Selectin-mucin interactions as a probable molecular explanation for the association of Trousseau syndrome with mucinous adenocarcinomas

Trousseau described spontaneous, recurrent superficial migratory thrombophlebitis associated with occult cancers, and this was later correlated with disseminated microangiopathy (platelet-rich clots in small blood vessels). Trousseau syndrome often occurs with mucinous adenocarcinomas, which secrete abnormally glycosylated mucins and mucin fragments into the bloodstream. Since carcinoma mucins can have binding sites for selectins, we hypothesized that selectin-mucin interactions might trigger this syndrome. When highly purified, tissue-factor free carcinoma mucin preparations were intravenously injected into mice, platelet-rich microthrombi were rapidly generated. This pathology was markedly diminished in P- or L-selectin-deficient mice. Heparin (an antithrombin-potentiating agent that can also block P- and L-selectin recognition of ligands) ameliorated this platelet aggregation, but had no additional effect in P- or L-selectin-deficient mice. Inhibition of endogenous thrombin by recombinant hirudin also did not block platelet aggregation. Mucins generated platelet aggregation in vitro in hirudinized whole blood, but not in platelet-rich leukocyte-free plasma nor in whole blood from L-selectin-deficient mice. Thus, Trousseau syndrome is likely triggered by interactions of circulating carcinoma mucins with leukocyte L-selectin and platelet P-selectin without requiring accompanying thrombin generation. These data may also explain why heparin ameliorates Trousseau syndrome, while vitamin K antagonists that merely depress thrombin production do not.

Gene therapy to target dendritic cells from blood to lymph nodes

Peripheral lymph nodes (PLN) are strategic microenvironments where antigen-presenting dendritic cells (DC), loaded with environmental antigens, and naive lymphocytes meet to initiate immune responses. The unique capacity of DC to induce primary immune responses has led to their use in clinical medicine; however, delivering DC to lymph nodes is problematic. Intravenously injected DC cannot access to PLN, while DC injected into tissue migrate inefficiently through lymphatics to PLN. We achieved DC targeting to T-cell areas of PLN by endowing DC with a novel receptor for peripheral node addressin (PNAd), an adhesion molecule present on the lymph node venular endothelium. This novel receptor is a chimeric E/L-selectin (ELS) that, we have previously shown, binds to PNAd. DC were genetically modified by retroviral transduction to express ELS. ELS expression was targeted to tips of microvilli, and mediated rolling of DC on PNAd both in vivo and in vitro. Such genetically engineered DC could extravasate directly from blood through the lymph node endothelium as opposed to nontransduced DC. This study provides evidence that the trafficking of DC can be modified using gene transfer technologies. More efficient delivery of DC to PLN should assist the development of improved vaccination strategies.

Acute psychological stress: effects on chemotaxis and cellular adhesion molecule expression

OBJECTIVE

Activation of a psychological stress response increases autonomic activity and enhances immune function by inducing a significant increase in numbers of leukocytes at sites of inflammation. Chemotaxis and cellular adhesion are thought to mediate leukocyte trafficking. In this study, we examine the effects of an acute psychological stress on chemotactic responses of PBMCs and on CAM expression in relation to measures of sympathetic activation.

METHODS

Subjects underwent either a public speaking task (N = 24) or a control condition (N = 13). Blood was drawn before the task, immediately after, and 20 minutes after, the task for changes in percentage of cells expressing cellular adhesion molecules, chemotaxis to chemokines, HR, blood pressure, and E and NE levels.

RESULTS

In response to the laboratory stressor, increases of PBMC chemotaxis to FMLP and SDF-1 were found, which were coupled with increases in the percentages of lymphocytes expressing the integrin Mac-1. Autonomic activity, including blood pressure and circulating levels of catecholamines, increased after administration of the stressor, and correlated with increases of Mac-1.

CONCLUSIONS

These data show that acute stress induces increase of chemotaxis and expression of CAM expression, which may contribute to increased migration and recruitment of immune cells to sites of infection and/or inflammation.

[Effects of bcr/abl fusion gene on expression of beta1 integrin and L-selectin in mouse chronic myeloid leukemia cells]

OBJECTIVES

To explore the effects of p210 bcr/abl fusion gene on expression of beta1 integrin and L-selectin mRNAs in mouse chronic myeloid leukemia (CML) cells.

