Leucocyte adhesion to cells. Molecular basis, physiological relevance, and abnormalities

CD18 deficiency evolving to megakaryocytic (M7) acute myeloid leukemia: case report

Leukocyte adhesion deficiency type 1 (LAD 1 - CD18 deficiency) is a rare disease characterized by disturbance of phagocyte function associated with less severe cellular and humoral dysfunction. The main features are bacterial and fungal infections predominantly in the skin and mucosal surfaces, impaired wound healing and delayed umbilical cord separation. The infections are indolent, necrotic and recurrent. In contrast to the striking difficulties in defense against bacterial and fungal microorganisms, LAD 1 patients do not exhibit susceptibility to viral infections and neoplasias. The severity of clinical manifestations is directly related to the degree of CD18 deficiency. Here, a 20 year-old female presenting a partial CD18 deficiency that developed a megakaryocytic (M7) acute myeloid leukemia is described for the first time. The clinical features of the patient included relapsing oral thrush due to Candida, cutaneous infections and upper and lower respiratory tract infections, followed by a locally severe necrotic genital herpetic lesion. The patient's clinical features improved for a period of approximately two years, followed by severe bacterial infections. At that time, the investigation showed a megakaryocytic acute myeloid leukemia, treated with MEC without clinical improvement. The highly aggressive evolution of the leukemia in this patient suggests that adhesion molecules could be involved in the protection against the spread of neoplastic cells.

Arachidonic acid metabolism in TNS-induced chronic and immunologic enteritis in rats, and the effect of 5-ASA

Inflammation of the rat distal intestine was induced by intradermal sensitization and subsequent multiple intrajejunal challenge with the hapten 2,4,6-trinitrobenzenesulphonic acid (TNBS) via an implanted catheter. The time course of the inflammatory reaction was followed by determination of the enteritis score and measurement of in vitro eicosanoid formation of homogenates of the gut after 0, 1, 2, 4, 7, 14 and 21 days of local daily challenge with 0.08% TNBS. There was a small initial increase of eicosanoid formation, reached at days 1 and 2, followed by a significant increase in metabolism of arachidonic acid on day 21. Although at day 1 a four-fold increase in inflammation score was reached, no further significant changes were observed during the following 3 weeks. The greatest increase in metabolite formation was observed in prostanoids TxB₂, PGE₂. and PGD₂ and the 5-lipoxygenase product LTC₄, whereas minor changes were found for LTB₄ and other lipoxygenase products such as 12- and 15-HETE. The formation of these metabolites was already inhibited by low-dose 5-aminosalicylic acid (5-ASA), given orally twice daily during the 3 weeks challenge period, while the enteritis score was affected dosedependently.

Mechanism of pentoxifylline mediated down-regulation of killer lineage cell functions

The authors reported recently that endotoxaemia mediated elevated levels of tumour necrosis factor (TNF-α) and interleukin-1α (IL-1α) were involved in the pathophysiology of acute heat stroke patients. Pentoxifylline (PTX) is known to modulate neutrophil functions. In the present study the effects of PTX on lipopolysaccharide (LPS) and cytokine induced T-cell and macrophage (ΦM) activation, and on natural killer (NK) cell and lymphokine activated killer (LAK) cell mediated cytotoxicity were examined. Finally, the effect of PTX on the expression of adhesion molecules (LFA-1, Mac-1 and ICAM-1), and cytokine (IL-1α, IL-2, TNF-α, IL-6 and IFN-γ) production and their surface receptor expression in response to LPS activation was investigated. PTX free cultures served as a control. Results revealed that PTX can down-regulate all the above-mentioned immunological parameters in a dosedependent manner. These findings might have far reaching clinical implications.

Binding of the Streptococcus gordonii DL1 surface protein Hsa to the host cell membrane glycoproteins CD11b, CD43, and CD50

Infective endocarditis is frequently attributed to oral streptococci. The mechanisms of pathogenesis, however, are not well understood, although interaction between streptococci and phagocytes are thought to be very important. A highly expressed surface component of Streptococcus gordonii, Hsa, which has sialic acid-binding activity, contributes to infective endocarditis in vivo. In the present study, we found that S. gordonii DL1 binds to HL-60 cells differentiated into monocytes, granulocytes, and macrophages. Using a glutathione S-transferase (GST) fusion to the NR2 domain, which is the sialic acid-binding region of Hsa, we confirmed that the Hsa NR2 domain also binds to differentiated HL-60 cells. To identify which sialoglycoproteins on the surface of differentiated HL-60 cells are receptors for Hsa, intrinsic membrane proteins were assessed by bacterial overlay and far-Western blotting. S. gordonii DL1 adhered to 100- to 150-kDa proteins, a reaction that was abolished by neuraminidase treatment. These sialoglycoproteins were identified as CD11b, CD43, and CD50 by GST pull-down assay and immunoprecipitation with each specific monoclonal antibody. These data suggest that S. gordonii DL1 Hsa specifically binds to three glycoproteins as receptors and that this interaction may be the initial bacterial binding step in infective endocarditis by oral streptococci.

Molecular markers (PECAM-1, ICAM-3, HLA-DR) determine prognosis in primary non-Hodgkin's gastric lymphoma patients

AIM

To investigate the prognostic significance of PECAM-1, ICAM-3 and HLA-DR antigens in patients with primary non-Hodgkin's gastric lymphoma.

METHODS

We immunohistochemically studied PECAM-1, ICAM-3 and HLA-DR antigen expression in 36 B-cell MALT-type primary gastric lymphoma patients. Ten non-malignant and ten healthy gastric tissue specimens were used as controls. Clinicopathological and survival data were correlated with the staining results.

RESULTS

HLA-DR antigen expression was detected in 33 gastric lymphoma patients (91.7%) and 6 non-malignant patients (54.5%). PECAM-1 stained tumor cells of 10 patients (27.8%), endothelial cells of 9 patients (25%) and inflammatory infiltrate of 4 patients (40%) with benign gastric disease. ICAM-3 expression was observed on the tumor cells of 17 patients (47.2%), while 5 non-malignant patients (50%) were stained positive as well. None of the healthy controls was stained for any of the genes studied. In the multivariate analysis, HLA-DR antigen and PECAM-1 were proved to be statistically significant independent prognostic factors associated with a favourable and an unfavourable prognosis respectively (P=0.009 and P=0.003). In the univariate analysis, PECAM-1(+)/ICAM-3(-) and HLA-DR(-)/ICAM-3(-) patients exhibited a significantly decreased overall survival compared to those with the exactly opposite gene expression patterns (P=0.0041 and P=0.0091, respectively). Those patients who were HLA-DR(+)/ICAM-3(+)/PECAM-1(-) (n=8) had a significantly higher survival rate compared to the rest of the group (n=24) (P=0.0289).

CONCLUSION

PECAM-1, ICAM-3 and HLA-DR are representative markers of tumor expansion potential and host immune surveillance respectively. Their combined use may help us to identify high-risk patients who could benefit from more aggressive therapeutic protocols.

