Antibodies and brain disease: a convergence of immunology and physiology

Alterations in Blood-Brain Barrier Permeability in Patients with Systemic Lupus Erythematosus

BACKGROUND AND PURPOSE

Neuropsychiatric systemic lupus erythematosus refers to central and peripheral nervous system involvement, which may occur secondary to antineuronal antibodies crossing the blood-brain barrier that preferentially target cells in the hippocampus leading to abnormal hypermetabolism and atrophy. Thus, we hypothesized that alterations in BBB permeability, detected on dynamic contrast-enhanced MR imaging, occur in the hippocampus in patients with systemic lupus erythematosus before development of neuropsychiatric systemic lupus erythematosus.

MATERIALS AND METHODS

Six patients with systemic lupus erythematosus without neuropsychiatric systemic lupus erythematosus and 5 healthy controls underwent dynamic contrast-enhanced MR imaging with postprocessing into BBB permeability parameters (K ^trans and Ve) and CBF. Standardized methods selected ROI sampling of the abnormal brain regions detected on FDG-PET. The mean and SD of K ^trans, Ve, and CBF were calculated. Linear regression and nonparametric Spearman rank correlation analyses of K ^trans and Ve with CBF were performed. Dynamic contrast-enhanced curves and the area under the curve were generated for each brain region. Student t test comparisons were performed.

RESULTS

Quantitative data revealed that patients with systemic lupus erythematosus have statistically increased K ^trans (P < .001) and Ve (P < .001) compared with controls. In patients with systemic lupus erythematosus, statistically significant positive correlations were seen between K ^trans (P < .001) and Ve (P < .001) with CBF. Furthermore, the mean area under the curve revealed statistically increased BBB permeability in the hippocampus (P = .02) compared with other brain regions in patients with systemic lupus erythematosus compared with controls.

CONCLUSIONS

These initial findings are proof-of-concept to support the hypothesis that patients with systemic lupus erythematosus have increased BBB permeability, specifically in the hippocampus, compared with other brain regions. These findings may advance our understanding of the underlying pathophysiology affecting the brain in autoimmune diseases.

A model for lupus brain disease

Systemic lupus erythematosus is an autoimmune disease characterized by antibodies that bind target autoantigens in multiple organs in the body. In peripheral organs, immune complexes engage the complement cascade, recruiting blood-borne inflammatory cells and initiating tissue inflammation. Immune complex-mediated activation of Fc receptors on infiltrating blood-borne cells and tissue resident cells amplifies an inflammatory cascade with resulting damage to tissue function, ultimately leading to tissue destruction. This pathophysiology appears to explain tissue injury throughout the body, except in the central nervous system. This review addresses a paradigm we have developed for autoantibody-mediated brain damage. This paradigm suggests that antibody-mediated brain disease does not depend on immune complex formation but rather on antibody-mediated alterations in neuronal activation and survival. Moreover, antibodies only access brain tissue when blood-brain barrier integrity is impaired, leading to a lack of concurrence of brain disease and tissue injury in other organs. We discuss the implications of this model for lupus and for identifying other antibodies that may contribute to brain disease.

Anti-alpha-internexin autoantibody from neuropsychiatric lupus induce cognitive damage via inhibiting axonal elongation and promote neuron apoptosis

BACKGROUND

Neuropsychiatric systemic lupus erythematosus (NPSLE) is a major complication for lupus patients, which often leads to cognitive disturbances and memory loss and contributes to a significant patient morbidity and mortality. The presence of anti-neuronal autoantibodies (aAbs) has been identified; as examples, anti-NMDA receptors and anti-Ribsomal P aAbs have been linked to certain pathophysiological features of NPSLE.

METHODS AND FINDINGS

In the current study, we used a proteomic approach to identify an intermediate neurofilament alpha-internexin (INA) as a pathogenetically relevant autoantigen in NPSLE. The significance of this finding was then validated in an expanded of a cohort of NPSLE patients (n = 67) and controls (n = 270) by demonstrating that high titers of anti-INA aAb was found in both the serum and cerebrospinal fluid (CSF) of approximately 50% NPSLE. Subsequently, a murine model was developed by INA immunization that resulted in pronounced cognitive dysfunction that mimicked features of NPSLE. Histopathology in affected animals displayed cortical and hippocampal neuron apoptosis. In vitro studies further demonstrated that anti-INA Ab mediated neuronal damage via inhibiting axonal elongation and eventually driving the cells to apoptosis.

CONCLUSIONS

Taken together, this study identified a novel anti-neurofilament aAb in NPSLE, and established a hitherto undescribed mechanism of aAb-mediated neuron damage that could have relevance to the pathophysiology of NPSLE.

Autoantibodies involved in neuropsychiatric manifestations associated with systemic lupus erythematosus

In the course of Systemic Lupus Erythematosus (SLE), a variety of neuropsychiatric disturbances is reported with a prevalence ranging from 17% to 75%. The diagnosis of these syndromes is difficult and requires a careful psychiatric evaluation. Distinct autoantibodies detectable in serum or cerebrospinal fluid of patients with SLE are associated with the presence of neuropsychiatric disorders. These autoantibodies may have a pathogenic relevance in neuropsychiatric SLE or they may be merely an epiphenomenon. This review describes the various autoantibodies reported to be associated with neuropsychiatric manifestations in SLE and discusses their possible role.

Non-MS autoimmune demyelination

Connective tissue diseases can be characterised by central nervous system (CNS) involvement, in some patients manifested by demyelination areas in the white matter of the brain and spinal cord, which are difficult to differentiate from multiple sclerosis (MS) and other demyelinating processes, such as transverse myelitis and optic neuritis. Demyelinating process may be the feature of nervous impairment in systemic lupus erythematosus, Behcet's disease (BD), Sjoegren's syndrome (SS), systemic sclerosis (SSc) or very rarely other systemic autoimmune diseases. An acute isolated neurological syndrome, as the most common symptom of MS can sometimes be the only feature or even first manifestation of nervous impairment in connective tissue disease, hence presenting the diagnostic problem. Although the white matter abnormalities seen by magnetic resonance imaging may be similar in non-MS autoimmune demyelination and MS, it is the most important diagnostic tool in the differential diagnosis of the mentioned conditions. Investigating the presence of various autoantibodies potentially involved in the pathogenesis of demyelinating lesions as well as cerebrospinal fluid (CSF) analysis can be helpful.