Neutrophil migration into indomethacin induced rat small intestinal injury is CD11a/CD18 and CD11b/CD18 co-dependent

BACKGROUND: Neutrophils may exacerbate intestinal inflammatory diseases through secretion of proteolytic enzymes and reactive oxygen and nitrogen intermediates. AIMS: To define the mechanisms involved in neutrophil infiltration into the non-steroidal anti-inflammatory disease inflamed intestine to develop strategies to regulate this process. METHODS: The small intestinal epithelium of (15 mg/kg) indomethacin treated rats was examined for cytokine mRNA. The kinetics of neutrophil accumulation into the gastrointestinal tract (including lumen contents) of inflamed rats was determined using radiolabelled (111In) neutrophils injected intravenously followed by a three hour migration period. To determine which adhesion molecules were critical for migration, rats were also injected with function blocking monoclonal antibodies to the beta2 (CD11/CD18) integrins. RESULTS: Interleukin 1beta, interleukin 1 receptor II, tumour necrosis factor alpha, and monocyte inflammatory peptide 2 but not monocyte chemoattractant protein 1 mRNA were detected in the epithelium within hours of indomethacin injection. Neutrophils were detectable in the small intestine and intestinal lumen by six hours and continued to accumulate until 48 hours post indomethacin injection. Neutrophil accumulation in the intestine was essentially blocked by anti-CD18, and partially blocked by either anti-CD11a or CD11b antibody treatment. Migration into the intestinal lumen was reduced by anti-CD11b. CONCLUSIONS: The small intestinal epithelium acts as one source of cytokines with properties important in the recruitment of neutrophils. In turn, neutrophil migration into the indomethacin inflamed small intestine is mediated by CD11a/CD18 and CD11b/CD18.     

Host fibrinogen stably bound to hemozoin rapidly activates monocytes via TLR-4 and CD11b/CD18-integrin: a new paradigm of hemozoin action

Natural hemozoin (nHZ), prepared after schizogony, consists of crystalline ferriprotoporphyrin-IX dimers from undigested heme bound to host and parasite proteins and lipids. Phagocytosed nHZ alters important functions of host phagocytes. Most alterations are long-term effects. We show that host fibrinogen (FG) was constantly present (at ~ 1 FG per 25 000 HZ-heme molecules) and stably bound to nHZ from plasma-cultured parasites. FG was responsible for the rapid 100-fold stimulation of reactive oxygen species production and 50-fold increase of TNF and monocyte chemotactic protein 1 by human monocytes. Those effects, starting within minutes after nHZ cell contact, were because of interaction of FG with FG-receptors TLR4 and integrin CD11b/CD18. Receptor blockage by specific mAbs or removal of FG from nHZ abrogated the effects. nHZ-opsonizing IgGs contribute to the stimulatory response but are not essential for FG effects. Immediate increase in reactive oxygen species and TNF may switch on previously described long-term effects of nHZ, largely because of HZ-generated lipo-peroxidation products 15(S,R)-hydroxy-6,8,11,13-eicosatetraenoic acid and 4-hydroxynonenal. The FG/HZ effects mediated by TLR4/integrins represent a novel paradigm of nHZ activity and allow expansion of nHZ effects to nonphagocytic cells, such as endothelia and airway epithelia, and lead to a better understanding of organ pathology in malaria.     

Platelet/polymorphonuclear leukocyte interaction in dynamic conditions: evidence of adhesion cascade and cross talk between P-selectin and the beta 2 integrin CD11b/CD18

