老化红细胞的分离和鉴定

根据本实验室的工作,老化红细胞表面可结合自身IgG的特点,建立了一种新的分离年轻及老化红细胞的方法。由于Protein A可与IgG有特异结合,用活化的Sepharose 6MB结合Protein A制成亲和层析柱,以此分离老化红细胞。同时对分离的红细胞作了谷胱甘肽还原酶、谷胱甘肽过氧化物酶、过氧化氨酶、6-磷酸脱氢酶的活性和变形性及吞噬情况的比较。     

红细胞老化过程中囊泡化作用的探讨

红细胞存活120天,在体内老化的过程中,不断产生囊泡,膜脂及膜蛋白随囊泡丢失,红细胞逐渐形成球形,易破溶而消亡。本文用密度梯度方法将年轻及老化红细胞分离,加Ca~(2+)及钙离子载体(A_(23187))诱导红细胞囊泡化,比较年轻及老化红细胞囊泡化后及释放出的囊泡膜蛋白的变化,观察囊泡化后红细胞的变形性、溶血度及被吞噬细胞吞噬的能力。实验结果发现在Ca~(2+)诱导下年轻红细胞比老化者更易囊泡化;释放的囊泡中主要含区带3蛋白及少量区带4.5及4.9,另外,区带7及Hb明显增多,囊泡化后的红细胞膜有聚集。囊泡化后的红细胞变形性明显降低,易溶血及被吞噬细胞吞噬的量明显增多。     

CD47-SIRPα在人类红细胞老化与吞噬过程中的作用

探讨CD47-SIRPα在人类红细胞衰老与吞噬过程中的作用。采用Western blot检测体外4℃和37℃保存红细胞(RBC)及老化过程中红细胞膜上CD47的表达量;用单核细胞单层分析试验(monocyte monolayer assay,MMA)观察人THP-1单核细胞系对不同年龄段红细胞和CD47抗体F(ab’)2端封闭红细胞的吞噬情况及Western blot检测THP-1细胞上SIRPα磷酸化情况。结果发现,无论是在体内老化还是体外老化过程中,红细胞膜上CD47的表达量均出现显著下降趋势,随着保存时间的延长,CD47的表达量最大可下降82.64%(4℃保存情况下);THP-1细胞对不同年龄段红细胞的吞噬情况存在差异性,更易吞噬年老红细胞,吞噬率为35.32%,对年轻红细胞的吞噬率为13.72%(n=7,P<0.02);对新鲜红细胞的吞噬率为2.22%,对CD47抗体F(ab’)2端封闭红细胞的吞噬率为31.51%(n=7,P<0.02);吞噬不同年龄段红细胞后,THP-1细胞上磷酸化SIRPα量不同,与吞噬年轻红细胞相比,吞噬年老红细胞后,磷酸化SIRPα的量下降了57.12%。表明人类红细胞的老化与吞噬过程和CD47-SIRPα相互作用存在密切关系。     

流式免疫微球技术定量检测人血清胰岛素方法学研究和评价

目的建立流式免疫微球定量检测人血清胰岛素的方法并对其重复性实验和线性实验以及最低检测限进行评价。方法将兔抗人胰岛素单克隆抗体标记在微球表面制备免疫诊断微球,与血清中胰岛素结合后,加入荧光标记的鼠抗人胰岛素单克隆抗体,使微球表面呈现荧光,并通过流式细胞仪检测其平均荧光强度(mean fluorescent intensity,MFI)并记录。结果微球表面MFI与人血清胰岛素浓度呈正比,流式免疫微球技术检测同一标本的重复性实验变异系数以及最低检测限均低于酶联免疫吸附试验,流式免疫微球技术线性范围大于酶联免疫吸附实验。结论流式免疫诊断微球技术可用于人血清胰岛素定量检测,其测定重复性,线性范围和灵敏度均优于酶联免疫吸附试验。     

人淋巴细胞Fc段受体流式细胞仪测定

本文研究了正常人外周血淋巴细胞(PBL)表面IgGFc段受体(FcrR)和IgMFc段受体(FeHR)。细胞荧光标记与常规免疫荧光法不同,以Avidin-Biotin放大体系为荧光载体标记细胞,使对Fc段受体的测定更灵敏和特异。取48名健康成人静脉血,制备单个核细胞。细胞和AggIgG-Biotin(生物素化聚合IgG),IgM-Biotin(生物素化IgM)及Avidin-FITC(结合异硫氰酸荧光黄的Avidin)分二步孵育,用荧光标记淋巴细胞表面FcrR与FcμR。流式细胞仪分析结果显示,正常人FcrR+PBL (X±SD)为36.63±9.07％,FcμR+PBL为12,76±5.39％。我们用自己建立的Fc段受体(FcR)流式细胞仪分析法,对国人淋巴细胞表面FcrR与FcμR的研究,为探索FcR对免疫系统的调节作用,及一些免疫性疾病的发病机理奠定了一定基础。     

