ISSN 00062979, Biochemistry (Moscow), 2014, Vol. 79, No. 8, pp. 812819. © Pleiades Publishing, Ltd., 2014. Published in Russian in Biokhimiya, 2014, Vol. 79, No. 8, pp. 10151023.

Role of CD11b/CD18 in Priming of Human Leukocytes by Endotoxin Glycoforms from Escherichia coli D. S. Kabanov1*, S. V. Grachev1,2, and I. R. Prokhorenko1 1

Institute of Basic Biological Problems, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia; Email: [email protected] 2 Sechenov First Moscow State Medical University, ul. Trubetskaya 8, 119992 Moscow, Russia Received March 10, 2014 Revision received April 28, 2014 Abstract—The primary objective of this study was to determine the role of β2 integrin αsubunit (CD11b) in the mechanism of human polymorphonuclear leukocyte (PML) priming by S or Re endotoxin glycoforms from Escherichia coli for fMLP induced respiratory burst. Similar priming activity of S and Re endotoxin glycoforms for fMLPinduced reactive oxygen species (ROS) generation from primed PML was found. AntiCD11b antibodies (clone ICRF 44) as well as isotype matched immunoglobulin G1 (clone MOPC21) do not influence the fMLPinduced ROS generation from unprimed PML. Antibodies against CD11b do not change fMLPinduced ROS generation from endotoxinprimed PML as well. The involvement of different isoforms of Fcγ receptors in fMLPinduced ROS generation from activated PML is proposed. DOI: 10.1134/S0006297914080094 Key words: lipopolysaccharide (endotoxin), β2 integrins (CD11b/CD18), Tolllike receptor 4, Fcγ receptors, receptor clus ter, immunoglobulins, antihuman CD11b antibody, reactive oxygen species

Infections by Gramnegative bacteria remain a glob al problem in medicine [1, 2]. Arriving to extravascular sites of inflammation, polymorphonuclear leukocytes (PML) find and eliminate opsonized bacteria by a series of rapid responses including phagocytosis and generation of reactive oxygen species (ROS) [3]. Lipopolysaccharides (LPSs, endotoxins) from Gramnegative bacteria are potent proinflammatory mediators for mammalian innate immune cells. In the bloodstream, endotoxinrecognizing proteins such as LPSbinding protein (LBP) and the soluble form of CD14 (sCD14) bind LPSs and deliver them to the surface receptors of target cells [48]. The membraneanchored form of CD14 (mCD14), Tolllike receptor 4 (TLR4), and TLR4associated adaptor protein MD2 are essential

Abbreviations: CD, cluster of differentiation; CR3, complement receptor 3; fMLP, NformylMetLeuPhe; GlcN, glu cosamine; GlcNAc, NacetylDglucosamine; ICAM, intra cellular adhesion molecule; Ig, immunoglobulins; LFA1, lym phocyte functionassociated antigen 1; Man, mannose; MD2, myeloid differentiation factor2; PML, polymorphonuclear leukocytes; rhLBP, recombinant human lipopolysaccharide binding protein; ROS, reactive oxygen species. * To whom correspondence should be addressed.

receptors involved in mammalian cell activation by LPS [9, 10]. In resting human monocytes, mCD14 is clustered with CD32, CD64, CD55, CD47, and other receptors in cell plasma membrane microdomains termed lipid raft. It had been shown that after cell stimulation by LPS from Salmonella minnesota, these receptor clusters were enriched by CD11b/CD18, TLR4, CD16A, and CD36 receptors, while CD47 was excluded from these lipid raft microdomains [9, 11]. Such association of mCD14 and CD11b/CD18 was earlier shown for human neutrophils after their exposure to LPS from Escherichia coli O55:B5 in the presence of rhLBP [12]. However, it remains to be determined – what is the role of CD11b/CD18 as a con stituent of the receptor cluster induced by endotoxins? CD11b/CD18 (Mac1, Mo1, CR3, αMβ2) is a het erodimeric transmembrane protein expressed on the sur face of polymorphonuclear leukocytes. It consists of a unique αsubunit (CD11b) noncovalently associated with βsubunit (CD18), which is a constituent of all β2 inte grins [13]. Association of α and βsubunits seems to occur before protein glycosylation in the Golgi complex and therefore before receptor expression on the cell sur face [14, 15]. It was recently shown that β2 integrins are involved in insideout and outsidein signaling mecha nisms [16, 17]. Unlike insideout signaling, when other

