The chemokine SDF-1 is a chemoattractant for human CD34+ hematopoietic progenitor cells and provides a new mechanism to explain the mobilization of CD34+ progenitors to peripheral blood.

Hematopoietic progenitor cells migrate in vitro and in vivo towards a gradient of the chemotactic factor stromal cell-derived factor-1 (SDF-1) produced by stromal cells. This is the first chemoattractant reported for human CD34+ progenitor cells. Concentrations of SDF-1 that elicit chemotaxis also induce a transient elevation of cytoplasmic calcium in CD34+ cells. SDF-1-induced chemotaxis is inhibited by pertussis toxin, suggesting that its signaling in CD34+ cells is mediated by seven transmembrane receptors coupled to Gi proteins. CD34+ cells migrating to SDF-1 include cells with a more primitive (CD34+/CD38- or CD34+/DR-) phenotype as well as CD34+ cells phenotypically committed to the erythroid, lymphoid and myeloid lineages, including functional BFU-E, CFU-GM, and CFU-MIX progenitors. Chemotaxis of CD34+ cells in response to SDF-1 is increased by IL-3 in vitro and is lower in CD34+ progenitors from peripheral blood than in CD34+ progenitors from bone marrow, suggesting that an altered response to SDF-1 may be associated with CD34 progenitor mobilization.

Inducible costimulator protein (ICOS) controls T helper cell subset polarization after virus and parasite infection.

It has been shown that certain pathogens can trigger efficient T cell responses in the absence of CD28, a key costimulatory receptor expressed on resting T cells. Inducible costimulator protein (ICOS) is an inducible costimulator structurally and functionally related to CD28. Here, we show that in the absence of CD28 both T helper cell type 1 (Th1) and Th2 responses were impaired but not abrogated after infection with lymphocytic choriomeningitis virus (LCMV), vesicular stomatitis virus (VSV), and the nematode Nippostrongylus brasiliensis. Inhibition of ICOS in CD28-deficient mice further reduced Th1/Th2 polarization. Blocking of ICOS alone had a limited but significant capacity to downregulate Th subset development. In contrast, cytotoxic T lymphocyte (CTL) responses, which are regulated to a minor and major extent by CD28 after LCMV and VSV infection, respectively, remained unaffected by blocking ICOS. Together, our results demonstrate that ICOS regulates both CD28-dependent and CD28-independent CD4(+) subset (Th1 and Th2) responses but not CTL responses in vivo.

Putative prethymic T cell precursors within the early human embryonic liver: a molecular and functional analysis.

Hematopoietic cells present in the liver in early human fetal life were characterized by phenotypic analysis using a broad panel of monoclonal antibodies. Expression of very late antigen 4 and leukocyte function-associated antigen 3 cell adhesion receptors and 4F2 cell activation molecules was found in all fetal liver hematopoietic cells before acquisition of T cell-, B cell-, or myeloid-specific surface markers, and before the time of intrathymic colonization. Molecular studies showed that expression of the interleukin 2 receptor beta (IL-2R beta) also occurred in the embryonic liver at this early ontogenic stage. In contrast, no expression of IL-2R alpha or IL-2 transcripts was found in fetal liver cells, whereas transcription of the IL-4 gene was detected in a small fetal liver cell subset. Putative T cell precursors were identified among the hematopoietic fetal liver cells by the expression of genes encoding the gamma, delta, epsilon, and zeta invariant chains of the CD3-T cell receptor (TCR) complex. However, no transcription of the polymorphic alpha and beta TCR genes was detected. Functional in vitro assays further demonstrated that fetal liver hematopoietic cells from those early embryos were capable of proliferating in response to T cell growth factors, including IL-4 and IL-2. However, whereas IL-4-induced proliferation paralleled the appearance in vitro of CD45+CD7-CD4dull cells expressing the CD14 myeloid antigen, as well as of CD34+ primitive hematopoietic progenitors, differentiation into CD45+CD7+CD8+CD3- immature T cells was observed when using IL-2. Moreover, coculture with thymic epithelial cell monolayers provided additional evidence that early fetal liver hematopoietic cells may include very primitive T cell precursors, which were able to differentiate in vitro into TCR alpha/beta+ mature T cells. Therefore, our results indicate that, after triggering of the T cell-specific maturation program in primitive fetal liver hematopoietic progenitors, specific signals provided intrathymically by epithelial cells may fulfill the requirements to drive terminal differentiation of prethymically committed T cell precursors.