抗角蛋白抗体进入活细胞的共聚焦显微镜观察

目的：观察抗角蛋白抗体能否进入活细胞。方法：以鼠单克隆抗体（mAb)IgG作用于培养中的人Tca8113细胞，以黑素瘤细胞和抗HBsAg抗体作用的Tca细胞作为阴性对照。细胞固定后与FITC标记的羊抗鼠IgG结合，用荧光显微镜及共聚焦显微镜，观察细胞的荧光着色。结果：抗角蛋白mAb作用的Tca8133细胞胞浆呈亮绿色，着色较均匀，细胞核未见着色。两种对照均未见着色。结论：抗角蛋白mAb可进入活细胞，并结合于胞浆成分。     

老化红细胞变形能力与膜钙依赖中性蛋白酶活性的关系

研究表明,老化红细胞变形能力明显降低,且其降低与血红蛋白浓度增高及膜弹性降低有关［１］。红细胞膜钙依赖中性蛋白酶（Ｃａｌｐａｉｎ）和它的内源性抑制剂（Ｃａｌｐａｓｔａｔｉｎ）形成红细胞中一个蛋白水解系统,参与红细胞中的信号传导,调节细胞形状、体积和细胞膜通透性,与高血压、细胞老化等生理、病理现象密切相关。Ｃａｌｐａｉｎ可限制性水解红细胞膜骨架蛋白和其它膜内蛋白,导致红细胞损伤［２,３］。而老化红细胞变形能力降低与Ｃａｌｐａｉｎ的关系尚不清楚,为此我们检测了４２例健康人老化及年轻红细胞变形能力、Ｃ…     

分泌性IgA能介导抗体依赖性细胞介导细胞毒性

虽然已知分泌性IgA可阻止微生物粘附于粘膜表面,但是以前没有证明抗原特异性分泌性IgA在与抗原相互直接作用后,能介导细胞毒性。本文报导作者从超免疫血清和免疫肠道分泌物分别提纯抗志贺氏菌脂多糖(LPS)IgG和分泌性IgA。用LPS包被鸡红细胞(CRBC),并用与提纯的IgG和IgA部分的血凝反应检验。应用酶联免疫吸附试     

辣根过氧化物酶结合物的质量鉴定

辣根过氧化物酶(HRP)和抗HBs(山羊IgG)按戊二醛二步法、苯醌法和改良过碘酸盐法交联反应分别制成酶结合物,用琼脂扩散、二氨基联苯胺染色法对酶结合物定性,并测定其HRP浓度和活性、羊IgG浓度和抗HBs免疫活性,阐明标记率(A403nm/A280nm)的含义,通过ELISA检测表明标记率可作为评价酶结合物质量的指标,且其计算简便。     

老化红细胞变形能力与膜钙依赖中性蛋白酶活性的关系

研究表明，老化红细胞变形能力明显降低，且其降低与血红蛋白浓度增高及膜弹性降低有关，而与红细胞膜钙依赖中性蛋白酶（Ｃａｌｐａｉｎ）活性的关系尚不清楚。为此，我们检测４２例健康人老化红细胞及年轻红细胞变形能力、Ｃａｌｐａｉｎ和Ｃａ２＋－ＡＴＰ酶活性及膜收...     

An age-specific cell antigen is present on senescent human red blood cell membranes. A brief note

Immunoglobulin G autoantibodies selectively bind to senescent human red blood cells (RBC) in situ and initiate their removal by phagocytosis. In this paper, we characterize the IgG binding receptor appearing on senescent RBC using glycophorin-enriched vesicles prepared by Triton X-100 extraction of young, middle-aged, and old RBC populations. These vesicles contain all known sialoglycoproteins and trace contaminants of other proteins. IgG binds predominantly to vesicles from old cells, as determined by both ¹²⁵I-labeled protein A binding to IgG molecules and an erythrophagocytosis-inhibition assay. Addition of lipids does not alter IgG binding. Liposomes prepared from lipids of young and old cell fractions do not bind significant amounts of IgG. IgG binding is reduced following trypsin treatment of vesicles. The data suggest that the age-specific cell antigen is a protein which co-purifies with sialoglycoproteins, but is not identical with glycophorin. Since it is extracted predominantly from senescent cells, a chemical modification within the membrane may either form the age-specific cell antigen during aging or render it accessible during senescence.     

