Masayuki Miyasaka

Regulation of humoral and cellular gut immunity by lamina propria dendritic cells expressing Toll-like receptor 5

The intestinal cell types responsible for defense against pathogenic organisms remain incompletely characterized. Here we identify a subset of CD11chiCD11bhi lamina propria dendritic cells (LPDCs) that expressed Toll-like receptor 5 (TLR5) in the small intestine. When stimulated by the TLR5 ligand flagellin, TLR5+ LPDCs induced the differentiation of naive B cells into immunoglobulin A–producing plasma cells by a mechanism independent of gut-associated lymphoid tissue. In addition, by a mechanism dependent on TLR5 stimulation, these LPDCs promoted the differentiation of antigen-specific interleukin 17–producing T helper cells and type 1 T helper cells. Unlike spleen DCs, the LPDCs specifically produced retinoic acid, which, in a dose-dependent way, supported the generation and retention of immunoglobulin A–producing cells in the lamina propria and positively regulated the differentiation interleukin 17–producing T helper cells. Our findings demonstrate unique properties of LPDCs and the importance of TLR5 for adaptive immunity in the intestine.

Detection of pathogenic intestinal bacteria by Toll-like receptor 5 on intestinal CD11c+ lamina propria cells

Toll-like receptors (TLRs) recognize distinct microbial components and induce innate immune responses. TLR5 is triggered by bacterial flagellin. Here we generated Tlr5−/− 1mice and assessed TLR5 function in vivo. Unlike other TLRs, TLR5 was not expressed on conventional dendritic cells or macrophages. In contrast, TLR5 was expressed mainly on intestinal CD11c+ lamina propria cells (LPCs). CD11c+ LPCs detected pathogenic bacteria and secreted proinflammatory cytokines in a TLR5-dependent way. However, CD11c+ LPCs do not express TLR4 and did not secrete proinflammatory cytokines after exposure to a commensal bacterium. Notably, transport of pathogenic Salmonella typhimurium from the intestinal tract to mesenteric lymph nodes was impaired in Tlr5−/− mice. These data suggest that CD11c+ LPCs, via TLR5, detect and are used by pathogenic bacteria in the intestinal lumen.

Anti‐ICAM‐1 antibody reduces ischemic cell damage after transient middle cerebral artery occlusion in the rat

Intercellular adhesion molecule-1 (ICAM-1) is a glycoprotein expressed on endothelial cells that facilitates leukocyte adhesion. To test the hypothesis that reduction of leukocytes in an ischemic lesion reduces ischemic brain damage, we measured the effect of administration of an anti-ICAM-1 monoclonal antibody on ischemic brain damage after transient middle cerebral artery occlusion in the rat. ICAM-1 expression increased in the ischemic lesion, and the lesion volume was significantly reduced by 41% in the anti-ICAM-1 antibody group compared with the control group (p < 0.05). Numbers of polymorphonuclear leukocytes (PMNs) were significantly reduced in the cortices of the anti-ICAM-1 antibody group compared with the control animals (p < 0.05). Our data indicate that administration of anti-ICAM-1 antibody results in a significant reduction of ischemic brain damage concomitant with a reduction of PMNs in the lesion after transient focal cerebral ischemia in the rat.

Lymphocyte trafficking across high endothelial venules: dogmas and enigmas

Lymphocytes are intrinsically mobile and circulate continuously between the blood and secondary lymphoid tissues. When naive lymphocytes first enter lymph nodes and Peyers patches, they adhere to and migrate across specific blood vessels known as high endothelial venules (HEVs). The local availability of chemokines in or near HEVs is crucial for the specificity of this process. Here, we summarize recent studies of the chemokine-directed events in lymphocyte trafficking across HEVs, and we examine the dogmas and enigmas concerning lymphocyte migration to lymph nodes and Peyers patches. A model is also discussed, in which we propose that the response to chemokines immobilized on extracellular-matrix components is important for lymphocyte positioning in vivo.

Molecular determinants of reperfusion-induced leukocyte adhesion and vascular protein leakage.

