Leukocyte Function-associated Antigen-1 Expression Research Articles

Adhesion of monocytes to periodontal fibroblasts requires activation of NOD1/2- and TLR4-mediated LFA-1 and VLA-4

ObjectiveThe aim of this study was to investigate the roles of nucleotide-binding oligomerization domain-containing protein 1/2 (NOD1/2) and Toll-like receptor 4 (TLR4) in mediating the adhesion of monocytes to periodontal fibroblasts through leucocyte function-associated antigen-1 (LFA-1) and very late antigen-4 (VLA-4). DesignThe expression of NOD1, NOD2, and TLR4 was detected in the gingival tissue of patients with chronic periodontitis by immunohistochemistry. Then the adhesion of cells of human monocytic cell line U937 to human gingival fibroblasts (hGFs) and human periodontal ligament cells (hPDLCs) was investigated after U937 cells were treated with the agonists of NOD1, NOD2, and TLR4 for 24h, or transfected with small interfering RNAs (siRNAs) targeting NOD1, NOD2, and TLR4 for 48h. Meanwhile, the expression of LFA-1 and VLA-4 was examined in U937 cells through real-time polymerase chain reaction (PCR), Western blot, and flow cytometry. To confirm the roles of LFA-1 and VLA-4 involved in the process of adhesion, the adhesion blockade assay was performed using the corresponding blocking antibodies against these adhesion molecules. ResultsThe immunostaining results showed that NOD1, NOD2, and TLR4 were highly expressed in the gingival tissue of patients with periodontitis, especially in the monocyte-infiltrated area. The activation of these receptors by agonists upregulated the expression of LFA-1 and VLA-4 in U937 cells, and it increased the affinity of U937 cells to hGFs or hPDLCs. On the other hand, knockdown of these receptors by specific siRNAs resulted in the opposite results. In addition, blocking either LFA-1 or VLA-4 in U937 cells significantly attenuated the agonist-triggered adhesion of U937 to periodontal fibroblasts (P<0.001). ConclusionsThese results suggested that NOD1/2 and TLR4 mediated monocyte–periodontal fibroblast adhesion via the modulation of LFA-1 and VLA-4.

Expression of Leucocyte Function-associated Antigen-1 and Intercellular Adhesion Molecule-1 in the Lungs of Pigs Infected with Actinobacillus pleuropneumoniae

The aim of this study was to determine the expression of leucocyte function-associated antigen (LFA)-1 (CD11a/CD18) by neutrophils and intercellular adhesion molecule (ICAM)-1 (CD54) by endothelial cells in the lungs of pigs that had been infected experimentally with Actinobacillus pleuropneumoniae. Sixty-four 7-week-old conventional pigs were allocated randomly into infected (n=40) or control (n=24) groups. Five infected and three uninfected pigs were killed at 3, 6, 9, 12, 24, 36, 48 and 60h post inoculation (hpi). Strong immunohistochemical expression of LFA-1 and ICAM-1 was detected frequently in neutrophils in the alveolar space and in endothelial cells in the capillaries of the alveolar septa, respectively. LFA-1 and ICAM-1 expression appeared to correlate with the onset of neutrophil infiltration into the alveolar space. The interaction between ICAM-1 and LFA-1 may be associated with the adherence of neutrophils to vascular endothelium, thereby permitting transmigration of these cells into inflamed lung.

