Arnon Karni

Increased T cell reactivity to amyloid β protein in older humans and patients with Alzheimer disease

Alzheimer disease (AD) is characterized by the progressive deposition of the 42-residue amyloid beta protein (Abeta) in brain regions serving memory and cognition. In animal models of AD, immunization with Abeta results in the clearance of Abeta deposits from the brain. However, a trial of vaccination with synthetic human Abeta1-42 in AD resulted in the development of meningoencephalitis in some patients. We measured cellular immune responses to Abeta in middle-aged and elderly healthy subjects and in patients with AD. A significantly higher proportion of healthy elderly subjects and patients with AD had strong Abeta-reactive T cell responses than occurred in middle-aged adults. The immunodominant Abeta epitopes in humans resided in amino acids 16-33. Epitope mapping enabled the identification of MHC/T cell receptor (TCR) contact residues. The occurrence of intrinsic T cell reactivity to the self-antigen Abeta in humans has implications for the design of Abeta vaccines, may itself be linked to AD susceptibility and course, and appears to be associated with the aging process.

Innate Immunity in Multiple Sclerosis: Myeloid Dendritic Cells in Secondary Progressive Multiple Sclerosis Are Activated and Drive a Proinflammatory Immune Response

Multiple sclerosis (MS) is postulated to be a T cell-mediated autoimmune disease characterized clinically by a relapsing-remitting (RR) stage followed by a secondary progressive (SP) phase. The progressive phase is felt to be secondary to neuronal degenerative changes triggered by inflammation. The status of the innate immune system and its relationship to the stages of MS is not well understood. Dendritic cells (DCs) are professional APCs that are central cells of the innate immune system and have the unique capacity to induce primary immune responses. We investigated circulating myeloid DCs isolated directly from the blood to determine whether there were abnormalities in myeloid DCs in MS and whether they were related to disease stage. We found that SP-MS subjects had an increased percentage of DCs expressing CD80, a decreased percentage expressing PD-L1, and an increased percentage producing IL-12 and TNF-α compared with RR-MS or controls. A higher percentage of DCs from both RR and SP-MS patients expressed CD40 compared with controls. We then investigated the polarization effect of DCs from MS patients on naive T cells taken from cord blood using a MLR assay. Whereas DCs from RR-MS induced higher levels of Th1 (IFN-γ, TNF-α) and Th2 (IL-4, IL-13) cytokines compared with controls, DCs from SP-MS only induced a polarized Th1 response. These results demonstrate abnormalities of DCs in MS and may explain the immunologic basis for the different stages and clinical patterns of MS.

Lower brain-derived neurotrophic factor in serum of relapsing remitting MS: Reversal by glatiramer acetate

Neuronal growth factors may exert a neuroprotective effect in multiple sclerosis (MS). We found reduced levels of brain-derived neurotrophic factors (BDNF) in the serum and CSF of relapsing-remitting MS patients, which was reversed by therapy with glatiramer acetate. BDNF may play a protective role in MS, and immunomodulation therapy, such as with glatiramer acetate, may enhance the action this mechanism.

IL-18 is linked to raised IFN-γ in multiple sclerosis and is induced by activated CD4+ T cells via CD40–CD40 ligand interactions

We investigated T cell receptor induced IL-18 secretion, the cellular and molecular mechanisms associated with the induction of IL-18 and the role of IL-18 in IFN-gamma production in the different stages of multiple sclerosis (MS). We found that anti-CD3/CD28 induced IL-18 production by peripheral blood mononuclear cells was increased in both relapsing-remitting and secondary progressive MS. In controls and relapsing-remitting MS neutralizing anti-IL-12 and anti-IL-18 alone equally suppressed IFN-gamma production whereas in progressive MS, maximum suppression of IFN-gamma was only observed when neutralizing anti-IL-12 and anti-IL-18 were given together, suggesting that in progressive MS, IL-12 and IL-18 function in a non-linked manner to induce IFN-gamma. Elevated IL-18 production in MS was dependent on the interaction of antigen presenting cells with activated CD4(+) T cells via CD40-CD40 ligand and the levels of IL-18 correlated with disease duration in secondary progressive MS. These results demonstrated that IL-18 has an important role in augmenting Th-1 type immune responses in MS and may be involved in immune changes that occur when patients enter the progressive stage.