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CD11b AND Fcγ RECEPTORS IN PRIMING BY ENDOTOXIN membrane receptors induce activation of intracellular signaling molecules (ICAM) that convert integrins into a highaffinity ligandbinding state [1820], the outsidein signaling is directed by integrins themselves at the moment of their ligand binding [19, 21, 22]. According to this scenario, the interaction of LPS with TLR4 is able to induce intracellular signaling, which should be transmit ted across intracellular signaling molecules to CD11b/CD18 as insideout activation [9, 10], whereas outsidein signaling by CD11b/CD18 might be done dur ing association of CD11b/CD18 with LPSbound mCD14 [2325]. Therefore, CD11b/CD18 can be con sidered as the coworker receptor for mCD14 in LPS sig naling [12, 26]. However, the cytoplasmic tail of CD11b is the shortest (19 amino acid residues) among other β2 integrin αsubunits, and it is believed that CD11b/CD18 is unable to transduce intracellular signaling by itself but, like mCD14, can bind and transfer LPS to a second sig nal transduction receptor [24, 25, 27, 28]. CD11b/CD18, like other β2 integrins, CD11a/CD18 (LFA1) and CD11c/CD18 (gp150/95), can recognize hydrophilic region of truncated endotoxin molecules such as ReLPS, lipid A, and lipid IVa [23]. In addition, within the βA region of CD18 two putative sites (216248 and 266318 amino acid sequences) for binding of ReLPS from S. minnesota have been revealed [29]. Although TLR4 is known as the main “outsidein” LPS signaling receptor [9, 10] on the surface of human neutrophils, TLR4 is expressed at a low level when compared to CD11c and CD11b of β2 integrins [2]. In PML, signaling via β2 inte grins predominantly occurs through CD11a/CD18 and CD11b/CD18 receptors [30, 31]. The role of CD11b in the mechanism of neutrophil priming by endotoxins is not well understood. Prevailing expression of CD11b/CD18 on surfaces of PML and monocytes in comparison with other members of the β2 integrin family [32] and data on the ability of CD11b/CD18 to interact with endotoxins [24, 25, 2729] may point to the importance of this receptor in LPS recognition. Usually, to evaluate a role of any surface receptor (for example CD11b/CD18) in certain cell functions, CD11b transfected cells [28, 33], antiCD11b and/or antiCD18 monoclonal antibodies [17, 27, 32, 3437], or their Fab/F(ab′)2 fragments [36, 38, 39] have been used. So as to decrease lateral interactions of CD11b/CD18 with glycosylated glycosylphosphatidylinositolanchored membrane proteins (for example CD16), which may be caused by lectinlike properties of the βsubunit, some monosaccharides such as NacetylDglucosamine (GlcNAc) or Dmannose may be applied [26, 40, 41]. Site, recognizing carbohydrate determinants, was also identified in αsubunit of CD11b/CD18 [42]. It should be emphasized that neither mannose nor GlcN and GlcNAc are indifferent monosaccharides according to the study of fMLPinduced ROS generation [4345]. BIOCHEMISTRY (Moscow) Vol. 79 No. 8 2014

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Taking these facts into consideration, to determine the role of CD11b in PML endotoxin priming for fMLP induced respiratory burst monoclonal antihuman CD11b antibodies have been used.

