Tuberculosis (TB), a global and deadly infectious disease caused by Mycobacterium tuberculosis (Mtb), is manifested with host immune reaction. The balanced regulation between protective immune and pathologic inflammatory responses is critical to control progression to TB. Chemokines are a large family of cytokines that play an essential role for chemotaxis of immune and inflammatory cells to the sites of infection. Numerous chemokines including CXCL10 were reported as potential biomarkers of various stages of TB infection. In addition, several chemokines and their receptors play as key players to coordinate host immune defense as innate effectors and mediators of adaptive immune responses.Accumulating evidence suggests that some chemokines, if uncontrolled, are associated with host pathological inflammation during infection. In this review, we will discuss recent advances in understanding which chemokines have potentials as diagnostic markers. In addition, we focus the roles and mechanisms by which chemokines and their receptors are involved in both host immune protection and pathology during TB infection. The controlled activation of chemokine system will determine the coordinated biological outcomes of innate immune responses during pathogenic infection.

Background: Observational studies of the ongoing coronavirus disease 2019 (COVID-19) outbreak suggest that a ‘cytokine storm’ is involved in the pathogenesis of severe illness.However, the molecular mechanisms underlying the altered pathological inflammation in COVID-19 are largely unknown. We report here that toll-like receptor (TLR) 4-mediated inflammatory signaling molecules are upregulated in peripheral blood mononuclear cells (PBMCs) from COVID-19 patients, compared with healthy controls (HC). Methods: A total of 48 subjects including 28 COVID-19 patients (8 severe/critical vs. 20 mild/ moderate cases) admitted to Chungnam National University Hospital, and age/sex-matched 20 HC were enrolled in this study. PBMCs from the subjects were processed for nCounter Human Immunology gene expression assay to analyze the immune related transcriptome profiles. Recombinant proteins of severe acute respiratory syndrome coronavirus-2 (SARSCoV-2) were used to stimulate the PBMCs and monocyte-derived macrophages, and real-time polymerase chain reaction was performed to quantify the mRNA expressions of the proinflammatory cytokines/chemokines. Results: Among the most highly increased inflammatory mediators in severe/critically ill patients, S100A9, an alarmin and TLR4 ligand, was found as a noteworthy biomarker, because it inversely correlated with the serum albumin levels. We also observed that recombinant S2 and nucleocapsid proteins of SARS-CoV2 significantly increased proinflammatory cytokines/chemokines and S100A9 in human primary PBMCs. Conclusion These data support a link between TLR4 signaling and pathological inflammation during COVID-19 and contribute to develop therapeutic approaches through targeting TLR4-mediated inflammation.