Increased levels of bioactive IL-16 correlate with disease activity during relapsing experimental autoimmune encephalomyelitis (EAE)

The Fidelity of Rheumatoid Arthritis Multivariate Diagnostic Biomarkers Using Discriminant Analysis and Binary Logistic Regression

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that causes multi-articular synovitis. The illness is characterized by worsening inflammatory synovitis, which causes joint swelling and pain. Synovitis erodes articular cartilage and marginal bone, resulting in joint deterioration. This bone injury is expected to be permanent. Cytokines play a prominent role in the etiology of RA and could be useful as early diagnostic biomarkers. This research was carried out at Riyadh's King Khalid University Hospital (KKUH). Patients were enrolled from the Rheumatology unit. Seventy-eight RA patients were recruited (67 (85.9%) females and 11 (14.1%) males). Patients were selected for participation by convenience sampling. Demographic data were collected, and disease activity measurements at 28 joints were recorded using the disease activity score (DAS-28). Age- and sex-matched controls from the general population were included in the study. A panel of 27 cytokines, chemokines, and growth factors was determined in patient and control sera. Binary logistic regression (BLR) and discriminant analysis (DA) were used to analyze the data. We show that multiple cytokine biomarker profiles successfully distinguished RA patients from healthy controls. IL-17, IL-4, and RANTES were among the most predictive variables and were the only biomarkers incorporated into both BLR and DA predictive models for pooled participants (men and women). In the women-only models, the significant cytokines incorporated in the model were IL-4, IL-17, MIP-1b, and RANTES for the BLR model and IL-4, IL-1Ra, GM-CSF, IL-17, and eotaxin for the DA model. The BLR and DA men-only models contained one cytokine each, eotaxin for BLR and platelet-derived growth factor-bb (PDGF-BB) for DA. We show that BLR has a higher fidelity in identifying RA patients than DA. We also found that the use of gender-specific models marginally improves detection fidelity, indicating a possible benefit in clinical diagnosis. More research is needed to determine whether this conclusion will hold true in various and larger patient populations.

Increased Levels of IL-16 in the Central Nervous System during Neuroinflammation Are Associated with Infiltrating Immune Cells and Resident Glial Cells

Interleukin (IL)-16, a CD4+ immune cell specific chemoattractant cytokine, has been shown to be involved in the development of multiple sclerosis, an inflammatory demyelinating disease of the central nervous system (CNS). While immune cells such as T cells and macrophages are reported to be the producers of IL-16, the cellular source of IL-16 in the CNS is less clear. This study investigates the correlation of IL-16 expression levels in the CNS with the severity of neuroinflammation and determines the phenotype of cells which produce IL-16 in the CNS of experimental autoimmune encephalomyelitis (EAE) mice. Our data show that IL-16 expression is significantly increased in the brain and spinal cord tissues of EAE mice compared to phosphate buffered saline (PBS) immunised controls. Dual immunofluorescence staining reveals that the significantly increased IL-16+ cells in the CNS lesions of EAE mice are likely to be the CD45+ infiltrating immune cells such as CD4+ or F4/80+ cells and the CNS resident CD11b+ microglia and GFAP+ astrocytes, but not NeuN+ neurons. Our data suggest cytokine IL-16 is closely involved in EAE pathology as evidenced by its increased expression in the glial and infiltrating immune cells, which impacts the recruitment and activation of CD4+ immune cells in the neuroinflammation.

Correlation of myomir-206 and proinflammatory cytokines (IL-16 and IL-17) in patients with rheumatoid arthritis

Introduction

Rheumatoid arthritis (RA) is a persistent autoimmune disease in which the activity of proinflammatory cytokines and the imbalance, related to the inflammatory process, between elements of bone tissue remodeling such as osteoclasts and osteoblasts play a key role in development of erosions and bone destruction. MicroRNAs are important regulators of skeletal remodeling and are involved in RA pathogenesis. Myomir-206 (miR-206) is unrivalled among the myomirRs, where it is expressed in skeletal muscle and either absent or minimally expressed in other tissues

Material and methods

This study was designed to analyze the miR-206 expression pattern in peripheral blood mononuclear cells (PBMCs) using quantitative real time polymerase chain reaction and its correlation with IL-16/IL-17 proinflammatory cytokines in two groups – 20 healthy individuals and 30 patients with RA.