Human IgM Anti-IgM Cytotoxin for B Lymphocytes

Blymphocytes were shown previously to be killed at 5*C by some autologous and allogeneic human sera. We show here that such cold cytotoxins are directed against immunoglobulins on the surface of B lymphocytes. The activity is partially removed by passing serum through IgG-coupled Sepharose and usually completely removed by passing serum through IgM-coupled Sepharose. Activity is regained from the columns by acid elution and IgM inhibits the cytotoxicity of these eluates. 125I-labeled eluates bind to IgG- and IgM-coupled Sepharose beads and binding is inhibited by IgM and to a lesser degree by IgG thus showing a primarily more avid binding to IgM as compared to IgG. Furthermore, the 12SI-labeled cytotoxic eluates recognize the same determinants) on IgM and IgG. We suggest that IgM anti-IgM antiimmunoglobulin may regulate immune reactivity by binding to B-lymphocyte surfaces.     

Effect of membrane-bound IgG and desialysation in the interaction of monocytes with senescent erythrocytes

Abstract Determination of the erythrocyte lifespan is a complex process affected by many cellular parameters. In the present study we measured and characterised the red blood cell (RBC) membrane proteins, mainly band 3, and quantified membrane-bound IgG in senescent RBC (SeRBC) and young RBC (YRBC). We also investigated, through a functional assay, the interaction between SeRBC and peripheral blood monocytes. We applied this erythrophagocytosis assay to study the phagocytosis of desialysed RBC. The results obtained showed no changes in the protein content between SeRBC and YRBC and no differences when examining membrane proteins by SDSPAGE. Then, considering that the accumulation of autologous IgG on RBC membrane provides a direct mechanism for the removal of SeRBC, we measured the IgG content of intact RBC using an enzyme-linked antiimmunoglobulin test finding that the number of IgG molecules bound to SeRBC was significantly higher than that observed for YRBC. The increase observed in the percentage of erythrophagocytosis with SeRBC and sensitised RBC (SRBC) confirmed the involvement of autologous IgG in the selective removal of erythrocytes. We also observed a higher percentage of monocytes with phagocytosed and adherent RBC (AM) obtained with neuraminidase-treated RBC than those obtained with YRBC. This finding suggests that a decrease in sialic acid content of SeRBC may be involved in physiological erythrophagocytosis     

Complement fixation by small, DNase-resistant DNA-anti-DNA immune complexes

125I-ds DNA-anti-DNA immune complexes (IC) formed at antibody excess and containing DNA of 300-350 base pairs (bp) fixed complement, incorporated C3b and bound to the C3b receptors (CR1) on human red blood cells (RBC). When the IC were treated with DNase to generate small, DNase-resistant IC, some of the IC incorporated C3b, but did not bind to RBC. In order to examine C3b incorporation and RBC binding by IC of specific sizes, the DNase treated IC were fractionated by sucrose density gradient (SDG) ultracentrifugation. Small IC containing one, two, three or four IgG molecules per fragment of 125I-ds DNA were identified by autoradiography after electrophoresis of the SDG fractions on 3-12% linear polyacrylamide gradient gels. The SDG fractions were tested for C3b incorporation and RBC binding ability. There was neither C3b incorporation nor RBC binding activity in fractions which corresponded to 9-11S (containing IC with one IgG/DNA). Fractions which corresponded to 12-22S (containing IC with up to four IgG/DNA fragment) demonstrated increased C3b incorporation with increased size, but did not show significant RBC binding activity. Fractions with IC containing four or more IgGs (22-24S) incorporated C3b and bound to RBC at approximately the same level. It is concluded that DNase digested IC which contain three-four IgG/DNA fragment are large enough to activate complement and incorporate C3b, but are too small to bind to RBC CR1. These IC could therefore escape rapid clearance from the circulation via the erythrocyte CR1 clearance mechanism. Such IC could persist in the circulation and potentially elicit pathogenic effects in patients with systemic lupus erythematosus.     