Adhesion between platelets and polymorphonuclear leukocytes (PMN) is a key event in thrombosis and inflammation. Double color fluorescence- activated cell sorter (FACS) analysis was used to determine the extent and kinetics of adhesion of thrombin-activated platelets to resting or activated PMN when mixed cell populations were incubated in dynamic conditions. Activated platelets bound very rapidly to PMN. Mixed cell conjugates reached a maximum at 1 minute and were reversible within 10 minutes. Platelet/PMN adhesion required both Ca2+ and Mg2+ and was markedly increased by the presence of Mn2+. The latter made mixed cell conjugates stable up to 10 minutes. Adhesion of platelets required metabolic activity of PMN and was abolished by tyrosine kinase inhibitors. Furthermore, adhesion of platelets to PMN resulted in binding of a monoclonal antibody (MoAb 24) known as beta 2 integrins "activation reporter." When PMN were activated by exogenous stimuli, the adhesion of platelets was markedly increased: fMLP induced a rapid and transient effect, while PMA resulted in a slower, but stable, increase in mixed conjugates formation. The hypothesis that activated PMN beta 2 integrins are able to bind a counter-receptor on platelets was directly demonstrated by the increase of mixed cell conjugates following PMN treatment with KIM127 and KIM185, two anti-CD18 antibodies able to induce the active conformation of beta 2 integrins. Consistently, two other anti-CD18, as well as an anti-CD11b inhibitory antibody abolished platelet/PMN adhesion. PMN beta 2 integrin activation was not the only mechanism for activated platelet/PMN adhesion to occur: indeed, this phenomenon could also be inhibited by two anti-P-selectin antibodies. Resting platelets did not adhere to resting PMN, but markedly adhered to fMLP- or PMA-activated PMN. Resting platelet/fMLP-activated PMN adhesion was abolished by anti-CD18 antibodies, but not by anti-P-selectin antibodies. In conclusion, activated platelet/PMN interaction can be modeled as an adhesion cascade involving a P-selectin-dependent recognition step and a functional signal. The latter proceeds through tyrosine kinase activation and enables a beta 2 integrin-dependent adhesion to a not yet identified counter-receptor constitutively expressed on platelet surface.     

Continuous activation and deactivation of integrin CD11b/CD18 during de novo expression enables rolling neutrophils to immobilize on platelets

In an in vitro flow model, unstimulated neutrophils rolled steadily over a surface coated with platelets, until superfusion of the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (fMLP) caused a dose-dependent (10(-11) to 10(-7) mol/L) transition from rolling to stationary attachment in seconds, followed more slowly by neutrophil shape change and spreading on the surface, However, at low concentrations of Ca2+ and Mg2+ (0.1 mmol/L and 0.05 mmol/L, respectively, rather than physiologic 1 mmol/L and 0.5 mmol/L), neutrophils first halted but then started to roll again and to detach from the surface over 5 to 10 minutes. At the low cation concentration, stopping was largely inhibited by antibodies to the neutrophil integrins CD18 or CD11b, but not CD11a. When neutrophils were pretreated with antibodies to CD11b or CD18 in 1 mmol/L Ca2+ 0.5 mmol/L Mg2+, stopping was not prevented but delayed. However, if antibodies were also included with the superfused fMLP, stopping was inhibited, and detachment followed. This indicates that CD11b/CD18 was newly expressed during shape change and mediated the second phase of neutrophil immobilization and spreading in a cation-dependent manner. Prestimulated neutrophils also bound to platelets and spread, but immobilization was blocked if they were perfused with antibody to CD18 or CD11b or with low Ca2+ and Mg2+. Examining the cation-dependence further, it was evident that the presence of Mg2+ was essential for integrin-mediated adhesion and that the Mg2+ concentration determined whether immobilization could be maintained or was transient. Continuous superfusion of fMLP was also essential for maintenance of stable adhesion and spreading. Thus, activation of constitutive CD11b/CD18 rapidly and reversibly converted rolling to stationary attachment, whereas maintenance of adhesion and neutrophil spreading required continual expression of additional CD11b/CD18 that was only functional at physiologic Mg2+. Continual activation and deactivation of CD11b/CD18 during de novo expression could mediate immobilization and onward migration of neutrophils in vivo, and activated platelets appear capable of supporting this process as well as endothelial cells.     

Expression of a soluble and functional form of the human beta 2 integrin CD11b/CD18.

Polymorphonuclear cells and monocytes (phagocytes) are a critical component of host defense against infections. However, these cells also play a significant role in host tissue damage in many noninfectious diseases, such as ischemia-reperfusion injury syndromes and rejection of transplanted organs. The leukocyte adhesion molecule family CD11/CD18 (beta 2 integrins) is critical to the function of polymorphonuclear cells and monocytes in inflammation and injury. Inherited deficiency of CD11/CD18 impairs phagocyte chemotaxis, adhesion and transmigration across endothelium, and clearance of invading microorganisms through phagocytosis and cell-mediated killing. Furthermore, murine monoclonal antibodies directed against the CD11b/CD18 (CR3) heterodimer have been shown to reduce, by 50%-80%, phagocyte-mediated ischemia-reperfusion injury in several organ systems, such as the myocardium, liver, and gastrointestinal tract and to inhibit development of insulin-dependent diabetes mellitus in nonobese diabetic (NOD) mice. Expression of CD11b/CD18 in a soluble and functional form might therefore be potentially useful as an anti-inflammatory agent. We have now expressed a recombinant soluble heterodimeric form of this human beta 2 integrin, normally expressed as two noncovalently associated membrane-bound subunits. The secreted receptor exhibited direct and specific binding to its ligand, iC3b, the major complement C3 opsonin, and inhibited binding of polymorphonuclear cells to recombinant interleukin 1-activated endothelium.     