MATERIALS AND METHODS Reagents. Luminol, chemotactic peptide Nformyl MetLeuPhe (fMLP), Percoll, mouse antihuman CD11b monoclonal antibodies (clone ICRF 44), and LPS from E. coli O55:B5 were purchased from Sigma (USA). Dextran 25GR was obtained from Fluka (Switzerland). The control isotypematched mouse IgG1 (clone MOPC21) was purchased from BioLegend (USA). ReLPS from E. coli JM103 was extracted according to [46]. Before each test, S or ReLPS sus pensions in distilled water were sonicated for 30 min. Phosphate buffered saline (PBS) (pH 7.4) and solution for determination of luminolenhanced chemilumines cence (138 mM NaCl, 0.01 mM CaCl2, 5.9 mM KCl, 5 mM NaHCO3, 1 mM Na2HPO4, 1 mM MgSO4, 10 mM HEPES, 5.5 mM glucose, pH 7.4) were passed through nitrocellulose filters with pore size of 0.20 μm. Autologous human serum was produced by spontaneous clotting of whole blood. PML isolation. Venous blood from healthy individu als was obtained under clinical conditions. PML were iso lated from whole blood in accordance with [47]. Heparinized (10 U/ml) blood was spun at 2000 rpm for 15 min to separate cells from plasma. Then 1.9 ml of 6% dextran solution in 12 ml of 0.9% NaCl was added to the cell pellet and incubated for 30 min to sediment red blood cells. After that, the upper phase enriched in leukocytes was centrifuged, and the resulting pellet was transferred into the plasma that had been aspirated beforehand. This suspension of leukocytes in plasma was layered on a Percoll density gradient (1.077 g/ml) and fractioned by centrifugation at 2000 rpm for 15 min. Contaminating erythrocytes were removed by 3 min exposure of the pel let to hypotonic lysing buffer (1 mM Na2EDTA, 150 mM NH4Cl, 10 mM NaHCO3, pH 7.7). The final cell preparation contained 9698% PML. The cells were determined to be >97% viable by the exclusion of trypan blue. Incubation of PML with antiCD11b antibodies or IgG1. To establish the role of CD11b in PML priming by LPS, the isolated cells were preexposed to monoclonal antibodies (mAbs) directed against human CD11b (or to IgG1 as isotypematched control) for 30 min at room temperature before LPS stimulation. Control (intact) cells did not contact these immunoglobulins. Subsequently, the cells were washed twice in PBS and resuspended in Ca2+free solution for chemilumines cence measurement. Then the cells were kept under rest ing conditions for 1 h at 4°C.

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PML priming by LPS. When the resting stage was complete, control (intact) cells and cells incubated with antiCD11b mAbs or IgG1 were placed in chemilumi nometer chambers containing solution for luminol enhanced chemiluminescence measurement that was supplemented with autologous serum (2%) and 0.01 mM CaCl2. Then the cells were allowed to adapt for 5 min at 37°C [6, 48, 49]. The priming state of PML was achieved by addition of S or ReLPS (100 ng/ml) followed by continuous gentle shaking for 30 min at 37°C [3, 50]. Chemiluminescence experiments. The respiratory (oxidative) burst response of PML was measured using luminolenhanced chemiluminescence in the twelve channel CHEMILUM12 elaborated at the Institute of Cell Biophysics, Russian Academy of Sciences [51]. The measurements were done at 37°C with acquisition fre quency 1/2.5 sec from 12 samples simultaneously. The PML in the chemiluminometer chambers were continu ously gently shaken with or without LPS under chemilu minescencemonitored conditions for 30 min at 37°C. To activate the system, 1 μM fMLP was added to the cells and the light emission was recorded continuously for 20 min. Total ROS production by control and LPSprimed PML were expressed as chemiluminescence relative units (CRU) within the first 50 sec after fMLP addition and calculated as the area under the curve of millivolts versus time. The values of chemiluminescence intensity were calculated using software designed by A. A. Grinevich (Institute of Cell Biophysics). Statistical analysis. The data were analyzed using the statistical package STATISTICA 7.0. Statistical signifi cance was determined by applying Wilcoxon’s signed ranks test; p < 0.05 was considered to be statistically sig nificant.

RESULTS fMLPinduced ROS generation by LPSunprimed cells. In all performed experiments, fMLPinduced ROS generation from PML was observed. This result confirms the viability of the cells used in our study. The responses of PML isolated from donor to donor varied considerably both in the magnitude of respiratory burst and by total amount of generated ROS (Table 1), revealing differences in their functional states. The fast and relative slow kinet ics of fMLPinduced ROS production from the cells are well distinguished in the figure. The most dramatic differ ences between these two phases were seen when PML became LPSprimed and subsequently fMLPstimulated. Influence of S or ReLPS on fMLPinduced ROS generation from PML. In the time course of S or Re LPS cell priming [52, 53] we did not observe any luminol enhanced chemiluminescence unless fMLP was added (figure). The values of fMLPtriggered chemilumines cence intensity in the samples of LPSunprimed PML

