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Microglial cells are a component of the perivascular glia limitans
H Lassmann1, F Zimprich, K Vass
1Institute of Brain Research, Austrian Academy of Sciences, Vienna.
Abstract:
The ultrastructural relation between microglial cells and cerebral blood vessels was studied in rat brains by immune electron microscopy using antibodies against the common leukocyte antigen (Ox1), the complement receptor 3 (Ox42), and against class I and class II histocompatibility antigens (MHC antigens; Ox3, Ox6, Ox18, and I1-69). Microglial cell processes were found incorporated between the astrocytic foot processes of the glia limitans in 4-13% of cerebral microvessels. After intravenous injection of gamma-interferon, either alone or in combination with tumor necrosis factor, these microglial cell processes expressed classes I and II MHC antigens. Studies in (Lewis X DA)F1-DA bone marrow chimeras demonstrated that these cell processes belonged to resident microglia. This study suggests that microglial cells may play an important role in antigen recognition at the blood-brain barrier.
Insights
Microglial cells interact with rat cerebral blood vessels, expressing MHC antigens after cytokine stimulation. These findings suggest microglia play a key role in blood-brain barrier antigen recognition.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia are the primary immune cells of the central nervous system.
- The interaction between microglia and cerebral vasculature is crucial for brain homeostasis and immune surveillance.
- Understanding the role of microglia at the blood-brain barrier is essential for neuroinflammatory diseases.
Purpose of the Study:
- To investigate the ultrastructural relationship between microglial cells and cerebral blood vessels in rat brains.
- To determine the expression of major histocompatibility complex (MHC) antigens on microglial cell processes at the blood-brain barrier.
- To identify the origin of microglial cell processes interacting with cerebral microvessels.
Main Methods:
- Immune electron microscopy was employed using specific antibodies against leukocyte and MHC antigens.
- Rat brains were analyzed to identify microglial cell processes associated with cerebral microvessels.
- Cytokine treatments (gamma-interferon and tumor necrosis factor) were administered to assess antigen expression.
- Bone marrow chimeras were used to trace the origin of microglial cells.
Main Results:
- Microglial cell processes were observed integrated within the glia limitans of 4-13% of cerebral microvessels.
- Intravenous administration of gamma-interferon and/or tumor necrosis factor induced expression of class I and II MHC antigens on these microglial processes.
- Studies using bone marrow chimeras confirmed that these cell processes originate from resident microglia.
Conclusions:
- Microglial cells establish direct contact with cerebral blood vessels, extending processes between astrocytic foot processes.
- Microglia at the blood-brain barrier can be activated to express MHC antigens, indicating a role in antigen presentation.
- These findings highlight the potential of resident microglia to participate in immune surveillance and antigen recognition at the blood-brain barrier.