Intact LFA-1 deactivation promotes T-cell activation and rejection of cardiac allograft

Leucocyte function-associated antigen-1 (LFA-1) is known to be involved in immune reactions leading to allograft rejection. The role of deactivating LFA-1 in this context has not been investigated yet, although it is accepted that regulating LFA-1 activity is essential for T-cell function. Expressing LFA-1 locked in an active state in mice (LFA-1(d/d)) allowed us to investigate the in vivo function of LFA-1 deactivation for allograft rejection in a model of heterotopic cardiac transplantation. We provide in vivo evidence that regulating LFA-1 activity from an active to an inactive state controls antigen-specific priming and proliferation of T cells in response to allogeneic stimuli. Consequently, defective LFA-1 deactivation significantly prolonged cardiac allograft survival. Furthermore, reduced numbers of alloantigen-specific T cells and non-allo-specific innate immune cells within allografts of LFA-1(d/d) recipients indicate that expression of active LFA-1 impairs inflammatory responses involving all major leucocyte subpopulations. Taken together, our in vivo data suggest that LFA-1 deactivation is important for the formation of inflammatory lesions and rejection of cardiac allografts. Thus, the dynamic regulation of LFA-1 activity, rather than the mere presence of LFA-1, appears to contribute to the control of immune reactions inducing allogeneic transplant rejection.

Diallyl disulphide, but not diallyl sulphide, increases leucocyte function-associated antigen-1 expression and cellular adhesion in monocytes

A steam distillation process at pH 9 was conducted to prepare garlic oil for food supplement. A garlic oil predominant in bioactive diallyl monosulphide (8.9%), diallyl disulphide (56.9%) diallyl trisulphide (7.6%) and diallyl tetrasulphide (2.6%) was obtained from peeled garlic cloves. The adhesion molecule leucocyte function-associated antigen-1 (LFA-1) mediates leucocyte adhesion and migration during immune responses. In this study, we investigated the effects of diallyl sulphide (DAS) and diallyl disulphide (DADS) on LFA-1 expression, cell adhesion and migration in the U937 and peritoneal macrophages from mice. After treatment, DADS, but not DAS, elevated the expression of LFA-1 in a dose- and time-dependent manner in U937 cells and peritoneal macrophages. Moreover, LFA-1 and intracellular adhesion molecular-1 (ICAM-1)-mediated adhesion also was increased by DADS in a dose- and time-dependent manner. After DADS treatment, LFA-1 clustering also increased on U937 surface. In contrast, there was no significant difference in migration of U937 cells between DADS treatment and no treatment. This study indicates the DADS, but not DAS, regulates immune responses by modulating LFA-1 expression, clustering and LFA-1-mediated adhesion in monocytes, evidences that DADS acts as an immune regulator of adhesion molecules during immune responses.

Appearance of LFA-1 in the initial stage of synaptogenesis of developing hippocampal neurons

In the present study, we found that leucocyte function-associated antigen-1 (LFA-1), and integrin (heterodimer complex of CD11a and CD18), which are abundant in immunological synapse, were expressed in developing hippocampal neurons. The expression of LFA-1 in hippocampal neurons was in the period of synaptogenesis, and synaptogenesis was inhibited by the blocking antibodies of anti-CD11a or anti-CD18 in vitro. Since it is known that LFA-1 has an important role in the immunological response, especially in immunological synapse, LFA-1 is considered to have an important role in neuronal synapse and is highly involved in synaptogenesis in the early developmental stage in vitro. In vivo, we also confirmed that CD18 was expressed in hippocampus in the early developmental stage. Telencephalin, which is a candidate for postsynaptic elements to contact LFA-1, was precisely opposed to CD18-positive structures in presynaptic elements, and telencephalin was considered to be involved in synaptogenesis. The present study showed that 17beta-estradiol of steroid hormones, which are well known to have various effects on hippocampal neurons, has a significant influence on the presynaptic expression of CD18 in synaptogenesis and inhibited synaptogenesis in the early developmental stage in vitro. These results suggest that LFA-1 plays some mechanisms in synaptic contacts and synaptogenesis of hippocampal neurons.