RANTES and monocyte chemoattractant protein-1 (MCP-1) play an important role in the inflammatory phase of crescentic nephritis, but only MCP-1 is involved in crescent formation and interstitial fibrosis.

The involvement of chemokines in inflammation is well established, but their functional role in disease progression, and particularly in the development of fibrosis, is not yet understood. To investigate the functional role that the chemokines monocyte chemoattractant protein-1 (MCP-1) and RANTES play in inflammation and the progression to fibrosis during crescentic nephritis we have developed and characterized a murine model for this syndrome. Significant increases in T-lymphocytes and macrophages were observed within glomeruli and interstitium, paralleled by an induction of mRNA expression of MCP-1 and RANTES, early after disease initiation. Blocking the function of MCP-1 or RANTES resulted in significant decreases in proteinuria as well as in numbers of infiltrating leukocytes, indicating that both MCP-1 and RANTES (regulated upon activation in normal T cells expressed and secreted) play an important role in the inflammatory phase of crescentic nephritis. In addition, neutralization of MCP-1 resulted in a dramatic decrease in both glomerular crescent formation and deposition of type I collagen. These results highlight a novel role for MCP-1 in crescent formation and development of interstitial fibrosis, and indicate that in addition to recruiting inflammatory cells this chemokine is critically involved in irreversible tissue damage.

CC chemokine receptor (CCR)3/eotaxin is followed by CCR4/monocyte-derived chemokine in mediating pulmonary T helper lymphocyte type 2 recruitment after serial antigen challenge in vivo.

Isolated peripheral blood CD4 cells from allergic individuals express CC chemokine receptor (CCR)3 and CCR4 after expansion in vitro. In addition, human T helper type 2 (Th2) cells polarized in vitro selectively express CCR3 and CCR4 at certain stages of activation/differentiation and respond preferentially to the ligands eotaxin and monocyte-derived chemokine (MDC). However, controversy arises when the in vivo significance of this distinct expression is discussed. To address the functional role of CCR3/eotaxin and CCR4/MDC during the in vivo recruitment of Th2 cells, we have transferred effector Th cells into naive mice to induce allergic airway disease. Tracking of these cells after repeated antigen challenge has established that both CCR3/eotaxin and CCR4/MDC axes contribute to the recruitment of Th2 cells to the lung, demonstrating the in vivo relevance of the expression of these receptors on Th2 cells. We have shown that involvement of the CCR3/eotaxin pathway is confined to early stages of the response in vivo, whereas repeated antigen stimulation results in the predominant use of the CCR4/MDC pathway. We propose that effector Th2 cells respond to both CCR3/eotaxin and CCR4/MDC pathways initially, but that a progressive increase in CCR4-positive cells results in the predominance of the CCR4/MDC axis in the long-term recruitment of Th2 cells in vivo.

Hematopoietic progenitor cell rolling in bone marrow microvessels: parallel contributions by endothelial selectins and vascular cell adhesion molecule 1.

We have used intravital microscopy to study physiologically perfused microvessels in murine bone marrow (BM). BM sinusoids and venules, but not adjacent bone vessels, supported rolling interactions of hematopoietic progenitor cells. Rolling did not involve L-selectin, but was partially reduced in wild-type mice treated with antibodies to P- or E-selectin and in mice that were deficient in these two selectins. Selectin-independent rolling was mediated by alpha4 integrins, which interacted with endothelial vascular cell adhesion molecule (VCAM)-1. Parallel contribution of the endothelial selectins and VCAM-1 is not known to direct blood cell trafficking to other noninflamed tissues. This combination of constitutively expressed adhesion molecules may thus constitute a BM-specific recruitment pathway for progenitor cells analogous to the vascular addressins that direct selective lymphocyte homing to lymphoid organs.

Inhibition of T1/ST2 during respiratory syncytial virus infection prevents T helper cell type 2 (Th2)- but not Th1-driven immunopathology.