Identification of the complement iC3b binding site in the beta 2 integrin CR3 (CD11b/CD18).

The divalent cation-dependent interaction of the beta 2 integrin CR3 (CD11b/CD18) with the major complement opsonic C3 fragment iC3b is an important component of the central role of CR3 in inflammation and immune clearance. In this investigation we have identified the iC3b binding site in CR3. A recombinant fragment representing the CR3 A-domain, a 200-amino acid region in the ectodomain of the CD11b subunit, bound to iC3b directly and in a divalent cation-dependent manner. The iC3b binding site was further localized to a short linear peptide that also bound iC3b directly and inhibited iC3b binding to the A-domain as well as to CR3 expressed by human neutrophils. These data establish a major recognition function for the integrin A-domain and have important implications for development of novel antiinflammatory therapeutics.     

Erythromycin inhibits beta2-integrins (CD11b/CD18) expression, interleukin-8 release and intracellular oxidative metabolism in neutrophils

Macrolides have therapeutic benefits on chronic inflammatory airway diseases. Thus, macrolides are supposed to have variable biological effects apart from antimicrobial activity. Neutrophil adherence and influx with oxidants and cytokines production implicates involvement in airway inflammation. To investigate whether erythromycin (EM) affects neutrophil activity in vitro, lipopolysaccharide (LPS)-treated neutrophils were continuously incubated for 4 h in the absence or presence of increasing doses of EM from 1 microg ml(-1) to 100 microg ml(-1) in the last 2 h. Leukocyte adhesion molecules Mac-1 and intracellular H2O2(DCFH) were determined by flowcytometric assay. IL-8 and TNFalpha in supernatant was measured by ELISA method. The expression of Mac-1 and mean intracellular DCF fluorescence intensity (DCFH) of neutrophils significantly increased after stimulation with LPS. Pretreatment with EM significantly decreased LPS induced Mac-1 expression on neutrophils compared with LPS stimulation only. EM alone (100 microg ml(-1)) also decreased Mac-1 expression on neutrophils. EM significantly reduced the LPS-increased DCFH. EM alone (100 microg ml(-1)) also caused a decrease in DCFH. Increasing doses of EM also significantly decreased the IL-8 released by LPS-stimulated neutrophils. In conclusion, EM exerts a direct effect on the neutrophils by downregulating the expression of beta2-integrin on neutrophils, thus leading to a decrease in the intracellular H2O2, as well as the production of IL-8. Our conclusion provides an explanation for the clinical efficacy of erythromycin in neutrophil-mediated airway inflammation.     

TNF-α induces spreading of B-CLL via the CD11C/CD18 molecule

Activation of malignant B cells can lead to extensive morphological changes of these cells. A combination of PMA and TNF-α can induce adherence of purified B-CLL cells, which acquire a dendritic cell-like appearance. This phenomenon that we have termed spreading, is accompanied by upregulation of expression of both β1 and β2 integrin molecules. Spreading was inhibited by the addition of antibodies against CD18 or CD11c. In other B cell malignancies (HCL and NHL), morphological changes could be induced by PMA in the absence of TNF-α. Culturing in the presence of prednisolone resulted in an inhibition of spreading, most likely mediated via a down regulation of CD18 and CD11c expression. These data indicate that the CD11c/CD18 complex might be important for the adhesive properties of B cells. © 1993 Wiley-Liss, Inc.     