Lipophilic statins suppress cytotoxicity by freshly isolated natural killer cells through modulation of granule exocytosis

NK cells, a component of the innate immune system, provide a first line of defense against viral infections and malignancies, interact with the adaptive immune system and have a role in rejection of allogeneic bone marrow transplants and solid allo- and xenotransplants. Immunoregulatory activity by the anti-hypercholesterolemia agents, 3-hydroxy-3-methyl-glutaryl Coenzyme A (HMG-CoA) reductase inhibitors, known as statins, has recently been reported. We analyzed the effects of three statins on human NK cell cytotoxicity. Two lipophilic statins (simvastatin and fluvastatin) suppressed the cytotoxic activity of fresh and IL-2-stimulated NK cells, while pravastatin, a hydrophilic statin, did not. Suppression was not associated with changes in intracellular perforin, granzyme A or granzyme B levels, or with changes in expression of leukocyte function-associated antigen-1, an integrin known to regulate NK activity and reported to be altered by statin treatment. Decreased cytotoxicity was associated with decreased CD107a surface expression, indicating that the exocytosis pathway was compromised by simvastatin and fluvastatin but not by pravastatin. Mevalonate, the immediate downstream product of HMG-CoA reductase, partially reversed the effect of lipophilic statins on cytotoxicity and CD107a expression. Lipophilic statins also suppressed the release of the granule component, granzyme B, by IL-2-activated NK cells following stimulation with K562. That lipophilic statins suppress NK cell activity through inhibition of the exocytosis pathway suggest an additional potential role for statins in inhibition of transplantation responses.

LFA-1-dependent lipid raft recruitment of DNAM-1 (CD226) in CD4+ T cell

Upon antigen recognition by the TCR, both the leukocyte adhesion molecules DNAM-1 and leukocyte function-associated antigen-1 (LFA-1) associate with lipid rafts and form peripheral supra-molecular activation clusters that surround central-supra-molecular activation clusters at the immunological synapse. The serine residue in the cytoplasmic tail of DNAM-1 is responsible for this association of DNAM-1 with lipid rafts. The TCR-mediated signal also induces physical association of DNAM-1 with LFA-1, for which the serine phosphorylation of DNAM-1 is also responsible. However, how the serine residue is involved in lipid raft recruitment of DNAM-1 has remained unclear. Here, we show that, although the TCR-mediated signal induced the serine phosphorylation of DNAM-1, DNAM-1 did not associate with lipid rafts in CD4+ T cells derived from mice deficient in LFA-1 expression, indicating that lipid raft recruitment of DNAM-1 depends on LFA-1 expression. These results suggest that the serine phosphorylation of DNAM-1 primarily induces physical association of DNAM-1 with LFA-1, which then takes DNAM-1 into lipid raft compartment.

Leukocyte Function-associated Antigen 1-mediated Adhesion Stability Is Dynamically Regulated through Affinity and Valency during Bond Formation with Intercellular Adhesion Molecule-1

Neutrophil rolling and transition to arrest on inflamed endothelium are dynamically regulated by the affinity of the beta(2) integrin CD11a/CD18 (leukocyte function associated antigen 1 (LFA-1)) for binding intercellular adhesion molecule (ICAM)-1. Conformational shifts are thought to regulate molecular affinity and adhesion stability. Also critical to adhesion efficiency is membrane redistribution of active LFA-1 into dense submicron clusters where multimeric interactions occur. We examined the influences of affinity and dimerization of LFA-1 on LFA-1/ICAM-1 binding by engineering a cell-free model in which two recombinant LFA-1 heterodimers are bound to respective Fab domains of an antibody attached to latex microspheres. Binding of monomeric and dimeric ICAM-1 to dimeric LFA-1 was measured in real time by fluorescence flow cytometry. ICAM-1 dissociation kinetics were measured while LFA-1 affinity was dynamically shifted by the addition of allosteric small molecules. High affinity LFA-1 dissociated 10-fold faster when bound to monomeric compared with dimeric ICAM-1, corresponding to bond lifetimes of 25 and 330 s, respectively. Downshifting LFA-1 into an intermediate affinity state with the small molecule I domain allosteric inhibitor IC487475 decreased the difference in dissociation rates between monomeric and dimeric ICAM-1 to 4-fold. When LFA-1 was shifted into the low affinity state by lovastatin, both monomeric and dimeric ICAM-1 dissociated in less than 1 s, and the dissociation rates were within 50% of each other. These data reveal the respective importance of LFA-1 affinity and proximity in tuning bond lifetime with ICAM-1 and demonstrate a nonlinear increase in the bond lifetime of the dimer versus the monomer at higher affinity.

