Prologue: The “Long Arm” of DAMPs in Shaping Adaptive Immune Responses and Tissue Repairing Processes

Abstract

This chapter provides a propaedeutic introduction to the leading topic of Part VIII, namely, the role of DAMPs in shaping adaptive immune responses. It begins with a few introductory remarks on the definition, nature, and mechanisms of the human adaptive immune system that is uniquely present in vertebrates and mainly made up of the thymus-derived lymphocytes (T cells) and bone marrow-derived lymphocytes (B cells). These cells are equipped with unique receptors that recognize virtually any foreign antigen presented to them by antigen-presenting cells of the innate immune system. The nature of the antigen receptor on T and B cells is different. The T cell antigen receptor is related to immunoglobulin and is specially adapted to detect antigens derived from foreign proteins or pathogens that have entered into host antigen-presenting cells. The B cell antigen receptor is a membrane-bound form of an antibody that the B cell will secrete after activation and differentiation to a plasma cell. A crucial role in instigating adaptive immune responses is played by the professionals among antigen-presenting cells, the dendritic cells. A unique feature of dendritic cells is their dichotomous function as grounded in their ability to maintain the intricate balance between immunity and tolerance by instigating and orchestrating adaptive destructive and protective immune responses. The chapter ends with the remark that the “long arm” of DAMPs is not restricted to shaping adaptive immune responses aimed at defending the host against injury but is also involved in subsequent restoration of tissue lesions induced by the damage. In fact, tissue regeneration and repair following pathogen-mediated or sterile tissue injury are critical biological processes that are fundamental to the survival of all living organisms.