CD11b Antibodies Research Articles

A surrogate method for assessment of β 2-integrin-dependent adhesion of human eosinophils to ICAM-1

We have developed and validated an inexpensive and equivalent method for measuring eosinophil adhesion by β 2-integrin to endothelial ICAM-1 using bovine serum albumin (BSA) as a surrogate for the immunoglobulin supergene. The number of adherent eosinophils on BSA or ICAM-1 coated microplates was quantified by residual eosinophil peroxidase activity. Non-stimulated eosinophils did not adhere to either BSA or ICAM-1. However, after IL-5 stimulation, either BSA or ICAM-1 caused comparable and concentration-dependent adhesion of eosinophils. Eosinophil adhesion was rapid and occurred within 15 to 30 min of incubation for either BSA or ICAM-1. Preincubation of cells with CD11b or CD18 antibody specifically decreased adhesion to either BSA or ICAM-1. IL-5, PAF and fMLP all induced adhesion of eosinophils to either BSA or ICAM-1 in a concentration-dependent manner, and the optimal IL-5, fMLP and PAF concentrations for adhesion to BSA were the same as for adhesion to ICAM-1. BSA-binding was specific for β 2-integrin; neither α-CD49d mAb directed against the α 4-chain or α-CD29 directed against the common β 1-chain of VLA-4 blocked adhesion to BSA or ICAM-1 controls. The protein tyrosine kinase inhibitor, genistein, the phosphatidylinositol 3-kinase (PI-3 kinase) inhibitor, wortmanin, and mitogen-activated protein kinase kinase (MEK) inhibitor, U0126, all inhibited IL-5-induced eosinophil adhesion to either BSA or ICAM-1 comparably. These results indicate that BSA is a reliable and economical surrogate ligand for ICAM-1 adhesion to β 2-integrin-dependent adhesion to ICAM-1. Ligation characteristics of BSA are identical to those for soluble ICAM-1, and the assay is suitable for assessment of signal transduction pathways mediating adhesion.

P-selectin and MAC-1 mediate monocyte rolling and adhesion to ECM-bound platelets under flow conditions.

Accumulation of monocyte-derived foam cells in focal areas of the atherosclerotic (A.S.-) lesion is one of the key events in early atherogenesis. Using a flow model for the damaged vessel wall, we examined the ability of ECM-bound platelets to induce monocyte tethering and adhesion. Whereas ECM-proteins alone induced monocyte adhesion only at low shear stresses (< 100 mPa), ECM-bound platelets induced monocyte rolling and adhesion at shear stresses up to 240 mPa. Studies with specific antibodies showed that monocyte adhesion to platelets was mainly mediated by P-selectin and monocyte PSGL-1 (maximum inhibition 90%). beta2-Integrin blocking CD18 and CD11b antibodies partly inhibited the arrest of rolling cells. Antibodies against other adhesion molecules such as LFA-1, PECAM-1, and beta1-integrins had no effect. Even sparsely adhered platelets (approximately 10% coverage of the surface) already strongly supported monocyte tethering. In conclusion, activated platelets present on ECM are a powerful adhesive substrate for monocyte recruitment under flow conditions.

Porphyromonas gingivalis fimbriae use beta2 integrin (CD11/CD18) on mouse peritoneal macrophages as a cellular receptor, and the CD18 beta chain plays a functional role in fimbrial signaling.

In this study, we demonstrate that Porphyromonas gingivalis fimbriae use molecules of beta2 integrin (CD11/CD18) on mouse peritoneal macrophages as cellular receptors and also show that the beta chain (CD18) may play a functional role in signalling for the fimbria-induced expression of interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha) genes in the cells. Using a binding assay with 125I-labeled fimbriae, we observed that fimbrial binding to the macrophages was inhibited by treatment with CD11a, CD11b, CD11c, or CD18 antibody but not by that with CD29 antibody. Western blot assays showed that the fimbriae bound to molecules of beta2 integrin (CD11/CD18) on the macrophages. Furthermore, Northern blot analyses showed that the fimbria-induced expression of IL-1beta and TNF-alpha genes in the cells was inhibited strongly by CD18 antibody treatment and slightly by CD11a, CD11b, or CD11c antibody treatment. Interestingly, intracellular adhesion molecule 1 (ICAM-1), a ligand of CD11/CD18, inhibited fimbrial binding to the cells in a dose-dependent manner. In addition, ICAM-1 clearly inhibited the fimbria-induced expression of IL-1beta and TNF-alpha genes in the cells. However, such inhibitory action was not observed with laminin treatment. These results suggest the importance of beta2 integrin (CD11/CD18) as a cellular receptor of P. gingivalis fimbriae in the initiation stage of the pathogenic mechanism of the organism in periodontal disease.