S-Nitrosoglutathione Reduces Inflammation and Protects Brain against Focal Cerebral Ischemia in a Rat Model of Experimental Stroke

Preservation of endothelial functions with low-dose nitric oxide (NO) and inhibition of excessive production of NO from inducible NO synthase (iNOS) is a potential therapeutic approach for acute stroke. Based on this hypothesis, an NO modulator, S-nitrosoglutathione (GSNO) was used, which provided neuroprotection in a rat model of focal cerebral ischemia. Administration of GSNO after the onset of ischemia reduced infarction and improved cerebral blood flow. To understand the mechanism of protection, the involvement of inflammation in ischemic brain injury was examined. Treatment with GSNO reduced the expression of tumor necrosis factor-alpha, interleukin-1beta, and iNOS; inhibited the activation of microglia/macrophage (ED1, CD11-b); and downregulated the expression of leukocyte function-associated antigen-1 and intercellular adhesion molecule-1 in the ischemic brain. The number of apoptotic cells (including neurons) and the activity of caspase-3 were also decreased after GSNO treatment. Further, the antiinflammatory effect of GSNO on expression of iNOS and activation of NF-kappaB machinery in rat primary astrocytes and in the murine microglial cell line BV2 was tested. Cytokine-mediated expression of iNOS and activation of NF-kappaB were inhibited by GSNO treatment. That GSNO protects the brain against ischemia/reperfusion injury by modulating NO systems, resulting in a reduction in inflammation and neuronal cell death was documented by the results.

Somatostatin down-regulates LFA-1 activation by modulating Rap1 expression in CD4 + and CD8 + T cells

Leukocyte function-associated antigen-1 (LFA-1) is one of the integrins that are expressed on the leukocytes, and has been shown to play an important role in leukocyte trafficking. The adhesive activity of LFA-1 is governed partially by the Rap1. This study examined that the relationship between LFA-1 and Rap1 mRNA expressions by anti-CD3 and anti-CD3+SOM treatment in the CD4 + and CD8 + T cells. The LFA-1 mRNA expression levels following the anti-CD3 and anti-CD3+SOM treatment for 30 min was greater on the CD8 + T cells, and the LFA-1 expression of the CD8 + T cells with anti-CD+SOM treatment was affected more severely than that of the CD4 + T cells. The Rap1 mRNA expression patterns following anti-CD3 and anti-CD3+SOM stimulation in the CD4 + and CD8 + T cells were similar to the LFA-1 expression patterns, and the expression level following anti-CD3+SOM treatment was suppressed more significantly in the CD8 + T cells. These results suggest that the difference in the Rap1 expression level after stimulation might explain the differences in the LFA-1 expression level on the T cell subsets, and that the down-regulation of Rap1 expression following SOM treatment is closely related to the diminished LFA-1 expression.

T-cell clones can be rendered specific for CD19: toward the selective augmentation of the graft-versus-B–lineage leukemia effect