T cells secreting interleukin (IL)-4 and IL-5 (T helper cell type 2 [Th2] cells) play a detrimental role in a variety of diseases, but specific methods of regulating their activity remain elusive. T1/ST2 is a surface ligand of the IL-1 receptor family, expressed on Th2- but not on interferon (IFN)-gamma-producing Th1 cells. Prior exposure of BALB/c mice to the attachment (G) or fusion (F) protein of respiratory syncytial virus (RSV) increases illness severity during intranasal RSV challenge, due to Th2-driven lung eosinophilia and exuberant Th1-driven pulmonary infiltration, respectively. We used these polar models of viral illness to study the recruitment of T1/ST2 cells to the lung and to test the effects of anti-T1/ST2 treatment in vivo. T1/ST2 was present on a subset of CD4(+) cells from mice with eosinophilic lung disease. Monoclonal anti-T1/ST2 treatment reduced lung inflammation and the severity of illness in mice with Th2 (but not Th1) immunopathology. These results show that inhibition of T1/ST2 has a specific effect on virally induced Th2 responses and suggests that therapy targeted at this receptor might be of value in treating Th2-driven illness.

Distinct expression and function of the novel mouse chemokine monocyte chemotactic protein-5 in lung allergic inflammation.

We have cloned a novel mouse CC chemokine cDNA from the lung during an allergic inflammatory reaction. The protein encoded by this cDNA is chemotactic for eosinophils, monocytes, and lymphocytes in vitro and in vivo. Based on its similarities in sequence and function with other CC chemokines, we have named it mouse monocyte chemotactic protein-5 (mMCP-5). Under noninflammatory conditions, expression of mMCP-5 in the lymph nodes and thymus is constitutive and is generally restricted to stromal cells. Neutralization of mMCP-5 protein with specific antibodies during an allergic inflammatory reaction in vivo resulted in a reduction in the number of eosinophils that accumulated in the lung. Moreover, mMCP-5 mRNA expression in vivo is regulated differently from that of other major CC chemokines in the lung during the allergic reaction, including Eotaxin. The presence of lymphocytes is essential for expression of mMCP-5 by alveolar macrophages and smooth muscle cells in the lung, and the induction of mMCP-5 RNA occurs earlier than that of the eosinophil chemokine Eotaxin during allergic inflammation. In contrast to Eotaxin, mRNA for mMCP-5 can be produced by mast cells. From these results, we postulate that mMCP-5 plays a pivotal role during the early stages of allergic lung inflammation.

Leukocytosis and resistance to septic shock in intercellular adhesion molecule 1-deficient mice.

Intercellular adhesion molecule 1 (ICAM-1) is one of three immunoglobulin superfamily members that bind to the integrins lymphocyte function associated 1 (LFA-1) and Mac-1 on leukocytes. We have generated mice that are genetically and functionally deficient in ICAM-1. These mice have elevated numbers of circulating neutrophils and lymphocytes, as well as diminished allogeneic T cell responses and delayed type hypersensitivity. Mutant mice are resistant to lethal effects of high doses of endotoxin (lipopolysaccharide [LPS]), and this correlates with a significant decrease in neutrophil infiltration in the liver. Production of inflammatory cytokines such as tumor necrosis factor alpha or interleukin 1 is normal in ICAM-1-deficient mice, and thus protection appears to be related to a diminution in critical leukocyte-endothelial interactions. After sensitization with D-galactosamine (D-Gal), ICAM-1-deficient mice are resistant to the lethal effect of low doses of exotoxin (Staphylococcus aureus enterotoxin B [SEB]), which has been shown to mediate its toxic effects via the activation of specific T cells. In this model, ICAM-1-mediated protection against SEB lethality correlates with a decrease in the systemic release of inflammatory cytokines, as well as with prevention of extensive hepatocyte necrosis and hemorrhage. ICAM-1-deficient mice sensitized with D-Gal, however, are not protected from lethality when challenged with low doses of endotoxin (LPS). These studies show that the different contribution of ICAM-1 in the activation of either T cells or macrophages is decisive for the fatal outcome of the shock in these two models. This work suggests that anti-ICAM-1 therapy may be beneficial in both gram-positive and -negative septic shock, either by reducing T cell activation or by diminishing neutrophil infiltration.

A role for Mac-1 (CDIIb/CD18) in immune complex-stimulated neutrophil function in vivo: Mac-1 deficiency abrogates sustained Fcgamma receptor-dependent neutrophil adhesion and complement-dependent proteinuria in acute glomerulonephritis.