Eosinophil Granulocyte Interaction with Serum-Opsonized Particles: Binding and Degranulation Are Enhanced by Tumor Necrosis Factor Alpha

Eosinophils participate in the inflammatory response seen in allergy and helminthic infestation. Their release of granule-bound cationic proteins may play a role in these diseases. Therefore, we investigated mechanisms involved in the release of eosinophil cationic protein (ECP). Serum-opsonized zymosan was phagocytosed by eosinophils, and ECP was released into the phagosomes as judged by immunoelectron microscopy. Degranulation to the external milieu was induced by serum-opsonized, non-phagocytosable Sephadex beads (SOS), and ECP release was determined by use of an enzyme-linked immunosorbent assay. CD11b, CD18, and CD32 monoclonal antibodies inhibited degranulation, demonstrating dependence on complement receptor type 3 (CR3), and the low-affinity Fc receptor for IgG. Tumor necrosis factor-α (TNF-α) and interleukin (IL)-5 both rapidly enhanced the binding of eosinophils to serum-opsonized zymosan, and also the release of ECP upon interaction with SOS. The cytokine-induced increase in ECP release was inhibited by the phospholipase A₂ (PLA₂) inhibitor mepacrine, indicating an involvement of PLA₂ in the enhanced response but not in baseline degranulation. Autocrine stimulation by the platelet-activating factor (PAF) is unlikely since the PAF receptor antagonist WEB 2086 did not inhibit the enhanced response. In conclusion, the main signals for eosinophil degranulation on serum-opsonized particles are mediated by CR3 and receptors for immunoglobulins. As for IL-5, TNF-α changes eosinophil phenotype from a resting to an activated state.

Intratumor distribution of doxorubicin following i.v. administration of drug encapsulated in egg phosphatidylcholine/cholesterol liposomes.

A pharmacological evaluation of an egg phosphatidylcholine/cholesterol (55:45 mole ratio, EPC/Chol) liposome doxorubicin formulation was carried out. The objective was to define liposomal lipid and drug distribution within sites of tumor growth following intravenous (i.v.) administration to female BDF1 mice bearing either Lewis lung carcinoma, B16/BL6 melanoma, or L1210 ascitic tumors. Mice were injected i.v. with EPC/Chol liposomal doxorubicin, and plasma and tumor levels of lipid and drug were determined 1, 4 and 24 h late with radiolabeled lipid and fluorimetry or fluorescence microscopy, respectively. In addition, single-cell suspensions of the Lewis lung and B16/BL6 tumors were prepared and the presence of macrophages was determined with an FITC-labeled rat antimouse CD11b (MAC-1) antibody. For mice bearing the Lewis lung solid tumors, there was a time-dependent accumulation of liposomal lipid, with a plateau of approximately 500 micrograms lipid/g tumor at 48 h. In contrast, the apparent plateau (microgram doxorubicin/g tumor) for doxorubicin was achieved at 1 h and remained constant over a 72-h time course. In comparison with free drug administered at the maximum tolerated dose (MTD, 20 mg/kg) doxorubicin levels in tumors were two- to threefold greater when the drug was administered in liposomal form. The increase in drug delivery was comparable for both solid tumors. With animals bearing the L1210 ascitic tumor, drug exposure was as much as ten times greater (in comparison with free drug) when doxorubicin was administered in liposomes. An evaluation of single-cell suspensions prepared from the two solid tumors suggested that more than 98% of the tumor-associated drug and liposomal lipid was not tumor cell-associated. Histological studies with the Lewis lung carcinoma, however, revealed that a proportion of the drug did colocalize with tumor-associated macrophages. Analysis of cells obtained from mice bearing ascitic tumors showed that more than 80% of the cell-associated drug could be removed by procedures designed to remove adherent cells. The results summarized here suggest drug concentrations within a solid tumor, such as the Lewis lung carcinoma, are constant over time when the drug is given in a "leaky" EPC/Chol formulation. The results also suggest that liposomal lipid within sites of tumor growth is primarily localized within the interstitial spaces or tumor-associated macrophages.

