Discontinuous expression of a membrane antigen (HB-7) during B lymphocyte differentiation

We have examined the expression of a cell surface antigen by B lineage cells in human fetuses, newborns and adults using a newly produced monoclonal antibody, HB-7. The HB-7 antigen was found to be a protease sensitive 45,000 MW molecule that appeared to be the same molecule recognized by the OKT-10 antibody. The HB-7 reactive molecule was expressed by all fetal pre-B and B cells, and 50% of newborn blood and adult bone marrow B cells. In contrast, only a small minority of B cells (2–12%) from blood, spleen and tonsil of adults were weakly HB-7⁺. The pokeweed mitogen-responsive B cell precursors of plasma cells were also HB-7⁻, but the HB-7 antigen was re-expressed during the plasma cell stage. We conclude that this antigen is unique among known B cell differentiation antigens in its intermittent pattern of expression during B cell development. The reactivity of the HB-7 antibody with immature, but not mature, B cells makes it well suited for studies of B cell ontogeny.     

Detection of Thy-1 on cell surface of human T lymphoid cell lines by a monoclonal antibody

A mouse IgG2b(kappa) monoclonal antibody (MAb) HB-2S-1 against human brain Thy-1 was secreted by a hybridoma clone after fusion of mouse myeloma cells with spleen cells from a mouse that went through a prolonged immunization procedure before fusion. When tested against isolated human Thy-1 by the enzyme-linked immunosorbent assay (ELISA), MAb HB-2S-1 in culture supernatant showed a titer of over 100,000, and a titer of over 10 million in ascites of a mouse injected with the hybrid clone. By immunoblotting, this antibody was found to bind a doublet of protein bands of approximately 25,000 daltons among all proteins solubilized by deoxycholate (DOC) from membrane of human brain cells. When tested on human lymphoid cell lines by immunofluorescence, MAb HB-2S-1 strongly stained four T lymphoma cell lines, C91-Pl, HUT-102, HUT-78, and C5-MJ; and weakly two leukemia cell lines, MOLT-3 and Jurkat(clone E6-1). It did not stain a third T leukemia cell line, CCRF-CEM; a human B cell line, Raji; a plasmacytoma cell line, HMy2; or a myelomonocytic cell line, HL-60. Peripheral blood lymphocytes from ten normal human adults and the viable T cells isolated from another normal individual were also negative.     

Identification and characterization of a novel membrane activation antigen with wide cellular distribution

A monoclonal antibody, 7F7, raised against the Raji B lymphoblastoid cell line reacted with about 35% of peripheral blood B cells, germinal center B cells, follicular dendritic cells and some vascular endothelial cells. Although not found on resting T cells this antigen was strongly expressed on CD4+ and CD8+ T cells activated with phytohemagglutinin, pokeweed mitogen and anti-T3, and its expression on B cells was enhanced after stimulation with pokeweed mitogen. It is strongly expressed 24 h after stimulation with phytohemagglutinin and its expression is reduced but not eliminated by cyclosporin A treatment. The molecule defined by antibody 7F7 is found on some, but not all, B cell lines, on an HTLV-I-transformed T cell line and on the promyelocytic cell line U937. Immunoprecipitation from externally and metabolically labeled Raji cells revealed a single-chain molecule of 85 kDa.     

Expression of CR2/EBV receptors on human thymocytes detected by monoclonal antibodies

The biologic effects of the third component of complement, C3, are mediated via receptors which specifically bind the enzymatic degradation products resulting from the cleavage of C3. One of the products, C3d, has been associated with binding to the second complement receptor CR2 (CD21). This receptor, which is identical to the receptor for Epstein-Barr virus (EBV), has been primarily found on cells of the B lineage, but not on mature T cells or other cells of erythroid or myeloid lineages. In the present investigation, we report the presence of CR2 on human thymocytes. Indirect immunofluorescence analysis employing monoclonal anti-CR2 antibodies revealed a range of thymocyte reactivity from 15% to 63% in thirteen experiments using cells of different donors. Reactivity was always greater with the monoclonal anti-CR2 (CD21) antibody HB-5 than with two other antibodies which recognize distinct epitopes on the CR2 molecule. Two-color immunofluorescence analysis indicated that the brightest of the HB-5-stained thymocytes also reacted with the monoclonal anti-CD1 antibody T6 (immature thymocyte marker) while some of the duller HB-5-staining cells reacted with the monoclonal anti-CD3 antibody Leu-4 (mature thymocyte marker). Immunoprecipitation of CR2 on thymocytes with antibody HB-5 and polyacrylamide gel electrophoretic analysis revealed a protein of 145 kDa molecular mass which is consistent with the size of CR2 found on B lymphocytes. These findings raise several questions regarding the biologic role of CR2-EBV receptor on cells of the T lineage.     

