High levels of CCL26 in blister fluid and sera of patients with bullous pemphigoid

Advancing Treatment in Bullous Pemphigoid: A Comprehensive Review of Novel Therapeutic Targets and Approaches

Bullous pemphigoid is one of the most common autoimmune bullous diseases occurring primarily in the elderly. Pathogenic autoantibodies against BP180 and BP230 at the dermal-epidermal junction cause subepidermal blisters, erosions, and intense pruritus, all of which adversely affect the patients' quality of life and may increase their morbidity and mortality. Current systemic treatment options for bullous pemphigoid are limited to corticosteroids and immunosuppressants, which can have substantial side effects on these vulnerable patients that even exceed their therapeutic benefits. Therefore, more precisely, targeting therapies to the pathogenic cells and molecules in bullous pemphigoid is an urgent issue. In this review, we describe the pathophysiology of bullous pemphigoid, focusing on autoantibodies, complements, eosinophils, neutrophils, proteases, and the T helper 2 and 17 axes since they are crucial in promoting proinflammatory environments. We also highlight the emerging therapeutic targets for bullous pemphigoid and their latest discoveries in clinical trials or experimental studies. Further well-designed studies are required to establish the efficacy and safety of these prospective therapeutic options.

The cytokine milieu of bullous pemphigoid: Current and novel therapeutic targets

Bullous pemphigoid (BP) is the most common autoimmune bullous disease, characterized by severe pruritus and skin blistering. The loss of tolerance against Collagen XVII, also referred to as BP180, is the main pathogenic event of BP, leading to production of IgG autoantibodies which mainly target the juxtamembranous extracellular non-collagenous 16th A (NC16A) domain of BP180. A complex inflammatory network is activated upon autoantibody binding to the basement membrane zone; this inflammatory loop involves the complement cascade and the release of several inflammatory cytokines, chemokines and proteases from keratinocytes, lymphocytes, mast cells and granulocytes. Collectively, these events disrupt the integrity of the dermal-epidermal junction, leading to subepidermal blistering. Recent advances have led to identify novel therapeutic targets for BP, whose management is mainly based on the long-term use of topical and systemic corticosteroids. As an example, targeting type-2 T-helper cell-associated cytokines, such as Interleukin-4 and interleukin-13 has shown meaningful clinical efficacy in case series and studies; targeting IL-17 and IL-23 has also been tried, owing to an important role of these cytokines in the chronic maintenance phase of BP. In this review article, we discuss the complex cytokine milieu that characterized BP inflammation, highlighting molecules, which are currently investigated as present and future therapeutic targets for this life-threatening disease.

Emerging Biomarkers and Therapeutic Strategies for Refractory Bullous Pemphigoid

Bullous pemphigoid (BP) is the most common autoimmune subepidermal blistering disorder in the elderly. Systemic and topical use of glucocorticoids and immunosuppressants has been shown to be effective in most patients. However, refractory BP patients are challenged to clinicians with severe clinical symptoms, resistance to treatment, and high relapse rate. How to predict and assess the refractory and severity of bullous pemphigoid is the key issue in clinical practice, and the urgent need for precision medicine in refractory patients is driving the search for biomarkers and biologics. Recently, some biomarkers, such as the level of specific autoantibodies and released cytokines, have been proposed as the potential parameters to reflect the disease severity and predict the treatment response and relapse of refractory BP. Moreover, new biologics targeting pathogenic antibodies, complement, Th2 axis, eosinophils, and Th17 axis have shown potent efficacy on refractory BP. Here, we review the literature and give an overview of emerging biomarkers and therapeutic strategies for refractory bullous pemphigoid to improve the prognosis of the patient.

Factors associated with the activity and severity of bullous pemphigoid: a review

Bullous pemphigoid (BP) is the most common subepidermal autoimmune blistering disease. It usually affects people older than 70 years of age. The two main autoantigens are BP180 and BP230, both of which are components of hemidesmosomes. Immunoglobulin (Ig)G and IgE autoantibodies to BP180 detected by the enzyme-linked immunoassay (ELISA) show close associations with the activity and severity of BP. In addition, inflammatory cells (eosinophils, neutrophils and mast cells) and cytokines (e.g. interleukins and CC chemokine ligands) play an important part in the pathogenesis, activity and severity of BP. We summarized the potential contribution of each factor postulated to be associated with the activity and severity of BP, and provide guidance for clinicians to pay timely and close attention to such parameters. This review may also promote the development of novel therapies for BP.Key MessagesBullous Pemphigoid Disease Area Index (BPDAI) is a scoring system which can reflect the extent of clinical involvement of BP patients.The titres of IgE autoantibodies and IgG autoantibodies against the NC16A domain of BP180 are closely correlated with the activity and severity of BP.Many inflammatory cells and molecules, such as eosinophils and interleukins, can also reflect the activity and severity of BP.