Platelet and Fibrin Deposition at the Damaged Vessel Wall: Cooperative Substrates for Neutrophil Adhesion Under Flow Conditions

At sites of vessel wall damage, the primary hemostatic reaction involves platelet and fibrin deposition. At these sites, circulating leukocytes marginate and become activated. Adhered platelets can support leukocyte localization; however, the role of fibrin in this respect is not known. We studied the adhesion of human neutrophils (polymorphonuclear leukocytes [PMNs]) to endothelial extracellular matrix (ECM)-bound fibrin and platelets under flow conditions. ECM alone did not show PMN adhesion. ECM-coated cover slips were perfused with plasma to form a surface-bound fibrin network, and/or with whole blood to allow platelet adhesion. Unstimulated PMNs adhered to fibrin at moderate shear stress (20 to 200 mPa). ECM-bound platelets induced rolling adhesion and allowed more PMNs to adhere at higher shear (320 mPa). ECM coated with both platelets and fibrin induced more static and shear-resistant PMN adhesion. PMN adhesion to fibrin alone but not to platelet/fibrin surfaces was inhibited by soluble fibrinogen. Adhesion to fibrin alone was inhibited by CD11b and CD18 blocking antibodies. Furthermore, fibrin formed under flow conditions showed up to threefold higher PMN adhesion compared with fibrin formed under static conditions, due to structural differences. These results indicate that circulating PMNs adhere to fibrin in an integrin-dependent manner at moderate shear stresses. However, at higher shear rates (> 200 mPa), additional mechanisms (ie, activated platelets) are necessary for an interaction of PMNs with a fibrin network.

Platelet and Fibrin Deposition at the Damaged Vessel Wall: Cooperative Substrates for Neutrophil Adhesion Under Flow Conditions

AbstractAt sites of vessel wall damage, the primary hemostatic reaction involves platelet and fibrin deposition. At these sites, circulating leukocytes marginate and become activated. Adhered platelets can support leukocyte localization; however, the role of fibrin in this respect is not known. We studied the adhesion of human neutrophils (polymorphonuclear leukocytes [PMNs]) to endothelial extracellular matrix (ECM)-bound fibrin and platelets under flow conditions. ECM alone did not show PMN adhesion. ECM-coated cover slips were perfused with plasma to form a surface-bound fibrin network, and/or with whole blood to allow platelet adhesion. Unstimulated PMNs adhered to fibrin at moderate shear stress (20 to 200 mPa). ECM-bound platelets induced rolling adhesion and allowed more PMNs to adhere at higher shear (320 mPa). ECM coated with both platelets and fibrin induced more static and shear-resistant PMN adhesion. PMN adhesion to fibrin alone but not to platelet/fibrin surfaces was inhibited by soluble fibrinogen. Adhesion to fibrin alone was inhibited by CD11b and CD18 blocking antibodies. Furthermore, fibrin formed under flow conditions showed up to threefold higher PMN adhesion compared with fibrin formed under static conditions, due to structural differences. These results indicate that circulating PMNs adhere to fibrin in an integrin-dependent manner at moderate shear stresses. However, at higher shear rates (<200 mPa), additional mechanisms (ie, activated platelets) are necessary for an interaction of PMNs with a fibrin network.

Porcine alveolar macrophage Mac‐1 (CD11b/CD18) adhesion molecule expression

Abstract: The adhesion molecule Mac‐1 plays an important role during leukocyte recruitment into inflammatory sites and also serves as a complement receptor type 3 (CR3). Mac‐1 is a noncovalent heterodimer consisting of an α‐chain (CD11b) and a β‐chain (CD 18). We report the cloning and sequencing (GenBank accession number U40072) of the porcine CD 11b cDNA using the reverse transcriptase‐polymerase chain reaction (RT‐PCR). Porcine CD 11b cDNA and deduced amino acid sequences demonstrated 84% and 80% sequence identity, respectively, with human CD11b. The 4.7 kb porcine CD11b transcript was also similar to the size of the human CD11b transcript. Northern blot analyses detected CD11b transcripts in spleen cells and peripheral blood leukocytes, but not in lung lavage cells. In contrast to Northern blot results, 72% of freshly isolated alveolar macrophages stained positive using a cross‐reactive anti‐human CD11b antibody (TMG6–5). Compared to spleen and peripheral blood cells, alveolar macrophages expressed the highest levels of CD 18 mRNA. Using anti‐CD 18 monoclonal antibodies which cross‐react with porcine CD 18, two different porcine CD 18 epitopes were identified by flow cytometric antibody competition assays. However, the majority of the anti‐CD 18 antibodies tested competed for the same CD 18 epitope. Mac‐1 expression in porcine alveolar macrophages was not altered at either the mRNA or surface expression level by inflammatory stimuli, including fMLP, PMA, LPS, hIL‐1α, hIL‐6, hTNF‐α, and hIFN‐γ.