Sequential binding of CD11a/CD18 and CD11b/CD18 defines neutrophil capture and stable adhesion to intercellular adhesion molecule-1

The relative contributions of CD11a/CD18 and CD11b/CD18 to the dynamics and strength of neutrophil adhesion to intercellular adhesion molecule (ICAM)-1-transfected cells were examined over the time course of chemotactic stimulation. Suspensions of neutrophils and transfectants were sheared in a cone-plate viscometer, and formation of heterotypic aggregates was measured by 2-color flow cytometry. The 2-body collision theory was used to compute adhesion efficiency, defined as the proportion of collisions between neutrophils and target cells that resulted in capture. ICAM-1 surface density and shear rate both regulated adhesion efficiency. Target cells expressing approximately 1000 ICAM-1 sites/microm(2) (I(low)) were captured with an efficiency of 0.15 at 100 s(-1), which decreased to zero at 300 s(-1). At 8-fold higher ICAM-1 expression (I(high)) corresponding to levels measured on interleukin-1-stimulated endothelium, efficiency was 0.3 at 100 s(-1) and remained above background to 900 s(-1). Shear alone was sufficient for CD11a/CD18-mediated adhesion to ICAM-1, and stimulation with formyl-methionyl-leucyl-phenylalanine boosted capture efficiency through CD11a/CD18 by 4-fold. In comparison, CD11b/CD18 supported one third of this efficiency, but was necessary for aggregate stability over several minutes of shear and at shear stresses exceeding 5 dyne/cm(2). Hydrodynamics influenced capture efficiency predominantly through the collisional contact duration, predicted to be approximately 9 milliseconds for successful capture of I(low) and 4 milliseconds for I(high). The implication is that an increase in ICAM-1 from resting levels to those on inflamed endothelium effectively increases the permissible shear in which capture through beta(2)-integrins may occur. Neutrophil adhesion to ICAM-1 appears to be a cooperative and sequential process of CD11a-dependent capture followed by CD11b-mediated stabilization.     

Fibrin(ogen) is internalized and degraded by activated human monocytoid cells via Mac-1 (CD11b/CD18): a nonplasmin fibrinolytic pathway

Fibrin(ogen) (FGN) is important for hemostasis and wound healing and is cleared from sites of injury primarily by the plasminogen activator system. However, there is emerging evidence in plasminogen activator- deficient transgenic mice that nonplasmin pathways may be important in fibrin(ogen)olysis, as well. Given the proximity of FGN and monocytes within the occlusive thrombus at sites of vascular injury, we considered the possibility that monocytes may play an ancillary role in the degradation and clearance of fibrin. We found that monocytes possess an alternative fibrinolytic pathway that uses the integrin Mac- 1, which directly binds and internalizes FGN, resulting in its lysosomal degradation. At 4 degrees C, FGN binds to U937 monocytoid cells in a specific and saturable manner with a kd of 1.8 mumol/L. Binding requires adenosine diphosphate stimulation and is calcium- dependent. At 37 degrees C, FGN and fibrin monomer (FM) are internalized and degraded at rates of 0.37 +/- 0.13 and 0.55 +/- 0.03 microgram/10(6) cells/h by U937 cells, 1.38 +/- 0.02 and 1.20 +/- 0.30 microgram/10(6) cells/h by THP-1 cells, and 2.10 +/- 0.20 and 2.52 +/- 0.18 micrograms/10(6) cells/h by human peripheral blood mononuclear cells, respectively. The serine protease inhibitors, PPACK and aprotinin, and the specific elastase inhibitor, AAPVCK, do not significantly inhibit degradation. However, degradation is inhibited by chloroquine, suggesting that a lysosomal pathway is involved. Factor X, a competitive ligand with FGN for the Mac-1 receptor, also blocks degradation, as does a monoclonal antibody to the alpha-subunit of Mac- 1. Autoradiography of radioiodinated, internalized FGN shows that FGN proteolysis by the pathway produces a unique degradation pattern distinct from that observed with plasmin. In a fibrin clot lysis assay, Mac-1-mediated fibrinolysis contributed significantly to total fibrinolysis. In summary, FGN is internalized and degraded by activated human monocytoid cells via Mac-1 in the absence of plasmin, thereby providing an alternative fibrinolytic pathway. Thus, in addition to the function of cell adhesion, integrins may also act as receptors that mediate the internalization and degradation of bound ligands.     

Crystal structure of the I-domain from the CD11a/CD18 (LFA-1, alpha L beta 2) integrin.