Results

Elevated expression of miR-206 was observed in RA patients compared with healthy controls (p < 0.001). A significant increase in both IL-17 and IL-16 serum levels was found in the RA group (p < 0.01 and p < 0.05; respectively) compared to the control group. miR-206 expression level and IL-17 production were directly positively correlated (r = 0.491; p < 0.01). ROC analysis of miR-206 showed a cutoff value of 2.7 with 70% sensitivity, 85% specificity, and the area under the curve was 0.802 (p < 0.001) with the 95% confidence interval from 0. 676 to 0.927

Conclusions

Taken together, our results indicate the importance of miR-206 expression in patients with RA, as a potential new biomarker that affects bone loss/deformity and its collaborative role with proinflammatory cytokines such as IL-16 and IL-17 in RA bone metabolism. Particular interest should be given to further research to determine the contribution of expression of miR-206 in RA pathogenesis

Repetitive Exposure of IL-17 Into the Murine Air Pouch Favors the Recruitment of Inflammatory Monocytes and the Release of IL-16 and TREM-1 in the Inflammatory Fluids

The infiltration of Th17 cells in tissues and organs during the development of many autoimmune diseases is considered a key step toward the establishment of chronic inflammation. Indeed, the localized and prolonged release of IL-17 in specific tissues has been associated with an increased severity of the inflammatory response that remains sustained over time. The cellular and molecular mechanisms behind these effects are far from being clear. In this study we investigated the effects of two repetitive administration of recombinant IL-17 into the murine air pouch to simulate a scenario where IL-17 is released over time in a pre-inflamed tissue. Consistent with our previous observations, mice receiving a single dose of IL-17 showed a transitory influx of neutrophils into the air pouch that peaked at 24 h and declined at 48 h. Conversely, mice receiving a double dose of the cytokine—one at time 0 and the second after 24 h—showed a more dramatic inflammatory response with almost 2-fold increase in the number of infiltrated leukocytes and significant higher levels of TNF-α and IL-6 in the inflammatory fluids. Further analysis of the exacerbated inflammatory response of double-injected IL-17 mice showed a unique cellular and biochemical profile with inflammatory monocytes as the second main population emigrating to the pouch and IL-16 and TREM-1 as the most upregulated cytokines found in the inflammatory fluids. Most interestingly, mice receiving a double injection of IL-1β did not show any change in the cellular or biochemical inflammatory response compared to those receiving a single injection or just vehicle. Collectively these results shed some light on the function of IL-17 as pro-inflammatory cytokine and provide possible novel ways to target therapeutically the pathogenic effects of IL-17 in autoimmune conditions.

Role of IL-16 in CD4+ T cell-mediated regulation of relapsing multiple sclerosis

In an important article published in Nature Medicine, Liu and colleagues described a novel CD4⁺ FoxA1⁺ regulatory T (Treg) cell population as distinct regulators of relapsing-remitting multiple sclerosis (RRMS) and experimental autoimmune encephalomyelitis (EAE). CD4⁺ FoxA1⁺ Treg cells appear as key regulators of responsiveness to therapy with interferon beta (IFN-β) in RRMS patients. Data indicate that CD4⁺FoxA1⁺ FOXP3⁻ Treg cells develop within the central nervous system (CNS), and a potential of cerebellar granule neurons (CGN) in generation of CD4⁺FoxA1⁺PD-L1^hiFOXP3⁻ Treg cells from encephalitogenic CD4⁺ T cells.

A CD4 co-receptor specific ligand, IL-16, governs trafficking and biological properties of CD4⁺ T cells irrespective of their activation state. Functions of IL-16, relevant to Treg cells, include expansion of CD4⁺CD25⁺ T cells in long-term cultures with IL-2, de novo induction of FOXP-3 and migration of FOXP-3⁺ T cells. IL-16 is highly conserved across species including human and mouse. CGN and neurons in hippocampus contain neuronal-IL-16 (NIL-16), splice variant of immune IL-16, and express CD4 molecule. In a CD4-dependent manner, IL-16 supports cultured CGN survival.

Concomitant studies of RRMS lesions and corresponding MOG_35–55-induced relapsing EAE in (B6 × SJL)F1 (H-2^b/s) mice discovered similar roles of IL-16 in regulation of relapsing disease. In RRMS and EAE relapse, peak levels of IL-16 and active caspase-3 correlated with CD4⁺ T cell infiltration and levels of T-bet, Stat-1(Tyr⁷⁰¹), and phosphorylated neurofilaments of axonal cytoskeleton [NF (M + H) P], suggesting a role of locally produced IL-16 in regulation of CD4⁺ Th1 inflammation and axonal damage, respectively. IL-16 was abundantly present in CD4⁺ T cells, followed by CD20⁺ B, CD8⁺ T, CD83⁺ dendritic cells, and Mac-1⁺ microglia. Apart from lesions, bioactive IL-16 was located in normal-appearing white matter (NAWM) and normal-appearing grey matter (NAGM) in RRMS brain and spinal cord.