Regulation of lymphocyte proliferation by eosinophils via chymotrypsin-like protease activity and adhesion molecule interaction

We investigated the regulatory mechanisms responsible for release of eosinophil cationic protein (ECP) from eosinophils activated by platelet-activating factor (PAF) and monitored intra-cellular pH (pHi) changes using a pH-sensitive fluorescent probe. We also explored the mechanisms by which eosinophils suppress T-lymphocyte proliferation induced by phytohaemagglutinin (PHA). In these experiments, a separated culture to investigate the ECP-mediated pathway and a coculture to identify the adhesion molecules involved in eosinophil-lymphocyte interactions were employed. Chymostatin (1x10(-6) M) inhibited ECP release by about 50% via stimulation by PAF or recombinant interleukin 5(rIL-5) plus IgG. PAF (1x10(-7) M) raised eosinophil pHi from 6.9 to 7.3 within 20 s and pretreatment of these cells with chymostatin (1x10(-6) M), but not with leupeptin or E64-d, completely prevented this increase. Calcium ionophore A23187 (1x10(-7) M) induced ECP release and raised pHi to within a range similar to that of PAF, however, chymostatin had no effect on either. Chymostatin reversed ECP-mediated suppression of PHA-induced T-lymphocyte proliferation in separated cultures, but not in cocultures. In coculture, eosinophils exhibited the same level of suppression of both CD4(+) and CD8(+) T-cell proliferation in response to PHA. Monoclonal antibodies against CD11a, CD18 and CD54, but not CD11b, restored eosinophil suppression of T-lymphocyte proliferation which was chymostatin-resistant in coculture. Eosinophils were unable to suppress the proliferative response to lymphocytes to anti-CD3 stimulation. In conclusion, chymostatin specifically inhibited both the eosinophil pHi increase and ECP release induced by PAF. Eosinophils regulate PHA-induced T-lymphocyte proliferation via the ECP-mediation associated with chymotrypsin-like protease activity. These cells also control interactions with lymphocyte between adhesion molecules, CD11a, CD18 and CD54.

Expression and functional activity of the very late activation antigen-4 molecule on human natural killer cells in different states of activation

In the present study we describe the expression and functional activity of the alpha4beta1 heterodimer molecule on human natural killer (NK) cells. Flow cytometric analyses showed that fresh and activated NK cells expressed high levels of very late activation antigen-4 (VLA-4) molecules. These cells bound to fibronectin (FN) and to its 38 000-MW proteolytic fragment through the VLA-4 integrin that was blocked with HP2/1 anti-alpha4 monoclonal antibodies (mAbs) and with the FN peptide fragment CS1. No inhibitory effects were observed in the presence of anti-alpha5 mAb, FN peptide fragment CS2 or other irrelevant mAb. Fresh NK cells were unable to aggregate, despite their expression of VLA-4, and only activated (cultured and lymphocyte-activated killer cells) NK cells showed homotypic aggregation with HP1/7 and HP2/4 anti-alpha4 mAb related to cellular activation. These results underline new evidence of how NK cells in different states of activation maintain different constitutive levels of alpha4beta1 integrin activity, and highlight the possibility of a different functional regulation by the cells bearing VLA-4, in the expression of these epitopes and their ability to interact with their ligands.

Endothelial adhesion molecule expression is enhanced in the aorta and internal mammary artery of diabetic patients

BACKGROUND

Diabetes mellitus is a major risk factor for the development of atherosclerosis but the mechanisms involved remain unclear. The expression of leukocyte adhesion molecules at the endothelial surface is a primary step in the recruitment of leukocytes into the intima and the subsequent development of lipid-containing foam cell lesions. Increased levels of circulating adhesion molecules have been identified in diabetic patients, but the distribution in the arterial wall has not been described.

MATERIALS AND METHODS

Frozen sections were prepared from aorta and internal mammary artery obtained during bypass surgery from 12 diabetic and 16 nondiabetic patients. Adhesion molecules (intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-Selectin), macrophages, and lymphocytes were identified and quantified using immunohistochemistry; intimal hyperplasia was quantified.

RESULTS

Endothelial expression of VCAM-1 and intimal smooth muscle cell expression of both VCAM-1 and ICAM-1 was increased in the aortas from diabetic patients. Intimal hyperplasia in aorta and internal mammary artery sections was significantly greater in diabetic tissue. Macrophages, T-lymphocytes, oil-red-O-stained lipid, glycated albumin, and glycated LDL were observed in the aorta of both diabetic and nondiabetic samples.

CONCLUSIONS

The increased incidence of VCAM-1 and ICAM-1 in the aorta may partly explain the enhanced atherosclerosis associated with diabetes mellitus, and their presence in established lesions may emphasize their long-term importance. The intimal hyperplasia observed in the bypass vessel may be a contributing factor to the increased incidence of restenosis in diabetic patients.

Expression of soluble endothelial adhesion molecules in clinical cardiopulmonary bypass

Soluble endothelial adhesion molecule expression in clinical cardiopulmonary bypass (CPB) was investigated. Neutrophil-mediated endothelial injury plays an important role in CPB-induced organ dysfunction. The adhesion of neutrophil to the endothelium is central to this process. It has been well documented that CPB induces neutrophil activation and changes in neutrophil adhesion molecule expression, but the effect of CPB on endothelial cell activation is not known. This study was designed to measure soluble endothelial adhesion molecules during CPB. We made serial measurements (by specific enzyme-linked immunoabsorbent assay) of plasma levels of the soluble endothelial adhesion molecules, ICAM-1 and E-selectin in patients undergoing routine CPB (n = 7) and in a control group (thoracotomy, n = 3). The results show an initial significant decrease during CPB followed by an increase in plasma E-selectin from 29.3 +/- 5.1 ng/ml (mean +/- SEM) prebypass to 34.0 +/- 5.4 ng/ml at 48 h postbypass. Likewise, plasma ICAM-1 significantly decreased during CPB and then increased from 246.3 +/- 38.0 ng/ml before bypass to 324.8 +/- 25.0 ng/ml and 355.0 +/- 23.0 ng/ml at 24 and 48 h after bypass, respectively. The rise in levels is statistically significant (p < 0.05). This study shows a decrease in circulating ICAM-1 and soluble E-selectin during CPB and an increase in their levels at 48 h after CPB.

Regulation of interleukin-12 by complement receptor 3 signaling

Complement receptor type 3 (CR3, CD11b/CD18) serves as a receptor for a number of endogenous ligands and infectious organisms, and is involved in adhesion and host defense functions. Here, we report that signaling via CR3 plays an important role in regulating production of interleukin-12 (IL-12), a key mediator of cell-mediated immunity (CMI). We demonstrate with a variety of stimuli a dose-dependent, specific downregulation of IL-12 secretion by human monocytes in vitro after exposure to antibodies to CR3 (anti-CD11b and anti-CD18), as well as to the natural CR3 ligands, iC3b, and Histoplasma capsulatum. CR3 antibodies also suppressed interferon-gamma (IFN-gamma) production in cultures of human peripheral blood mononuclear cells (PBMC). We determined that one mechanism by which CR3 antibodies may suppress IL-12 production is by the inhibition of IFN-gamma-induced tyrosine phosphorylation. Finally, in a murine model of IL-12-dependent septic shock, we provide evidence that administration of CR3 antibodies leads to suppression of IL-12 and IFN-gamma in vivo. Our studies thus define a novel role for CR3 in regulating CMI functions via IL-12.