Soluble intercellular adhesion molecule-1 provokes polymorphonuclear leukocyte elastase release by CD18

Elevated levels of soluble intercellular adhesion molecule-1 (sICAM-1) correlate with the development of postinjury multiple organ failure. Soluble ICAM-1 secretion is known to be induced in endothelial cells and monocytes by diverse inflammatory stimuli. We have found that incubation of quiescent polymorphonuclear leukocytes (PMNs) with sICAM-1 elicits elastase release and, more recently, that cross-linking CD18 receptors on PMNs also produces elastase release. Consequently, our study hypothesis was that sICAM-1 provokes PMN elastase release through its interaction with CD18. To obtain sICAM-1, Chinese hamster ovarian cells transfected with human ICAM-1 were lysed and centrifuged at 150,000 g for 1 hour; the supernatant was passed over an ICAM-1 affinity column, eluted with 0.1 mmol/L glycine HCl, and concentrated with dialysis filter. Human PMNs (2.5 x 10(5)) were saturated with specific monoclonal antibodies for the beta 2 subunits (CD11a, CD11b, CD18) or nonspecific monoclonal antibodies for 30 minutes on ice before a 1-hour incubation with sICAM-1 (75 ng/ml) at 37 degrees C. Elastase activity was measured by the cleavage of n-methoxysuccinyl-A-A-P-V-p-nitroanilide. Neutrophil incubation with sICAM-1 resulted in 19.2% +/- 2.8% of total PMN elastase, compared with 2.4% +/- 0.5% in the controls. Blockade of CD18 abrogated sICAM-1 provoked elastase release with monoclonal antibodies to CD18 (TS1/18, 31H8) resulting in 4.3% +/- 1.0% and 5.5% +/- 1.4% elastase release, respectively. Blockade of CD11a, CD11b, and nonspecific antibody controls had no effect on sICAM-1 induced elastase release. In vitro, sICAM-1 provokes PMN elastase release through CD18. This may represent a mechanism by which elevated levels of circulating sICAM-1, released from local injury sites, provoke distal organ dysfunction.

Preferential binding of heparin to granulocytes of various species

Abstract Objectives To address the problem of heparin binding to leukocytes of various animal species. Design Leukocytes of the various species were incubated with fluorescent-labeled, low molecular mass heparin (LMMH). Fluorescence intensity on granulocytes, lymphocytes, and monocytes was analyzed by flow cytometry analysis. Sample Population Leukocytes were prepared from EDTA-anticoagulated blood of human subjects, rats, rabbits, dogs, pigs, and sheep 3 times. Procedure The leukocyte populations were identified by their light scatter properties. In addition, phycoerythrin-labeled CD4, CD13, and CD14 antibodies were used to identify human lymphocytes, granulocytes, and monocytes; CD4, GR-1, and CD11b antibodies were used for mouse, and CD45, RP 3, and ED 9 antibodies were used for identification of rat leukocyte subpopulations. Results Granulocytes, monocytes, and lymphocytes of all species bound LMMH in dose-dependent manner. Binding of LMMH-tyramine (tyr)-fluorescein-5-isothiocyanate (FITC) to granulocytes was higher in human subjects, rats, rabbits, dogs, and pigs, compared with binding to monocytes and lymphocytes. Mouse and sheep granulocytes did not bind more heparin than monocytes or lymphocytes. Binding of LMMH-tyr-FITC was reversible in the presence of unlabeled heparin or LMMH. More than 99% of human, rat, rabbit, dog, and sheep granulocyte populations were distinguished from monocytes and lymphocytes by means of their fluorescence intensity owing to LMMH-tyr-FITC. This separation was not obtained for mouse and pig granulocytes. Conclusion Evidence of specific heparin binding to granulocytes of many species indicates the relevance of fluorescent-labeled LMMH for biological investigations. Clinical Relevance Binding of heparin and LMMH to granulocytes, lymphocytes, and monocytes may have a substantial role in atherosclerosis, inflammation, malignancy, and immunologic diseases. (Am J Vet Res 1996;57:1016–1020)

Novel anticoagulants for flow cytometric analysis of live leucocytes in whole blood.