A cytokine IL-16 emerges as an important regulator of relapsing MS and EAE. Better understanding of immune cell-neuron interactions mediated by IL-16 will foster development of more specific CD4⁺ T cell subset-targeted therapies to prevent or ameliorate progression of neuroinflammation and axonal and neuronal damage. Translational studies necessitate corresponding EAE models.

Interferon β-1a reduces increased interleukin-16 levels in multiple sclerosis patients

OBJECTIVES

There is convergent evidence for an important role of interleukin-16 (IL-16) in the pathogenesis of multiple sclerosis (MS). IL-16 serves as a chemoattractant for different immune cells that are involved in developing lesions. Here, we compared IL-16 levels of MS patients and controls and addressed the long-term effect of IFN-β, the most common immunomodulatory MS therapy, on IL-16 serum levels in MS patients over 2 years. Beyond this, we analysed the expression of IL-16 in two CD4(+) T-cell subsets, Th1 and Th17 cells, which are important autoimmune mediators and affected by IFN-β treatment, derived from myelin-specific T-cell transgenic mice.

MATERIALS AND METHODS

IL-16 serum levels of 17 controls and of 16 MS patients before therapy and at months 1, 2, 3, 6, 9, 12 and 24 during IFN-β1a therapy were determined by ELISA. MRI was performed before therapy, at months 12 and 24. IL-16 expression of in vitro differentiated murine myelin oligodendrocyte glycoprotein (MOG)-specific Th1 and Th17 cells was quantified by real-time PCR.

RESULTS

Before therapy, MS patients showed significantly elevated IL-16 levels compared with controls irrespective of disease activity determined by MRI. Therapy with IFN-β1a led to a significant linear decrease in IL-16 serum levels beginning after 2 months. MOG-specific Th17 cells expressed more IL-16 than Th1 cells.

CONCLUSIONS

Reduction in increased IL-16 levels may be of relevance for the therapeutic effect of IFN-β1a in MS. Easily accessible IL-16 serum levels hold a potential as biomarker of treatment efficacy in MS.

Expression of cathepsins S and D signals a distinctive biochemical trait in CD34+ hematopoietic stem cells of relapsing-remitting multiple sclerosis patients

BACKGROUND

The elucidation of mechanistic aspects of relapsing-remitting multiple sclerosis (RRMS) pathogenesis may offer valuable insights into diagnostic decisions and medical treatment.

RESULTS

Two lysosomal proteases, cathepsins S and D (CatS and CatD), display an exclusive pattern of expression in CD34(+) hematopoietic stem cells (HSCs) from peripheral blood of acute MS (A-MS) patients (n = 20). While both enzymes normally exist as precursor forms in the HSCs of healthy individuals (n = 30), the same cells from A-MS patients consistently exhibit mature enzymes. Further, mature cathepsins are expressed at lower rates in stable MS subjects (S-MS, n = 15) and revert to precursor proteins after interferon-β1a treatment (n = 5). Mature CatD and CatS were induced in HSCs of healthy donors that were either co-cultured with PBMCs of A-MS patients or exposed to their plasma, suggesting a functional involvement of soluble agents. Following HSC exposure to several cytokines known to be implicated in MS, and based on relative cytokine levels displayed in A-MS, S-MS and control individuals, we identified IL-16 as a specific cell signaling factor associated with cathepsin processing.

CONCLUSIONS

These data point to an evident correlation between CatS and CatD expression and MS clinical stage, and define a biochemical trait in HSCs with functional, medical, and diagnostic relevance.

Interleukin-16 deficiency suppresses the development of chronic rejection in murine cardiac transplantation model

BACKGROUND

IL-16 promotes the recruitment of various cells expressing CD4, a receptor for IL-16. The precise role of IL-16 in transplant rejection remains unknown; therefore, the present study investigated the contribution of IL-16 to the development of chronic rejection in heart transplants.

