The macrophage CD163 surface glycoprotein is an erythroblast adhesion receptor

Erythropoiesis occurs in erythroblastic islands, where developing erythroblasts closely interact with macrophages. The adhesion molecules that govern macrophage-erythroblast contact have only been partially defined. Our previous work has implicated the rat ED2 antigen, which is highly expressed on the surface of macrophages in erythroblastic islands, in erythroblast binding. In particular, the monoclonal antibody ED2 was found to inhibit erythroblast binding to bone marrow macrophages. Here, we identify the ED2 antigen as the rat CD163 surface glycoprotein, a member of the group B scavenger receptor cysteine-rich (SRCR) family that has previously been shown to function as a receptor for hemoglobin-haptoglobin (Hb-Hp) complexes and is believed to contribute to the clearance of free hemoglobin. CD163 transfectants and recombinant protein containing the extracellular domain of CD163 supported the adhesion of erythroblastic cells. Furthermore, we identified a 13-amino acid motif (CD163p2) corresponding to a putative interaction site within the second scavenger receptor domain of CD163 that could mediate erythroblast binding. Finally, CD163p2 promoted erythroid expansion in vitro, suggesting that it enhanced erythroid proliferation and/or survival, but did not affect differentiation. These findings identify CD163 on macrophages as an adhesion receptor for erythroblasts in erythroblastic islands, and suggest a regulatory role for CD163 during erythropoiesis.     

CD163 is the macrophage scavenger receptor for native and chemically modified hemoglobins in the absence of haptoglobin

CD163 mediates the internalization of hemoglobin-haptoglobin (Hb-Hp) complexes by macrophages. Because Hp binding capacity is exhausted during severe hemolysis, an Hp-independent Hb-clearance pathway is presumed to exist. We demonstrate that Hb interacts efficiently with CD163 in the absence of Hp. Not only is Hb internalized into an endosomal compartment by CD163 as a result of active receptor-dependent endocytosis; it also inhibits the uptake of Hb-Hp complexes, suggesting a common receptor-binding site. Free Hb further induces heme oxygenase mRNA expression in CD163+ HEK293 cells, but not in CD163- cells. Additional evidence for Hp-independent Hb-CD163 interaction is provided by the demonstration that CD163 mediates the uptake of alpha alpha-DBBF crosslinked Hb, a chemically modified Hb that forms minimal Hp complexes. Moreover, certain modifications to Hb, such as polymerization or the attachment of specific functional groups (3 lysyl residues) to the beta-Cys93 can reduce or enhance this pathway of uptake. In human macrophages, Hp-complex formation critically enhances Hb uptake at low (1 microg/mL), but not at high (greater than 100 microg/mL), ligand concentrations, lending support for a concentration-dependent biphasic model of macrophage Hb-clearance. These results identify CD163 as a scavenger receptor for native Hb and small-molecular-weight Hb-based blood substitutes after Hp depletion.     

Soluble hemoglobin-haptoglobin scavenger receptor CD163 as a lineage-specific marker in the reactive hemophagocytic syndrome

Reactive hemophagocytic syndrome (RHS) is a disease of overwhelming macrophage activity triggered by infection, malignancy or autoimmune disorders. Currently used laboratory markers for the quantitative assessment of monocyte/macrophage activation lack lineage-restricted expression patterns and thus specificity. Serum levels of the macrophage specific scavenger receptor CD163 were determined by enzyme-linked immunosorbent assay (ELISA) and were found to be highly increased in patients with RHS (median 39.0 mg/L). Significantly lower levels were determined in patients with sepsis (median 9.1 mg/L), acute mononucleosis (median 8.2 mg/L), Leishmania infection (median 6.7 mg/L) and healthy controls (median 1.8 mg/L). Follow-up of patients with a relapsing course of the disease revealed close correlations of sCD163 with clinical disease activity, serum ferritin and other markers of macrophage activity. Large sinusoidal accumulations of CD163 expressing macrophages actively engaged in phagocytosis of blood cells were detected in spleen sections of RHS patients. Our data suggests sCD163 to be a macrophage-specific marker in patients with disorders of inappropriate macrophage activation.     

Identification of the hemoglobin scavenger receptor/CD163 as a natural soluble protein in plasma.

