The Renal Mononuclear Phagocytic System

Abstract

The renal mononuclear phagocytic system, conventionally composed of macrophages (Mø) and dendritic cells (DCs), plays a central role in health and disease of the kidney. Overlapping definitions of renal DCs and Mø, stemming from historically separate research tracks and the lack of experimental tools to specifically study the roles of these cells in vivo, have generated confusion and controversy, however, regarding their immunologic function in the kidney. This brief review provides an appraisal of the current state of knowledge of the renal mononuclear phagocytic system interpreted from the perspective of immunologic function. Physical characteristics, ontogeny, and known functions of the main subsets of renal mononuclear phagocytes as they relate to homeostasis, surveillance against injury and infection, and immune-mediated inflammatory injury and repair within the kidney are described. Gaps and inconsistencies in current knowledge are used to create a roadmap of key questions to be answered in future research.

Physiology of the Renal Interstitium

“…In addition, it is believed that the interstitium plays a role in fluid and electrolyte exchange and insulation (1). Here we focus on fibroblasts and specifically on fibroblasts with endocrine function and their biology in health and disease (other articles have extensively reviewed cellular constituents of the immune system within the renal interstitium [9,10]) ( Figure 1). …”

CX3CR1 Reduces Kidney Fibrosis by Inhibiting Local Proliferation of Profibrotic Macrophages

“…T he renal mononuclear phagocyte system consists of an extensive network of mononuclear phagocytes (i.e., dendritic cells [DCs] and macrophages) (1,2). Although there is no clear demarcation between these cell types, DCs are typically specialized at regulating other immune effector cells, especially T cells, whereas macrophages preferentially act as immune effectors in innate immune responses or contribute to tissue repair (3)(4)(5)(6).…”

“…Furthermore, CD11c + kidney cells possess a transcriptome that resembles that of DCs but not of macrophages (8,9). Although kidney DCs have been shown to perform sentinel and regulatory functions in inflammation and infection (10), macrophages contributed to host protection from infection and maintained tissue homeostasis (1,11,12). In contrast, inappropriate macrophage functions promoted fibrosis in various organs (13,14).…”

Innate Immune Response to Urinary Tract Infections Involving Escherichia coli

“…As an infection progresses, or becomes complicated, neutrophils recruit monocytes and macrophages, and recruit and activate dendritic cells [58][59][60]. The macrophages also function in phagocytosis and produce proinflammatory cytokines and additional toxic metabolites [61]. Dendritic cells acting as antigen-presenting cells are a primary inducer of adaptive immunity.…”

“…Dendritic cells acting as antigen-presenting cells are a primary inducer of adaptive immunity. Dendritic cells may also function in innate immune regulation [61,62]. Neutrophils may additionally function as a bridge to adaptive immunity by acting as antigen-presenting cells [63].…”