Abstract
The complement system, an evolutionarily ancient component of innate immunity, is capable of protecting hosts from invading pathogens, either directly, by lysis of target cells, or indirectly, by mobilization of host immune mechanisms. However, this potentially cytotoxic cascade must be tightly regulated, since improperly controlled complement can damage healthy cells and tissues. The practical importance of this axis is highlighted when impairment of complement regulators or bacterial mechanisms of complement evasion result in pathogenic conditions. Recognition of complement as a “double-edged sword” is widely acknowledged, but another, currently underappreciated aspect of complement function has emerged as an important player in homeostatic balance—the dual outcome of complement-mediated inflammation. In most cases, the proinflammatory properties of complement are beneficial to the host. However, certain pathogens have developed the ability to utilize local inflammation as a source of nutrients and as a way to establish a niche for further colonization. Such a strategy can be illustrated in the example of periodontitis. Interestingly, certain tumors also seem to benefit from complement activation products, which promote a proangiogenic and immunosuppressive microenvironment.
Highlights
Frontiers in ImmunologyThe complement system, an evolutionarily ancient component of innate immunity, is capable of protecting hosts from invading pathogens, either directly, by lysis of target cells, or indirectly, by mobilization of host immune mechanisms
The term “inflammo-philic” (=loving or attracting inflammation) was introduced in 2014 by George Hajishengallis to describe dysbiotic microbiome on the tooth surface below the gum line, which thrive in the inflammatory environment of periodontal pockets [1]
Another study showed a 3.6-fold increase in human umbilical vein endothelial cells (HUVECs) expression of complement receptor 1 (CR1 or CD35) after 48 h of hypoxia [48]. These results suggest that endothelial cells actively counteract complement activation under hypoxic conditions, and the expression of complement inhibitors in hypoxic NSCLC cells was studied [49]
Summary
The complement system, an evolutionarily ancient component of innate immunity, is capable of protecting hosts from invading pathogens, either directly, by lysis of target cells, or indirectly, by mobilization of host immune mechanisms. This potentially cytotoxic cascade must be tightly regulated, since improperly controlled complement can damage healthy cells and tissues. Certain pathogens have developed the ability to utilize local inflammation as a source of nutrients and as a way to establish a niche for further colonization. Such a strategy can be illustrated in the example of periodontitis.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