Mac-1 (alphambeta2), a leukocyte adhesion receptor, has been shown in vitro to functionally interact with Fcgamma receptors to facilitate immune complex (IC)-stimulated polymorphonuclear neutrophil (PMN) functions. To investigate the relevance of Mac-1-FcgammaR interactions in IC-mediated injury in vivo, we induced a model of Fc-dependent anti-glomerular basement membrane (GBM) nephritis in wild-type and Mac-1-deficient mice by the intravenous injection of anti-GBM antibody. The initial glomerular PMN accumulation was equivalent in Mac-1 null and wild-type mice, but thereafter increased in wild-type and decreased in mutant mice. The absence of Mac-1 interactions with obvious ligands, intercellular adhesion molecule 1 (ICAM-1), and C3 complement, is not responsible for the decrease in neutrophil accumulation in Mac-1- deficient mice since glomerular PMN accumulation in mice deficient in these ligands was comparable to those in wild-type mice. In vitro studies showed that spreading of Mac-1-null PMNs to IC-coated dishes was equivalent to that of wild-type PMNs at 5-12 min but was markedly reduced thereafter, and was associated with an inability of mutant neutrophils to redistribute filamentous actin. This suggests that in vivo, Mac-1 is not required for the initiation of Fc-mediated PMN recruitment but that Mac-1-FcgammaR interactions are required for filamentous actin reorganization leading to sustained PMN adhesion, and this represents the first demonstration of the relevance of Mac-1-FcgammaR interactions in vivo. PMN-dependent proteinuria, maximal in wild-type mice at 8 h, was absent in Mac-1 mutant mice at all time points. Complement C3-deficient mice also had significantly decreased proteinuria compared to wild-type mice. Since Mac-1 on PMNs is the principal ligand for ic3b, an absence of Mac-1 interaction with C3 probably contributed to the abrogation of proteinuria in Mac-1-null mice.

The coordinated action of CC chemokines in the lung orchestrates allergic inflammation and airway hyperresponsiveness.

The complex pathophysiology of lung allergic inflammation and bronchial hyperresponsiveness (BHR) that characterize asthma is achieved by the regulated accumulation and activation of different leukocyte subsets in the lung. The development and maintenance of these processes correlate with the coordinated production of chemokines. Here, we have assessed the role that different chemokines play in lung allergic inflammation and BHR by blocking their activities in vivo. Our results show that blockage of each one of these chemokines reduces both lung leukocyte infiltration and BHR in a substantially different way. Thus, eotaxin neutralization reduces specifically BHR and lung eosinophilia transiently after each antigen exposure. Monocyte chemoattractant protein (MCP)-5 neutralization abolishes BHR not by affecting the accumulation of inflammatory leukocytes in the airways, but rather by altering the trafficking of the eosinophils and other leukocytes through the lung interstitium. Neutralization of RANTES (regulated upon activation, normal T cell expressed and secreted) receptor(s) with a receptor antagonist decreases significantly lymphocyte and eosinophil infiltration as well as mRNA expression of eotaxin and RANTES. In contrast, neutralization of one of the ligands for RANTES receptors, macrophage-inflammatory protein 1alpha, reduces only slightly lung eosinophilia and BHR. Finally, MCP-1 neutralization diminishes drastically BHR and inflammation, and this correlates with a pronounced decrease in monocyte- and lymphocyte-derived inflammatory mediators. These results suggest that different chemokines activate different cellular and molecular pathways that in a coordinated fashion contribute to the complex pathophysiology of asthma, and that their individual blockage results in intervention at different levels of these processes.

Crucial role of the interleukin 1 receptor family member T1/ST2 in T helper cell type 2-mediated lung mucosal immune responses.

T1/ST2 is an orphan receptor of unknown function that is expressed on the surface of murine T helper cell type 2 (Th2), but not Th1 effector cells. In vitro blockade of T1/ST2 signaling with an immunoglobulin (Ig) fusion protein suppresses both differentiation to and activation of Th2, but not Th1 effector populations. In a nascent Th2-dominated response, anti-T1/ST2 monoclonal antibody (mAb) inhibited eosinophil infiltration, interleukin 5 secretion, and IgE production. To determine if these effects were mediated by a direct effect on Th2 cells, we next used a murine adoptive transfer model of Th1- and Th2-mediated lung mucosal immune responses. Administration of either T1/ST2 mAb or T1/ST2-Ig abrogated Th2 cytokine production in vivo and the induction of an eosinophilic inflammatory response, but failed to modify Th1-mediated inflammation. Taken together, our data demonstrate an important role of T1/ST2 in Th2-mediated inflammatory responses and suggest that T1/ST2 may prove to be a novel target for the selective suppression of Th2 immune responses.