METHODS

C-H-2(bm12)KhEg (H-2(bm12)) donor hearts were transplanted into (1) IL-16-deficient (IL-16(-/-)) C57BL/6J or (b) wild type (WT) control recipients (MHC class II mismatch). Grafts were harvested at 52 days, parenchymal rejection was assessed by the ISHLT grading system, and CAV was examined morphometrically. Graft infiltrating cells were detected 10 and 52 days after transplantation. Intragraft cytokine and chemokine profiles were assessed. To confirm the role of IL-16 in CAV development, C-H-2(bm12)KhEg (H-2(bm12)) donor hearts were transplanted into C57BL/6J WT recipients treated with (1) anti-IL-16-neutralization monoclonal antibody or (b) control immunoglobulin G. Grafts were harvested at 52 days, and CAV was quantified morphometrically. Graft-infiltrating cells were examined histologically.

RESULTS

Parenchymal rejection and CAV was significantly attenuated in donor hearts transplanted into IL-16(-/-) recipient mice compared with WT controls. Donor hearts transplanted into IL-16(-/-) recipients had a significant reduction in coronary artery luminal occlusion, intima-to-media ratio, and percentage of diseased vessels. CAV was associated with decreased donor organ inflammation, as well as donor organ cytokine (IL-1β and IL-6) and chemokine (MCP-1 and KC) protein expression. Intimal proliferation and inflammatory cell infiltration were significantly reduced in hearts transplanted into recipients treated with an IL-16-neutralization antibody.

CONCLUSIONS

IL-16-deficiency reduced graft inflammatory cell recruitment, and allograft inflammatory cytokine and chemokine production. Therefore, IL-16 neutralization may provide a potential target for novel therapeutic treatment for cardiac allograft rejection.

A homologous form of human interleukin 16 is implicated in microglia recruitment following nervous system injury in leech Hirudo medicinalis

In contrast to mammals, the medicinal leech Hirudo medicinalis can completely repair its central nervous system (CNS) after injury. This invertebrate model offers unique opportunities to study the molecular and cellular basis of the CNS repair processes. When the leech CNS is injured, microglial cells migrate and accumulate at the site of lesion, a phenomenon known to be essential for the usual sprouting of injured axons. In the present study, we demonstrate that a new molecule, designated HmIL-16, having functional homologies with human interleukin-16 (IL-16), has chemotactic activity on leech microglial cells as observed using a gradient of human IL-16. Preincubation of microglial cells either with an anti-human IL-16 antibody or with anti-HmIL-16 antibody significantly reduced microglia migration induced by leech-conditioned medium. Functional homology was demonstrated further by the ability of HmIL-16 to promote human CD4+ T cell migration which was inhibited by antibody against human IL-16, an IL-16 antagonist peptide or soluble CD4. Immunohistochemistry of leech CNS indicates that HmIL-16 protein present in the neurons is rapidly transported and stored along the axonal processes to promote the recruitment of microglial cells to the injured axons. To our knowledge, this is the first identification of a functional interleukin-16 homologue in invertebrate CNS. The ability of HmIL-16 to recruit microglial cells to sites of CNS injury suggests a role for HmIL-16 in the crosstalk between neurons and microglia in the leech CNS repair.

Gene expression changes in multiple sclerosis relapse suggest activation of T and non-T cells

A defining feature of multiple sclerosis (MS) is the occurrence of clinical relapses separated by periods of clinical stability. Better understanding of the events underlying clinical relapse might suggest new approaches to treatment. The objective of this study was to measure changes in the expression of RNA in the blood during relapse. We used microarrays to measure mRNA expression in paired samples from 14 MS patients during clinical relapse and while stable. Seventy-one transcripts changed expression at the P < 0.001 significance level. The most notable finding was decreased expression of transcripts with regulatory function, expressed primarily in non-T cells. These decreased transcripts included the interleukin-1 receptor antagonist, which had a corresponding decrease in the protein concentration in serum. Transcripts with increased expression were expressed primarily in T cells. Pathways analysis suggested involvement of the cytokine network, coagulation and complement cascades, IL-10 signaling and NF-κB signaling. We conclude that there are alterations of mRNA expression in both T cells and non-T cells during MS relapse.