were chosen as the controls. The median values of lumi nolenhanced chemiluminescence in the samples of con trol and LPSprimed PML are summarized in Table 1. From the comparison of fMLPtriggered ROS generation versus control and Re or SLPSprimed cells, it might be formally concluded that the first endotoxin glycoform had more potent priming activity than the last. However, as judged by statistical data analysis these differences had no significance (Table 1). Thus, under the used experi mental conditions similar priming activity of S and Re LPS glycoforms for further fMLPtriggered ROS genera tion from human PML was recorded. It should be mentioned that the decay of luminol enhanced chemiluminescence in the samples of S and ReLPSprimed PML detected within ~800 sec after fMLP addition reached the baseline (figure, panel (a)). These results confirm the ability of LPS to potentiate fMLPtriggered ROS generation from human PML [48, 50]. Influence of isotypematched IgG1 on fMLPinduced ROS generation from control and ReLPSprimed PML. To block the CD11b subunit on the cell surface, we used full mAbs against human CD11b. So that the effect of the Fc region of the mAbs on fMLPinduced luminol enhanced chemiluminescence of control LPSunprimed cells must be verified. Thus, PML were exposed to iso typematched IgG1 followed by fMLP activation. The comparison of fMLPtriggered ROS generation from control and IgG1 preincubated PML revealed negligible inhibitory effect of IgG1 (p > 0.05) (Table 2). Taking this fact into consideration, the effect of iso typematched IgG1 on ROS production from ReLPS primed PML has been examined. The fMLPinduced ROS generation after PML preincubation with IgG1 fol lowed by ReLPS priming was twofold higher than those of control and IgG1 preexposed cells (Table 2 and figure, panel (b)). Keep in mind that isotypematched IgG1 caused negligible inhibitory effect on fMLPinduced ROS generation from LPSunprimed cells (Table 2), so we concluded that the observed increased ROS produc tion from PML that had been preexposed to IgG1 and then primed by ReLPS was completely attributed to the priming effect of ReLPS. Influence of antiCD11b mAbs on fMLPinduced ROS generation from S or ReLPSprimed PML. The fMLPtriggered release of different ROS amounts by PML isolated from the blood of various donors and exposed to antiCD11b mAbs was observed. Incubation of PML with antiCD11b mAbs followed by S or Re LPS priming augmented the quantities of fMLPinduced ROS (~120 and ~140%, respectively) in comparison to the control cells (Table 1). Comparing these responses across donors, we might formally conclude that after cell exposure to antiCD11b mAbs somewhat higher priming activity by SLPS in comparison to ReLPS was detected (Table 1). It is necessary to point out that the median BIOCHEMISTRY (Moscow) Vol. 79 No. 8 2014

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Table 1. Influence of ICRF 44 antibodies and different LPS glycoforms on fMLPtriggered ROS generation by human leukocytes (first 50 sec) Luminolenhanced chemiluminescence, RU

Median (range) and interquartile (range) values

Control, fMLP (n = 7)

SLPS, fMLP (n = 7)

ICRF 44, SLPS, fMLP (n = 7)

ReLPS, fMLP (n = 7)

ICRF 44, ReLPS, fMLP (n = 7)

ICRF 44, fMLP (n = 7)

57.4 34.771.7

77.7 62.1168.2 р < 0.05

106.1 79.8139.0 р < 0.05

102.4 69.4191.7 р < 0.05

90.4 76.8176.0 р < 0.05

50.9 33.167.5 р > 0.05

р > 0.05

р > 0.05

Table 2. Effect of isotypematched mouse IgG1 and ReLPS on fMLPtriggered ROS generation by human leukocytes (first 50 sec) Luminolenhanced chemiluminescence, RU

Median (range) and interquartile (range) values

Control, fMLP (n = 7)

IgG1, fMLP (n = 7)

IgG1, ReLPS, fMLP (n = 7)

34.0 33.846.2

30.0 28.437.3 р > 0.05

55.2 38.8112.8 р < 0.05

value of fMLPinduced chemiluminescence intensity of cells exposed to antiCD11b mAbs followed by SLPS priming was increased up to ~30% (p > 0.05), whereas in the case of priming by ReLPS by only ~20% (p > 0.05). This slight difference in the priming activity of S and Re glycoforms of LPS, which is illustrated in Table 1, may partly be the consequence of antiCD11b mAbs influenc ing the receptor spatial conformation. Although such

a

b

c 44/ReLPS

16 Chemiluminescence, RU

speculation has not been confirmed by experimental investigations, we suppose that antibodydependent (clone ICRF 44) changes in CD11b spatial conformation may favor not only to recognition of endotoxins (Sglyco form especially) by the cell, but to activation of intracel lular signaling pathway(s) as well. Another possible inter pretation of the increased ROS generation from PML exposed to antiCD11b mAbs and then primed by endo

ReLPS

44/SLPS

14 IgG1/ReLPS

SLPS 12 10 8

IgG1

6

Control

Control

44(IgG1)

4 2

LPS

fMLP

0 100 300 700 900 1100

LPS 0 100

LPS

fMLP

300

700

900 1100

0 100

300

fMLP 700

900 1100

Time, sec Influence of LPS (a), IgG1 and ReLPS (b), and ICRF 44 antibodies and LPS (c) on fMLPtriggered respiratory burst from human PML

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toxins is that the Fc region of antiCD11b mAb bound to αsubunits of the receptor could be recognized by Fcγ receptors during formation of endotoxininduced recep tor complex [9, 11].