Adhesion molecule CD11a/CD18-deficient Burkitt's lymphoma cells lack the transcript for the beta, but not the alpha, integrin subunit

Adhesion to cells and matrices participates in the regulation of lymphocyte proliferation, maturation and tissue localization. Consequently, abnormal patterns of adhesion molecule expression may contribute to the pathophysiology of lymphoproliferative disorders. Integrins are major cell-surface adhesive proteins composed by alpha and beta subunits. In contrast to normal lymphocytes, Burkitt's lymphoma (BL) cells lack the beta2 integrin CD11a/CD18. To study the molecular mechanism underlying this deficiency, presence of the transcript for each subunit was analysed by Northern blotting in group I BL lines (BL biopsy-like) and, for comparison, Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs). While transcripts for both CD11a (alpha subunit) and CD18 (beta subunit) were readily detected in LCLs, BL lines contained the transcript for the alpha subunit only. Treatment of BL cells with phorbol ester for 72 h induced expression of the beta subunit mRNA and the CD11a and CD18 antigens on the cell surface. The results indicate that the CD11a/CD18 deficiency of BL is due to absence of the beta subunit transcript and that this defect is restored by stimulation of the cells.

Leflunomide, a novel immunomodulating drug, inhibits homotypic adhesion of peripheral blood and synovial fluid mononuclear cells in rheumatoid arthritis

OBJECTIVE AND DESIGN

A novel immunomodulating drug, leflunomide has been shown recently to be effective and well tolerated in patients suffering from rheumatoid arthritis (RA). The present study evaluated the effect of the drug on cell adhesion in RA.

MATERIAL AND TREATMENT

Peripheral blood and synovial fluid mononuclear cells were obtained from a clinical trial, undertaken primarily to evaluate the efficacy and pharmacokinetic profile of multiple-dose pulsing leflunomide therapy in RA patients. PB MNC and corresponding synovial fluid (SF) MNC for in vitro homotypic aggregation (HA) assay were obtained from healthy volunteers and RA patients with active disease not treated with leflunomide in vivo.

METHODS

Expression of activation antigens (CD25, CD54, CD69, CD71, HLA-DR) on peripheral blood mononuclear cells (PB MNC), as well as ex vivo ability of cells to aggregate spontaneously were determined in patients before entering into the clinical trial and at the end of 6 months treatment. HA was measured by aggregation in vitro. Data were compared by Student's t-test.

RESULTS

There was a decreased expression of activation antigens and decreased spontaneous MNC clustering after leflunomide therapy. We found in the in vitro study that HA of PB and SF MNC was mainly mediated through beta 2-integrin molecules. The active metabolite of leflunomide, A77 1726, effectively suppressed both spontaneous and phorbol-ester (PMA)-induced HA. Disruption of cell aggregates by A77 1726 was dose-dependent and, most likely, unrelated to the quantitative modulation of integrin receptors.

CONCLUSIONS

Results from this study support the idea that leflunomide elicits its immunomodulatory action, at least partially, by modulating the adhesion process.

Serum protects against azurophil granule dependent down-regulation of complement receptor type 1 (CR1) on human neutrophils

We have investigated the effect of gradual degranulation on the expression of functional receptors (CR1 and CR3) on human neutrophils. Incubation with increasing concentrations of fMLP (10(-10) - 10(-7) M) translocated CR1 and CR3 to the cell surface in a similar kinetic pattern. When reaching maximal expression of receptors (10(-7) M fMLP), 78 +/- 10% and 87 +/- 9% of the total pool of CR1 and CR3, respectively, were translocated to the cell surface. To drive the mobilization process further, cytochalasin B was introduced to increase the stimulatory effect of fMLP. No further increase in CR1 surface expression was obtained. However, we found a characteristic time course of surface appearance of CR1 and CR3 with a maximal surface expression within 1 minute, followed by a time-related down-regulation of CR1 but not CR3. In addition, the total pool of CR1 in cytochalasin B treated neutrophils was reduced after 15 minutes stimulation with fMLP measured by flow cytometry and immunoblotting, indicating degradation of CR1. The down-regulation of CR1 was concomitant with a translocation of azurophil granules, in terms of upregulation of CD63. Azurophil, but not specific nor secretory, granule fractions caused a down-regulation of CR1 on fMLP activated neutrophils. The presence of human sera and serine protease inhibitor protected CR1 from down-regulation. Together, these findings indicate that intracellular stored proteases, released in the late part of the sequential mobilization process, alters the expression of functional receptors mobilized in the early part of the mobilization process. The findings also focus on the importance of the microenvironment for the net outcome of neutrophil activation in terms of functional receptor expression.

Effects of cytokine-mediated modulation of nm23 expression on the invasion and metastatic behavior of B16F10 melanoma cells

The molecular mechanisms of tumor invasion and metastasis are yet to be fully elucidated. A potential tumor-metastasis-suppressor gene nm23 has been described in certain rodent and human tumors. In the present study, we examined the potential anti-invasive and anti-metastatic effect of nm23 gene in B16F10 cells, a malignant murine melanoma cell line. Transfection of nm23 gene into B16F10 melanoma cells resulted in significant suppression of the invasiveness and metastatic ability of melanoma cells and significantly enhanced the survival of tumor-bearing mice. B16F10 melanoma cells transfected with nm23 produced significantly less soluble ICAM-I and were more susceptible to LAK-cell-mediated cytotoxicity. Co-culture of B16F10 melanoma cells with IL-2 had no effect on nm23 expression, whereas treatment with PGE2, TNF-alpha and IFN-gamma resulted in down-regulation of nm23 expression. Concomitantly, in vivo treatment with TNF-alpha or IFN-gamma in experimental mice increased pulmonary metastases and lowered the overall survival period, as compared with IL-2 treatment alone. These results provide evidence that nm23, in addition to its anti-metastatic function, could also be involved in modulating tumor-target-structure expression, in down-regulating invasive potential and in production of soluble intracellular adhesion molecules. The down-regulation of nm23 by TNF-alpha, IFN-gamma and particularly by PGE2 warrants re-examination of current immunotherapeutic protocols and of the role played by PGE2 in tumor progression.

Role of intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) in peripheral blood mononuclear cell activation by human renal carcinoma cells

We examined the role of intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) during the activation of peripheral blood mononuclear cells (PBMCs) by the human renal carcinoma cell line CaKi-1. ICAM-1 antigen expression was induced on CaKi-1 cells by incubation with either phorbol-12-myristate 13 acetate (PMA) or interferon-gamma (IFN-gamma). Following a thorough washout of PMA and IFN-gamma and subsequent paraformaldehyde fixation, CaKi-1 cell monolayers were cocultered with allogenic PBMCs. While PMA-treated CaKi-1 cells induced PBMC proliferation and interleukin-2 receptor antigen expression, this was not the case for control or IFN-gamma-treated CaKi-1 cells. Furthermore, the induced PBMC proliferation was inhibited by specific monoclonal antibodies against ICAM-1 and LFA-1. Finally, although PMA induced human leukocyte antigen (HL)-A, B, C antigen expression on CaKi-1 cells, a monoclonal antibody against this antigen did not inhibit PBMC proliferation. We conclude that PMA can modulate CaKi-1 cells to stimulate allogenic PBMC proliferation in an ICAM-1/LFA-1 dependent, but HLA-A, B, C-independent, fashion. This stimulation might reside in the long-term activation of protein kinase C, induced by PMA.