IL-12 p40 homodimer, but not IL-12 p70, induces the expression of IL-16 in microglia and macrophages

IL-16, a leukocyte chemoattractant factor (LCF), is involved in the disease process of multiple sclerosis and other autoimmune disorders. However, mechanisms by which this LCF is expressed are poorly understood. The present study underlines the importance of IL-12 p40 homodimer (p40(2)), the so-called biologically inactive molecule, in inducing the expression of IL-16 in primary mouse and human microglia, mouse BV-2 microglial cells, mouse peritoneal macrophages, and RAW264.7 cells. In contrast, IL-12 p70, the bioactive heterodimeric cytokine, was unable to induce the expression of IL-16 in any of these cell types. Similarly IL-12 p40(2) also induced the activation of IL-16 promoter in microglia. Among various stimuli tested, p40(2) was the most potent one followed by p40 monomer, IL-16 and IL-23 in inducing the activation of IL-16 promoter in microglial cells. Furthermore, induction of IL-16 mRNA expression by over-expression of p40, but not p35, cDNA and induction of IL-16 expression by p40(2) in microglia isolated from IL-12p35 (-/-) mice confirm that p40, but not p35, is responsible for the induction of IL-16. Finally, by using primary microglia isolated from IL-12Rbeta1 (-/-) and IL-12Rbeta2 (-/-) mice, we demonstrate that p40(2) induces the expression of this LCF via IL-12Rbeta1 but not IL-12Rbeta2. These results delineate a novel biological function of p40(2) and raise the possibility that biological function of IL-12 p40(2) may be different from IL-12 p70.

Autoimmune-induced preferential depletion of myelin-associated glycoprotein (MAG) is genetically regulated in relapsing EAE (B6 x SJL) F1 mice

Background

Experimental autoimmune encephalomyelitis (EAE) is commonly used to investigate mechanisms of autoimmune-mediated damage to oligodendrocytes, myelin, and axons in multiple sclerosis (MS). Four distinct autoimmune mechanisms with subsequently distinct patterns of demyelination have been recognized in acute MS lesions. EAE correlates for those distinct patterns of MS lesions are unknown. An excessive loss of myelin-associated glycoprotein (MAG), as a result of distal oligodendrogliopathy, is found exclusively in the subtype III lesion. We sought to answer if types of demyelination in acute lesions during onset and relapse of EAE can replicate the specific patterns observed in MS acute lesions.

Methods

In parental H-2^b (C57BL/6, B6) and hybrid H-2^b/s [(B6 × SJL) F1] EAE mice, we examined spinal cord levels of MOG, MAG, and myelin basic protein (MBP), and compared to levels of axonal neurofilament (NF160) to assess axonal function, and levels of PARPp85 as an indicator of irreversible apoptosis.

Results

During disease onset, levels of MOG significantly dropped in both strains, although more profoundly in H-2^b/s mice. Levels of MOG recovered in relapsing mice of both strains. Regulation of MAG was dissimilar to MOG. Modest loss of MAG was found at disease onset in both strains of mice. Unexpectedly, in relapsing H-2^b/s mice, a major depletion of MAG and NF160, accompanied with sharp elevation of PARPp85 levels, was measured. PARPp85 immunoreactivity was observed in cytoplasm and nuclei of some MBP containing cells.

Conclusion

Taken together, our results show genetically controlled distinct patterns of MOG and MAG depletion, in MOG_35–55 induced EAE in H-2^b and H-2^b/s mice. The data also suggest distinctive immune regulation of acute lesions that develop in relapsing compared to disease onset. A profound depletion of MAG, concomitant with marked depletion of axonal NF160, and sharp elevation of PARPp85 levels, occurred exclusively in relapsing H-2^b/s mice. Our findings suggest concurrence of sharp decrease of MAG levels, axonal dysfunction and irreversible apoptosis with severe relapsing disease in H-2^b/s mice. We propose that MOG-induced EAE in H-2^b/s mice may prove as a useful model in studying mechanisms, which govern autoimmune-induced preferential loss of MAG, and its impact on oligodendroglial pathology.

Preferential migration of T regulatory cells induced by IL-16

As a natural ligand for CD4, IL-16 has been shown to preferentially induce migration in Th1 cells, and, in long-term cultures with IL-2, IL-16 facilitates the expansion of CD4(+)CD25(+) cells. In addition, IL-16 has an immunomodulatory role in asthmatic inflammation, as exogenous administration significantly reduces inflammation and airway hyperreactivity. The mechanism for this, however, is not clear. Based on its functional characteristics and potential immunomodulatory role, we investigated the ability of IL-16 to recruit and influence the development of T regulatory (Treg) cells. We now demonstrate that IL-16 preferentially induces migration in a CD25(+)CTLA-4(+) human T cell subset and that responding cells produce IFNgamma and TGFbeta but not IL-10. These cells are relatively unresponsive to antigenic stimulation and can suppress proliferation and IL-5, but not IFNgamma, production by autologous T cells. We further demonstrate that IL-16-recruited cells are enriched for Forkhead box P3 (Foxp3). In addition, we find that IL-16 stimulation may facilitate de novo induction of Foxp3(+) Treg cells, because the stimulation of FoxP3-negative T cells for 48 h results in the expression of FoxP3 mRNA and protein. These data indicate that at sites of inflammation IL-16 may contribute to selective Treg cell expansion through the preferential induction of a migratory response from existing Treg cells, as well as by the induction of de novo generation of FoxP3(+) cells. These findings offer a potential mechanism for the immunosuppressive effects of IL-16 seen in Th2-mediated inflammation.