The ability of normal human monocytes to phagocytose IgG-coated red blood cells is related to the number of accessible galactosyl and mannosyl residues in the Fc domain of the anti-red blood cell IgG antibody molecules

The percentage of normal human monocytes (MCs) that are able to form rosettes with, and subsequently phagocytose, IgG-coated red blood cells (RBCs) has been determined in vitro using five batches of anti-RBC IgG antibodies. These antibodies differed from each other by their capacity to bind to lectins recognizing two of the oligosaccharide structures of the Fc domain, namely, peanut agglutinin (PNA) and concanavalin A (ConA) which specifically bind to beta-galactosyl and alpha-mannosyl residues, respectively. The threshold between high (H) and low (L) binding capacities (BC) was arbitrarily fixed at 15% of mean specific binding. For each level of RBC sensitization tested (1500-6000 Ab molecules/one RBC), the percentage of MCs binding at least three IgG-RBCs was similar whatever the IgG Ab preparations used. In contrast, the percentage of MCs capable of phagocytosing at least three IgG-RBCs coated with 3000, 4500 and 6000 IgG/cell, as well as the phagocytosis index (number of IgG-RBCs ingested/100 MCs) of IgG-RBCs coated with 1500, 3000, 4500 and 6000 IgG/cell, were significantly lower (P less than 0.01 at least) using IgG Ab molecules with either [(PNA-H)(ConA-H)] BC, [(PNA-L) (ConA-H)] BC or with [(PNA-L)(ConA-L)] BC than the corresponding values measured using RBCs coated with IgG Ab molecules exhibiting [(PNA-H)(ConA-L)] BC. The binding to MCs of 125I-labelled anti-RBC IgG Ab molecules exhibiting different binding profiles to PNA and to ConA was studied by Scatchard plot analysis. A single class of binding sites was observed in each case. MCs bound a mean of 23,000 IgG molecules with a mean association constant (Ka) for IgG binding of about 1.4 X 10(8) M-1. These data indicate that terminal (and/or accessible) galactosyl and mannosyl residues of IgG Ab molecules play a role in the ingestion of IgG-RBCs by human MCs, despite the fact IgG Ab binding to IgG(Fc) receptors is not significantly affected. Thus, when studying the phagocytosis of IgG-coated RBC by human MC monolayers, the assay should be performed not only using similar RBC/MC ratios and IgG coating values, but also with IgG antibodies having comparable mean PNA and ConA binding capacities.     

Immune elimination of aging platelets by autologous monocytes: role of membrane-specific autoantibody

Membrane-bound IgG was found only on old populations of platelets from normal individuals. This IgG could be dissociated from senescent cells by repeatedly heating the cells. Heat-eluted IgG (He-IgG) prepared from senescent red blood cells was capable of binding to either heat-treated old platelets or Vibrio cholerae neuraminidase (VCN)-treated young platelets, suggesting expression of a common age-dependent antigen on the senescent red blood cells and old platelets. We analyzed the role of membrane-bound IgG in the immune elimination of aging platelets by direct phagocytosis of different platelet subpopulations by autologous monocytes in vitro. While removal of He-IgG from old platelets inhibited their phagocytosis, preincubation of either heat-treated old or VCN-treated young platelets promoted phagocytosis of these cells by autologous monocytes. The phagocytosis of senescent cells required intact IgG on these cells. Either removal of Fc fragments from He-IgG or treatment of autologous monocytes with Fc fragments prior to the phagocytosis assay resulted in a marked reduction of phagocytosis (greater than 75%). We conclude that Fc receptors on the monocytes and the presence of membrane-specific IgG are crucial elements for immune elimination of senescent platelets.     

The relationship between sialic acid content and peanut agglutinin binding on senescent and enzyme treated human erythrocytes

Young, old and neuraminidase treated human red blood cells (RBC) were investigated with peanut agglutinin (PNA), a lectin with a specificity similar to that of serum T-agglutinin. The effect of serum agglutinins on this interaction was also investigated. The density and distribution of PNA receptors were evaluated by agglutination with PNA and binding of ferritin-conjugated PNA (PNA-F), or PNA labeled with radioactive iodine ([¹³¹I]PNA). The results were correlated with the distribution of membrane bound sialic acids, as evaluated by chemical analysis and rate of agglutination with poly-l-lysine (PLL). Untreated RBC of all ages did not agglutinate with PNA and failed to bind PNA-F and [¹³¹I]PNA. Treatment of young RBC with neuraminidase, which resulted in reduction of membrane-bound sialic acids to an extent similar to that of physiologically aged RBC, resulted in the concomitant exposure of PNA binding sites and in the agglutination of these cells by autologous serum. Pretreatment of the neuraminidase treated RBC with autologous serum resulted in partial inhibition of the binding capacity of PNA on the RBC. The results indicate that the normal age-related loss of sialic acids in circulating RBC is not identical with enzymatic removal of sialic acids by neuraminidase. The observations suggest that different mechanisms are functional in the recognition and sequestration of old RBC and of RBC treated with neuraminidase.     

