Research finds microglia consume living motor neurons in mice with late-stage ALS — Evidence Review

Scientists at the Salk Institute have discovered that immune cells in the central nervous system can actively consume living motor neurons in a mouse model of late-stage ALS, accelerating disease progression. Related research generally supports the involvement of microglia and immune dysregulation in ALS pathology, while highlighting the complex and sometimes dual roles of these cells in disease progression and repair.

• Previous studies have established that microglia become activated and contribute to motor neuron loss in ALS, particularly during later stages of the disease, and that immune system modulation can influence disease progression 1 2 5 7 8.
• The new findings build upon evidence that immune cells can mediate both harmful and protective effects in ALS, with some studies suggesting that microglia can also support motor neuron recovery under specific conditions 4 5 8.
• This study’s identification of TAM receptor-mediated targeting of living neurons expands on existing knowledge of immune mechanisms in neurodegeneration and aligns with recent research showing context-dependent roles for immune signaling pathways in synapse and neuron removal 6.

Study Overview and Key Findings

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease marked by progressive loss of motor neurons, leading to muscle paralysis and eventual respiratory failure. While much research has focused on the intrinsic vulnerability of motor neurons, growing evidence implicates immune cells, particularly microglia, in disease progression. This study is significant because it reveals a previously unrecognized mechanism by which microglia, through TAM receptors, can target and consume living motor neurons in a mouse model of ALS—a process that may contribute directly to neuronal loss and disease severity.

The importance of the study lies in its potential to shift therapeutic strategies by identifying new molecular targets (TAM receptors) involved in neurodegeneration, and by highlighting the nuanced role of immune cells in ALS—sometimes harmful, sometimes protective. Additionally, the findings have broader implications for other neurodegenerative diseases, cancer, and autoimmune therapy development.

Property	Value
Study Year	2026
Organization	Salk Institute, Harvard Medical School, UC San Diego
Journal Name	Nature Communications
Authors	Youtong Huang, Ananya Mavinkurve, Bristy Sabikunnahar, Beth Stevens, Greg Lemke
Population	Mice with late-stage ALS
Methods	Animal Study
Outcome	Microglial activity and motor neuron survival
Results	Microglia used TAM receptors to consume living motor neurons.

Literature Review: Related Studies

To contextualize these findings, we searched the Consensus research database, which indexes over 200 million scientific papers. The following queries were used to identify key literature relevant to this topic:

1. microglia motor neurons ALS
2. TAM receptors neuron consumption
3. immune cells neuronal degeneration ALS

Summary Table of Key Topics and Findings

Topic	Key Findings
How do microglia contribute to motor neuron degeneration in ALS?	- Microglia become activated and promote motor neuron death, especially during later disease stages 1 2 3 7 8. - Microglial activation can be harmful, but may also play protective roles depending on timing and context 4 5 8.
What roles do TAM receptors play in neural cell removal?	- TAM receptors are critical for recognizing and clearing dying cells, but can also mediate removal of live neurons or synapses under certain conditions 6. - Manipulation of TAM signaling can alter immune targeting of neural cells, with potential for both beneficial and deleterious effects 6.
Are immune cells beyond microglia involved in ALS progression?	- Peripheral immune cells (e.g., NK cells, cytotoxic T cells, mast cells, neutrophils) participate in motor neuron degeneration and disease progression in ALS 9 10 11. - Modulation of these immune cell populations can influence survival and symptom severity in animal models 9 10 11.

How do microglia contribute to motor neuron degeneration in ALS?

Research consistently shows that microglia, the resident immune cells of the central nervous system, are key players in ALS progression. Their activation has been linked to both exacerbation of motor neuron loss and, under certain circumstances, neuroprotection. The new study’s findings that microglia can consume living neurons via TAM receptors further clarify the mechanisms by which these cells can actively drive neurodegeneration in ALS.

• Microglia-mediated neuroinflammation is a hallmark of ALS and contributes to disease progression, especially in later stages 1 2 3 7 8.
• Targeting microglial signaling pathways (e.g., NF-κB) can slow disease progression in animal models 2.
• Microglia may also participate in recovery and repair, particularly after removal of pathological triggers 4 5.
• The dual role of microglia—harmful or protective—depends on their activation state and timing relative to disease phase 4 5 8.

What roles do TAM receptors play in neural cell removal?

TAM receptors (Tyro3, Axl, Mer) are essential for immune clearance of apoptotic cells, and recent data indicate they may also mediate the removal of living neural elements. The current study’s identification of TAM-driven phagocytosis of viable motor neurons in ALS mice provides direct evidence for this mechanism in disease, expanding on prior research about TAM function in neural remodeling and neurodegeneration.

• TAM receptor signaling enables immune cells to recognize “eat me” signals on dying cells, but can also direct removal of live synapses and, in some cases, neurons 6.
• Pharmacological or genetic modulation of TAM pathways can influence the extent and selectivity of neural cell removal, with implications for neurodevelopment as well as disease 6.
• The study’s findings suggest that aberrant TAM activation in ALS may lead to inappropriate targeting of viable neurons, contributing to pathology 6.
• These insights open possible avenues for therapeutic modulation of TAM signaling in neurodegenerative and autoimmune diseases.

Are immune cells beyond microglia involved in ALS progression?

ALS progression is not solely determined by microglial activity; other immune cell types also play important roles in motor neuron degeneration. Studies have identified contributions from NK cells, T lymphocytes, mast cells, and neutrophils in different aspects of ALS pathology, often acting through interactions with microglia or directly targeting neurons and peripheral nerves.

• Natural killer (NK) cells infiltrate ALS-affected neural tissue and can accelerate neuron loss and motor impairment 9.
• Cytotoxic CD8+ T cells expressing mutant SOD1 selectively kill spinal motoneurons, highlighting the role of adaptive immunity in ALS 11.
• Mast cells and neutrophils mediate degeneration of peripheral motor pathways, and their inhibition can reduce axonal pathology in animal models 10.
• These findings underscore the complex interplay between central and peripheral immune responses in ALS, suggesting multiple therapeutic targets.

Future Research Questions

Although the current study advances understanding of ALS pathology, several important questions remain. Future research is needed to clarify the context-dependent roles of microglia and TAM receptors, determine translational relevance to human disease, and explore therapeutic implications for ALS and related disorders.

Research Question	Relevance
Do TAM receptors mediate microglial consumption of motor neurons in human ALS patients?	Translational studies are needed to confirm whether the TAM-mediated mechanism observed in mice also operates in humans, which could inform therapeutic strategies 6 7.
Can therapeutic modulation of TAM signaling reduce motor neuron loss without impairing beneficial immune functions?	Given the dual roles of TAM receptors in both harmful and protective immune processes, targeted therapies must avoid unintended consequences 5 6 8.
What molecular triggers induce “eat me” signals on living motor neurons in ALS?	Understanding why living neurons display these signals could identify upstream targets for intervention and clarify disease mechanisms 3 5 8.
How do microglial activation states (M1 vs M2) influence motor neuron survival in ALS?	The balance between pro-inflammatory and reparative microglial states is crucial for disease outcome and may be modulated for therapeutic benefit 5 8.
What role do other immune cell types (e.g. T cells, NK cells, mast cells) play in the TAM-mediated removal of neurons in ALS?	Interactions between various immune cell populations and TAM signaling could affect disease course and response to treatment, warranting further study 9 10 11.