Increased levels of circulating IL-16 and apoptosis markers are related to the activity of Whipple's disease

Background

Whipple's disease (WD) is an infectious disease caused by Tropheryma whipplei, which replicates in macrophages and induces the release of interleukin (IL)-16, a substrate of caspase 3, and macrophage apoptosis. The disease is characterized by intestinal, cardiac or neurological manifestations; its diagnosis is based on invasive analysis requiring tissue biopsies or cerebrospinal fluid puncture. The disease progression is slow and often complicated by relapses despite empirical antibiotic treatment.

Methodology/Principal findings

We monitored circulating levels of IL-16 and nucleosomes in 36 French patients with WD; among them, some patients were enrolled in a longitudinal follow-up. As compared to control subjects, the circulating levels of both IL-16 and nucleosomes were increased in untreated patients with WD presenting as intestinal, cardiac or neurological manifestations. This finding was specific to WD since the circulating levels of IL-16 and nucleosomes were not increased in patients with unrelated inflammatory diseases such as inflammatory bowel disease or Q fever endocarditis. We also found that increased levels of IL-16 and nucleosomes were related to the activity of the disease. Indeed, successful antibiotic treatment decreased those levels down to those of control subjects. In contrast, patients who suffered from relapses exhibited circulating levels of IL-16 and nucleosomes as high as those of untreated patients.

Conclusions/Significance

Circulating levels of both IL-16 and nucleosomes were increased in WD. This finding provides simple and non-invasive tools for the diagnosis and the prognosis of WD.

Production of IL-16 correlates with CD4+ Th1 inflammation and phosphorylation of axonal cytoskeleton in multiple sclerosis lesions

Background

Multiple sclerosis (MS) is a central nervous system-specific autoimmune, demyelinating and neurodegenerative disease. Infiltration of lesions by autoaggressive, myelin-specific CD4+Th1 cells correlates with clinical manifestations of disease. The cytokine IL-16 is a CD4+ T cell-specific chemoattractant that is biased towards CD4+ Th1 cells. IL-16 precursor is constitutively expressed in lymphocytes and during CD4+ T cell activation; active caspase-3 cleaves and releases C-terminal bioactive IL-16. Previously, we used an animal model of MS to demonstrate an important role for IL-16 in regulation of autoimmune inflammation and subsequent axonal damage. This role of IL-16 in MS is largely unexplored. Here we examine the regulation of IL-16 in relation to CD4+ Th1 infiltration and inflammation-related changes of axonal cytoskeleton in MS lesions.

Methods

We measured relative levels of IL-16, active caspase-3, T-bet, Stat-1 (Tyr ⁷⁰¹), and phosphorylated NF(M+H), in brain and spinal cord lesions from MS autopsies, using western blot analysis. We examined samples from 39 MS cases, which included acute, subacute and chronic lesions, as well as adjacent, normal-appearing white and grey matter. All samples were taken from patients with relapsing remitting clinical disease. We employed two-color immunostaining and confocal microscopy to identify phenotypes of IL-16-containing cells in frozen tissue sections from MS lesions.

Results

We found markedly increased levels of pro- and secreted IL-16 (80 kD and 22 kD, respectively) in MS lesions compared to controls. Levels of IL-16 peaked in acute, diminished in subacute, and were elevated again in chronic active lesions. Compared to lesions, lower but still appreciable IL-6 levels were measured in normal-appearing white matter adjacent to active lesions. Levels of IL-16 corresponded to increases in active-caspase-3, T-bet and phosphorylated Stat-1. In MS lesions, we readily observed IL-16 immunoreactivity confined to infiltrating CD3+, T-bet+ and active caspase-3+ mononuclear cells.

Conclusion

We present evidence suggesting that IL-16 production occurs in MS lesions. We show correlations between increased levels of secreted IL-16, CD4+ Th1 cell inflammation, and phosphorylation of axonal cytoskeleton in MS lesions. Overall, the data suggest a possible role for IL-16 in regulation of inflammation and of subsequent changes in the axonal cytoskeleton in MS.