The hemoglobin scavenger receptor (HbSR/CD163) is an interleukin-6- and glucocorticoid-regulated macrophage/monocyte receptor for uptake of haptoglobin-hemoglobin complexes. Moreover, there are strong indications that HbSR serves an anti-inflammatory function. Immunoprecipitation and immunoblotting enabled identification of a soluble plasma form of HbSR (sHbSR) having an electrophoretic mobility equal to that of recombinant HbSR consisting of the extracellular domain (scavenger receptor cysteine-rich 1-9). A sandwich enzyme-linked immunosorbent assay was established and used to measure the sHbSR level in 130 healthy subjects (median, 1.87 mg/L; range, 0.73-4.69 mg/L). To evaluate the sHbSR levels in conditions with increased leukocyte stimulation and proliferation, 140 patients admitted to a hematological department were screened. Several patients, with a broad spectrum of diagnoses, had a level of sHbSR above the range of healthy persons. Patients with myelomonocytic leukemias and pneumonia/sepsis exhibited the highest levels (up to 67.3 mg/L). In conclusion, sHbSR is an abundant plasma protein potentially valuable in monitoring patients with infections and myelomonocytic leukemia.     

Serum amyloid A is an innate immune opsonin for Gram-negative bacteria

Serum amyloid A (SAA) is the major acute-phase protein in man and most mammals. Recently we demonstrated that SAA binds to many Gram-negative bacteria including Escherichia coli and Pseudomonas aeruginosa through outer membrane protein A (OmpA) family members. Therefore we investigated whether SAA altered the response of innate phagocytic cells to bacteria. Both the percentage of neutrophils containing E coli and the number of bacteria per neutrophil were greatly increased by SAA opsonization, equivalent to the increase seen for serum opsonization. In contrast, no change was seen for Streptococcus pneumoniae, a bacteria that did not bind SAA. Neutrophil reactive oxygen intermediate production in response to bacteria was also increased by opsonization with SAA. SAA opsonization also increased phagocytosis of E coli by peripheral blood mononuclear cell-derived macrophages. These macrophages showed strong enhancement of TNF-alpha and IL-10 production in response to SAA-opsonized E coli and P aeruginosa. SAA did not enhance responses in the presence of bacteria to which it did not bind. These effects of SAA occur at normal concentrations consistent with SAA binding properties and a role in innate recognition. SAA therefore represents a novel innate recognition protein for Gram-negative bacteria.     

The type I macrophage scavenger receptor binds to gram-positive bacteria and recognizes lipoteichoic acid.

Macrophage scavenger receptors exhibit unusuallybroad binding specificity for polyanionic ligands and have been implicated inatherosclerosis and various host defense functions. Using a radiolabeled,secreted form of the type I bovine macrophage scavenger receptor in an in vitrobinding assay, we have found that this receptor binds to intact Gram-positivebacteria, including Streptococcus pyogenes, Streptococcus agalactiae,Staphylococcus aureus, Enterococcus hirae, and Listeria monocytogenes.Competition binding studies using purified lipoteichoic acid, an anionic polymerexpressed on the surface of most Gram-positive bacteria, show that lipoteichoicacids are scavenger receptor ligands and probably mediate binding of thereceptor to Gram-positive bacteria. Lipoteichoic acids, for which no host cellreceptors have previously been identified, are implicated in the pathogenesis ofseptic shock due to Gram-positive bacteria. Scavenger receptors may participatein host defense by clearing lipoteichoic acid and/or intact bacteria fromtissues and the circulation during Gram-positive sepsis. Since scavengerreceptors have been previously shown to bind to and facilitate bloodstreamclearance of Gram-negative bacterial endotoxin (lipopolysaccharide), thesereceptors may provide a general mechanism for macrophage recognition andinternalization of pathogens and their cell surface components.     

血红蛋白清道夫受体在冠心病患者中的表达及其与冠状动脉病变的关系

目的 观察血红蛋白清道夫受体(CD163)在冠心病患者中的表达及其与冠状动脉病变的关系,并探讨CD163与炎症和脂质过氧化反应的关系.方法 按美国心脏病学会/美国心脏协会冠心病处理指南的诊断标准并经冠状动脉造影确诊的84例冠心病患者纳入该研究,分为3组:急性心肌梗死(AMI)组30例,不稳定性心绞痛(UA)组30例,稳定性心绞痛(SA)组24例;并选择冠状动脉造影正常的20例非冠心病患者作为对照组.用流式细胞术检测4组患者全血单核细胞表面CD163表达水平,以平均荧光强度mfi为单位,并行冠状动脉造影,按照Jenkins评分系统进行评分.比较各组CD163的表达情况,并对CD163与冠状动脉造影评分、C反应蛋白(CRP)、低密度脂蛋白胆固醇(LDL-C)进行Spearman直线相关分析.结果 4组患者外周血单核细胞表面CD163表达水平差异有统计学意义(P<0.01).AMI组CD163表达水平[(84.4±6.9)mi]明显高于UA组[(64.1 ±5.5)mil,P<0.01]、SA组[(46.7±6.5)mfi,P<0.01]和对照组[(22.0±6.1)mfi,P<0.01],UA组CD163表达水平明显高于SA和对照组(P<0.01),SA组CD163表达水平明显高于对照组(P<0.01).冠心病患者外周血单核细胞表面CD163表达水平与Jenkins评分(r=0.9107,P<0.01)、CRP(r=0.766,P<0.01)和LDL-C水平(r=0.749,P<0.01)呈正相关.结论 随着冠心病病情加重,CD163表达水平升高,CD163表达水平可反映冠状动脉病变严重程度,CD163与炎症和脂质过氧化反应有关.     