Myeloid dendritic cells induce Th2 responses to inhaled antigen, leading to eosinophilic airway inflammation.

The aim of this study was to investigate whether dendritic cells (DCs) can induce sensitization to aeroallergen in a mouse model of allergic asthma. Ovalbumin-pulsed (OVA-pulsed) or unpulsed myeloid DCs that were injected into the airways of naive mice migrated into the mediastinal lymph nodes. When challenged 2 weeks later with an aerosol of OVA, activated CD4 and CD8 lymphocytes, eosinophils, and neutrophils were recruited to the lungs of actively immunized mice. These CD4(+) lymphocytes produced predominantly IL-4 and IL-5 but also IFN-gamma, whereas CD8(+) lymphocytes produced predominantly IFN-gamma. Histological analysis revealed perivascular and peribronchial eosinophilic infiltrates and goblet cell hyperplasia. Studies in IL-4(-/-) and CD28(-/-) mice revealed that production of IL-4 by host cells and provision of costimulation to T cells by DCs were critical for inducing the response. Lung CD4(+) T cells strongly expressed the Th2 marker T1/ST2, and signaling through this molecule via a ligand expressed on DCs was essential for the establishment of airway eosinophilia. These data demonstrate that DCs in the airways induce sensitization to inhaled antigen and that molecules expressed on the surface of these cells are critical for the development of Th2-dependent airway eosinophilia.

Intercellular adhesion molecule-1 deficiency prolongs survival and protects against the development of pulmonary inflammation during murine lupus.

One of the characteristic features of the lupus syndrome in humans and mice is the organ-specific accumulation of leukocytes within a variety of different tissues; however, the etiology of this phenomenon remains unclear. The work presented here determined the role of intercellular adhesion molecule (ICAM)-1 in the development of pulmonary leukocyte accumulation by generating MRL/MpJ-Faslpr mice that are genetically deficient in this critical adhesion molecule. Interestingly, these MRL/MpJ-Faslpr ICAM-1 knockout mice exhibit prolonged survival times compared to littermates expressing ICAM-1. We have determined that lack of ICAM-1 completely abrogates the development of pulmonary inflammation but does not prevent the development of autoantibodies, lymphadenopathy, and glomerulonephritis. Furthermore, the lack of pulmonary inflammation was found to be due to decreased migration of leukocytes to the lung rather than decreased in situ proliferation of cells.

Cerebral protection in homozygous null ICAM-1 mice after middle cerebral artery occlusion. Role of neutrophil adhesion in the pathogenesis of stroke.

Acute neutrophil (PMN) recruitment to postischemic cardiac or pulmonary tissue has deleterious effects in the early reperfusion period, but the mechanisms and effects of neutrophil influx in the pathogenesis of evolving stroke remain controversial. To investigate whether PMNs contribute to adverse neurologic sequelae and mortality after stroke, and to study the potential role of the leukocyte adhesion molecule intercellular adhesion molecule-1 (ICAM-1) in the pathogenesis of stroke, we used a murine model of transient focal cerebral ischemia consisting of intraluminal middle cerebral artery occlusion for 45 min followed by 22 h of reperfusion. PMN accumulation, monitored by deposition of 111In-labeled PMNs in postischemic cerebral tissue, was increased 2.5-fold in the ipsilateral (infarcted) hemisphere compared with the contralateral (noninfarcted) hemisphere (P < 0.01). Mice immunodepleted of neutrophils before surgery demonstrated a 3.0-fold reduction in infarct volumes (P < 0.001), based on triphenyltetrazolium chloride staining of serial cerebral sections, improved ipsilateral cortical cerebral blood flow (measured by laser Doppler), and reduced neurological deficit compared with controls. In wild-type mice subjected to 45 min of ischemia followed by 22 h of reperfusion, ICAM-1 mRNA was increased in the ipsilateral hemisphere, with immunohistochemistry localizing increased ICAM-1 expression on cerebral microvascular endothelium. The role of ICAM-1 expression in stroke was investigated in homozygous null ICAM-1 mice (ICAM-1 -/-) in comparison with wild-type controls (ICAM-1 +/+). ICAM-1 -/- mice demonstrated a 3.7-fold reduction in infarct volume (P < 0.005), a 35% increase in survival (P < 0.05), and reduced neurologic deficit compared with ICAM-1 +/+ controls. Cerebral blood flow to the infarcted hemisphere was 3.1-fold greater in ICAM-1 -/- mice compared with ICAM-1 +/+ controls (P < 0.01), suggesting an important role for ICAM-1 in the genesis of postischemic cerebral no-reflow. Because PMN-depleted and ICAM-1-deficient mice are relatively resistant to cerebral ischemia-reperfusion injury, these studies suggest an important role for ICAM-1-mediated PMN adhesion in the pathophysiology of evolving stroke.