We report the 1.8-A crystal structure of the CD11a I-domain with bound manganese ion. The CD11a I-domain contains binding sites for intercellular adhesion molecules 1 and 3 and can exist in both low- and high-affinity states. The metal-bound form reported here is likely to represent a high-affinity state. The CD11a I-domain structure reveals a strained hydrophobic ridge adjacent to the bound metal ion that may serve as a ligand-binding surface and is likely to rearrange in the absence of bound metal ion. The CD11a I-domain is homologous to domains found in von Willebrand factor, and mapping of mutations found in types 2a and 2b von Willebrand disease onto this structure allows consideration of the molecular basis of these forms of the disease.     

Reductions in physiologic shear rates lead to CD11/CD18-dependent, selectin-independent leukocyte rolling in vivo

In this study, we tested the hypothesis that reducing shear rates in postcapillary venules causes CD18-dependent, selectin-independent leukocyte rolling. Intravital microscopy was used to assess shear rate- dependent leukocyte rolling in 25- to 40-microns rat mesenteric venules. Pretreatment of animals with 25 mg/kg fucoidin, a carbohydrate moiety that binds to and inhibits selectin function, essentially abolished the number of spontaneously rolling leukocytes. When shear rates were reduced by 50% (from 438 +/- 36 s-1 to 222 +/- 19 s-1) in the presence of fucoidin, leukocyte rolling increased fourfold, suggesting a selectin-independent mechanism of leukocyte rolling. Administration of CL26, an anti-CD18 antibody, prevented the leukocyte rolling associated with reduced shear rates. A second objective was to determine if the integrin-mediated leukocyte rolling at reduced shear rates would lead to firm adhesion of leukocytes in the presence of a chemotactic stimulus. Animals were pretreated with fucoidin and 100 nmol/L platelet-activating factor (PAF) was superfused over the mesentery. Fucoidin prevented leukocyte rolling and subsequent PAF- induced adhesion at normal shear rates; however, when shear rates were reduced by 50%, a significant CD18-dependent increase in leukocyte rolling (10-fold) and adhesion (5-fold) was noted within 15 minutes. These data raise the possibility that, at lower shear rates, as is the case in various inflammatory conditions, selectin-independent, CD18- dependent leukocyte rolling and subsequent adhesion can occur in postcapillary venules.     

肿瘤坏死因子、白细胞介素8、可溶性细胞间粘附分子1和CD11b/CD18在良恶性胸腔积液的价值

目的 研究结核性及恶性胸腔积液患者及血清中肿瘤坏死因子（TNF）、白细胞介素－8（IL－8）、胸液中可溶性细胞间粘附分子1（sICAM-1）及外周血多形核白细胞（PMN）上粘附分子CD11d/CD18在参与胸膜病变的病理生理过程中的作用和在鉴别诊断上的价值。方法 采用放射免疫分析法（RIA法）、双抗体夹心ELISA法及流式细胞仪技术,检测31结核性、31例恶性胸腔积液患者胸液和（或）血清中TNF、IL－8、sICAM－1和CD11d/CD18表达水平,并与31例健康献血者对照。结果 结核性和恶性胸腔积液患者血清中TNF、IL－8含量以及PMN上CD11d/CD18表达显著高于正常对照组（P＜0．01）, 结核性胸液中TNF与IL－8水平和血PMN上CD11d/CD18表达明显高于恶性胸液患者（P＜0．01）,结核性胸粹中sICAM－1水平明显低于恶性胸液（P＜0．01）。胸腔积液中TNF与IL－8、sICAM－1水平呈显著正相关（r＝0．74和r＝0．79,P＜0．01）,血清TNF与PMN上CD11d/CD18的表达呈显著正相关（r＝0．61,P＜0．01）,胸腔积液中sICAM－1水平与血PMN上CD11d/CD18的表达呈显著负相关（经作曲线拟合,Y=1442．31－36．85X∧2＋0．25X∧2,R∧2＝0．59,F＝19．83,P＜0．01）。结论 细胞因子TNF、IL－8和粘附子sICAM－1、CD11b/CD18相互联系,在结核和肿瘤性胸膜病变的免疫 理生理过程中起着重要作用。它们在结核性和肿瘤性胸腔积液患者的表达水平不同,可作为临床上鉴别诊断的参考指标。     