A novel anti-rat CD18 monoclonal antibody triggers lymphocyte homotypic aggregation and granulocyte adhesion to plastic: different intracellular signaling pathways in resting versus activated thymocytes

We have raised a monoclonal antibody (mAb), NG2B12, directed against rat CD18, capable of inducing lymphocyte homotypic adhesion and granulocyte adherence to plastic. NG2B12-induced aggregation is temperature sensitive and requires metabolic energy, an intact cytoskeleton and the presence of Mg2+, but is independent of protein synthesis. Ca2+ is not only dispensable but exerts a suppressive effect on the NG2B12-induced adhesion. The adhesion is readily observed in thymocytes and concanavalin A blasts of thymocytes and splenocytes but is very weak in resting spleen and lymph node cells. NG2B12 also enhances phorbol 12-myristate 13-acetate (PMA)-induced aggregation in an additive fashion. The NG2B12-induced homotypic adhesion is mediated by LFA-1. mAb against ICAM-1 completely inhibited the induced adhesion of activated cells but inhibited only partially and in a time-dependent manner the adhesion of resting thymocytes. The activation of protein phosphatases 1 and 2A (as assessed by the use of okadaic acid) is necessary for the NG2B12-induced adhesion of both resting and activated thymocytes. In contrast, H-7 (an inhibitor of protein kinase C and A), substantially suppressed the adhesion of resting thymocytes, whereas W-7 (an inhibitor of calmodulin-dependent protein kinase) inhibited the adhesion of activated thymocytes. NG2B12 induces both adherence to plastic and homotypic aggregation of granulocytes; the events being blocked by anti-CD18 (WT.3) and anti-CD11b/CD11c (OX-42) mAb, augmented by okadaic acid and not modified by H-7 and W-7. Additionally, we have demonstrated that NG2B12 and PMA employ distinct intracellular signaling pathways in inducing adhesion of both thymocytes and granulocytes.

Interferon-gamma induces a decrease in the susceptibility of human glioma cells to lysis by lymphokine-activated killer cells

We studied the effect that treating two types of glioblastoma cell lines, U-87 MG and U-251 MG, with interferon (IFN)-gamma had on their susceptibility to lysis by lymphokine-activated killer (LAK) cells. We also examined the participation of cell-adhesion molecules and major histocompatibility complex (MHC) class I and II antigens present on the target cells in lysis by LAK cells. Treatment with IFN-gamma (1000 U/ml) for 48 hours resulted in the increased expression of both intercellular-adhesion molecule 1 and MHC class I antigens on tumor cells. In addition, untreated tumor cells expressed neural-cell-adhesion molecules and MHC class II antigens highly, but their expression was not affected by IFN-gamma treatment. These changes in expression were accompanied by a decreased susceptibility to lysis by LAK cells. Treatment with antisense-intercellular-adhesion molecule-1 oligonucleotide further inhibited LAK lysis of target cells, following treatment with IFN-gamma. In contrast, acid treatment of tumor cells after treatment with IFN-gamma increased their susceptibility to lysis by LAK cells. These findings suggest that treatment of glioblastoma cells with IFN-gamma decreased their susceptibility to lysis by LAK cells, and that this decrease in susceptibility is attributable principally to the increased expression of MHC class I antigen on target cells.

Molecular analysis of antigen-independent adhesion forces between T and B lymphocytes

The low-affinity interactions underlying antigen recognition by T-cell receptors (TCRs) are thought to involve antigen-independent adhesion mechanisms. Using a hydrodynamic approach, we found that antigen-independent adhesion occurred between human B cells and resting T cells in a transient and temperature-dependent fashion. The mean cell-cell adhesion force was 0.32 x 10(-9) N and was generated by similar contributions (0.16 x 10(-9) N) of the LFA-1- and CD2-dependent adhesion pathways. After T-cell stimulation with a phorbol ester, the force contributed by LFA-1 was drastically increased, while that of CD2 was unaffected. We propose that weak receptor-mediated adhesion initiates antigen-independent intercellular contacts required for antigen recognition by the TCR and is upregulated following TCR engagement. The method used permits adhesion forces between living cells to be resolved at the molecular level and should prove valuable for the rapid assessment of interaction forces between various types of cells and cell-sized particles.

Expression of adhesion molecules CD11/CD18 (Leu-CAMs, beta 2-integrins), CD54 (ICAM-1) and CD58 (LFA-3) in B-chronic lymphocytic leukemia

Cell adhesion molecules (CAMs) are cell surface proteins with unique specificities that allow intercellular adhesion. The importance of CAMs for normal lymphocyte growth and differentiation is underscored by the association between neoplastic disease states and abnormal CAM expression. In the present study we analysed the cell surface expression of several CAMs on peripheral blood lymphocytes from patients with progressive chronic lymphocytic leukemia of B-cell type (B-CLL) (n = 21) and stable monoclonal B-lymphocytosis of undetermined significance (B-MLUS) (n = 20). The CAM expression was analysed on the B-cell clone and on normal T- and NK-cell populations separately using monoclonal antibodies (MAbs). A phorbol ester-induced lymphocyte aggregation assay and blocking MAbs were also used. The B-cell clone in B-CLL expressed ICAM-1 (CD54) more frequently and at a higher density than in B-MLUS. The brightest CD54 expression was noted in patients with prominent lymphadenopathy and/or splenomegaly. The beta 2 integrin CD11a (Leu-CAMa, LFA-1) was detected on some B-cell clones and seemed to relate to tissue localization of the disease. T and NK cells showed a low expression of CD11a in B-CLL patients, while in B-MLUS a high proportion of non-clonal cells coexpressed CD11a with a high staining intensity. The relative numbers of both CD18+ as well as CD2+ cells showed a positive correlation with phorbol ester induced cell aggregation in B-MLUS patients (p < 0.05). The aggregation was blocked by adding MAbs against CD18 in most cases but to a greater extent in B-CLL. These results extend and corroborate our earlier findings on surface phenotypic characteristics of clonal and non-clonal lymphocytes in different clinical subtypes of B-CLL. CAM expression on the monoclonal lymphocytes may play a role in their interaction with regulatory immune cells and their tissue localization.

Neutrophil recruitment in Clostridium difficile toxin A enteritis in the rabbit

Neutrophil infiltration is a prominent feature of Clostridium difficile-associated enteritis and colitis. The aim of this study was to examine the importance of neutrophil recruitment and neutrophil-mediated tissue damage in C. difficile toxin A-induced enteritis. Competitive binding experiments using purified 3H-toxin A demonstrated the presence of a single class of medium affinity receptors on rabbit neutrophils (Kd 7 x 10(-8) M). Pertussis toxin and the nonhydrolyzable GTP analog GTPgamma S both inhibited 3H-toxin A binding (by 56 and 65%, respectively), indicating that the rabbit neutrophil toxin A receptor is G protein linked. Toxin A elicited a dose-dependent (25-200 micrograms/ml) stimulation of neutrophil migration in vitro, and this functional effect was also pertussis toxin sensitive (69% inhibition). Treatment of neutrophils with R15.7, a blocking monoclonal antibody to the leuocyte adhesion molecule CD18, inhibited toxin A-stimulated neutrophil migration by 85% in vitro. Pretreatment of rabbits with R15.7 also prevented neutrophil infiltration of toxin A-exposed ileal loops in vivo as determined by histologic examination and by ileal tissue myeloperoxidase levels. Furthermore, R15.7 effected a substantial inhibition of fluid secretion (by 65%), mannitol permeability (by 66%), and histologic damage in toxin A-exposed ileal loops. Anti-CD18 (R15.7) had no inhibitory effect on cholera toxin enterotoxicity. These data demonstrate that C. difficile toxin A is a proinflammatory toxin whose enterotoxic effects are substantially dependent upon neutrophil recruitment.