Relapse of B-lineage acute lymphoblastic leukemia (B-ALL) after allogeneic hematopoietic stem cell transplantation (HSCT) commonly results from the failure of a graft-versus-leukemia (GVL) effect to eradicate minimal residual disease. Augmenting the GVL effect by the adoptive transfer of donor-derived B-ALL-specific T-cell clones is a conceptually attractive strategy to decrease relapse rates without exacerbating graft-versus-host disease (GVHD). Toward this end, we investigated whether a genetic engineering approach could render CD8(+) cytotoxic T lymphocytes (CTLs) specific for tumor cells that express the B-cell lineage cell surface molecule CD19. This was accomplished by the genetic modification of CTLs to express a chimeric immunoreceptor composed of a CD19-specific single-chain immunoglobulin extracellular targeting domain fused to a CD3-zeta intracellular signaling domain. CD19-redirected CTL clones display potent CD19-specific lytic activity and chimeric immunoreceptor-regulated cytokine production and proliferation. Because B-ALL cells can evade T-cell/natural killer- cell recognition by down-regulation of cell surface accessory molecules that participate in the formation of a functional immunologic synapse, we compared the CD19-specific effector function of genetically modified CD8(+) CTLs toward CD19(+) cells with disparate levels of intercellular adhesion molecule 1 (ICAM-1), leukocyte function-associated antigen 1 (LFA-1), and LFA-3. We observed that recognition of B-lineage tumor lines by CD19-specific CTLs was not impaired by low levels of ICAM-1, LFA-1, and LFA-3 cell surface expression, a functional attribute that is likely a consequence of our high-affinity CD19-specific chimeric immunoreceptor. Furthermore, the CD19-specific CTLs could lyse primary B-ALL blasts. These preclinical observations form the basis for implementing clinical trials using donor-derived CD19-specific T-cell clones to treat or prevent relapse of B-ALL after allogeneic HSCT.

Expression of adhesion molecules LFA-I and ICAM-I on osteoclast precursors during osteoclast differentiation and involvement of estrogen deficiency

Objectives Estrogen deficiency caused by the menopause or ovariectomy leads to stimulation of osteoclastogenesis. The adhesion molecules, leukocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1), are necessary for osteoclast formation. In this study, the expression of LFA-1 and ICAM-1 on osteoclast precursors during osteoclast differentiation, and the involvement of ovariectomy in the expression, were investigated.Methods Spleen cells isolated from normal or ovariectomized (OVX) mice were co-cultured with TMS14, stromal cells derived from mouse bone marrow, in the absence or presence of 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) for 7 days. On days 3, 5 and 7 of culture, the expression of LFA-1 and ICAM-1 on osteoclast precursors was quantitated using indirect immunofluorescence and confocal laser cytometry, and, on day 7, the number of formed osteoclasts was measured by tartrate-resistant acid phosphatase (TRAP) stain.Results The level of ICAM-1 expression on osteoclast precursors gradually increased with osteoclast differentiation, whereas that of LFA-1 did not change. A high level of ICAM-1 was observed on the integrin β3-positive mononuclear cells. On the osteoclast precursors isolated from OVX mice, both the level of ICAM-1 expression per cell and the number of cells showing a high expression of ICAM-1 significantly increased, with an increase in the number of osteoclast-like cells. However, the level of LFA-1 did not change.Conclusions These results indicate that the expression level of ICAM-1, but not that of LFA-1, is involved in osteoclast differentiation. Estrogen deficiency results in an increase in ICAM-1 expression on osteoclast precursors, which may be one of the mechanisms underlying bone loss following the menopause or ovariectomy.

Leukocyte function-associated antigen-1 expression on decidual natural killer cells in patients with early pregnancy loss.