The amino-terminal domain of the CCR2 chemokine receptor acts as coreceptor for HIV-1 infection.

The chemokines are a homologous serum protein family characterized by their ability to induce activation of integrin adhesion molecules and leukocyte migration. Chemokines interact with their receptors, which are composed of a single-chain, seven-helix, membrane-spanning protein coupled to G proteins. Two CC chemokine receptors, CCR3 and CCR5, as well as the CXCR4 chemokine receptor, have been shown necessary for infection by several HIV-1 virus isolates. We studied the effect of the chemokine monocyte chemoattractant protein 1 (MCP-1) and of a panel of MCP-1 receptor (CCR2)-specific monoclonal antibodies (mAb) on the suppression of HIV-1 replication in peripheral blood mononuclear cells. We have compelling evidence that MCP-1 has potent HIV-1 suppressive activity when HIV-1-infected peripheral blood lymphocytes are used as target cells. Furthermore, mAb specific for the MCP-1R CCR2 which recognize the third extracellular CCR2 domain inhibit all MCP-1 activity and also block MCP-1 suppressive activity. Finally, a set of mAb specific for the CCR2 amino-terminal domain, one of which mimics MCP-1 activity, has a potent suppressive effect on HIV-1 replication in M- and T-tropic HIV-1 viral isolates. We conjecture a role for CCR2 as a coreceptor for HIV-1 infection and map the HIV-1 binding site to the amino-terminal part of this receptor. This concurs with results showing that the CCR5 amino terminus is relevant in HIV-1 infection, although chimeric fusion of various extracellular domains shows that other domains are also implicated. We discuss the importance of CCR2 structure relative to its coreceptor role and the role of anti-CCR2 receptor antibodies in the prevention of HIV-1 infection.

Eosinophil recruitment to the lung in a murine model of allergic inflammation. The role of T cells, chemokines, and adhesion receptors.

Eosinophil accumulation is a distinctive feature of lung allergic inflammation. Here, we have used a mouse model of OVA (ovalbumin)-induced pulmonary eosinophilia to study the cellular and molecular mechanisms for this selective recruitment of eosinophils to the airways. In this model there was an early accumulation of infiltrating monocytes/macrophages in the lung during the OVA treatment, whereas the increase in infiltrating T-lymphocytes paralleled the accumulation of eosinophils. The kinetics of accumulation of these three leukocyte subtypes correlated with the levels of mRNA expression of the chemokines monocyte chemotactic peptide-1/JE, eotaxin, and RANTES (regulated upon activation in normal T cells expressed and secreted), suggesting their involvement in the recruitment of these leukocytes. Furthermore, blockade of eotaxin with specific antibodies in vivo reduced the accumulation of eosinophils in the lung in response to OVA by half. Mature CD4+ T-lymphocytes were absolutely required for OVA-induced eosinophil accumulation since lung eosinophilia was prevented in CD4+-deficient mice. However, these cells were neither the main producers of the major eosinophilic chemokines eotaxin, RANTES, or MIP-1alpha, nor did they regulate the expression of these chemokines. Rather, the presence of CD4+ T cells was necessary for enhancement of VCAM-1 (vascular cell adhesion molecule-1) expression in the lung during allergic inflammation induced by the OVA treatment. In support of this, mice genetically deficient for VCAM-1 and intercellular adhesion molecule-1 failed to develop pulmonary eosinophilia. Selective eosinophilic recruitment during lung allergic inflammation results from a sequential accumulation of certain leukocyte types, particularly T cells, and relies on the presence of both eosinophilic chemoattractants and adhesion receptors.

Intercellular adhesion molecule-1-deficient mice are protected against ischemic renal injury.