血清E-选择素和白细胞CD11b/CD18在冠心病中的意义

目的 :探讨血清E 选择素水平、中性粒细胞和单核细胞膜CD11b/CD18的表达在冠心病 (CHD)中的意义。方法 :选择 2 4例稳定型心绞痛 (SAP组 )患者、2 4例不稳定型心绞痛 (UAP组 )患者和 2 2例急性心肌梗死 (AMI组 )患者 ,30例冠状动脉造影阴性作对照组。Gensini积分法评价冠状动脉病变程度有统计学将CHD分为两个亚组 :A组 (1～ 2 0分 ) ,B组 (>2 0分 )。酶联免疫吸附法检测E 选择素 ;流式细胞仪检测CD11b/CD18的表达。结果 :CHD各组血清E 选择素水平、中性粒细胞和单核细胞膜CD11b/CD18的表达均显著高于对照组 (P<0 .0 1) ;CHD各组间差异有统计学意义 (P <0 .0 5 ) ;B组上述参数显著高于A组 (分别P <0 .0 5 ,P <0 .0 1,P<0 .0 5 )。结论 :E 选择素和CD11b/CD18可能参与了CHD的发病过程 ,且与冠状动脉粥样硬化程度有关     

The "ex vivo" patterns of CD2/CD7, CD57/CD11c,CD38/CD11b,CD45RA/CD45RO,and CD11a/HLA-DR expression identify acute/early and chronic/late NK-cell activation states

To define a dynamic sequence of phenotypic changes related to early and late phases of NK-cell activation, we have analyzed by four-color flow cytometry the immunophenotype of normal blood NK-cells from 12 healthy individuals and compared it with those from 15 patients with acute viral infections and 15 patients with either chronic infections or tumors. Although a great interindividual variability was found, nonstimulated CD56(+) NK-cells, present in normal blood samples, usually were CD2(-/+lo), CD7(+hi), HLA-DR(-), CD11b(+), CD38(+), CD11a(+hi), CD45RA(+hi), and CD45RO(-), the expression of CD11c and CD57 being heterogeneous and variable. Recently activated NK-cells, herein corresponding to NK-cells from patients with acute viral infections, displayed a pattern of expression of CD2/CD7 similar to that referred to above, but they typically showed higher levels of CD11a, CD38, and HLA-DR, as well as downregulation of CD11b and CD45RA, accompanied in some cases by coexpression of CD45RO; in addition, these NK-cells were CD11c(+) and CD57(-/+lo). Late-activated NK-cells, represented by NK-cells present in patients with chronic infections and tumors, converted into a CD2(+hi)/CD7(-/+lo) immunophenotype and expressed heterogeneously low levels of CD38 and CD11b; moreover, they were CD57(+) and CD11c(-/+). At this stage, most NK-cells had already reverted into their original CD45RA(+)/CD45RO(-)/HLA-DR(-) phenotype. In summary, we show that the patterns of expression of CD2/CD7, CD57/CD11c, CD38/CD11b, CD45RA/CD45RO, and CD11a/HLA-DR may help us to define the immunophenotypic profiles associated with early and late NK-cell activation phases in 'in vivo' models.     

Total cell content of CR3 (CD11b/CD18) and LFA-1 (CD11a/CD18) in neonatal neutrophils: relationship to gestational age

Neonatal neutrophils (PMN) exhibit a well-documented defect in chemotaxis that is associated with several abnormalities of PMN structure and function, including deficient surface expression of CR3 (CD11b/CD18), a critical adhesion molecule, on chemoattractant- activated PMN. We recently documented that deficient surface expression of CR3 on stimulated neonatal PMN is due principally to a deficiency in total cell content of CR3. In the current studies, we tested the hypothesis that total cell CR3 content of PMN is even more profoundly deficient in premature infants and that PMN CR3 content is directly related to gestational age. A sandwich enzyme-linked immunosorbent assay for CR3 showed that PMN lysates from term neonates ( > or = 37 weeks gestation) contain about 60% of adult PMN levels of CR3, whereas PMN from premature infants (range of 27 to 36 weeks gestation) contained a mean of about 30%, ranging from 10% to 48% (P < .001 for term [n = 6] v premature [n = 11] by unpaired t-test). When the relationship between total cell CR3 and gestational age (n = 15) was analyzed, the correlation coefficient was .94 by linear regression, and the Spearman rank correlation was significant with P < .001. PMN content of LFA-1 (CD11a/CD18) was similarly measured for 14 neonates. Term neonates were equivalent to adults in LFA-1 content of their PMN (99.4% +/- 3.2% of paired adult values, n = 6), whereas prematures (28 to 36 weeks gestation) were deficient, overall (69.1% +/- 10.4%, n = 8, P = .035). Below 35 weeks gestation, LFA-1 values ranged from 26% to 65% of paired adult control values, but no infant of > or = 35 weeks gestation had PMN LFA-1 content that was less than 85% of its adult control. We concluded that CR3 total cell content is more profoundly deficient in premature than in term neonates, that at birth there is a direct relationship between PMN CR3 content and gestational age, and that LFA-1 is deficient only in prematures less than 35 weeks of gestational age. Below 30 weeks gestation, CR3 content of PMN approached that seen in genetic deficiency of the CD18 family of leukocyte integrins, or type 1 leukocyte adhesion deficiency, underscoring the severity of this host impairment in very early preterm neonates.     