METHODS

Comparisons of beta1 integrin and L-selectin mRNA levels among p210 bcr/abl negative, p210 bcr/abl positive, and p210 bcr/abl-Rb-C-Box positive cells were undertaken by quantity RT-PCR.

RESULTS

In p210 bcr/abl positive cells, L-selectin mRNA level was decreased, but beta1 integrin mRNA expression had no change as compared to those in p210 bcr/abl negative cells. When inhibition of bcr-abl tyrosine kinase activity by Rb-C-Box, the L-selectin mRNA expression restored to normal (similar to p210 bcr/abl negative cells).

CONCLUSION

p210 bcr/abl oncoprotein inhibits expression of L-selectin mRNA, but not of beta1 integrin mRNA.

Intravital microscopy comparing T lymphocyte trafficking to the spleen and the mesenteric lymph node

Lymphocyte rolling velocity is determined largely by interactions between leukocyte alpha(4)-integrin (CD49d) and L-selectin and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in mesenteric postcapillary venules and Peyer's patch high endothelial venules (HEVs). The role of these interactions in other tissue sites of lymphocyte emigration is not known. With the use of real-time intravital confocal microscopy, we found that rolling velocities of T lymphocytes in the murine mesenteric lymph node (MLN) HEV also depend on L-selectin and CD49d. However, in the murine spleen, rolling velocities of T lymphocytes are not influenced by the loss of L-selectin and CD49d. With the use of FITC-dextran and TIE2-GFP mice, we further defined the microvascular compartments of the spleen and showed that adherence of T cells is localized to regions in the white pulp that are not lined by endothelial cells and have shear rates similar to bone marrow sinusoids. These results establish that T cell trafficking to the spleen differs from trafficking to other secondary lymphoid organs and suggest that the mechanical properties of the blood-filtering role of the spleen are important in T cell accumulation in the organ.

[Study on expression of cell surface L-selectin and soluble L-selectin in patients with acute leukemia]

To study the relationship between the level of the soluble L-selectin (sL-selectin) in plasma and surface L-selectin expression on leukemic cells and episode and state of illness in acute leukemia patients, the plasma level of sL-selectin was measured by a sandwich enzyme-linked immunosorbent assay, and the expressions of surface L-selectin and its gene (lyam-1) were detected by immunohistochemistry and RT-PCR. The results showed that the levels of sL-selectin were significantly higher in untreated and therapy-resistant acute leukemia patients, and expression of L-selectin mRNA and cell surface L-selectinin in untreated and NR patients were significantly lower than that in CR patients and control group (P < 0.05). The plasma levels of sL-selectin were significantly increased in patients with splenomegaly and hepatomegaly (extramedullary infiltration). The levels of sL-selectin were related to the clinical course of the acute leukemia patients. A significant correalation existed between expressions of L-selectin mRNA and surface L-selectin in acute leukemia patients (gamma = 0.782, P < 0.05). It is concluded that expression of L-selectin gene was down-regulated in level of mRNA and protein in acute leukemia patients and both changes were highly correlated. Monitoring of the plasma level of sL-selectin is possibly useful for early diagnosis of relapse and extramedullary infiltration in acute leukemia.

High-resolution SNP map in the 55-kb region containing the selectin gene family on chromosome 1q24-q25

Immunoglobulin A nephropathy (IgAN) is the most common form of glomerulonephritis characterized by predominant IgA deposits in glomerular mesangium. By means of a genome-wide case-control association study, we previously demonstrated that eight single-nucleotide polymorphisms (SNPs) within the selectin gene cluster are significantly associated with IgAN. Here we provide more detailed information of variations corresponding to selectin loci, consisting of 88 SNPs and two insertion-deletion polymorphisms in the Japanese population: 27 in 5' flanking regions, 1 in 5' untranslated regions, 6 within coding regions, 46 in introns, 4 within 3' untranslated regions, and 4 in 3' flanking regions. The SNP map presented here will be a useful resource not only for examining the relationships between selectin genotypes and susceptibility to the IgAN phenotype, but also for analyzing gene scans of complex diseases mapped to this local segment on chromosome 1.