Studies in the rat have pointed to a role for intercellular adhesion molecule-1 (ICAM-1) in the pathogenesis of acute tubular necrosis. These studies used antibodies, which may have nonspecific effects. We report that renal ICAM-1 mRNA levels and systemic levels of the cytokines IL-1 and TNF-alpha increase 1 h after ischemia/ reperfusion in the mouse. We sought direct proof for a critical role for ICAM-1 in the pathophysiology of ischemic renal failure using mutant mice genetically deficient in ICAM-1. ICAM-1 is undetectable in mutant mice in contrast with normal mice, in which ICAM-1 is prominent in the endothelium of the vasa recta. Mutant mice are protected from acute renal ischemic injury as judged by serum creatinine, renal histology, and animal survival . Renal leukocyte infiltration, quantitated morphologically and by measuring tissue myeloperoxidase, was markedly less in ICAM-1-deficient than control mice. To evaluate whether prevention of neutrophil infiltration could be responsible for the protection observed in the mutant mice, we treated normal mice with antineutrophil serum to reduce absolute neutrophil counts to < 100 cells/mm3. These neutrophil-depleted animals were protected against ischemic renal failure. Anti-1CAm-1 antibody protected normal mice against renal ischemic injury but did not provide additional protection to neutrophil-depleted animals. Thus, ICAM-1 is a key mediator of ischemic acute renal failure likely acting via potentiation of neutrophilendothelial interactions.

Generation of experimental allergic airways inflammation in the absence of draining lymph nodes.

The objective of this study was to investigate the contribution of secondary lymphoid organs in the generation and maintenance of experimental allergic airway inflammation. We employed a previously reported murine model of respiratory mucosal allergic sensitization, induced by repeated aerosolizations of ovalbumin in the context of a GM-CSF airway environment. We executed this protocol in wild-type (WT) and lymphotoxin-alpha-deficient mice (LTalpha-KO) mice, which are devoid of lymph nodes (LNs) and possess rudimentary spleen structures. Despite the lack of pulmonary LNs draining the airway compartment, LTalpha-KO mice were fully capable of mounting a robust inflammatory response in the airways, consisting of Th2 polarized CD4+ T cells and eosinophils. This was accompanied by IL-5, IL-13, and IFN-gamma production by splenocytes and generation of ovalbumin-specific serum IgE. Exposure to the same antigen 7 weeks after complete resolution of airway inflammation once again induced a Th2 polarized infiltrate, demonstrating intact immunological memory. To investigate inherent plasticity in establishing antigen-specific immunity, mice were splenectomized before sensitization. Allergic sensitization was completely abrogated in splenectomized LTalpha-KO mice, compared with eusplenic LTalpha-KO controls. These data demonstrate that secondary lymphoid organs, either LN or spleen, are essential for the generation of allergic airway responses.

A major role for VCAM-1, but not ICAM-1, in early atherosclerosis.

VCAM-1 and ICAM-1 are endothelial adhesion molecules of the Ig gene superfamily that may participate in atherogenesis by promoting monocyte accumulation in the arterial intima. Both are expressed in regions predisposed to atherosclerosis and at the periphery of established lesions, while ICAM-1 is also expressed more broadly. To evaluate functions of VCAM-1 in chronic disease, we disrupted its fourth Ig domain, producing the murine Vcam1(D4D) allele. VCAM-1(D4D) mRNA and protein were reduced to 2-8% of wild-type allele (Vcam1(+)) levels but were sufficient to partially rescue the lethal phenotype of VCAM-1-null embryos. After crossing into the LDL receptor-null background, Vcam1(+/+) and Vcam1(D4D/D4D) paired littermates were generated from heterozygous intercrosses and fed a cholesterol-enriched diet for 8 weeks. The area of early atherosclerotic lesions in the aorta, quantified by en face oil red O staining, was reduced significantly in Vcam1(D4D/D4D) mice, although cholesterol levels, lipoprotein profiles, and numbers of circulating leukocytes were comparable to wild-type. In contrast, deficiency of ICAM-1 either alone or in combination with VCAM-1 deficiency did not alter nascent lesion formation. Therefore, although expression of both VCAM-1 and ICAM-1 is upregulated in atherosclerotic lesions, our data indicate that VCAM-1 plays a dominant role in the initiation of atherosclerosis.