The Roles of Chemokines in Immune Response to Mycobacterial Infection

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.

The Roles of Chemokines in Immune Response to Mycobacterial Infection

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.

Effector Pathways of Toll-like Receptor-inducible Innate Immune Responses in Macrophages

Toll-like receptors (TLR) are well-characterized pattern recognition receptors that can recognize and respond to diverse pathogen-associated or danger-associated molecular patterns during infection. TLR signaling in macrophages triggers in the intracellular signaling pathways through the recruitment of various adaptor and signaling proteins, and results in the activation of effector mechanisms and pathways that are important for host defense to intracellular bacteria. Effector mechanisms include inflammatory responses, cytokine generation, production of reactive oxygen species, and antimicrobial proteins. Accumulating studies showed that autophagy is a key pathway in the maintenance of homeostasis and housekeeping functions during infection and inflammation. In this review, we summarize the major effector pathways and mechanisms in the activation of TLR-inducible innate immune responses in macrophages. In addition, we focus the emerging evidence of crosstalk between autophagy and TLR-mediated signaling in terms of effector function of innate immune responses. A better understanding of effector functions by the activation of TLR-mediated signaling cascades contributes to the development of new therapeutics and vaccines against various intracellular pathogenic infections.

Mitochondrial Control of Innate Immunity and Inflammation

Mitochondria are key organelles involved in energy production, functioning as the metabolic hubs of cells. Recent findings emphasize the emerging role of the mitochondrion as a key intracellular signaling platform regulating innate immune and inflammatory responses. Several mitochondrial proteins and mitochondrial reactive oxygen species have emerged as central players orchestrating the innate immune responses to pathogens and damaging ligands. This review explores our current understanding of the roles played by mitochondria in regulation of innate immunity and inflammatory responses. Recent advances in our understanding of the relationship between autophagy, mitochondria, and inflammasome activation are also briefly discussed. A comprehensive understanding of mitochondrial role in toll-like receptor-mediated innate immune responses and NLRP3 inflammasome complex activation, will facilitate development of novel therapeutics to treat various infectious, inflammatory, and autoimmune disorders.