Expression and modulation of adhesion molecules on human bronchial epithelial cells

Epithelial damage in the airways is a feature often observed in patients with asthma and is probably caused by the interaction of epithelial cells with leukocytes. As adhesion molecules are thought to be important in this interaction, we analyzed the expression and modulation of adhesion molecules on primary cultured human bronchial epithelial cells and the bronchial epithelial cell lines BEAS-2B and NCI-H292. E-selectin, P-selectin, and VCAM-1 were absent under basal and stimulated conditions. The adhesion molecules ICAM-1 (CD54), LFA-3 (CD58), and CD44 (H-CAM) were expressed basally on primary cultured human bronchial epithelial cells and the BEAS-2B and NCI-H292 cell lines. CD44 and LFA-3 expression did not change after stimulation with IFN-gamma or TNF-alpha. In contrast, ICAM-1 expression on human bronchial epithelial cells and BEAS-2B cells could be increased by incubation with PMA, IFN-gamma, TNF-alpha, and especially with the combination of IFN-gamma and TNF-alpha. The maximal ICAM-1 expression on both epithelial cell types was obtained with the combination of TNF-alpha and IFN-gamma after 48 h of incubation. The NCI-H292 cell line was different in that it only showed increased ICAM-1 expression after stimulation with PMA and IFN-gamma and not by the combination of IFN-gamma and TNF-alpha or with TNF-alpha alone. In conclusion, the bronchial epithelial cells tested express several adhesion molecules, but only ICAM-1 expression was influenced by inflammatory cytokines.

Local and systemic immune response in Helicobacter pylori-associated chronic gastritis before and after treatment

Ten patients with Helicobacter pylori-associated chronic gastritis were given combination therapy for 6 weeks with a bismuth subnitrate-containing compound and bacampicillin. The eradication rate was 40% 6 weeks after the end of treatment. Two patients remained H. pylori-negative at long-term follow-up after 6 and 17 months; that is, H. pylori was only eradicated in 20% of the patients after long-term observation. By dot blot and immunoblotting both urease and an urease-associated heat shock protein (HSP62) were found to be specific and constant immunodominant H. pylori antigens. The immunohistologic pattern showed induced expression of HLA-DR and HSP62, but not of ICAM-1, in all but two biopsy specimens of gastric epithelial cells. This study suggests i) that long-term observation is important when evaluating the efficacy of anti-H. pylori therapy; ii) that the immune defense mechanisms in the gastric mucosa differ from those in inflammatory conditions affecting other organs, where ICAM-1 and HLA-DR seem to be governed by a common regulator; and iii) that the immunopathologic effects of H. pylori may be caused by autologous and/or bacterial HSPs, which act as triggering factors in the development and persistence of the chronic inflammation in the gastric mucosa.

LFA-1 and ICAM-1 in homotypic aggregation of rat alveolar macrophages: organic dust-mediated aggregation by a non-protein kinase C-dependent pathway

We have examined the role of cell adhesion molecules in the homotypic aggregation of rat alveolar macrophages after exposure to wool and grain dusts. Molecules such as bacterial lipopolysaccharide (LPS) and phorbol myristate acetate (PMA) can upregulate adhesion molecules, resulting in aggregation of lymphocytes. In rats treated intratracheally with an inspirable sample of wool dust collected from the air of British wool textile mills, and sieved grain dust, aggregates of macrophages were present in the bronchoalveolar lavage (BAL). Our hypothesis was that substances present on the dust surface could activate and upregulate adhesion molecules of the CD11/CD18 complex on the BAL cells and account for the aggregates. Macrophages from untreated rats form aggregates in vitro, which averaged 19 cells/aggregate; when treated with both wool and grain dusts, this rose to 25 and 24 cells/aggregate, respectively. LPS, PMA, and the proinflammatory cytokine tumor necrosis factor (TNF) also caused increases in aggregate size. Staurosporine, an inhibitor of protein kinase C (PKC), reduced the number of cells per aggregate from 35 cells/aggregate in LPS- and PMA-treated macrophages to 18 cells/aggregate, the same as untreated. In contrast, staurosporine had no effect in reducing the size of aggregates produced by the organic dusts. Removal of divalent cations, which are essential for maintaining integrin stability and PKC activity, resulted in complete abolition of aggregate formation. Treatment with monoclonal antibodies to lymphocyte function-associated antigen-1 (LFA-1) alpha and beta and intercellular adhesion molecule-1 (ICAM-1) resulted in the inhibition of aggregate formation in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors affecting neutrophil transit during acute pulmonary inflammation: minireview

Recent studies confirm data that for over a century have suggested that the lungs are an important source of noncirculating neutrophils. Many factors control how neutrophils pass through the normal lungs, including the unique and complex structure of the pulmonary capillary bed, local hemodynamic factors, neutrophil deformability, and neutrophil-endothelial interactions. Alterations in these factors are likely to influence neutrophil traffic in the lungs in disease processes where neutrophil-induced lung injury has been implicated. In recent years experimental approaches using in vitro techniques have been used to study neutrophil function. Such studies, together with in vivo studies in whole animals and to a limited extent in humans, will help to elucidate the important mechanisms in neutrophil sequestration in the acute and chronically inflamed lung. Novel avenues of therapeutic intervention in neutrophil traffic through the lungs may then be possible. However, whether interference with this cell, which forms a major defense mechanism in the lungs, is advisable, remains a matter for debate.

Activation of neutrophils within pulmonary microvessels of rabbits exposed to cigarette smoke

Previous studies have shown that polymorphonuclear leukocytes (PMN) are delayed in the pulmonary capillaries by the presence of cigarette smoke. To determine if the PMN delayed by smoking are activated, we estimated the in vivo expression of CD11/CD18 and L-selectin on the surface of PMN in lungs and peripheral blood of rabbits because these molecules are known to be upregulated and downregulated, respectively, on the surface of activated PMN. New Zealand white rabbits (3.5 +/- 0.1 kg) were exposed to either air (n = 5) or cigarette smoke (n = 5), and we used an established protocol to measure pulmonary vascular blood flow, volume, and red blood cell (RBC) transit time in the left lung. The right lungs were then fixed in 0.025% glutaraldehyde and stored in liquid nitrogen. Ultrathin sections were immuno-labeled with either the anti-CD18 monoclonal antibody 60.3 or the anti-L-selectin antibody Dreg-200, followed by a secondary antibody conjugated to 10 nm colloidal gold. The target antigens were quantified by counting the number of gold particles per micron (G/microns) of PMN surface membrane. The data show that smoke exposure had no effect on pulmonary blood flow, volume, or RBC transit time. However, it increased the expression of CD11/CD18 on intravascular PMN in the upper region of the lung (control, 7.4 +/- 1.3 G/microns; smoke-exposed, 13.2 +/- 3.3 G/microns; P < 0.05) and decreased the expression of L-selectin on intravascular PMN in both the lower (control, 5.5 +/- 2.0 G/microns; smoke-exposed, 2.6 +/- 1.5 G/microns; P = 0.05) and the upper (control, 6.8 +/- 1.4 G/microns; smoke-exposed, 2.6 +/- 1.2 G/microns; P < 0.05) regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemotaxins inhibit neutrophil adherence to and transmigration across cytokine-activated endothelium: correlation to the expression of L-selectin