Enzyme inhibitors have been compared with conventional anticoagulants for the flow cytometric analysis of live leucocytes in whole blood. At 18 to 20 degrees C in vitro, PPACK (60 microM), hirudin (10 units ml-1), leupeptin (20 microg ml-1) and aprotinin (50 microg ml-1) inhibited blood clotting for 4 h or more, whereas PMSF (8 mg ml-1) or AEBSF (5 mg ml-1) inhibited clotting for only 20 or 40 min, respectively. When labelled with CD11b antibodies and analysed immediately ex vivo at 4 degrees C, the percentages of lymphocytes, monocytes, and polymorphs which stained positively and their mean fluorescence intensities were similar, irrespective into which anticoagulant blood was collected. Less than 1.5-fold increases in expression occurred on monocytes and polymorphs when blood anticoagulated with enzyme inhibitors or conventional anticoagulants was kept at 4 degrees C, or when blood anticoagulated with citrate, heparin, or hirudin was kept at 18 to 20 degrees C for 1 h before labelling and analysis, whereas approximately 2-fold increases in expression occurred in blood kept with K3EDTA, leupeptin, or aprotinin and more than 3-fold increases in blood kept with AEBSF or PPACK at 18 to 20 degrees C for 1 h. Further studies showed that leupeptin could be used effectively as the anticoagulant when investigating functional responses of live leucocytes in whole blood samples by flow cytometry and for the isolation of leucocytes with minimal modulation of adhesion molecules.

Anticoagulant selection influences flow cytometric determination of CD11b upregulation in vivo and ex vivo

We recently devised three-colour flow cytometic assay for evaluating expression of CD11b on neutrophils and monocytes in circulation. Artefactual upregualtion of CD11b ex vivo was minimized by cooling blood samples on ice. In this communication we further characterize the method in terms of differet anticoagulants. EDTA was less optimal than ACD or heparin because (i) saturating concentrations of CD11b antibody (clone D12) were not achieved with resting cells; (ii) CD11b fluorescence intensity of synovial fluid cells, i.e., in vivo activated cells expressing CD11b at high levels, was significantly lower in EDTA plasma, and (iii) EDTA mediated more cell damage at 37°C, as determined by PI staining. The fluorescence data suggested that D12 antibody binding was dependent on divalent cations. Saturating concentrations in the presence of EDTA in medium were easily obtained with synovial fluid cells and peripheral blood phagocytes activated with chemotactic peptide FMLP, suggesting that cell activation decreased cation concentrations required for D12 antibody binding. Using another CD11b antibody (2MPL19c), whose binding proved to be cation independent, it was shown that CD11b upregulation was not affected by EDTA. ACD was superior to heparin and phenylalanylprolylarginyl chloromethyl ketone (PPACK), a thrombin inhibitor, because cell counts were significantly lower in heparinized samples in cold, and in PPACK-anticoagulated samples treated with LPS at 37°C. Kinetics of l-selectin shedding was similar in heparin and ACD, suggesting that cell loss did not derive from differences in cell activation. In comparison of buffy coat cell assay and whole blood assay, neutrophil CD11b expression was similar but background fluorescence was significantly higher in whole blood preparations. This implies that nonspecific antibody binding may occur more in whole blood assay, whereas in the buffy coat cell assay, sample manipulation procedures may slightly increase CD11b antibody binding, but not control antibody binding. Finally, it was confirmed that warming from 0°C, but not from room temperature, to 37°C increased CD11b expression significantly on neutrophils, and it was further shown that monocytes undergo similar changes. Cooling did not upregulate CD11b, and completely prevented LPS-induced upregulation. In conclusion, the results support use of ACD in evaluating CD11b expression; if EDTA is used, it is important to make sure that binding of CD11b antibody selected does not require presence of divalent cations in medium.

Successive emergence of two CD8 subsets in primary CMV infection of allograft recipients.