Imatinib restores expression of CD62L in BCR-ABL-positive cells

Chronic myelogenous leukemia (CML) is characterized by aberrant trafficking of malignant hematopoietic progenitor cells in the peripheral blood. Expression of the cell adhesion molecule CD62L was reported to be significantly lower in CML patients than in normal controls. We studied whether the transcription of CD62L in CML cells is dependent on the activity of the BCR-ABL tyrosine kinase. Following addition of the Abelson (ABL) tyrosine kinase inhibitor imatinib (formerly STI571) to two BCR-ABL-positive cell lines (BV173, SD-1), we observed a dose-dependent increase in CD62L RNA levels of up to 45-fold by a quantitative, real-time polymerase chain reaction and an increase in the amount of cell surface-bound CD62L of up to 18-fold by quantitative flow cytometry, respectively. These data are validated by an increased CD62L expression in the bone marrow of patients (n=6) with advanced CML who received imatinib. Restoration of defective cell adhesion mediated via the CD62L pathway may be one mechanism of action of imatinib in BCR-ABL-positive leukemias.

L-selectin or ICAM-1 deficiency reduces an immediate-type hypersensitivity response by preventing mast cell recruitment in repeated elicitation of contact hypersensitivity

Repeated Ag exposure results in a shift in the time course of contact hypersensitivity (CH) from a typical delayed-type to an immediate-type response followed by a late phase reaction. Chronic CH responses are clinically relevant to human skin allergic diseases, such as atopic dermatitis, that are usually caused by repeated stimulation with environmental Ags. Chronic inflammatory responses result in part from infiltrating leukocytes. To determine the role of leukocyte adhesion molecules in chronic inflammation, chronic CH responses were assessed in mice lacking L-selectin, ICAM-1, or both adhesion molecules. Following repeated hapten sensitization for 24 days at 2-day intervals, wild-type littermates developed an immediate-type response at 30 min after elicitation, followed by a late phase reaction. By contrast, loss of ICAM-1, L-selectin, or both, eliminated the immediate-type response and inhibited the late phase reaction. Similar results were obtained when wild-type littermates repeatedly exposed to hapten for 22 days were treated with mAbs to L-selectin and/or ICAM-1 before the elicitation on day 24. The lack of an immediate-type response on day 24 paralleled a lack of mast cell accumulation after 30 min of elicitation and decreased serum IgE production. Repeated Ag exposure in wild-type littermates resulted in increased levels of serum L-selectin, a finding also observed in atopic dermatitis patients. The current study demonstrates that L-selectin and ICAM-1 cooperatively regulate the induction of the immediate-type response by mediating mast cell accumulation into inflammatory sites and suggests that L-selectin and ICAM-1 are potential therapeutic targets for regulating human allergic reactions.

Viscosity-independent velocity of neutrophils rolling on p-selectin in vitro or in vivo

OBJECTIVE

To determine whether selectin-mediated leukocyte-rolling velocity in inflamed venules in vivo is determined by wall shear rate (WSR) or by wall shear stress (WSS).

METHODS

WSS was manipulated independently of WSR by altering the viscosity of blood plasma in mice with an isovolemic exchange of blood for low- or high-viscosity dextran solutions. Rolling of neutrophils or beads coated with P-selectin glycoprotein ligand-1 (PSGL-1) was reconstituted on P-selectin immobilized on the wall of a parallel plate flow chamber at two different viscosities of the perfusion medium.

RESULTS

Leukocytes in vivo showed no increase in rolling velocity when shear stress was doubled by doubling viscosity. Neutrophils in the parallel-plate flow chamber in vitro showed the same dependence on WSR as leukocytes in vivo, but bead-rolling velocities correlated best with WSS. Rolling leukocytes, but not beads, deformed significantly in shear flow, and deformation correlated better with WSS.

CONCLUSION

These data suggest leukocyte deformation during rolling offsets increased bond breakage at higher shear stress. The stable rolling velocity allows sufficient surveillance of the endothelial surface, even in venules with high WSS. doi:10.1038/sj.mm.7800165

Absence of L-selectin delays mucosal B cell responses in nonintestinal effector tissues

