Macrophage Receptors and Immune Recognition

Abstract

Macrophages express a broad range of plasma membrane receptors that mediate their interactions with natural and altered-self components of the host as well as a range of microorganisms. Recognition is followed by surface changes, uptake, signaling, and altered gene expression, contributing to homeostasis, host defense, innate effector mechanisms, and the induction of acquired immunity. This review covers recent studies of selected families of structurally defined molecules, studies that have improved understanding of ligand discrimination in the absence of opsonins and differential responses by macrophages and related myeloid cells.

Chemokine receptor Ccr5 deficiency induces alternative macrophage activation and improves long‐term renal allograft outcome

“…On the one side macrophage populations exist, which are negative for F4/80 (e.g. three of the four macrophage subpopulations in the spleen); on the other side several non-macrophage cell types stain positive for F4/80 (eosinophils, some DC) [36]. We did not observe significant differences concerning F4/80 1 cells in allografts from WT or Ccr5-deficient recipients.…”

“…Macrophages are involved in innate as well as adaptive immunity and play a key role for the initiation as well as the resolution phase of immune responses [36]. They are also able to shape the type of immune response.…”

EMR1, the human homolog of F4/80, is an eosinophil‐specific receptor

“…Due to its cell specificity, the F4/80 antigen has been of crucial importance, initially, for the characterization of the murine mononuclear phagocyte system [2,3] and, later, for the detection of macrophages in innumerable in vivo studies. F4/80 is highly expressed on resident tissue phagocytic cells including macrophages in the BM, the thymic cortex, the lymph node medulla, and the splenic red pulp, Kupffer cells in the liver, Langerhans cells in the skin, and microglia in the central nervous system.…”

Requirement of phospholipase C‐γ2 (PLCγ2) for Dectin‐1‐induced antigen presentation and induction of TH1/TH17 polarization

“…Because they bridge innate and adaptive immunity, DC are equipped with a multitude of intracellular and cell surface receptors that sense microbial components and trigger host responses to invading pathogens. These receptors, collectively known as PRR, include TLR [3], C-type lectins such as Dectin-1 [4], scavenger receptors [5], the nucleotide-binding oligomerization domain (NOD) proteins NOD1 and NOD2, the NOD-like receptors and the RIG-like receptors [6].Dectin-1 recognizes b-glucan, a major constituent of many fungi's outer cell wall [4,7] and triggers intracellular signals through a cytoplasmic tyrosine motif resembling the ITAM. Upon ligand binding, this motif is phosphorylated by src family kinases [8] and recruits the tyrosine kinase Syk [9], which initiates a signaling cascade leading to NF-kB [10], NFAT [11] and MAPK [12] activation.…”

“…Because they bridge innate and adaptive immunity, DC are equipped with a multitude of intracellular and cell surface receptors that sense microbial components and trigger host responses to invading pathogens. These receptors, collectively known as PRR, include TLR [3], C-type lectins such as Dectin-1 [4], scavenger receptors [5], the nucleotide-binding oligomerization domain (NOD) proteins NOD1 and NOD2, the NOD-like receptors and the RIG-like receptors [6].…”