DISCUSSION The fMLPtriggered ROS generation from endotox inprimed PML should be regulated at least by two sig naling pathways. The first is induced by LPSdependent activation of intracellular signaling molecules, while the second is induced during the response to fMLP [50]. The results show that S and ReLPS glycoforms iso lated from E. coli having differences in their hydrophilic regions but being structurally identical in their hydropho bic regions – lipid A, revealed the same priming activity for fMLPtriggered respiratory burst from human PML (Table 1). The investigation of whether CD11b plays a role in PML priming by different endotoxin glycoforms was the primary objective of our work. AntiCD11b mAbs (clone ICRF 44) did not inhibit PML priming by S or ReLPS but augmented the fMLPinduced ROS generation from S or ReLPSprimed cells (Table 1 and figure, panels (a) and (c)). These results are in agreement with the findings of other studies showing that antiCD11b mAbs (OKM 1; IgG2b) with shielded Fc regions did not inhibit priming of human neutrophils by SLPS from E. coli O55:B5 [54, 55]. However, when mAbs against CD11b/CD18 were used together with mAbs against CD11c/CD18, superox ide production by human peripheral blood mononuclear cells in the response to Ra/RbLPS from E. coli K12 LCD25 was significantly reduced [56]. Thus for sufficient triggering of the LPSdependent signaling pathway(s), the formation of a finetuning LPS receptor complex involving CD11b/CD18, CD11c/CD18 and TLR4 should be done [2, 57, 58]. To induce endotoxindependent cell adhesion, CD11b/CD18 can be associated with LBP/LPS/mCD14 complex. Then mCD14/LPS can be released from this complex so as to be associated with CD11c/CD18 to trig ger intracellular pathway(s) for cytokine synthesis [13, 26]. According to crosstalk between mCD14/LPS and CD11b/CD18, the latter receptor may be able to bind LPS and transfer it to another receptor that in turn medi ates LPS signaling [12, 2428]. Here we showed that anti CD11b mAbs (clone ICRF 44) did not influence fMLP induced ROS generation by S or ReLPSprimed PML. The simplest interpretation of these data is that after exposure of the cells to antiCD11b mAbs, the LPS bind ing site(s) on CD11b remained unblocked [59]. In trying to answer the question whether CD11b is a constituent of the endotoxinpriming mechanism for cell respiratory burst, further investigations involving mAbs against the different epitopes of CD11b should be carried out.

