Intrathecal Immune Responses in Multiple Sclerosis

Multiple sclerosis (MS) is characterised by chronic inflammation within the central nervous system, where aberrant immune responses contribute to demyelination and neurodegeneration. Intrathecal immune responses arise when B cells and plasma cells migrate into the leptomeninges and perivascular spaces, establishing local antibody production detectable in cerebrospinal fluid (CSF). A hallmark of MS is the presence of oligoclonal immunoglobulin G (IgG) bands in CSF, reflecting persistent intrathecal synthesis. This polyspecific humoral reaction often targets neurotropic viruses—including measles, rubella and varicella zoster—forming the so-called MRZ reaction (MRZR), which serves both as a diagnostic biomarker and as a window into underlying disease biology. Beyond IgG, intrathecal production of IgM and IgA has been implicated in more aggressive disease courses, correlating with lesion burden on magnetic resonance imaging and higher risk of early disability. Recent work has elucidated how cerebrospinal cytokine milieus, chemokines and B-cell-activating factors shape plasma cell survival and antibody secretion within tertiary lymphoid structures in the meninges. Such structures may drive epitope spreading, recruiting plasmablasts against a broad array of antigens and perpetuating local inflammation. Understanding the balance between protective and pathogenic intrathecal immunity is vital for the development of therapies that target central compartments of MS pathology, with the aim of limiting progression without compromising systemic immune competence.

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Intrathecal Immune Responses in Multiple Sclerosis publication trend

The graph below shows the total number of articles in intrathecal immune responses in multiple sclerosis across all publications each year (not limited to Nature Index journals).

Technical terms

Intrathecal synthesis: Local production of immunoglobulins within the subarachnoid space rather than in peripheral blood.

Oligoclonal bands (OCB): Discrete bands of IgG detected by electrophoresis in CSF, indicating clonal expansion of B cells.

MRZ reaction (MRZR): Polyspecific intrathecal IgG response against measles (M), rubella (R) and varicella zoster (Z) viruses.

Antibody index (AI): Ratio comparing virus-specific antibody levels in CSF to those in serum, indicating intrathecal production when elevated.

Cerebrospinal fluid (CSF): Clear fluid surrounding the brain and spinal cord, used to assess central nervous system immune activity.

References

1. Intrathecal immune reactivity against Measles-, Rubella-, and Varicella Zoster viruses is associated with cerebrospinal fluid inflammation in multiple sclerosis. Multiple Sclerosis Journal (2024).
2. Parvovirus B19 and mumps virus antibodies are major constituents of the intrathecal immune response in European patients with MS and increase the diagnostic sensitivity and discriminatory power of the MRZ reaction. Journal of Neurology (2021).
3. Identification of the Immunological Changes Appearing in the CSF During the Early Immunosenescence Process Occurring in Multiple Sclerosis. Frontiers in Immunology (2021).
4. Does Disease-Irrelevant Intrathecal Synthesis in Multiple Sclerosis Make Sense in the Light of Tertiary Lymphoid Organs?. Frontiers in Neurology (2014).