Previous studies suggest that lymphocyte trafficking to head and neck lymph nodes, also referred to as cranial-, oral-, nasal-associated lymphoid tissue (CONALT), is L-selectin (L-Sel) dependent, despite coexpression of alpha(4)beta(7), resulting in their marked reduction in L-Sel-deficient (L-Sel(-/-)) mice. Consequently, early phase (16 days) Ab responses to cholera toxin (CT) are diminished. The following studies reveal that lack of mucosal effector responses is not caused by loss of inductive immune responses in the L-Sel(-/-) CONALT. Indeed, there was an increased accumulation of total IgA, but not Ag-specific IgA Ab-forming cells (AFC) in L-Sel(-/-) CONALT. This increased accumulation was not evident in L-Sel(+/+) CONALT. Identification of lymphocyte-homing receptors on L-Sel(-/-) and L-Sel(+/+) CONALT lymphocytes revealed no significant differences in expression of alpha(4)beta(7), which might contribute to lymphocyte homing in the absence of L-Sel. Studies of CONALT responses during the late phase (6 wk post-intranasal immunization) revealed the number of lymphocytes recovered from L-Sel(-/-) CONALT was less than L-Sel(+/+) CONALT; however, L-Sel(-/-) CT-specific and total AFC did not vary from 16-day responses, suggesting a defect in CT-specific B cell export. No significant differences in alpha(4)beta(7) expression between L-Sel(-/-) and L-Sel(+/+) CONALT were noted. Yet, these increases in CONALT AFC correlated with restoration of immunity in L-Sel(-/-) nasal passages and reproductive tracts.

Intercellular adhesion molecule-1 and L-selectin regulate bleomycin-induced lung fibrosis

The development of bleomycin-induced lung injury, a model of pulmonary fibrosis, results from inflammatory cell infiltration, a process highly regulated by the expression of multiple adhesion molecules. At present, the identity and role of the adhesion molecules involved in the fibrotic process are unknown. Therefore, bleomycin-induced pulmonary fibrosis was examined in mice lacking L-selectin (L-selectin(-/-)) expression, intercellular adhesion molecule-1 (ICAM-1) expression, or both. After 16 days of intratracheal bleomycin challenge, collagen deposition was inhibited in both L-selectin(-/-) and ICAM-1(-/-) mice when compared with wild-type littermates. Interestingly, collagen deposition was virtually eliminated in L-selectin/ICAM-1(-/-) mice relative to either the L-selectin(-/-) or ICAM-1(-/-) mice. Decreased pulmonary fibrosis was associated with reduced accumulation of leukocytes, including neutrophils and lymphocytes. Decreased mRNA expression of proinflammatory cytokines and transforming growth factor (TGF)-beta1 paralleled the inhibition of collagen deposition. The present study indicates that L-selectin and ICAM-1 play a critical role in pulmonary fibrosis by mediating the accumulation of leukocytes, which regulate the production of proinflammatory cytokines and TGF-beta1. This suggests that these adhesion molecules are potential therapeutic targets for inhibiting human pulmonary fibrosis.

Leukocyte rolling velocities and migration are optimized by cooperative L-selectin and intercellular adhesion molecule-1 functions

Selectin family members largely mediate initial tethering and rolling of leukocytes on vascular endothelium, whereas integrin and Ig family members are essential for leukocyte firm adhesion. To quantify functional synergy between L-selectin and Ig family members during leukocyte rolling, the EA.hy926 human vascular endothelial line was transfected with either fucosyltransferase VII (926-FtVII) cDNA to generate L-selectin ligands alone or together with ICAM-1 cDNA (926-FtVII/ICAM-1). The ability of transfected 926 cells to support human leukocyte interactions was assessed in vitro using parallel plate flow chamber assays. Lymphocyte rolling on 926-FtVII cells was increased by approximately 70% when ICAM-1 was expressed at physiological levels. Although initial tether formation was similar for both cell types, lymphocyte rolling was 26% slower on 926-FtVII/ICAM-1 cells. Pretreatment of lymphocytes with an anti-CD18 mAb eliminated the increase in rolling, and all rolling was blocked by anti-L-selectin mAb. In addition, rolling velocities of lymphocytes from CD18-hypomorphic mice were 48% faster on 926-FtVII/ICAM-1 cells, with a similar reduction in rolling frequency relative to wild-type lymphocytes. CD18-hypomorphic lymphocytes also showed an approximately 40% decrease in migration to peripheral and mesenteric lymph nodes during in vivo migration assays compared with wild-type lymphocytes. Likewise, wild-type lymphocyte migration to peripheral lymph nodes was reduced by approximately 50% in ICAM-1(-/-) recipient mice. Similar to human lymphocytes, human neutrophils showed enhanced rolling interactions on 926-FtVII/ICAM-1 cells, but also firmly adhered. Thus, in addition to mediating leukocyte firm adhesion, CD18 integrin/ICAM-1 interactions regulate leukocyte rolling velocities and thereby optimize L-selectin-mediated leukocyte rolling.