Colon mucosa of patients both with spondyloarthritis and Crohn's disease is enriched with macrophages expressing the scavenger receptor CD163

BACKGROUND: Crohn's disease is associated with an increased number of macrophages in ileal and colonic mucosa. Data on macrophages in gut mucosa of patients with spondyloarthritis (SpA) are scarce. OBJECTIVE: To investigate macrophages and other antigen presenting cells in gut mucosa from patients with SpA and Crohn's disease, given the relationship between both entities. METHODS: Biopsy specimens from patients with SpA, Crohn's disease, ulcerative colitis, and from controls were immunohistochemically stained with different markers for macrophages and dendritic cells. Slides were scored semiquantitatively on a four point scale. RESULTS: SpA and Crohn's disease were associated with large numbers of CD68+ macrophages. Colon mucosa of both patients with SpA and Crohn's disease, but not ulcerative colitis, showed increased numbers of macrophages expressing the scavenger receptor CD163. CONCLUSIONS: Macrophages expressing the scavenger receptor CD163 are increased in colonic mucosa in SpA and in Crohn's disease, highlighting the relationship between these entities. The increased number of CD163+ macrophages in colon mucosa of patients with SpA suggests this is another argument for a role of macrophage scavenger receptors in this group of diseases.     

Antibodies from a patient with type 1 diabetes and celiac disease bind to macrophages that express the scavenger receptor CD163

Antibodies against the wheat storage globulin Glo-3A from a patient with both type 1 diabetes (T1D) and celiac disease were enriched to identify potential molecular mimicry between wheat antigens and T1D target tissues. Recombinant Glo-3A was used to enrich anti-Glo-3A immunoglobulin G antibodies from plasma by batch affinity chromatography. Rat jejunum and pancreas, as well as human duodenum and monocytes were probed, and binding was evaluated by immunohistochemistry and confocal microscopy. Glo-3A-enriched antibodies bound to a specific subset of cells in the lamina propria of rat jejunum that co-localized mostly with a marker of resident, alternatively activated CD163-positive (CD163⁺) macrophages. Blood monocytes and macrophage-like cells in human duodenum were also labelled with the enriched antibodies. Blocking studies revealed that binding to CD163⁺ macrophages was not due to cross-reactivity with anti-Glo-3A antibodies, but rather to non-Glo-3A antibodies co-purified during antibody enrichment. The novel finding of putative autoantibodies against tolerogenic intestinal CD163⁺ macrophages suggests that regulatory macrophages were targeted in this patient with celiac disease and T1D.     

The natural polyamine spermine functions directly as a free radical scavenger

The polyamines are small organic cations that are absolutely required for eukaryotic cell growth. Although their growth requirements are well established, the molecular functions of the polyamines are ill-defined. Oxidative damage to DNA by reactive oxygen species is a continual problem that cells must guard against to survive. The polyamine spermine, which is normally found in millimolar concentrations in the nucleus, is shown here to function directly as a free radical scavenger, and adducts formed as a result of this function are identified. These data suggest that spermine is a major natural intracellular compound capable of protecting DNA from free radical attack.     

CD68 and CD163 as prognostic factors for Korean patients with Hodgkin lymphoma

Background: Limited progress had been made in prognostic stratification of patients with Hodgkin lymphoma (HL) until recent studies suggested that the number of CD68‐expressing macrophages is prognostic in classical HL. However, its significance in Asian patients with HL has not been explored yet perhaps because of its low incidence in Asia. Methods: In this work, we performed immunohistochemical analysis of CD163, as well as CD68, in 144 Korean patients with HL treated between November 1990 and December 2009 in a single center. The relative percentages of CD68+ and CD163+ cells with respect to the overall cellularity (CD68 index and CD163 index, respectively) were correlated with clinical outcomes. Results: Both high CD68 and CD163 indices (>20%) were associated with a rise in treatment‐related deaths and poorer event‐free survival (P = 0.009 and P = 0.0023, respectively), disease‐specific survival (P = 0.011 and P = 0.001), and overall survival (P = 0.023 and P = 0.001). In particular, a high CD163 index was related to lower complete response (CR) rate (P = 0.022) and shorter duration of CR (P = 0.030). Conclusions: High index of either CD68 or CD163 (>20%) is significantly correlated with poor prognosis in Korean patients with HL. CD163, a specific marker of macrophages, seems to be another prognostic factor for classical HL.