Choroid plexus selectively accumulates T-lymphocytes in normal controls and after peripheral immune activation

Area of Science:

• Neuroimmunology
• Immunology

Background:

• Systemic immune activation can lead to immune cell infiltration into the central nervous system.
• The choroid plexus (CPx) acts as a barrier and interface between the blood and cerebrospinal fluid (CSF).

Purpose of the Study:

• To investigate T-lymphocyte migration into the brain and CPx following systemic immune activation induced by enterotoxin.
• To determine the preferential site of T-lymphocyte accumulation within the central nervous system.

Main Methods:

• Induction of systemic immune activation using enterotoxin in a mouse model.
• Quantification of T-lymphocyte populations in the brain and CPx via cell counting and flow cytometry.
• Assessment of T-cell apoptosis to rule out cell death as a factor in accumulation.

Main Results:

• T-lymphocyte numbers in the CPx were significantly higher than in the brain in control mice.
• Enterotoxin administration led to a substantial, up to 150-fold, increase in CPx T-lymphocytes and up to 17-fold increase in brain T-lymphocytes.
• T-lymphocytes were observed to accumulate in the subependymal and periventricular regions of the brain.
• No evidence of T-cell apoptosis was found, indicating active migration and accumulation.

Conclusions:

• T-lymphocytes show a preferential migration pattern towards the choroid plexus over the brain parenchyma following systemic immune activation.
• The choroid plexus may serve as a critical entry point or reservoir for T-lymphocytes that subsequently infiltrate the brain.
• Brain T-cells may originate from the CPx through direct migration or dissemination via the cerebrospinal fluid.