Leukocyte-endothelial cell adhesion molecule 1 (LECAM-1) polymorphism is associated with diabetic nephropathy in type 2 diabetes mellitus

BACKGROUND/AIMS

Glomerular infiltration with monocytes/macrophages has been implicated in the pathogenesis of diabetic nephropathy. In this study, we evaluated the relationship between the genetic polymorphism in leukocyte-endothelial adhesion molecule-1 (LECAM-1) and diabetic nephropathy in patients with type 2 diabetes mellitus.

METHODS

We determined the frequency of the LECAM-1 P213S genotype in 102 diabetic patients with diabetic nephropathy, 90 diabetic patients with no evidence of diabetic nephropathy, and 200 healthy control individuals.

RESULTS

The frequency of the LECAM-1 213PP genotype and P allele in patients with diabetic nephropathy was significantly higher than that in patients without nephropathy (genotype 68% vs. 53%, chi(2)=6.78, P=.034; allele 83% vs. 72%, chi(2)=6.26, P=.012). The LECAM-1 P213 genotype was associated with a 1.86-fold increased risk for nephropathy independently of other risk factors.

CONCLUSION

The data suggest that the LECAM-1 213PP genotype is a genetic risk factor for the development of nephropathy in type 2 diabetes mellitus.

A functional role for circulating mouse L-selectin in regulating leukocyte/endothelial cell interactions in vivo

L-selectin mediates the initial capture and subsequent rolling of leukocytes along inflamed vascular endothelium and mediates lymphocyte migration to peripheral lymphoid tissues. Leukocyte activation induces rapid endoproteolytic cleavage of L-selectin from the cell surface, generating soluble L-selectin (sL-selectin). Because human sL-selectin retains ligand-binding activity in vitro, mouse sL-selectin and its in vivo relevance were characterized. Comparable with humans, sL-selectin was present in adult C57BL/6 mouse sera at approximately 1.7 micro g/ml. Similar levels of sL-selectin were present in sera from multiple mouse strains, despite their pronounced differences in cell surface L-selectin expression levels. Adhesion molecule-deficient mice prone to spontaneous chronic inflammation and mice suffering from leukemia/lymphoma had 2.5- and 20-fold increased serum sL-selectin levels, respectively. By contrast, serum sL-selectin levels were reduced by 70% in Rag-deficient mice lacking mature lymphocytes. The majority of serum sL-selectin had a molecular mass of 65-75 kDa, consistent with its lymphocyte origin. Slow turnover may explain the relatively high levels of sL-selectin in vivo. The t(1/2) of sL-selectin, assessed by transferring sera from wild-type mice into L-selectin-deficient mice and monitoring serum sL-selectin levels by ELISA, was >20 h, and it remained detectable for longer than 1 wk. Short-term in vivo lymphocyte migration assays demonstrated that near physiologic levels ( approximately 0.9 micro g/ml) of sL-selectin decreased lymphocyte migration to peripheral lymph nodes by >30%, with dose-dependent inhibition occurring with increasing sL-selectin concentrations. These results suggest that sL-selectin influences lymphocyte migration in vivo and that the increased sL-selectin levels present in certain pathologic conditions may adversely affect leukocyte migration.

Heparin's anti-inflammatory effects require glucosamine 6-O-sulfation and are mediated by blockade of L- and P-selectins

Heparin has been used clinically as an anticoagulant and antithrombotic agent for over 60 years. Here we show that the potent anti-inflammatory property of heparin results primarily from blockade of P-selectin and L-selectin. Unfractionated heparin and chemically modified analogs were tested as inhibitors of selectin binding to immobilized sialyl Lewis(X) and of cell adhesion to immobilized selectins or thrombin-activated endothelial cells. Compared with unfractionated heparin, the modified heparinoids had inhibitory activity in this general order: over-O-sulfated heparin > heparin > 2-O,3-O-desulfated > or = N-desulfated/N-acetylated heparin > or = carboxyl-reduced heparin > or= N-,2-O,3-O-desulfated heparin >> 6-O-desulfated heparin. The heparinoids also showed similar differences in their ability to inhibit thioglycollate-induced peritonitis and oxazolone-induced delayed-type hypersensitivity. Mice deficient in P- or L-selectins showed impaired inflammation, which could be further reduced by heparin. However, heparin had no additional effect in mice deficient in both P- and L-selectins. We conclude that (a) heparin's anti-inflammatory effects are mainly mediated by blocking P- and L-selectin-initiated cell adhesion; (b) the sulfate groups at C6 on the glucosamine residues play a critical role in selectin inhibition; and (c) some non-anticoagulant forms of heparin retain anti-inflammatory activity. Such analogs may prove useful as therapeutically effective inhibitors of inflammation.