Subcellular distribution and mobilization of MAC-1 (CD11b/CD18) in neonatal neutrophils

The CD11b/CD18 (Mac-1) heterodimeric surface glycoprotein contributes to a broad range of adherence-dependent neutrophil inflammatory functions. Previous investigations have indicated that diminished expression or regulation of Mac-1 may underlie abnormalities of stimulated adhesion and chemotaxis of neonatal neutrophils in vitro and inflammatory deficits in human neonates. To define the pathogenic mechanisms contributing to these findings, we compared the distribution and translocation of Mac-1 in subcellular fractions of neonatal and adult neutrophils before and after chemotactic stimulation. The total cell content of Mac-1 and the proportions of Mac-1 in beta fractions (vitamin B12 binding protein-rich granules), pre-gamma fractions (gelatinase-rich granules), or gamma fractions (plasma membrane) of neonatal neutrophils were comparable with those of adult neutrophils. However, after stimulation with N-formyl-methionyl-leucyl-phenylalanine (FMLP; 10 nmol/L, 37 degrees C, 15 minutes), neonatal neutrophils demonstrated (1) diminished translocation of Mac-1 from pre-gamma fractions (P less than .05), and (2) diminished surface expression of Mac-1 (P less than .05), as compared with healthy adult neutrophils. As shown in enzymatic and immunochemical assays, neonatal cells contained significantly (P less than .01) diminished levels of neutrophil gelatinase. In response to FMLP (0.1 to 10 nmol/L, 37 degrees C, 15 minutes), neonatal suspensions also released significantly (P less than .001) less gelatinase, as compared with adult neutrophil suspensions. These observations demonstrate that diminished mobilization of Mac-1 from gelatinase-rich granular pools in neonatal neutrophils is associated with abnormal surface expression of this glycoprotein after chemotactic stimulation. This abnormality may contribute, in part, to abnormal migratory properties of neonatal neutrophils in response to inflammatory stimuli.     

同型半胱氨酸与白细胞黏附分子CD11b、CD18关系的体内外研究

目的 研究探讨同型半胱氨酸(HCY)与炎性指标白细胞黏附分子CD11b/CD18之间的关系.方法 体外研究:用免疫萤光流式细胞仪检测体外HCY和健康人血白细胞表面黏附分子CD11b、CD18的表达.体内研究:选择75例急性冠脉综合征(ACS)患者为ACS组,35例稳定性心绞痛(NACS)患者为NACS组,35名健康人为对照组.采用酶联免疫法测定血浆HCY水平,通过流式细胞仪采用直接免疫荧光法测定白细胞黏附分子CD11b/CD18的表达,同时对血浆C-反应蛋白(CRP)含量和白细胞计数等进行检测和分析.结果 ①HCY在体外明显增加CD11b和CD18在各种白细胞的表达,这种作用随HCY浓度升高而增强.②ACS组血浆HCY水平、平均白细胞表面黏附分子CD11b和CD18表达、CRP含量和白细胞计数显著高于NACS组和对照组(P<0.05).③与对照组相比,稳定型心绞痛组仅HCY水平轻度升高,余差异无统计学意义.结论 ①同型半胱氨酸导致体外白细胞黏附分子的表达;ACS患者同型半胱氨酸、CD11b/CD18,C-反应蛋白含量和白细胞计数明显升高.②炎症可能是ACS发生的重要原因之一,同型半胱氨酸、白细胞、及其CD11b/CD18表达和CRP等共同参与了ACS的发生.