A large number of CD56(bright) natural killer (NK) cells, which comprise a very small fraction of peripheral blood lymphocytes, appear in the endometrium during the late secretory phase and early pregnancy. These cells are thought to immunologically maintain or inhibit pregnancy. However, the details regarding their contribution to the immuno-elimination systems of embryonic cells or decidual stromal cells remain unclear. Recently, leukocyte function-associated antigen-1 (LFA-1) was shown to play a critical role in the regulation of NK cytolysis in peripheral blood lymphocytes. We speculated that LFA-1 on the decidual CD56(bright) NK may be involved in the regulation of pregnancy. The expression of LFA-1 on the decidual CD56(bright) NK cells was analysed using flow cytometry with fluorescent monoclonal antibodies; CD56 (NKH1), CD16 (Fcg-R3) and CD11a (LFA-1 alpha-chain). In comparison with non-pregnant endometrium during the late secretory phase, the subpopulation of CD56(bright)CD16(-) cells in decidual lymphocytes was significantly increased during normal pregnancy, but was less than that in early pregnancy loss (P < 0.05). Furthermore, the number of CD56(bright) NK cells expressing LFA-1 was significantly higher in early pregnancy loss, and the late secretory phase, than during normal pregnancy (P < 0.05). Our results indicate that up-regulation of LFA-1 on CD56(bright) NK cells is related to spontaneous abortion or the onset of menstruation.

Measles virus infection causes transient depletion of activated T cells from peripheral circulation.

Natural measles virus infection as well as vaccination with attenuated measles virus induce temporary immunosuppression, which is responsible for part of the morbidity and mortality associated with measles. The underlying molecular mechanisms are not known. Recently, in vitro studies have revealed a marked increase of LFA-1 expression of lymphocytes in the presence of infectious measles virus. In order to further investigate immune dysfunction in measles we analyzed the expression of leukocyte function-associated antigen 1 (LFA-1) on ex vivo derived circulating human T cells. Expression of LFA-1 was measured by flow cytometry using monoclonal antibodies directed against CD11a and CD18. LFA-1 expression was followed in the course of infection in four adult seronegative vaccinees and in four patients with natural measles. There was a remarkable loss of LFA-1-bright cells during natural measles and after measles vaccination. The number of LFA-1-bright cells reached a minimum on day 7-14 after vaccination, and at the onset of rash during natural measles infection, and approached normal levels within 3-5 weeks. It is suggested that measles virus infection interferes with lymphocyte trafficking and reallocation. Disruption of recirculation and random homing of lymphocytes might contribute to the immunosuppression, which is characteristic for measles virus infection.

Murine Hematopoietic Progenitor Cells With Colony-Forming or Radioprotective Capacity Lack Expression of the β2-Integrin LFA-1

AbstractRecently, we have demonstrated that antibodies that block the function of the β2-integrin leukocyte function-associated antigen-1 (LFA-1) completely abrogate the rapid mobilization of hematopoietic progenitor cells (HPC) with colony-forming and radioprotective capacity induced by interleukin-8 (IL-8) in mice. These findings suggested a direct inhibitory effect of these antibodies on LFA-1–mediated transmigration of stem cells through the bone marrow endothelium. Therefore, we studied the expression and functional role of LFA-1 on murine HPC in vitro and in vivo. In steady state bone marrow ± 50% of the mononuclear cells (MNC) were LFA-1neg. Cultures of sorted cells, supplemented with granulocyte colony-stimulating factor (G-CSF)/granulocyte-macrophage colony-stimulating factor (GM-CSF)/IL-1/IL-3/IL-6/stem cell factor (SCF) and erythropoietin (EPO) indicated that the LFA-1neg fraction contained the majority of the colony-forming cells (CFCs) (LFA-1neg 183 ± 62/7,500 cells v LFA-1pos 29 ± 17/7,500 cells,P < .001). We found that the radioprotective capacity resided almost exclusively in the LFA-1neg cell fraction, the radioprotection rate after transplantation of 103, 3 × 103, 104, and 3 × 104 cells being 63%, 90%, 100%, and 100% respectively. Hardly any radioprotection was obtained from LFA-1pos cells. Similarly, in cytokine (IL-8 and G-CSF)–mobilized blood, the LFA-1neg fraction, which comprised 5% to 10% of the MNC, contained the majority of the colony-forming cells, as well as almost all cells with radioprotective capacity. Subsequently, primitive bone marrow-derived HPC, represented by Wheat-germ-agglutinin (WGA)+/Lineage (Lin)−/Rhodamine (Rho)− sorted cells, were examined. More than 95% of the Rho− cells were LFA-1neg. Cultures of sorted cells showed that the LFA-1neg fraction contained all CFU. Transplantation of 150 Rho− LFA-1neg or up to 600 Rho−LFA-1pos cells protected 100% and 0% of lethally irradiated recipient mice, respectively. These results show that primitive murine HPC in steady-state bone marrow and of cytokine-mobilized blood do not express LFA-1.