The adherence and emigration of leukocytes have been implicated as a rate-limiting step in the microvascular dysfunction associated with reperfusion of ischemic tissues. The objective of the present study was to define the relation between leukocyte-endothelial cell adhesion and albumin leakage in rat mesenteric venules exposed to ischemia and reperfusion (I/R). Leukocyte adherence and emigration as well as albumin extravasation were monitored in single post-capillary venules using intravital fluorescence microscopy. Ischemia (0, 10, 15, or 20 minutes) was induced by complete occlusion of the superior mesenteric artery, and all parameters were monitored for 30 minutes after reperfusion. The magnitude of the leukocyte adherence and emigration and albumin leakage elicited by I/R was positively correlated with the duration of ischemia. The albumin leakage response was also highly correlated with the number of adherent and emigrated leukocytes. Monoclonal antibodies against the adhesion glycoproteins CD18, CD11b, intercellular adhesion molecule-1 (ICAM-1) (at 10 and 30 minutes), and L-selectin (at 10 minutes), but not P- or E-selectin, reduced I/R-induced leukocyte adherence and emigration as well as albumin leakage. Platelet-leukocyte aggregates were formed in postischemic venules; the number of aggregates was reduced by antibodies against P-selectin, CD11b, CD18, and ICAM-1, but not E- or L-selectin. These results indicate that reperfusion-induced albumin leakage is tightly coupled to the adherence and emigration of leukocytes in postcapillary venules. This adhesion-dependent injury response is primarily mediated by CD11b/CD18 on activated neutrophils and ICAM-1 on venular endothelium and appears to require L-selectin-dependent leukocyte rolling.

CCR7 is critically important for migration of dendritic cells in intestinal lamina propria to mesenteric lymph nodes

Although dendritic cells (DCs) located in the small intestinal lamina propria (LP-DCs) migrate to mesenteric lymph nodes (MLNs) constitutively, it is unclear which chemokines regulate their trafficking to MLNs. In this study we report that LP-DCs in unperturbed mice require CCR7 to migrate to MLNs. In vitro, LP-DCs expressing CCR7 migrated toward CCL21, although the LP-DCs appeared morphologically and phenotypically immature. In MLNs, DCs bearing the unique LP-DC phenotype (CD11chighCD8αintCD11blowαLlowβ7high and CD11chighCD8α−CD11bhighαLlowβ7high) were abundant in wild-type mice, but were markedly fewer in CCL19-, CCL21-Ser-deficient plt/plt mice and were almost absent in CCR7-deficient mice, indicating the critical importance of CCR7 in LP-DC trafficking to MLNs. Interestingly, CCR7+ DCs in MLNs with the unique LP-DC phenotype had numerous vacuoles containing cellular debris in the cytoplasm, although MLN-DCs themselves were poorly phagocytic, suggesting that the debris was derived from the LP, where the LP-DCs ingested apoptotic intestinal epithelial cells (IECs). Consistent with this, LP-DCs ingested IECs vigorously in vitro. By presenting IEC-associated Ag, the LP-DCs also induce T cells to produce IL-4 and IL-10. Collectively, these results strongly suggest that LP-DCs with unique immunomodulatory activities migrate to MLNs in a CCR7-dependent manner to engage in the presentation of IEC-associated Ags acquired in the LP.

Role of cell adhesion molecules in brain injury after transient middle cerebral artery occlusion in the rat

Activated neutrophils appear to be directly involved in tissue injury after focal cerebral ischemia and reperfusion. Intercellular adhesion molecules-1 (ICAM-1) and CD11/CD18 integrins have been implicated in ischemia-reperfusion induced neutrophil endothelial adhesion and transmigration. We therefore investigated the roles of CD11a/CD18 (LFA-1) and ICAM-1 in cerebral ischemia-reperfusion injury by using monoclonal antibodies, WT1 (anti-CD11a), WT3 (anti-CD18), and 1A29 (anti-ICAM-1). Rats were subjected to 1 h of middle cerebral artery occlusion (MCAO). Individual antibodies were administered at a dose of 5 mg/kg intraperitoneally at 15 min before ischemia and immediately after reperfusion. Rats were killed at 24 h after reperfusion, and brain edema, neutrophil infiltration and infarct size were measured. Sustained enhancement of ICAM-1 expression on capillaries was observed up to 24 h (beginning between 1 and 3 h after reperfusion). While, leukocytes began to infiltrate into the ischemic hemisphere between 6 and 12 h after reperfusion. Treatment with individual antibodies against cell adhesion molecules reduced edema formation and infarct size in addition to neutrophil accumulation 24 h after reperfusion. These results strongly implicate the invasion of neutrophils in the development of post-ischemic brain injury, and suggest that interactions between CD11a/CD18 and ICAM-1 contribute to neutrophil infiltration into the ischemic brain.

