COVID-19 and immune-mediated inflammatory diseases: Why don't our patients get worse?

Platelet-leukocyte crosstalk in COVID-19: How might the reciprocal links between thrombotic events and inflammatory state affect treatment strategies and disease prognosis?

Platelet-leukocyte crosstalk is commonly manifested by reciprocal links between thrombosis and inflammation. Platelet thrombus acts as a reactive matrix that recruits leukocytes to the injury site where their massive accumulation, activation and migration promote thrombotic events while triggering inflammatory responses. As a life-threatening condition with the associations between inflammation and thrombosis, COVID-19 presents diffuse alveolar damage due to exaggerated macrophage activity and cytokine storms. These events, together with direct intracellular virus invasion lead to pulmonary vascular endothelialitis, cell membranes disruption, severe endothelial injury, and thrombosis. The developing pre-alveolar thrombus provides a hyper-reactive milieu that recruits circulating leukocytes to the injury site where their activation contributes to thrombus stabilization and thrombosis propagation, primarily through the formation of Neutrophil extracellular trap (NET). NET fragments can also circulate and deposit in further distance where they may disseminate intravascular thrombosis in severe cases of disease. Thrombi may also facilitate leukocytes migration into alveoli where their accumulation and activation exacerbate cytokine storms and tissue damage, further complicating the disease. Based on these mechanisms, whether an effective anti-inflammatory protocol can prevent thrombotic events, or on the other hand; efficient antiplatelet or anticoagulant regimens may be associated with reduced cytokine storms and tissue damage, is now of interests for several ongoing researches. Thus shedding more light on platelet-leukocyte crosstalk, the review presented here discusses the detailed mechanisms by which platelets may contribute to the pathogenesis of COVID-19, especially in severe cases where their interaction with leukocytes can intensify both inflammatory state and thrombosis in a reciprocal manner.

Rise and exacerbation of oral lichen planus in the background of SARS-CoV-2 infection

Oral Lichen Planus (OLP) is a chronic inflammatory disorder whose exact etiology remains unknown. Inflammatory mediators, cytotoxic CD8+ T cells and mast cells have been hypothesized to mediate the pathogenesis of OLP. COVID-19 pandemic caused by SARS-CoV-2 is marked by cytokine storms in the affected patients. Altered T-cell responses marked by exhaustion of T-cell count with hyperaggressive remaining T-cells and presence of cross-reactive antibodies render infected humans as fertile grounds for development of multisystem disorders. In addition, Vitamin D deficiency in COVID-19 patients can further modify the T cell mediated immunity. Increased circulating cytokines and hyperactive CD8+ T cells can alter the oral immune barriers rendering them susceptible to oral disorders. Due to the widespread immune dysregulation, it is possible that patients of COVID-19 may develop OLP in the aftermath or during recovery. The paper explores the pathogenic mechanism behind development OLP as post-COVID condition on account of their target receptor, T-cell responses, cytokine profile, mucosal immune barriers and nutrition deficiency.