Intercellular adhesion molecule-1 (ICAM-1) polymorphism is associated with diabetic retinopathy in Type 2 diabetes mellitus

AIMS

Leucocyte adhesion to the diabetic retinal vasculature has been implicated in the pathogenesis of diabetic retinopathy. We evaluated the relationship between genetic polymorphisms in leucocyte and endothelial cell adhesion molecules and diabetic retinopathy in Type 2 diabetes mellitus.

METHODS

We determined ICAM-1, platelet endothelial cell adhesion molecule-1 (PECAM-1), and leucocyte endothelial adhesion molecule-1 (LECAM-1) genotypes in 81 patients with and 50 without diabetic retinopathy.

RESULTS

The frequency of ICAM-1 469KK genotype and K allele were significantly higher in the patients with diabetic retinopathy than in those without retinopathy (genotype 42% vs. 20%, chi2 = 6.70, P = 0.035; allele 66% vs. 50%, chi2 = 6.49, P = 0.011). With regard to the PECAM-1 V125L and LECAM-1 P213S polymorphisms, there were no significant associations between the distribution of genotypes or allele frequencies and the presence of diabetic retinopathy. Independent of other risk factors, the ICAM-1 469KK genotype was associated with a 3.51-fold increased risk for retinopathy.

CONCLUSIONS

These data suggest that the ICAM-1 469KK genotype could be a genetic risk factor for retinopathy in Type 2 diabetes mellitus.

Neonatal infection with a milk-borne virus is independent of beta7 integrin- and L-selectin-expressing lymphocytes

Mouse mammary tumor virus (MMTV) is acquired by neonates through milk and first infects lymphocytes in Peyer's patches. We show here that newborn mice lacking beta7 integrin or L-selectin were infected with MMTV at wild-type levels in both their lymphoid and mammary tissues. Superantigen-mediated activation and cognate T cell deletion were also unimpaired in both types of null mice. A large proportion of neonatal Peyer's patch lymphocytes in wild-type mice were beta7 and beta1 integrin low and both populations increased in response to MMTV infection. These results suggest that adhesion molecules other than beta7 integrin or L-selectin play a role in lymphocyte homing in the gut, peripheral lymph nodes and mammary gland in response to MMTV infection.

L-selectin is not required for T cell-mediated autoimmune diabetes

Administration of anti-L-selectin (CD62L) mAb to neonatal nonobese diabetic (NOD) mice mediates long term protection against the development of insulitis and overt diabetes. These results suggested that CD62L has a key role in the general function of beta cell-specific T cells. To further examine the role of CD62L in the development of type 1 diabetes, NOD mice lacking CD62L were established. The onset and frequency of overt diabetes were equivalent among CD62L(+/+), CD62L(+/-), and CD62L(-/-) NOD littermates. Furthermore, patterns of T cell activation, migration, and beta cell-specific reactivity were similar in NOD mice of all three genotypes. Adoptive transfer experiments with CD62L(-/-) CD4(+) T cells prepared from BDC2.5 TCR transgenic mice revealed no apparent defects in migration to pancreatic lymph nodes, proliferation in response to beta cell Ag, or induction of diabetes in NOD.scid recipients. In conclusion, CD62L expression is not essential for the development of type 1 diabetes in NOD mice.