Murine Hematopoietic Progenitor Cells With Colony-Forming or Radioprotective Capacity Lack Expression of the β2-Integrin LFA-1

Recently, we have demonstrated that antibodies that block the function of the β2-integrin leukocyte function-associated antigen-1 (LFA-1) completely abrogate the rapid mobilization of hematopoietic progenitor cells (HPC) with colony-forming and radioprotective capacity induced by interleukin-8 (IL-8) in mice. These findings suggested a direct inhibitory effect of these antibodies on LFA-1–mediated transmigration of stem cells through the bone marrow endothelium. Therefore, we studied the expression and functional role of LFA-1 on murine HPC in vitro and in vivo. In steady state bone marrow ± 50% of the mononuclear cells (MNC) were LFA-1neg. Cultures of sorted cells, supplemented with granulocyte colony-stimulating factor (G-CSF)/granulocyte-macrophage colony-stimulating factor (GM-CSF)/IL-1/IL-3/IL-6/stem cell factor (SCF) and erythropoietin (EPO) indicated that the LFA-1neg fraction contained the majority of the colony-forming cells (CFCs) (LFA-1neg 183 ± 62/7,500 cells v LFA-1pos 29 ± 17/7,500 cells,P &lt; .001). We found that the radioprotective capacity resided almost exclusively in the LFA-1neg cell fraction, the radioprotection rate after transplantation of 103, 3 × 103, 104, and 3 × 104 cells being 63%, 90%, 100%, and 100% respectively. Hardly any radioprotection was obtained from LFA-1pos cells. Similarly, in cytokine (IL-8 and G-CSF)–mobilized blood, the LFA-1neg fraction, which comprised 5% to 10% of the MNC, contained the majority of the colony-forming cells, as well as almost all cells with radioprotective capacity. Subsequently, primitive bone marrow-derived HPC, represented by Wheat-germ-agglutinin (WGA)+/Lineage (Lin)−/Rhodamine (Rho)− sorted cells, were examined. More than 95% of the Rho− cells were LFA-1neg. Cultures of sorted cells showed that the LFA-1neg fraction contained all CFU. Transplantation of 150 Rho− LFA-1neg or up to 600 Rho−LFA-1pos cells protected 100% and 0% of lethally irradiated recipient mice, respectively. These results show that primitive murine HPC in steady-state bone marrow and of cytokine-mobilized blood do not express LFA-1.

Decrease of LFA-1 Is Associated with Upregulation of TGF-β in CD4+T Cell Clones Derived from Rats Nasally Tolerized against Experimental Autoimmune Myasthenia Gravis

Tolerance to experimental autoimmune myasthenia gravis by nasal administration of microgram amounts of acetylcholine receptor (AChR) has been reported. To elucidate the mechanisms behind tolerance induction via the respiratory tract and the involvement of CD4+T cells, we established AChR-specific CD4+CD8−T cell clones from nasally tolerized rats. Nasal tolerance decreased leukocyte function-associated antigen-1 (LFA-1) expression in CD4+T cells from tolerized rats. There was no difference between nasally tolerized and control rats in expression of intercellular adhesion molecule-1. The levels of transforming growth factor-β (TGF-β) mRNA-expressing cells were upregulated in CD4+T cell clones after tolerance induction. These findings suggest that decreased LFA-1 expression in CD4+T cells contributes to reduction of the infiltration of inflammatory CD4+T cells, while upregulated TGF-β may inhibit lymphocyte functions.