Association of MS with thyroid disorders

Article abstract A controlled prospective study was conducted to determine whether thyroid disorders are present with increased frequency in patients with MS. We found that thyroid disorders were at least three times more common in women with MS than in female controls. This was accounted for mainly by the prevalence of hypothyroidism among the female MS patients. Because hypothyroidism is usually due to Hashimoto’s thyroiditis, its association with MS may support the hypothesis of autoimmune pathogenesis for MS. Our findings might have therapeutic implications because interferon treatment can induce antithyroid antibodies and thyroiditis.

Low and dysregulated BDNF secretion from immune cells of MS patients is related to reduced neuroprotection.

Multiple sclerosis (MS) is characterized by lesions with inflammatory infiltration, demyelination and axonal damage in the CNS white matter that correlates with the extent of disease disability. Knowledge of up-regulatory triggers of neuroprotective pathways in the CNS is essential for the development of the next generation of disease therapies. Recent studies have suggested a neuroprotective activity of the lesion-infiltrating immune cells. We studied the secretion of brain-derived neurotrophic factor (BDNF) from the immune cells of untreated patients with relapsing remitting (RR) MS with mild to moderate disability and sought immune factors that regulate the BDNF levels and affect the survival of neuronal cells in vitro. We found lower than normal secreted levels of BDNF from the immune cells of these patients. The normal effect of CD40 stimulation that up-regulates BDNF secretion levels and induces neuroprotection was absent in the MS patients, while the expression of CD40 on their monocytes was elevated. The failure of BDNF availability from immune cells in patients with RR-MS and the loss of a neuroprotective effect by these cells may be related to a more widespread phenomenon of deviated immunity in MS, and may be linked to the continuous CNS neuronal tissue loss during the course of this disease.

Cyclophosphamide modulates CD4+ T cells into a T helper type 2 phenotype and reverses increased IFN-γ production of CD8+ T cells in secondary progressive multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system considered to be mediated by T helper type-1 cells. Several agents have been found to modify the disease course of MS, including interferon-beta1 (IFN-beta1), glatiramer acetate mitoxantrone. We have employed pulse therapy with cyclophosphamide in a selected group of patients with actively progressive disease. Chemokine receptors have been found to differentiate between polarized T helper type-1 (Th1) and type-2 (Th2) lymphocytes. The chemokine receptors CCR5 and CXCR3 are expressed primarily on Th1 cells and CCR3, CCR4 and CCR8 on Th2 cells. Previous studies of the expression of chemokine receptors in MS have shown that active MS plaques are infiltrated by CCR5(+) and CXCR3(+) T cells. Some of these T cells may express both CCR5 and CXCR3. These T cells are major producers of IFN-gamma, which worsens the clinical condition of patients with MS. We previously found that patients with MS had a high proportion of CXCR3(+) T cells and that those with chronic progressive MS had a high proportion of CCR5(+) T cells in their peripheral blood. We report here that in patients with secondary progressive MS, cyclophosphamide induces a marked increase in the percentage of CCR4(+) T cells that produce high levels of IL-4 and reverses the increase in the percentages of IFN-gamma-producing CCR5(+) and CXCR3(+) CD8(+) T cells. Furthermore, therapy with cyclophosphamide increases IL-4-producing CD4(+) T cells and reverses the increase in IFN-gamma-producing CD8(+) T cells. Our study shows that cyclophosphamide has immunomodulatory properties besides its suppressive effects, and that chemokine receptors can be important tools both for understanding the immune dysregulation in MS and for monitoring response to therapy.