The cutaneous reverse Arthus reaction requires intercellular adhesion molecule 1 and L-selectin expression

The deposition of immune complexes (IC) induces an acute inflammatory response with tissue injury. IC-induced inflammation is mediated by inflammatory cell infiltration, a process highly regulated by expression of multiple adhesion molecules. To assess the role of L-selectin and ICAM-1 in this pathogenetic process, the cutaneous reverse passive Arthus reaction was examined in mice lacking L-selectin (L-selectin(-/-)), ICAM-1 (ICAM-1(-/-)), or both (L-selectin/ICAM-1(-/-)). Edema and hemorrhage, which peaked 4 and 8 h after IC challenge, respectively, were significantly reduced in L-selectin(-/-), ICAM-1(-/-), and L-selectin/ICAM-1(-/-) mice compared with wild-type littermates. In general, edema and hemorrhage were more significantly inhibited in ICAM-1(-/-) mice than in L-selectin(-/-) mice, but were most significantly reduced in L-selectin/ICAM-1(-/-) mice compared with ICAM-1(-/-) or L-selectin(-/-) mice. Decreased edema and hemorrhage correlated with reduced neutrophil and mast cell infiltration in all adhesion molecule-deficient mice, but leukocyte infiltration was most affected in L-selectin/ICAM-1(-/-) mice. Reduced neutrophil and mast cell infiltration was also observed for all mutant mice in the peritoneal Arthus reaction. Furthermore, cutaneous TNF-alpha production was inhibited in each deficient mouse, which paralleled the reductions in cutaneous inflammation. These results indicate that ICAM-1 and L-selectin cooperatively contribute to the cutaneous Arthus reaction by regulating neutrophil and mast cell recruitment and suggest that ICAM-1 and L-selectin are therapeutic targets for human IC-mediated disease.

Association between single-nucleotide polymorphisms in selectin genes and immunoglobulin A nephropathy

Although intensive efforts have been undertaken to elucidate the genetic background of immunoglobulin A nephropathy (IgAN), genetic factors associated with the pathogenesis of this disease are still not well understood. We designed a case-control association study that was based on linkage disequilibrium among single-nucleotide polymorphisms (SNPs) in the selectin gene cluster on chromosome 1q24-25, and we found two SNPs in the E-selectin gene (SELE8 and SELE13) and six SNPs in the L-selectin gene (SELL1, SELL4, SELL5, SELL6, SELL10, and SELL11) that were significantly associated with IgAN in Japanese patients. All eight SNPs were in almost complete linkage disequilibrium. SELE8 and SELL10 caused amino acid substitutions from His to Tyr and from Pro to Ser (chi2=9.02, P=.0026, odds ratio = 2.73 [95% confidence interval [CI] 1.38--5.38] for His-to-Tyr substitutions; chi2=17.4, P=.000031, odds ratio = 3.61 [95% CI 1.91--6.83] for Pro-to-Ser substitutions), and SELL1 could affect promoter activity of the L-selectin gene (chi2=19.5, P=.000010, odds ratio = 3.77 [95% CI 2.02--7.05]). The TGT haplotype at these three loci was associated significantly with IgAN (chi2=18.67, P=.000016, odds ratio = 1.88 [95% CI 1.41--2.51]). Our results suggest that these eight SNPs in selectin genes may be useful for screening populations susceptible to the IgAN phenotype that involves interstitial infiltration.

L-selectin-dependent lymphoid occupancy is required to induce alloantigen-specific tolerance

Maneuvers that interfere with signals 1, 2, 3, or Ag processing can result in indefinite allograft survival. However, they are not applicable to all tissues, strains, or species, suggesting that there are additional levels of immune regulation. We hypothesized that secondary lymphoid organs are important for interactions among lymphocytes, alloantigen, and immunosuppressants that lead to tolerance. To explore this, cardiac allografts were performed with a tolerogenic immunosuppressive regimen. Concurrent administration of anti-L-selectin (CD62L) Ab, which prevents lymph node homing, prevents indefinite allograft survival and tolerance. Anti-CD62L Ab is not costimulatory, and Fab and F(ab')(2) anti-CD62L have similar activities. Flow cytometry and histologic examination show that Ab shifts T cells away from lymph nodes and into spleen, peripheral blood, and graft. Tolerance is not induced in CD62L(-/-) mice, and adoptive transfer of CD62L(-/-), but not CD62L(+/+), T cells prevents tolerization in wild-type recipients. FTY720, an immunosuppressant that promotes chemokine-dependent, but CD62L-independent, lymph node homing, reverses the Ab effect. Blockade of other homing receptors also prevents tolerization. These results indicate that T lymphocytes use CD62L-dependent migration for alloantigen-specific tolerance, and suggest that lymph nodes or other lymphoid tissues are an important site for peripheral tolerization to alloantigen.