Strain-specific differences in LFA-1 induction on measles virus-infected monocytes and adhesion and viral transmission to endothelial cells.

Measles virus (MV) infection of monocytes induces leukocyte function-associated antigen-1 (LFA-1), an integrin that mediates intercellular adhesion to the endothelium. Thus, an increase in LFA-1 expression could lead to enhanced monocyte adherence and virus dissemination to endothelial cells (ECs) and potentially be an important means of distinction between MV strains. We identified both vaccine and wild-type strains that induced LFA-1 and others that failed to induce. Although adhesion of MV-infected monocytes and viral transmission to ECs was demonstrated, strain-specific differences were not correlated with LFA-1 induction. MV infection of ECs was dramatically reduced in the absence of cell contact, suggesting virus dissemination by cell-cell transmission.

LFA-1-dependent tumoricidal activity of cisplatin-treated macrophages.

The role of leucocyte function associated antigen-1 (LFA-1) (CD11a/18) in the tumoricidal activity of cisplatin-treated macrophages was investigated. Anti-LFA-1 antibodies inhibited cisplatin-induced macrophage cytotoxicity towards three different tumour cell lines. The decrease in tumoricidal activity of cisplatin-treated macrophages was attributed to their decreased binding to tumour cells in the presence of anti-LFA-1 (CD11a/18) antibodies. Western blot analysis revealed that cisplatin treatment leads to the expression of LFA-1 on macrophages which otherwise remains non-detectable. Because there is no information regarding the mechanism of cisplatin-induced LFA-1 expression and tumour cell binding by macrophages, the role of various second messenger molecules in these processes was investigated. Results suggest that protein phosphatase 2A (PP2A) is not involved in these processes whereas protein tyrosine phosphatases (PTP) negatively regulate LFA-1 expression and tumour-cell binding of cisplatin-treated macrophages. Inhibitors of protein phosphatase 1 (PP1), protein kinase C (PKC), protein tyrosine kinase (PTK), calmodulin and calmodulin-dependent kinase-II (CamK II) prevented LFA-1 expression on cisplatin-treated macrophages. A comparison with earlier results indicated that LFA-expression follows a distinct signalling pathway which is separate from the signalling pathway involved in NO or tumour necrosis factor/interleukin-1 (TNF/IL-1) expression in cisplatin-stimulated macrophages.

Intercellular adhesion molecule-1 (ICAM-1), leucocyte function-associated antigen-1 (LFA-1) and leucocyte infiltration in proliferative human glomerulonephritis

The expression of the intercellular adhesion molecule-1 (ICAM-1), infiltrating cells positive for its ligand leucocyte adhesion molecule-1(LFA-1), and the markers of total leucocytes (CD45RB), T cells (CD45RO), and monocytes/macrophages (CD68) were examined by an indirect immunoperoxidase method on renal biopsy specimens from 20 patients with mesangial proliferative glomerulonephritis-IgA negative (MesProGN) and 20 with IgA nephropathy (IgAN). Histologically, normal portions of the kidney tissue (n = 15) obtained from patients with renal trauma or renal tumours were used as controls. The expression of ICAM-1 was evident and extended in mesangium, on endothelial cells of peritubular capillaries, interstitial cells, several infiltrating immune cells and on tubular epithelial cells, particularly on atrophic tubuli in renal biopsies of MesProGN and IgAN. In both types of glomerulopathies a significant increase in the number of glomerular and interstitial LFA-1-positive cells correlated positively with the expression of ICAM-1. The number of glomerular and interstitial LFA-1-positive cells correlated positively with the number of monocytes/macrophages in glomeruli and interstitium. The strong correlation between expression of ICAM-1 and LFA-1 and between LFA-1-positive cells and immune cells makes these adhesion molecules useful markers of activity and suggest that they are involved in recruitment of leucocytes in the studied types of proliferative glomerulopathies.