ADAMTS-1 cleaves a cartilage proteoglycan, aggrecan

A disintegrin‐like and metalloproteinase with thrombospondin type I motifs‐1 (ADAMTS‐1) is an extracellular matrix‐anchored metalloproteinase. In this study we have demonstrated that ADAMTS‐1 is able to cleave a major cartilage proteoglycan, aggrecan. N‐terminal sequencing analysis of the cleavage product revealed that ADAMTS‐1 cleaves the Glu1871–Leu1872 bond within the chondroitin sulfate attachment domain of aggrecan. In addition, deletional analysis demonstrated that the C‐terminal spacer region of ADAMTS‐1 is necessary to degrade aggrecan. These results suggest that ADAMTS‐1 may be involved in the turnover of aggrecan in vivo.

Intercellular adhesion molecule 1 (ICAM-1) expression and its role in neutrophil-induced ischemia-reperfusion injury in rat liver.

The potential role of intercellular adhesion molecule‐1 (ICAM‐1) in the pathogenesis of reperfusion injury was investigated in male Fischer rats subjected to 45 min of hepatic ischemia and 24 h of reperfusion. ICAM‐1 mRNA levels increased during ischemia in the ischemic liver lobes; however, during reperfusion mRNA levels increased in both the ischemic and nonischemic lobes. Immunohistochemical evaluation indicated ICAM‐1 expression only on sinusoidal lining cells in controls; ischemia‐reperfusion enhanced ICAM‐1 expression in the sinusoids and induced some expression on hepatocytes. The monoclonal anti–ICAM‐1 antibody 1A29, but not an immunoglobulin G control antibody, administered at 1 h and 8 h of reperfusion (2 mg/kg) significantly attenuated liver injury as indicated by 51% lower plasma alanine aminotransferase activities and 32–36% less hepatic necrosis at 24 h without affecting reactive oxygen formation by Kupffer cells and hepatic neutrophils. Although 1A29 reduced neutrophil extravasation in a glycogen peritonitis by 60%, the antibody had no significant effect on hepatic neutrophil infiltration during reperfusion. These data suggest that ICAM‐1 plays a significant role during the neutrophil‐dependent injury phase after hepatic ischemia and reperfusion and therefore blocking this adhesion molecule may have therapeutic potential against postischemic acute liver failure. J. Leukoc. Biol. 57: 368–374; 1995.

Oversulfated Chondroitin/Dermatan Sulfates Containing GlcAβ1/IdoAα1–3GalNAc(4,6-O-disulfate) Interact with L- and P-selectin and Chemokines

We previously reported that versican, a large chondroitin/dermatan sulfate (CS/DS) proteoglycan, interacts through its CS/DS chains with adhesion molecules L- and P-selectin and CD44, as well as chemokines. Here, we have characterized these interactions further. Using a metabolic inhibitor of sulfation, sodium chlorate, we show that the interactions of the CS/DS chains of versican with L- and P-selectin and chemokines are sulfation-dependent but the interaction with CD44 is sulfation-independent. Consistently, versicans binding to L- and P-selectin and chemokines is specifically inhibited by oversulfated CS/DS chains containing GlcAβ1–3GalNAc(4,6-O-disulfate) or IdoAα1–3GalNAc(4,6-O-disulfate), but its binding to CD44 is inhibited by all the CS/DS chains, including low-sulfated and unsulfated ones. Affinity and kinetic analyses using surface plasmon resonance revealed that the oversulfated CS/DS chains containing GlcAβ1/IdoAα1–3GalNAc(4,6-O-disulfate) bind directly to selectins and chemokines with high affinity (K d 21.1 to 293 nm). In addition, a tetrasaccharide fragment of repeating GlcAβ1–3GalNAc(4,6-O-disulfate) units directly interacts with L- and P-selectin and chemokines and oversulfated CS/DS chains containing GlcAβ1/IdoAα1–3GalNAc(4,6-O-disulfate) inhibit chemokine-induced Ca2+ mobilization. Taken together, our results show that oversulfated CS/DS chains containing GlcAβ1/IdoAα1–3GalNAc(4,6-O-disulfate) are recognized by L- and P-selectin and chemokines, and imply that these chains are important in selectin- and/or chemokine-mediated cellular responses.