Decreased Neurofilament L Chain Levels in Cerebrospinal Fluid and Tolerogenic Plasmacytoid Dendritic Cells in Natalizumab-Treated Multiple Sclerosis Patients - Brief Research Report

Multiple faces of multiple sclerosis in the era of highly efficient treatment modalities: Lymphopenia and switching treatment options challenges daily practice

The expanded treatment landscape in relapsing-remitting multiple sclerosis (MS) has resulted in highly effective treatment options and complexity in managing disease- or drug-related events during disease progression. Proper decision-making requires thorough knowledge of the immunobiology of MS itself and an understanding of the main principles behind the mechanisms that lead to secondary autoimmunity affecting organs other than the central nervous system as well as opportunistic infections. The immune system is highly adapted to both environmental and disease-modifying agents. Immune reconstitution following cell depletion or cell entrapment therapies eliminates pathogenic aspects of the disease but can also lead to distorted immune responses with harmful effects. Atypical relapses occur with second-line treatments or after their discontinuation and require appropriate clinical decisions. Lymphopenia is a result of the mechanism of action of many drugs used to treat MS. However, persistent lymphopenia and cell-specific lymphopenia could result in disease exacerbation, secondary autoimmunity, or the emergence of opportunistic infections. Clinicians treating patients with MS should be aware of the multiple faces of MS under novel, efficient treatment modalities and understand the intricate brain-immune cell interactions in the context of an altered immune system. MS relapses and disease progression still occur despite the current treatment modalities and are mediated either by failure to control effector mechanisms inherent to MS pathophysiology or by new drug-related mechanisms. The multiple faces of MS due to the highly adapted immune system of patients impose the need for appropriate switching therapies that safeguard disease remission and further clinical improvement.

Impact of disease-modifying therapy on dendritic cells and exploring their immunotherapeutic potential in multiple sclerosis

Dendritic cells (DCs) are the most potent professional antigen-presenting cells (APCs), which play a pivotal role in inducing either inflammatory or tolerogenic response based on their subtypes and environmental signals. Emerging evidence indicates that DCs are critical for initiation and progression of autoimmune diseases, including multiple sclerosis (MS). Current disease-modifying therapies (DMT) for MS can significantly affect DCs' functions. However, the study on the impact of DMT on DCs is rare, unlike T and B lymphocytes that are the most commonly discussed targets of these therapies. Induction of tolerogenic DCs (tolDCs) with powerful therapeutic potential has been well-established to combat autoimmune responses in laboratory models and early clinical trials. In contrast to in vitro tolDC induction, in vivo elicitation by specifically targeting multiple cell-surface receptors has shown greater promise with more advantages. Here, we summarize the role of DCs in governing immune tolerance and in the process of initiating and perpetuating MS as well as the effects of current DMT drugs on DCs. We then highlight the most promising cell-surface receptors expressed on DCs currently being explored as the viable pharmacological targets through antigen delivery to generate tolDCs in vivo.

Neuroprotective Potential of Dendritic Cells and Sirtuins in Multiple Sclerosis

Myeloid cells, including parenchymal microglia, perivascular and meningeal macrophages, and dendritic cells (DCs), are present in the central nervous system (CNS) and establish an intricate relationship with other cells, playing a crucial role both in health and in neurological diseases. In this context, DCs are critical to orchestrating the immune response linking the innate and adaptive immune systems. Under steady-state conditions, DCs patrol the CNS, sampling their local environment and acting as sentinels. During neuroinflammation, the resulting activation of DCs is a critical step that drives the inflammatory response or the resolution of inflammation with the participation of different cell types of the immune system (macrophages, mast cells, T and B lymphocytes), resident cells of the CNS and soluble factors. Although the importance of DCs is clearly recognized, their exact function in CNS disease is still debated. In this review, we will discuss modern concepts of DC biology in steady-state and during autoimmune neuroinflammation. Here, we will also address some key aspects involving DCs in CNS patrolling, highlighting the neuroprotective nature of DCs and emphasizing their therapeutic potential for the treatment of neurological conditions. Recently, inhibition of the NAD⁺-dependent deac(et)ylase sirtuin 6 was demonstrated to delay the onset of experimental autoimmune encephalomyelitis, by dampening DC trafficking towards inflamed LNs. Thus, a special focus will be dedicated to sirtuins’ role in DCs functions.