Non-activated neutrophils strongly adhere to cytokine-activated human umbilical vein endothelial cells (HUVE). However, activation of neutrophils by different chemotactic mediators led to potent inhibition of this endothelial-dependent interaction. For different formylated peptides, concentrations leading to maximal adherence inhibition coincided with those known for inducing maximal chemotactic migration of neutrophils. In terms of maximal adherence inhibition, a rank list was found in the order of N-formyl-Met-Leu-Phe > C5adesArg > interleukin-8 > C5a > or = leukotriene B4, whereas platelet-activating factor, and lipopolysaccharide showed no inhibition. This rank order was congruent to that of down-regulation of neutrophil L-selectin detected by the monoclonal antibody Leu-8. Moreover, the dose-dependent increase of neutrophil adherence inhibition corresponded to the loss of L-selectin expression. Concentrations higher than that required for maximal inhibition led to a dose-dependent decrease of inhibition, which was accompanied by increasing expression of neutrophil CD11/CD18. In contrast to the capacity of non-activated neutrophils to migrate across interleukin-1-activated HUVE monolayers, transmigration was significantly impaired after chemotactic activation.

Interleukin-4 (IL-4) enhances homotypic adhesion of activated B-chronic lymphocytic leukaemia (B-CLL) cells via a selective up-regulation of CD54

It is well established that cell-to-cell contact modifies cytokine signalling but little is known on the role of homotypic cell adhesion for proliferation and differentiation of B cells. Homotypic adhesion involves mainly the interaction between the adhesion molecules Leukocyte Function Antigen-1 (LFA-1) and its ligand CD54 (ICAM-1). A well-characterized B-chronic lymphocytic leukaemia (B-CLL) clone (I-83) was used as a source of monoclonal B cells inducible to DNA synthesis and differentiation by using 12-O-tetradecanoyl-phorbol-13-acetate (TPA) in combination with interleukin-4 (IL-4) and thioredoxin (Trx)-containing supernatant from a T-cell hybridoma (BSF-MP6). This paper shows that IL-4 alone was able to induce aggregation of B-CLL cells and to strongly enhance TPA+BSF-MP6-induced aggregation. The results from studying the expression of CD11a and CD18, the two subunits of LFA-1, and CD54 during stimulated DNA synthesis and differentiation suggest that IL-4-induced, or enhanced, aggregation was mainly mediated by a selective up-regulation of CD54. It was further demonstrated by antibody blockade to either CD11a, CD18 or CD54 that aggregation could be inhibited without affecting induced DNA synthesis or differentiation.

Angiopeptin, the octapeptide analogue of somatostatin, decreases rat heart endothelial cell adhesiveness for mononuclear cells

The effect of angiopeptin, a stable analogue of somatostatin, was studied on basal and interleukin-1-beta-induced endothelial cell adhesiveness for mononuclear cells, and compared to the effect of somatostatin. Angiopeptin and somatostatin decreased basal and interleukin-1-beta-induced endothelial cell adhesiveness for mononuclear cells. The decreased mononuclear cells adhesion to endothelial cells exposed to angiopeptin and somatostatin is not due to modulation of the expression of intrecellular adhesion molecule-1 because neither angiopeptin nor somatostatin decreased basal and interleukin-1-beta-induced expression of this adhesion molecule. The effect of angiopeptin in inhibiting endothelial cell adhesiveness for mononuclear cells was abolished by addition of dibutyryl-cyclic AMP. Angiopeptin induced a transient decrease in basal and interleukin-1-beta-induced cyclic AMP levels in endothelial cells. Exposure of unstimulated and interleukin-1-beta-activated endothelial cells to KT5720, a specific inhibitor of cyclic AMP-dependent protein kinase, decreased endothelial cell adhesiveness for mononuclear cells. Thus, angiopeptin most likely diminishes endothelial adhesiveness for mononuclear cells by affecting the cyclic AMP-dependent protein kinase signal transduction pathway. The findings suggest that angiopeptin and somatostatin may modify the development of the immune response by attenuating endothelial cell adhesiveness for mononuclear cells. Angiopeptin may have a potential clinical application as a modulator of some aspects of the immune response due to its long half-life and prolonged inhibitory effect on interleukin-1-beta induced endothelial adhesiveness for mononuclear cells.

New perspectives on basic mechanisms in lung disease. 2. Neutrophil traffic in the lungs: role of haemodynamics, cell adhesion, and deformability

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Leukotriene B4-induced hyperadhesiveness of endothelial cells for neutrophils: relation to CD54

Leukotriene B4 (LTB4) induced an in vitro transient state of hyperadhesiveness in cultured human umbilical vein endothelial cells (HUVEC), leading to a 2.2-fold increase in the binding of neutrophil granulocytes (PMN), which was less than that conferred by platelet activating factor (PAF) though more than thrombin did (3.4- or 2.0-fold increases, respectively). This study concerns the role of the adhesive molecules CD18 and CD54 for the LTB4- (as well as thrombin- and PAF-) induced endothelial hyperadhesiveness. The MoAbs 60.3 (to the CD18 molecule on PMN) and 84H10 (to one epitope of CD54 on the HUVEC) blocked the adherence of PMN to LTB4-treated HUVEC, whereas MoAb LB-2 (directed at another CD54 epitope) failed to do so. MoAb 84H10 blocked 43% of the thrombin-induced hyperadhesiveness, whereas the PAF response was unaffected. Thus, LTB4-induced HUVEC hyperadhesiveness may therefore be related to a specific domain on the CD54 (or on an antigenically related molecule) as well as being dependent on CD18, whereas the involvement of CD54 was much less or non-existent for the thrombin and PAF responses, respectively.

Expression of adhesion molecules by bladder cancer cells: modulation by interferon-gamma and tumour necrosis factor-alpha

The constitutive expression by eight human bladder cancer cell lines of the cell adhesion molecules intercellular adhesion molecule-1 and intercellular adhesion molecule-2 was studied using monoclonal antibody probes in conjunction with flow-cytometry. Tumour lines of low grade (G1) did not constitutively express intercellular adhesion molecule-1, rather they were found to express intercellular adhesion molecule-2. The G2 cells expressed no intercellular adhesion molecule-2, however, a low percentage did express intercellular adhesion molecule-1. High grade cells (G3) only expressed intercellular adhesion molecule-1 on their cell surface but at higher levels than the G2 cell line. Exposure of the bladder cancer cell lines to interferon-gamma induced and augmented the expression of intercellular adhesion molecule-1 by all except one of the cell lines (UMUC3). Intercellular adhesion molecule-2 expression remained unaltered. The modulation of intercellular adhesion molecule-1 expression was dependent on the concentration of interferon-gamma and the duration of stimulus. De novo intercellular adhesion molecule-1 expression, induced by interferon-gamma, was rapid (< 4 hours) with only a short period of stimulation being required (< 10 seconds). The rapid increase in expression of intercellular adhesion molecule-1 required de novo protein synthesis and was not the result of release of intercellular adhesion molecule-1 from an intracellular pool. Interferon-gamma and tumour necrosis factor-alpha were found to act synergistically in the induction and augmentation of intercellular adhesion molecule-1 expression. Optimal induction occurred with 10 Uml-1 of both molecules. These results suggest a correlation between constitutive adhesion molecule expression and the histopathological grade of the tumour. The implications of these findings for Bacillus Calmette Guerin and interferon-gamma immunotherapy of bladder cancer is discussed.