Selectins mediate macrophage infiltration in obstructive nephropathy in newborn mice

BACKGROUND

Urinary tract obstruction during development leads to tubular atrophy and causes interstitial fibrosis. Macrophage infiltration into the interstitium plays a central role in this process. Selectins, a family of three adhesion molecules, are involved in leukocyte recruitment to sites of inflammation and immune activity. We investigated the role of selectins in obstructive nephropathy in newborn mice.

METHODS

Triple selectin-deficient mice (EPL-/-), L-selectin deficient mice (L-/-) and wild type mice (WT) were subjected to complete unilateral ureteral obstruction (UUO) or sham operation within the first 48 hours of life, and were sacrificed 5 and 12 days later. Kidneys were removed, and sections were stained for macrophage infiltration (mAb F4/80), apoptosis (TUNEL), tubular atrophy (periodic acid-Schiff) and interstitial fibrosis (Masson trichrome).

RESULTS

Selectin deficient mice showed a marked reduction in macrophage infiltration into the obstructed kidney compared to WT at day 5 and day 12 after UUO. Tubular apoptosis was strongly reduced in EPL-/- at day 5 after UUO, and in EPL-/- and L-/- at day 12 after UUO when compared to WT. The number of apoptotic tubular cells was correlated with macrophage infiltration, suggesting that macrophages stimulate tubular apoptosis in obstructive nephropathy. In addition, tubular atrophy and interstitial fibrosis were significantly diminished in EPL-/- and L-/- compared to WT at day 12 after UUO.

CONCLUSION

Following UUO, selectins mediate macrophage infiltration into the obstructed kidney, which in turn may induce tubular apoptosis, tubular atrophy and interstitial fibrosis.

Pre-translational regulation of neutrophil L-selectin in glucocorticoid-challenged cattle

L-selectin (CD62L) gene expression in neutrophils is commonly referred to as "constitutive" because circulating neutrophils require a constant supply of this adhesion molecule for continuous trafficking into peripheral tissues. Under normal circumstances, marginating blood neutrophils and neutrophils that become activated for migration into infected tissues rapidly shed surface CD62L that is ligated to the vascular endothelium. However, this does not shut down CD62L gene expression because these cells continue to express surface CD62L. In contrast, glucocorticoid challenges resulting from stress and hormone injections result in gradual and chronic down-regulation of CD62L on the surface of blood neutrophils. Rather than being associated with migration, this type of CD62L down-regulation associates with pronounced neutrophilia and increased susceptibility to infections. Nothing is currently known about glucocorticoid regulation of CD62L expression in neutrophils. In other cell systems, however, this steroid hormone binds to cytoplasmic glucocorticoid receptors (GR) that influence expression of glucocorticoid-responsive genes at multiple pre-translational levels. Thus, the hypothesis of the present study was that glucocorticoid challenge suppresses CD62L mRNA expression in blood neutrophils. Suppressed CD62L gene expression might help explain the chronic down-regulation of surface CD62L in neutrophils and accompanying neutrophilia. The main objectives of the study were to monitor neutrophil CD62L mRNA abundance before and during subtle and severe glucocorticoid challenges and to determine if CD62L mRNA expression correlates with degree of glucocorticoid challenge. Parturient dairy cows and dexamethasone-treated steers were used as models of subtle and severe (respectively) glucocorticoid challenges. Data presented from both models support the hypothesis and show for the first time that glucocorticoids regulate neutrophil CD62L at a pre-translational level. Results also showed that inhibited CD62L mRNA expression correlated precisely with down-regulated surface expression of CD62L on neutrophils and peak neutrophilia during severe glucocorticoid challenge. Therefore, results of this study indicate that bovine neutrophils are highly sensitive to the blood environment, displaying full capacity to alter CD62L gene expression and trafficking patterns in response to changing glucocorticoid levels. This may serve animals well when heightened inflammatory responses begin to lead to tissue damage, but may be detrimental to overall health if animals are exposed to opportunistic pathogens while stressed or undergoing glucocorticoid therapy. Although this study did not elucidate how glucocorticoids inhibit neutrophil CD62L mRNA expression, presented data implicate GR as possibly being involved because neutrophils from cattle in both models expressed GR mRNA. Further in vitro studies using purified populations of neutrophils will be required to determine if GR is directly involved in glucocorticoid regulation of CD62L gene expression and, if so, at what level.