Proinflammatory role of blister fluid-derived exosomes in bullous pemphigoid

Bullous pemphigoid is an autoimmune inflammatory disorder characterized by the presence of autoantibodies against bullous pemphigoid autoantigens, leading to dermal-epidermal separation with consequent blister formation. However, whether and how the components of blister fluid exacerbate the progression of bullous pemphigoid is unclear. Exosomes are nanometre-sized vesicles released from cells into the body fluid, where they can transmit signals throughout the body. In the present study, we isolated and characterized exosomes from blister fluids of patients with bullous pemphigoid, evaluated their proinflammatory role, and identified the underlying molecular mechanisms. We found that exosomes isolated from blister fluids of patients with bullous pemphigoid showed the expected size and expressed the marker proteins CD63, CD81, and CD9. Additionally, blister fluid-derived exosomes were internalized by human primary keratinocytes, inducing the production of critical inflammatory cytokines and chemokines. Western blotting analysis showed robust and rapid activation of the extracellular signal-regulated kinase 1/2 and signal transducer and activator of transcription 3 signalling pathways in human primary keratinocytes after stimulation with blister fluid-derived exosomes. We also found that blister fluid-derived exosomes indirectly induced neutrophil trafficking by upregulating C-X-C motif chemokine ligand 8 in vitro. Furthermore, CD63 was localized mostly to keratinocytes and infiltrative granulocytes in skin lesions, suggesting that these cells were the possible sources of exosomes in blister fluid. Using mass spectrometry, we analysed the proteomes of blister fluid-derived exosomes and identified a variety of proteins implicated in inflammatory and immune responses. Together, our findings provide strong evidence that blister fluid-derived exosomes are involved in the local autoinflammatory responses of the skin associated with bullous pemphigoid. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

BP180 Is Critical in the Autoimmunity of Bullous Pemphigoid

Bullous pemphigoid (BP) is by far the most common autoimmune blistering dermatosis that mainly occurs in the elderly. The BP180 is a transmembrane glycoprotein, which is highly immunodominant in BP. The structure and location of BP180 indicate that it is a significant autoantigen and plays a key role in blister formation. Autoantibodies from BP patients react with BP180, which leads to its degradation and this has been regarded as the central event in BP pathogenesis. The consequent blister formation involves the activation of complement-dependent or -independent signals, as well as inflammatory pathways induced by BP180/anti-BP180 autoantibody interaction. As a multi-epitope molecule, BP180 can cause dermal-epidermal separation via combining each epitope with specific immunoglobulin, which also facilitates blister formation. In addition, some inflammatory factors can directly deplete BP180, thereby leading to fragility of the dermal-epidermal junction and blister formation. This review summarizes recent investigations on the role of BP180 in BP pathogenesis to determine the potential targets for the treatment of patients with BP.

Differential serum levels of eosinophilic eotaxins in primary sclerosing cholangitis, primary biliary cirrhosis, and autoimmune hepatitis

To investigate pathogenic mechanisms of primary sclerosing cholangitis (PSC), primary biliary cirrhosis (PBC), and autoimmune hepatitis (AIH), serum levels of 26 chemokines and cytokines were determined and compared with patients with chronic hepatitis C or in healthy controls. The chemokine eotaxin-3 (E3; CCL26), which recruits eosinophils to sites of inflammation, was found to be highly elevated in all PSC, PBC, and AIH patients compared with HCV patients and healthy controls. Eotaxin-1 (E1; CCL11), another eosinophil-specific chemokine, was elevated in PSC but reduced in PBC and AIH, while the macrophage-derived chemokine (MDC; CCL22) was lower in all PSC, PBC, and AIH patients compared with HCV patients and controls. By incorporating levels of the interleukin (IL)-15 into a diagnostic algorithm, PSC, PBC, and AIH patients could each be differentiated with good sensitivity and specificity. These findings represent the first study to compare the level of serum cytokine/chemokine levels among these related autoimmune-like liver diseases. Furthermore, our data indicate that the measurement of serum E3, E1, CCL22, and IL-15 levels can aid in the diagnosis of these clinically challenging diseases and shed light on the potential pathogenic mechanisms underlying these diseases. By suggesting a potential role for an allergic phenomenon involving eosinophils, which may define them as liver-specific allergic diseases, this may open up potential new therapeutic avenues by abrogating the action of these disease-associated immune modulators.