In vitro induction of regulatory T cells by anti-CD3 antibody in humans

Therapy with anti-CD3 antibody is effective in controlling models of autoimmune diseases and can reverse or prevent rejection of grafts. We studied the in vitro immunomodulatory effect of anti-CD3 treated human T cells. CD4(+) T cells were stimulated with plate-bound anti-CD3 and cultured for 12 days after which they were cultured with autologous peripheral blood mononuclear cells (PBMCs) and stimulated with soluble anti-CD3. We found that CD4(+) T cells that were stimulated with anti-CD3 (T(alphaCD3)) markedly suppressed the proliferation and cytokine production of autologous PBMCs. These regulatory T cells were not induced by incubation with isotype control (T(control)) antibody or when anti-CD3 was combined with high doses of anti-CD28 (T(alphaCD3/CD28)). T(alphaCD3) regulatory cells were anergic and produced lower levels of IFN-gamma, TNF-alpha and IL-2, and higher levels of TGF-beta than T(control) or T(alphaCD3/CD28). There were no differences in the expression of CD25 or CTLA4 on T(alphaCD3) as compared to T(control) or T(alphaCD3/CD28), and CD4(+) CD25(-) T(alphaCD3) cells were identical to CD4(+) CD25(+) T(alphaCD3) cells in their in vitro suppressive properties. Recombinant IL-2 in vitro abrogated the suppressive effect of T(alphaCD3). The suppressive effect was not related to apoptosis, was independent of HLA since T(alphaCD3) also suppressed allogeneic PBMCs, and was not related to soluble factors. Finally, no suppression was observed when non-T cells were removed from culture or when cultures were stimulated with plate-bound anti-CD3, consistent with the ability of T(alphaCD3) to downregulate CD80 on dendritic cells in co-culture experiments. Thus, we have identified human T cells with strong in vitro regulatory properties induced in vitro by anti-CD3 which appear to act in a non-HLA restricted fashion by affecting antigen presenting cells.

Extra-cranial venous flow in patients with multiple sclerosis

INTRODUCTION Recently, a chronic state of impaired venous drainage from the central nervous system, termed chronic cerebrospinal venous insufficiency (CCSVI) was claimed to be a pathologic condition exclusively seen in patients with multiple sclerosis (MS), suggesting that cerebral venous congestion plays a significant role in the pathogenesis of MS. This hypothesis has gained enormous attention among patients and physicians but has been questioned since. METHODS Twenty seven patients with MS and 32 healthy controls underwent color extra cranial Doppler exam aimed to detect four parameters of abnormal venous flow: no Doppler-detected flow in the IJV or vertebral veins (VV), reflux in the internal jugular veins (IJVs), venous flow stenosis in the IJVz (cross sectional area <0.3 cm) or reverted postural control in the IJV. RESULTS Except for one healthy patient, blood flow direction in the IJVs was normal in all subjects. When aiming to detect at least one parameter of abnormal venous flow per subject, two parameters or three parameters no significant difference was found between subjects and controls (p = 0.707, 0.62, 0.849 respectively). CONCLUSION We found no evidence to suggest that MS patients have excess of CCSVI. In addition we failed to observe a typical venous flow pattern in MS patients. Until carefully designed controlled studies to investigate CCVSI have been completed, invasive and potentially dangerous endovascular procedures as therapy for MS should be discouraged.

Interferon-β therapy up-regulates BDNF secretion from PBMCs of MS patients through a CD40-dependent mechanism

We had reported that immune cells from relapsing remitting multiple sclerosis (RR-MS) patients secrete low levels of BDNF and that there is a defective regulation of its secretion via DC40. We now studied the effect of interferon-beta (IFN-beta1) on the secretion and regulation of BDNF from immune cells in patients with RR-MS. The PBMCs of IFN-beta1a treated RR-MS patients secreted higher BDNF levels vs. untreated patients. Anti CD40 mAb stimulation of PBMCs of IFN-beta1a treated patients upregulated the BDNF levels. There was no significant effect of CD40 stimulation on PBMCs of untreated patients. CD40(+) expression on CD14(+) cells was higher in IFN-beta treated patients vs. untreated patients. In vitro treatment with IFN-beta1a of PBMCs from healthy controls and untreated patients led to a significant increase in CD40 expression on CD14(+) cells in both groups. The addition of IFN-beta1a to CD40 stimulated PBMCs of untreated patients restored the up regulatory effect of CD40 stimulation on BDNF levels. Therefore, reduced BDNF secretion from PBMCs and defective regulation effect of CD40 stimulation on BDNF levels in untreated RR-MS are reversible by therapy with IFN-beta1a.