Isolation of Binding Sites to Glycophorin from Mycoplasma pneumoniae Membranes

Sialoglycoproteins are major receptor sites for attachment of Mycoplasma pneumoniae to respiratory epithelium and erythrocytes (RBC). We used glycophorin, the major sialoglycoprotein of human RBC, as a ligand in affinity chromatography for the isolation of the binding sites from M. pneumoniae membranes. Membranes isolated from M. pneumoniae cells, radioiodinated by the lactoperoxidase technique, were treated with 0.5% deoxycholate. The insoluble residue, exhibiting an increased capacity to bind to RBC, was solubilized by 0.1% sodium dodecyl sulfate. The solubilized material was subjected to chromatography on a glycophorin-Sepharose column. The fraction retained on the column was eluted with 0.2% sodium dodecyl sulfate. It lacked the high-molecular-weight polypeptides and was highly enriched with two polypeptides (apparent molecular weights, 45,000 and 25,000). The eluted fraction exhibited a high capacity to bind to glycophorin-Sepharose beads and a lower capacity to bind to RBC. The binding of the eluted fraction to RBC was almost completely abolished by glycophorin, but not by its hydrophobic moiety. Binding of the fraction to glycophorin-Sepharose beads was inhibited to about the same extent by both glycophorin and its hydrophobic moiety, suggesting that components of the eluted fraction are also capable of binding to the hydrophobic moiety of glycophorin, which is apparently exposed on the beads but not on the RBC surface.     

Non-complement-dependent adsorption of soluble immune complexes to human red cells

Heat aggregated IgG and soluble immune complexes (IC) prepared by combining human serum albumin with rabbit anti-serum albumin and tetanus toxoid with rabbit antiserum to tetanus toxoid were shown to bind to human O+ RBC. The binding was greater for soluble IC prepared at antigen excess, and although it was usually maximal when IC were pre-opsonized, it could also be demonstrated using non-opsonized heat aggregated IgG or soluble IC prepared in the absence of complement. These observations suggest that two types of receptors may be involved in binding of soluble IC to human RBC: the classical C3b receptor, and a non-complement-dependent receptor, perhaps recognizing the Fc region of the immunoglobulin molecule exposed after heat aggregation or antigen-antibody reaction.     

A single amino acid distinguishes the high-responder from the low-responder form of Fc receptor II on human monocytes.

The low-affinity Fc receptor on human peripheral blood monocytes (Fc gamma RIIA) is polymorphic with respect to its ability to bind murine IgG1. The two allelic forms of the receptor, high responder (HR) and low responder (LR), yield characteristic patterns after isoelectric focusing and react differently with the anti-Fc gamma RII monoclonal antibody (mAb), 41H16. We recently cloned cDNA encoding the extracellular domains of Fc gamma RIIA on monocytes from one HR and two LR donors, and found that they differed at only a single base. The cDNA isolated from the HR donor had a G at position 519 and would be expected to encode an aginine at residue 133 in the mature protein, while the cDNA isolated from both LR donors had an A at position 519 and would be expected to encode a histidine at the same residue. To determine whether this single amino acid substitution actually accounts for the functional polymorphism involving Fc gamma RIIA, we transfected COS cells with full-length HR and LR Fc gamma RIIA cDNA, and examined them for their ability to react with anti-Fc gamma RIIA mAb and to bind red blood cells (RBC) coated with either murine IgG2b or murine IgG1. Whereas COS cells transfected with either the HR cDNA or the LR cDNA reacted with the anti-Fc gamma RII mAb, IV.3, and bound murine IgG2b-coated RBC, only COS cells transfected with the HR cDNA formed rosettes with murine IgG1-coated RBC and reacted strongly with mAb 41H16. A total of nine LR donors were identified, and all were homozygous for the A substitution at position 519. We conclude that at an A at position 519 in the cDNA encoding Fc gamma RIIA is the primary molecular basis for the LR form of the receptor, and that the amino acid at residue 133 determines whether Fc gamma RIIA efficiently binds murine IgG1.