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Updated: Dec 14, 2025
Isolation of Cortical Microglia with Preserved Immunophenotype and Functionality From Murine Neonates
Published on: January 30, 2014
Microglia Require CD4 T Cells to Complete the Fetal-to-Adult Transition
Emanuela Pasciuto1, Oliver T Burton2, Carlos P Roca2
1VIB Center for Brain and Disease Research, VIB, Leuven 3000, Belgium; Department of Microbiology and Immunology, KU Leuven-University of Leuven, Leuven 3000, Belgium.
Insights
The study identified CD4 T cells residing in the brain, distinct from circulating ones. Their absence impairs microglia maturation, impacting neuronal development and behavior.
Area of Science:
- Neuroimmunology
- Central Nervous System (CNS) Immunity
- Developmental Neuroscience
Background:
- The brain's immune privilege is well-established, but the presence and role of T cells, specifically CD4 T cells, in the healthy brain remain debated.
- Previous reports of CD4 T cells in the CNS are often linked to disease states, leaving their function in a healthy brain largely unexplored.
Purpose of the Study:
- To identify and characterize a distinct CD4 T cell population within the healthy brain.
- To elucidate the function of these brain-resident CD4 T cells in neurodevelopment and neurological processes.
Main Methods:
- Utilized a multi-pronged approach combining advanced imaging, single-cell sequencing, and surgical techniques in both mouse and human brain tissues.
- Investigated the origin and differentiation pathways of brain-resident CD4 T cells, including their interaction with self-antigens and the microbiome.
- Examined the consequences of CD4 T cell absence on microglial maturation and neuronal development in a murine model.
Main Results:
- Identified a unique CD69+ CD4 T cell population resident in the brain, distinguishable from circulating CD4 T cells.
- Demonstrated that brain-resident CD4 T cells originate from in situ differentiation of activated circulating cells, influenced by self-antigen and the peripheral microbiome.
- Revealed that the absence of murine CD4 T cells leads to immature microglial states, resulting in excess immature neuronal synapses and associated behavioral abnormalities.
Conclusions:
- CD4 T cells play a crucial role in brain development, influencing microglial maturation and synaptic development.
- A dynamic interplay exists between the immunological and neurological systems, with CD4 T cells acting as a key link.
- These findings challenge the traditional view of immune privilege and highlight the active involvement of adaptive immunity in brain homeostasis and development.
Abstract:
The brain is a site of relative immune privilege. Although CD4 T cells have been reported in the central nervous system, their presence in the healthy brain remains controversial, and their function remains largely unknown. We used a combination of imaging, single cell, and surgical approaches to identify a CD69+ CD4 T cell population in both the mouse and human brain, distinct from circulating CD4 T cells. The brain-resident population was derived through in situ differentiation from activated circulatory cells and was shaped by self-antigen and the peripheral microbiome. Single-cell sequencing revealed that in the absence of murine CD4 T cells, resident microglia remained suspended between the fetal and adult states. This maturation defect resulted in excess immature neuronal synapses and behavioral abnormalities. These results illuminate a role for CD4 T cells in brain development and a potential interconnected dynamic between the evolution of the immunological and neurological systems. VIDEO ABSTRACT.
