool to study macrophage activation can help in drug screening, identify drugs that revert macrophage activation, and eventually help with patient characterisation and personalised medicine."