Identification of a novel conserved signaling motif in CD200 receptor required for its inhibitory function

Mast cell silencing: A novel therapeutic approach for urticaria and other mast cell-mediated diseases

Chronic urticaria (CU) is a mast cell (MC)-dependent disease with limited therapeutic options. Current management strategies are directed at inhibiting IgE-mediated activation of MCs and antagonizing effects of released mediators. Due to the complexity and heterogeneity of CU and other MC diseases and mechanisms of MC activation-including multiple activating receptors and ligands, diverse signaling pathways, and a menagerie of mediators-strategies of MC depletion or MC silencing (i.e., inhibition of MC activation via binding of inhibitory receptors) have been developed to overcome limitations of singularly targeted agents. MC silencers, such as agonist monoclonal antibodies that engage inhibitory receptors (e.g., sialic acid-binding immunoglobulin-like lectin8 -[Siglec-8] [lirentelimab/AK002], Siglec-6 [AK006], and CD200R [LY3454738]), have reached preclinical and clinical stages of development. In this review, we (1) describe the role of MCs in the pathogenesis of CU, highlighting similarities with other MC diseases in disease mechanisms and response to treatment; (2) explore current therapeutic strategies, categorized by nonspecific immunosuppression, targeted inhibition of MC activation or mediators, and targeted modulation of MC activity; and (3) introduce the concept of MC silencing as an emerging strategy that could selectively block activation of MCs without eliciting or exacerbating on- or off-target, immunosuppressive adverse effects.

Immune Targeted Therapies for COVID-19 Infection: A Narrative Review

In December 2019, the coronavirus disease-2019 (COVID-19) outbreak emerged in Wuhan, China. The World Health Organization officially declared it a pandemic on March 11, 2020. Reports indicated that the associated mortality of the infection is quite higher in the elderly, individuals with specific comorbidities (such as diabetes mellitus), and generally the ones with a compromised immune system. A cohort study in Wuhan, China, reported a dysregulated immune response in 452 patients with laboratory-confirmed COVID-19. As a result of this suppressed immune response, an increase in neutrophil to lymphocyte ratio, T lymphopenia, and a decrease in CD4⁺ T cells were all common laboratory findings, especially in severe cases. On the other hand, there is substantial evidence of T cell exhaustion in critically ill patients. Accordingly, the immune system seems to play an important role in the prognosis and pathogenesis of the disease. Therefore, this study aims to review the evidence on the immune response dysregulation in COVID-19 infection and the potential role of immunoregulatory treatments such as immune checkpoint inhibitors, interferons, and CD200 inhibitors in altering disease prognosis, especially in critically ill patients.