Allograft recipients with cytomegalovirus (CMV) infection develop increased proportions of circulating CD8+ lymphocytes. A longitudinal study of 11 kidney and 5 liver allograft recipients with primary CMV infection but no other aetiological factor to explain graft dysfunction revealed selective imbalances in peripheral blood CD8+ T cell subsets. Initially, CMV viraemia was associated with elevated CD8+bright T cell numbers and T cell activation. Activation markers fell to normal when viral cultures became negative (before the end of the 1st month). During the 2nd-6th months, most (12/16) patients continued to have high CD8+ T cell counts (1050-2900 CD8+ cells/mm3), comprising an uncommon CD8+ T cell subset, as 45-73% of CD8+bright lymphocytes were CD3+ and TCRalphabeta+ but were not stained by anti-CD28, CD11b, CD16, CD56 and CD57 antibody. Unexpectedly, CD8+ CD57+ T cells, a hallmark of CMV infection, did not appear until the 2nd-6th months of primary CMV infection, and their numbers increased progressively thereafter. They became the predominant CD8+ T cell subset after about 6 months of infection and their persistence for several (up to 4) years was strongly correlated (r = 0.87) with expansion of CD8+ cells. Persistence of CD8 lymphocytosis was, thus, directly related to the rate of expansion of an uncommon CD8+ CD57- subset and its progressive replacement by CD8+ CD57+ T cells that were chronically elicited by CMV.

Lipocortin-1 fragments inhibit neutrophil accumulation and neutrophil-dependent edema in the mouse. A qualitative comparison with an anti-CD11b monoclonal antibody.

The activity of the steroid-inducible protein lipocortin-1 (LC1; with a primary sequence of 346 amino acids; also called annexin 1), a fragment corresponding to amino acids 1-188 and a short peptide from the N-terminus (amino acid 2-26) were tested for anti-inflammatory actions in three models of acute inflammation in the mouse in comparison with a mAb anti-CD11b (alpha CD11b). In the mouse air-pouch model LC1, fragment 1-188 and peptide Ac2-26 exhibited powerful inhibitory effects (ED50 approximately 5.2, 38 and 88 micrograms/mouse, respectively) on leukocyte migration elicited by IL-1. LC1 was approximately 200 times more potent than Ac2-26 on a molar basis although both gave maximal inhibitions, in contrast fragment 1-188 only produced a partial dose-response curve. LC1 was approximately 20 times more potent on a molar basis in this assay than the alpha CD11b mAb. Peptide Ac2-26 and the mAb alpha CD11b also blocked cell migration into the air-pouch induced by IL-8 with approximately the same potency. In the mouse skin edema and zymosan peritonitis assays Ac2-26 was inhibitory (ED50 of 200 micrograms/mouse) but less so than the alpha CD11b antibody (ED50 approximately 0.5 mg/mouse). Both LC1 (10 micrograms) and Ac2-26 (200 micrograms) completely blocked FMLP-induced neutropenia in the mouse. Studies using an inactivated LC1 preparation, which binds to the same high affinity binding sites as the biologically active material, indicated that the short peptide acts on the same sites as the native LC1. This study confirms the activity of LC1 in another model of experimental inflammation and suggests that it acts partly through inhibition of leukocyte activation with an overall effect qualitatively comparable to the blocking of CD11b portion of a beta 2-integrin complex. It also shows that peptides derived from the N-terminal domain of LC1 may mimic the activity of the full length molecule and points the way for a new family of anti-inflammatory substances that inhibit leukocyte trafficking.

Functional inactivation of neutrophils with a Mac-1 (CD11b/CD18) monoclonal antibody protects against ischemia-reperfusion injury in rat liver

The role of neutrophil CD11b/CD18 (Mac-1) adhesion proteins in the pathogenesis of hepatic reperfusion injury was investigated in an experimental model. Male Fischer rats were treated with a CD11b monoclonal antibody or an isotype-matched IgM control antibody and subjected to 45 min of hepatic ischemia followed by 24 hr of reperfusion. Large numbers of neutrophils were present in postischemic liver lobes (1,241 ± 64 polymorphonuclear cells/50 high-power fields) compared with numbers in baseline measurements (14 ± 3 polymorphonuclear cells/50 high-power fields), and severe liver injury was observed after 24 hr of reperfusion (hepatic necrosis: 88% ± 2%). Pretreatment with the CD11b antibody (two doses of 2 mg/kg each) significantly attenuated liver injury and reduced the number of polymorphonuclear cells in the postischemic liver by 59%. Selective treatment with the antibody only during reperfusion was similarly effective. The increased spontaneous superoxide formation of neutrophils isolated from postischemic liver (1.05 ± 0.11 nmol O2−/hr/106 cells) was reduced by 56% in neutrophils from CD11b antibody-treated animals. Flow cytometric analysis of CD11b/CD18 expression on circulating neutrophils demonstrated significant upregulation at all time points during reperfusion. Clone 17 also effectively inhibited neutrophil extravasation in a glycogen peritonitis model. Our data are consistent with a dual protective effect of the CD11b antibody in hepatic reperfusion injury in vivo (i.e., reduced accumulation of neutrophils and their functional inactivation). (HEPATOLOGY 1993;17:915–923.)

