C1q: A Molecular Bridge to Innate and Adaptive Immunity

Abstract

Like in most fields in science, the complement system is also in a fast gear of self-evolution, with new discoveries of unanticipated pathways and functions capable of cross-talk with other biologic systems. An emerging area that has been gaining much attention recently is the role of locally synthesized complement proteins, which mediate a plethora of cellular functions thereby enhancing either health or disease. Prominent among the locally synthesized proteins is C1q, the first subcomponent of the complement classical pathway, which has been shown to regulate a wide range of immunological and pathological processes in autocrine or paracrine manners. Although the main source of the local synthesis of C1q has been attributed to the potent antigen presenting cells such as macrophages and dendritic cells, where it plays as a powerful molecular sensor of danger and regulator of self-tolerance, the list of the type of cells that locally synthesize C1q has been expanding over the years and now includes various types of proliferating and non-proliferating cells including malignant cells. The aim of the current “Frontiers Topic” is, therefore, to compile a comprehensive list of review and research articles by experts in the field, so that they can be a major source of information for researchers and clinicians alike.