Central memory CD4+ T cells dominate the normal cerebrospinal fluid

Area of Science:

• Neuroimmunology
• Immunology
• Cell Biology

Background:

• Cerebrospinal fluid (CSF) immune phenotyping requires established reference values for white blood cell (WBC) subsets.
• Understanding normal immune cell populations in CSF is vital for diagnosing and researching neuro-inflammatory conditions.

Purpose of the Study:

• To establish reference values for WBC subsets in CSF using immune phenotyping.
• To characterize the distribution and phenotype of immune cells in the central nervous system (CNS) under normal conditions.

Main Methods:

• 6-color flow cytometry was used to analyze paired CSF and blood samples from 84 healthy individuals.
• Absolute counts and percentages of various leukocyte subsets, including lymphocytes (T, NK, NKT, B cells), granulocytes, monocytes, and dendritic cells, were quantified.
• T cell subsets were further analyzed for naive, central memory, effector memory, and regulatory phenotypes.

Main Results:

• CSF demonstrated a higher proportion of T cells compared to blood, with granulocytes, B cells, and NK cells being less frequent.
• CD4(+) T cells constituted the majority (approximately 70%) of T cells in CSF, predominantly exhibiting a central memory phenotype (approximately 90%).
• B cells were nearly absent (<1%) in CSF, while myeloid dendritic cells were more abundant than plasmacytoid dendritic cells in CSF compared to blood.

Conclusions:

• The study provides essential reference values for WBC subsets in CSF, aiding in the investigation of neuro-inflammatory diseases.
• The significant presence of CD4(+) T cells with a central memory phenotype and dendritic cells in CSF indicates an active adaptive immune response in the normal CNS.