To investigate whether CD11b is involved in PML priming by LPS, we used full antiCD11b mAbs. As a result the increase in fMLPinduced ROS production after incubation of cells with mAbs followed by LPS priming might in part be a consequence of Fcγ receptor engagement as seen early in studies of others [30, 31]. CD32A, a transmembrane Fcγ receptor, has cytoplasmic immunoreceptor tyrosinebased activation motif (ITAM). So this receptor is able to regulate the Fc region dependent intracellular signaling by Ab. On the surface of resting neutrophils, CD32A is expressed in lowavidity state for IgG1 and with that for the isotypematched region of the used antiCD11b mAbs (clone ICRF 44; IgG1). However, it is certainly possible that the endotox ininduced receptor clustering of CD32A and CD11b bound by mAb in lipid raft will favor CD32A recognition of the Fcregion of antiCD11b mAb [11, 31, 60, 61]. Thus, CD32A followed by their ligand binding is able to affect Gproteins, which in turn can activate the intracel lular signaling pathway for NADPH oxidase assembly [37]. In addition, the actin polymerization and assembly of NADPH oxidase occurred after the action of CD11b/CD18 in concert with CD16B, another Fcγ receptor that is anchored to the membrane by a glyco sylphosphatidylinositol moiety [37]. It is necessary to note that enhanced CD16 surface expression was detect ed when neutrophils had been exposed to LPS from S. minnesota L4641 (100 ng/ml) for 10 min [58, 62]. As a result, the recognition of the Fcregion of antiCD11b mAb bound to CD11b might be favored by increased cell surface expression of CD16 induced by LPS. As we have already mentioned in Tables 1 and 2, the antiCD11b mAbs as well as isotypematched IgG1 had negligible inhibitory effect on fMLPinduced respiratory burst from control unprimed PML (p > 0.05). This insignificant inhibitory effect of studied Igs might also be explained by involvement of Fcγ receptors [63]. On the surface of human neutrophils CD32A and CD16B are the most abundant Fcγ receptors in comparison to CD32B (isoform of CD32, which has an inhibitory intracellular motif) [34, 6466]. As shown early, one of the CD32 iso forms, namely CD32IIALR, exhibits weak affinity to mouse IgG1, whereas two other isoforms, CD32IIAHR and CD32B2, are able to recognize this Ig well [67]. Unlike CD32A having a cytoplasmic ITAM motif, CD32B2 contains a cytoplasmic ITIM motif whose acti vation leads to diminishing downstream events from acti vated tyrosinebased immunoreceptors [63]. Taking these facts into consideration, it seems reasonable to assume that the intensity of fMLPinduced respiratory burst from PML incubated with antiCD11b or IgG1 is dependent on the ratio of CD32IIB2 and CD32IIA receptors that had been activated during exposure of cells to the studied immunoglobulins. The data obtained in our current work are in agree ment with other investigators showing that at least some BIOCHEMISTRY (Moscow) Vol. 79 No. 8 2014

CD11b AND Fcγ RECEPTORS IN PRIMING BY ENDOTOXIN intracellular signaling pathway(s) can be activated after interaction of specific mAbs with their target receptor. It is known that Fab (from OKM1; IgG2b) directed against CD11b did not cause respiratory burst in human neu trophils [37]. Similar results involving the range of anti CD11b mAbs recognizing different epitopes on CD11b and belonging to various subclasses of immunoglobulins IgG1 (VIM12, 5A4.C5, JML.H11, 44), IgG2a (Leu15), IgG2b (OKM1), IgG (LM2/1), and IgM (Mo1) were obtained in the study of intracellular ROS generation by human neutrophils [35]. As follows from those results, the interaction of antiCD11b mAbs 44 with target receptor did not significantly affect signaling pathway(s) associated with intracellular ROS generation. It was revealed that 44 mAbs stabilized CD11b in their bent (inactive) closely apposed with CD18 conformation [39]. In addition, the exhibition of a specific site on CD18 required for “outside in” signaling by CD11b/CD18 was prevented by 44 Fab [39]. In the current study we found that antiCD11b mAbs (clone ICRF 44) as well as isotypematched IgG1 insignif icantly inhibited fMLPtriggered respiratory burst from unprimed PML (p > 0.05). It seems that recognition of antiCD11b mAbs and isotypematched IgG1 by Fcγ receptors might occur before as well as after formation of LPSinduced receptor complex in lipid raft microdomains. The mode of action of Abs on cell functions could also be defined by the specificity of an antibody to certain sites on the receptor. The unique M522 mAbs directed against CD11b and their F(ab′)2 fragments can serve as an exam ple of mAbs producing by themselves the activation of res piratory burst from human neutrophils [32, 36]. As evidenced from the median values of chemilumi nescence intensity of control and LPSprimed PML, the antiCD11b mAbs (clone ICRF 44) did not inhibit the PML priming by S as well as ReLPS. To answer the question of whether CD11b is really important for endo toxintriggered PML priming, further studies involving mAbs against specific epitopes on CD11b, especially those that are involved in LPS recognition, should be per formed. Our results tend to indicate some contribution of certain isoforms of Fcγ receptors in fMLPinduced ROS generation by antiCD11b mAbs pretreated and subse quently LPSprimed PML. This work was supported by Grant 16.N08.12.1014 established 14.05.2012 by the Russian Ministry of Education and Science under the federal targeted pro gram “Extension of pharmaceutical and medical industry of the Russian Federation until 2020 year with possibility for prolongation”. REFERENCES 1.

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CD18 in priming of human leukocytes by endotoxin glycoforms from Escherichia coli.

The primary objective of this study was to determine the role of β2 integrin α-subunit (CD11b) in the mechanism of human polymorphonuclear leukocyte (...
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