Markers of inflammatory activation: upregulation of complement receptors CR1 and CR3 on synovial fluid neutrophils from patients with inflammatory joint disease

Expression of the C3 receptors CR1 and CR3 was investigated on neutrophils from paired peripheral blood and synovial fluid samples from 34 patients with inflammatory joint disease (21 patients with rheumatoid arthritis (RA) and 13 patients with other articular diseases (OAD)). Using monoclonal antibodies (anti-CD35, anti-CD11b) and immunofluorescence flow cytometric analyses the percentages of positively labeled cells and the relative fluorescence intensities (as a measure of receptor number) were determined. CR1 and CR3 were found to be present on the majority (> 85%) of circulating neutrophils from normal subjects, RA and OAD patients, and on synovial fluid neutrophils from both patient groups. A strong correlation between neutrophil CR1 and CR3 expression was observed in peripheral blood samples from normal subjects (r = 0.81; P = 0.001), RA (r = 0.79; P = 0.001), and OAD patients (r = 0.83; P = 0.001); in each case the levels of CR3 expression were approximately twice those recorded for CR1. Both CR1 and CR3 expression was upregulated on synovial fluid neutrophils compared with that observed on the corresponding peripheral blood cells. Mean percentage increases observed were: RA patients: CR1, 16.5% (P < 0.001) and CR3, 28.7% (P < 0.001); and OAD patients: CR1, 4.1% and CR3, 26.9% (P = 0.001). Correlation of serum and synovial fluid IL-6, IL-8, and immune complex levels with neutrophil CR1 and CR3 expression failed to demonstrate any significant relationship between the concentrations of these soluble factors and receptor expression. Upregulation of CR1 and CR3 receptors, reflecting neutrophil activation within the inflamed joint, is a consistent finding in patients with inflammatory arthropathies.

Inhibition of neutrophil adherence and movement by acute cigarette smoke exposure

Peripheral blood neutrophils were harvested and exposed acutely in vitro to physiologically attainable levels of cigarette smoke. The adherence of radiolabeled neutrophils subsequently to alveolar epithelial cell monolayers was measured. In contrast to control cells, smoke-exposed neutrophils were significantly less adherent and failed to increase their adherence following stimulation with phorbol ester or f-met-leu-phe (fMLP). Flow cytometric analysis of the cell surface adhesion protein CD18 demonstrated no significant change in expression following in vitro smoke exposure and, furthermore, no increase in surface CD18 of smoke-exposed cells following consecutive fMLP stimulation was demonstrated. Acute in vivo cigarette smoking of up to 4 cigarettes also did not alter peripheral blood neutrophil CD18 expression. Cell spreading and chemokinesis, but not chemotaxis, was also impaired following in vitro smoke exposure. These data suggest that acute cigarette smoke may impair the crucial neutrophil functions of adherence and movement. However, the chronic effects of cigarette smoke exposure may clearly differ.

Expression of the CD11/CD18 cell surface adhesion glycoprotein family and MHC class II antigen on blood monocytes and alveolar macrophages in interstitial lung diseases

The expression of molecules of the CD11/CD18 cell surface adhesion glycoprotein family and HLA/DR antigen was studied on peripheral blood monocytes (PBM) and alveolar macrophages (AM) in bronchoalveolar lavage (BAL) fluid from patients with sarcoidosis, idiopathic pulmonary fibrosis (IPF), and extrinsic allergic alveolitis (EAA). Patients with these interstitial lung diseases showed increased numbers of macrophages in BAL fluid. This was probably caused by an increased influx of PBM to the alveoli since the numbers of cells with a monocytic morphology were also significantly increased in BAL samples from patients with interstitial lung disease, most prominently in IPF and EAA. The increased influx of PBM into the alveoli in patients with interstitial lung diseases was not reflected by an increased expression of the CD11/CD18 leukocyte function antigens on PBM. In healthy volunteers as well as in those with sarcoidosis, IPF, and EAA, the percentages of AM positive for CD11b (the C3bi complement receptor) and CD11c were lower than among PBM. This indicates that the expression of these cell surface adhesion molecules is downregulated during maturation and migration of PBM to the alveoli. The absolute numbers of AM positive for CD11b were increased in BAL fluid of IPF and EAA patients compared to healthy volunteers. EAA patients also showed increased absolute numbers of AM positive for CD11a and CD11c. This differentially increased expression of these leukocyte function antigens on AM suggests the influence of locally produced cytokines.

Expression of intercellular adhesion molecule 1 (ICAM-1) during the development of invasion and/or metastasis of gastric carcinoma

In this study, using two-color flow-cytometric analysis, we examined the expression of histocompatibility locus antigens (HLA) classes I and II, and intercellular adhesion molecule 1 (ICAM-1) in 10 cases of normal gastric mucosa, 13 cases of primary carcinoma on the stomach, 16 cases of metastatic carcinoma from malignant ascites in patients with gastric carcinoma and 14 samples of their cultured carcinoma cells. Compared with normal gastric mucosa, HLA class I were highly expressed in a considerable number of tumor cells in each experimental group. The expression of HLA class II tended to reduce in the order of normal gastric mucosa, primary gastric carcinoma and peritoneal-effusion-associated carcinoma. Altogether, 85.7% of cases of cultured tumor cells showed abrogation and loss of HLA class II. The ICAM-1 molecule was not detected on normal gastric epithelial cells. In few cases, carcinoma cells from large volumes of tumor located in the stomach showed detectable amounts of ICAM-1. On the other hand, all of the metastatic carcinoma cells from peritoneal effusions showed a high level of expression of the ICAM-1 molecule. The expression of ICAM-1 on adenocarcinoma cells was maintained and/or augmented by in vitro cultivation with tumor-infiltrating lymphocytes (TIL). Furthermore, two-color fluorescence-activated cell sorting analysis of TIL revealed that significant correlation was observed between the expression of ICAM-1 and the degree of TIL, composed mainly of CD3+ T cells including CD8+CD11b-, CD8+CD28+, CD8+S6F1+ and CD4+Leu8+, and CD57+CD16- and CD57+CD16+ NK cells, and HLA-DR+LeuM3+ macrophages.