Functional inactivation of neutrophils with a Mac-1 (CD11b/CD18) monoclonal antibody protects against ischemia-reperfusion injury in rat liver

The role of neutrophil CD11b/CD18 (Mac-1) adhesion proteins in the pathogenesis of hepatic reperfusion injury was investigated in an experimental model. Male Fischer rats were treated with a CD11b monoclonal antibody or an isotype-matched IgM control antibody and subjected to 45 min of hepatic ischemic followed by 24 hr of reperfusion. Large numbers of neutrophils were present in postischemic liver lobes (1,241 +/- 64 polymorphonuclear cells/50 high-power fields) compared with numbers in baseline measurements (14 +/- 3 polymorphonuclear cells/50 high-power fields), and severe liver injury was observed after 24 hr of reperfusion (hepatic necrosis: 88% +/- 2%). Pretreatment with the CD11b antibody (two doses of 2 mg/kg each significantly attenuated liver injury and reduced the number of polymorphonuclear cells in the post-ischemic liver by 59%. Selective treatment with the antibody only during reperfusion was similarly effective. The increased spontaneous superoxide formation of neutrophils isolated from postischemic liver (1.05 +/- 0.11 nmol O2-/hr/10(6) cells) was reduced by 56% in neutrophils from CD11b antibody-treated animals. Flow cytometric analysis of CD11b/CD18 expression on circulating neutrophils demonstrated significant upregulation at all time points during reperfusion. Clone 17 also effectively inhibited neutrophil extravasation in a glycogen peritonitis model. Our data are consistent with a dual protective effect of the CD11b antibody in hepatic reperfusion injury in vivo (i.e., reduced accumulation of neutrophils and their functional inactivation).

Calcium signaling capacity of the [formula omitted] integrin on human neutrophils

The CD11b CD18 integrin is a major cell adhesion molecule of myelomonocytic cells. Exposure of human neutrophils in suspension to CD11b or CD18 monoclonal antibodies (mAbs) 2 does not affect the resting level of cytosolic free Ca 2+ in these cells; however, a subsequent cross-linking of either of these antibodies triggers a prompt and significant cytosolic-free Ca 2+ transient lasting about 10 min. The rise in cytosolic-free Ca 2+ (from 130 ± 2 to 414 ± 12 n M or 111 ± 12 to 331 ± 22 n M caused by cross-linking of CD11b or CD18 subunits, respectively) is due to both mobilization of Ca 2+ from intracellular stores and influx of Ca 2+ across the plasma membrane. Cross-linking of the common leukocyte antigen (CD45) did not alter the basal level of cytosolic free Ca 2+. In accordance with other adherence-induced phenomena and with CD11 CD18 -mediated phagocytosis, these Ca 2+ signals were only modestly affected by pertussis toxin. Thus, the present data clearly indicate that the CD11b CD18 integrin on human neutrophils is capable of inducing a prompt cytosolic-free Ca 2+ signal. These findings directly support the recent suggestion that the CD11b CD18 integrin is responsible for the “spontaneous oscillations” of cytosolic-free Ca 2+ observed in adherent neutrophils and, at least partially, also explain how integrin-mediated adherence can modify the functional responsiveness of neutrophils to a subsequent agonist stimulation.

Chronic Omphalitis in a 4-Month-Old Girl

A case of chronic omphalitis present for birth in a 4-month-old girl is presented. The biopsy of the bud-like lesion failed to reveal a local malformation or remnants of umbilical cord but showed a common loose edematous tissue in which the inflammatory cells appeated remarkably scanty. The contrast existing between this poorly cellular local infiltrate and the high level of peripheral blood leucocytes (over 30,000/microliters) was in fact the most striking feature that allowed to evoke the diagnosis of Deficiency Leucocyte Adhesion molecules. Immunocytochemical investigations using anti CD11a, CD11b and CD18 monoclonal antibodies on fresh tissue or, better, peripheral leucocytes are necessary to confirm the diagnosis of this uncommon immunological autosomic recessive inherited disorder.