Inhibition of leukocyte extravasation with a monoclonal antibody to CD18 during formation of experimental intimal thickening in rabbit carotid arteries

In the rabbit model of electrically induced intimal thickening, the adherence processes of different leukocyte subsets as well as the functional significance of leukocyte invasion in the initial migration of smooth muscle cells (SMCs) into the intima were studied by using monoclonal antibody (MAb) 60.3 (directed to the leukocyte adherence glycoprotein CD18), a known potent inhibitor of leukocyte adhesive functions. In control carotid arteries exposed to two periods of electrical stimulation within 36 hours, leukocytes, including all granulocyte subsets, monocytes, and lymphocytes, invaded the cell-free subendothelium. Concomitantly, SMCs were observed to migrate from the media into the intima. In the MAb 60.3-treated rabbits, however, neutrophil emigration into the stimulated arteries was abolished, whereas mononuclear leukocyte accumulation in the intima was only partially inhibited, indicating a complete CD18-dependent mechanism for neutrophil extravasation and additional receptor-ligand systems for the emigration of mononuclear leukocytes. SMCs moved into the intima despite complete blockage of neutrophils and the reduced accumulation of mononuclear cells within the subendothelium after MAb administration. These results preclude neutrophils as initiators of SMC migration into the intima. The influence of mononuclear cells on the migratory behavior of SMCs in intimal thickening formation, however, needs further elucidation.

The LFA-3 adhesion pathway is differently utilized by superantigen-activated human CD4+ T-cell subsets

The superantigen SEA binds to MHC class II molecules and activates a large fraction of T cells as a result of interaction with particular TCR-V beta sequences. MHC class II transfected CHO cells induce a marginal CD4+ T-cell proliferation in the presence of SEA. CHO cells transfected with both MHC class II and LFA-3 (HLA-DR4/LFA-3 double transfectants) supported a vigorous T-cell proliferation and required 1000-fold lower SEA concentration than DR4-transfected cells. DR4/LFA-3 double transfectants presenting SEA to CD4+ T cells induced large amounts of IFN-gamma, while single DR4 transfectants failed to elicit IFN-gamma production. CD4+45RA+ naive T cells proliferated much more strongly compared with CD4+45R0+ memory T cells when SEA was presented by the DR4/LFA-3-transfected cells. In contrast, IFN-gamma production was only detected in CD4+45R0+ memory cells. The enhanced proliferation by the CD4+45RA+ naive T cells was not due to a stronger binding to the accessory DR4/LFA-3 cells. Human CD4+ T-cell lines mediated a low level of SEA-dependent cell-mediated cytotoxicity (SDCC) against DR4 target cells, whereas a strong SDCC was mediated against DR4/LFA-3-expressing target cells. These results demonstrate that superantigen-activated human CD4+ T cells require the adhesion molecule LFA-3 for optimal stimulation and that the CD4+ naive and memory T-helper cells are different in their response to LFA-3 as an accessory molecule.

Flow cytometry analysis of adhesion molecules on human Langerhans cells

The Langerhans cell (LC) migrates between the epidermis and the regional lymph nodes to present antigens. This migration pattern requires the expression of a changing repertoire of cell-surface molecules. In this work, we have investigated the expression of the adhesion molecules CD 11/CD 18 and CD 58 on LCs. Human epidermal cell suspensions were enriched in LCs (mean enrichment 75%) using a two-step technique including a Ficoll-Hypaque gradient followed by Fc receptor panning with IgG-coated sheep erythrocytes. The number of cells obtained per experiment was 750,000 (extremes 280,000-1,800,000), and the following antibodies were tested on fresh suspensions and/or after 48 hours in culture: BB3 (antithyroglobulin negative control IgG2a), OKT6 (anti CD1a, Ortho), anti HLA-DR (Becton-Dickinson), MHM 24 (anti CD 11a, leukocyte typing workshop n(0)3), MO1 and 44 (anti CD 11b, leukocyte typing workshop n(0)3), anti CD 11c (Immunotech), 60.3 and MHM 23 (anti CD 18, leukocyte typing workshop n(0)2), TS2/9.1.1 (anti CD 58, leukocyte typing workshop n(0)3). We found that amongst CD 11 subunits, only CD 11c was expressed in fresh suspensions, but was weaker than CD 18, and disappeared with culture. CD 58 was not detected in fresh suspensions but appeared after 2 days of culture, confirming earlier work. Thus the LC exhibits cell surface characteristics similar to tissue macrophages (CD 18 and CD 11c) prior to culture. The expression of CD 58 after culture is in accordance with the interaction of LC with CD2 bearing T-lymphocytes during antigen presentation in peripheral lymph-nodes.

Expression of integrins and other adhesion molecules in Epstein-Barr virus-transformed B lymphoblastoid cells and Burkitt's lymphoma cells

Lymphocytes adhere to cells or extracellular matrices to perform functions relating to cytotoxicity, extravasation and tissue localization, as well as modulation of lymphocyte growth and maturation. This adherence is mainly mediated by 3 families of cell-surface adhesion molecules: integrins, immunoglobulin-related molecules and selectins. Since variations in the degree of adherence may affect the pathophysiology of lymphoproliferative disorders, the expression of a large number of adhesion molecules was analysed on Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs), and on EBV-positive or EBV-negative Burkitt's lymphoma (BL) lines, by immunofluorescence flow cytometry and immunoprecipitation with monoclonal antibodies. With regard to the beta 1, beta 2 and beta 3 integrin subfamilies, LCLs strongly expressed CD49d/CD29 (VLA-4), CD11a/CD18 (Leu-CAMa, LFA-1) and CD51/CD61 (vitronectin receptor). These cells also abundantly expressed CD54 (ICAM-1) and CD58 (LFA-3) as well as the "homing receptors" L-selectin (LECAM-1) and CD44. BL lines had considerably lower amounts of VLA-4 than LCLs, and ICAM-1 was expressed only by some of the tumor lines. All other adhesion molecules were absent or minimally expressed in the BL cells.

Physical separation of ICAM-1 binding cells

Studies of interactions between specific molecules involved in adhesion between cells are often complicated since cells possess many different types of surface molecules influencing adhesion. To be able to further study interactions between the adhesive cell surface molecule LFA-1 and its ligand ICAM-1, we have produced an ICAM-1 fusion protein in which the extracellular part of ICAM-1 has been fused to a part of an IgG heavy chain. The fusion protein was produced by CHO cells and was easily purified in large quantities from the cell culture supernatant. The protein was coupled to magnetic beads and was shown to have binding characteristics similar to native ICAM-1. The coupled beads were used for magnetic isolation of ICAM-1 binding cells thereby providing a method for detecting changes in avidity for ICAM-1 and also for the analysis of ICAM-1 binding cells.

Integrin modulating factor-1: a lipid that alters the function of leukocyte integrins

The avidity of integrin CR3 (also known as alpha M beta 2, Mac-1, Mo-1, and CD11b/CD18) may be reversibly altered without changes in the number of cell surface receptors. Here we describe a molecule termed integrin modulating factor (IMF-1), which controls CR3 avidity. Addition of IMF-1 to polymorphonuclear leukocytes (PMNs) or to purified CR3 causes enhanced binding of ligand. IMF-1 is not present in resting PMNs, but stimulation of cells results in a transient rise in IMF-1 content that parallels a transient rise in CR3 activity. We suggest that PMNs control adhesivity by controlling synthesis of IMF-1, which then acts as an allosteric activator of leukocyte integrins. IMF-1 is an acidic, amphiphilic molecule of Mr340 +/- 16 that does not contain ester, phosphate, amide, sialic acid, or glycosidic or vicinal hydroxyl functionalities, but does contain a carbon-carbon double bond. These results suggest that IMF-1 is an unsaturated fatty acid or an isoprenoid acid.