Two distinct antigen systems in human B lymphocytes: identification of cell surface and intracellular antigens using monoclonal antibodies.

Two distinct antigen systems (L26 and L27) specifically expressed in human B lymphocytes were identified using TB2-2B3 (2B3) and T3-5B3 (5B3) monoclonal antibodies, respectively. Whereas L26 antigen defined by 2B3 were rarely expressed on the surface of B cells but abundant in the cytoplasm, 127 antigens detected by 5B3 was clearly expressed on the cell surface. These two antigens appeared to be restricted in their expression to B cells, as they were found in most B cells but not other cell types including thymocytes, T cells, monocytes and granulocytes. Functional studies demonstrated that L27 was more easily lost from B cells after activation with pokeweed mitogen than was L26. Likewise, plasma cell myeloma, as well as normal plasma cells, was devoid of both L26 and L27, whereas immunoblastic sarcoma of B cell type expressed L26 but not L27. These two antigens co-existed in the same B cell lines including Epstein-Barr virus transformed B cell lines, B cell type acute lymphatic leukaemia (B-ALL) cell line, Burkitt's lymphoma cell lines and myeloma cell lines, but pre-B and common ALL cell lines were entirely negative for both L26 and L27. Immunoprecipitation studies showed that L26 consisted of at least two polypeptide chains with molecular weights of 30K and 33K daltons, which were clearly distinct from HLA-DR antigens. The antigen L27 is presently under study.     

Immunoglobulin Expression in Human Lymphoblastoid Cell Lines with Early B Cell Features

Immunoglobulin expression was studied by direct immunofluorescence and by biosynthesis experiments in two human cell lines Raji and T 5.1. The basic phenotype of these cells was close to that of pre-B cells: large cells with intracytoplasmic IgM with a predominance of mu chains over light chains and no detectable surface immunoglobulins. The apparent molecular weight of heavy and light chains was abnormally large. Immunoglobulins were secreted at a low rate as pentameric IgM in the T 5.1 line and as subunits and free light chains in the Raji line. Spontaneous variations of this phenotype were observed: the cultured cells acquired mu and lambda chains, then additionally delta chains while they progressively lost detectable cytoplasmic mu chains, thus leading to a mature B cell phenotype. Subsequently, the cells had no detectable surface and cytoplasmic immunoglobulins and then they displayed a pre-B cell phenotype again. Attempts to induce further maturation using various potential inducers were unsuccessful.     

A monoclonal antibody against an epitope common to HLA-B locus antigens

A monoclonal antibody G4 that appears to be directed against a determinant common to akl HLA-B locus antigens is described. This antibody reacted with a large panel of B and T lymphocytes and cell lines, but it did not react with two lines that do not serologically express HLA antigens (Daudi and K562) and two lines that expressed A-locus but not B-locus antigens (8402 and HPBMLT). The F(ab′)₂ fragment of G4 blocked B-locus but not A-locus HLA alloantisera. By immunoprecipitation and SDS-polyacrylamide gel electrophoresis G4 reacted with a dimer consisting of a heavy chain of 44,000 daltons and a light chain of 12,7000 daltons.     

抗人淋巴细胞T8抗原样McAb的研制和初步鉴定

用杂交瘤技术,将经人外周血E花环阳性细胞免疫小鼠脾细胞与NS-1骨髓瘤细胞融合后,产生一分泌IgG_1亚型McAb杂交瘤株。其所分泌抗体经微量放射免疫测定及间接免疫荧光法分析,表明它只能与T细胞系、76％的胸腺细胞及22％的外周血T淋巴细胞反应,不与其它各种不同细胞反应。将此抗体所识别入外周血T淋巴细胞亚群与抗Leu-2a识别T8~+细胞、抗Leu-3a识别T4~+细胞比较,发现此抗体与抗Leu-2a识别同一群细胞。此抗体能从T细胞表面沉淀出30KD(还原条件)或78KD(非还原条件)分子,并完全阻断FITC标记抗Leu-2a与T细胞的结合,说明此抗体是识别T8抗原样的McAb。     

Characterization of three different human T cell membrane antigens,two being present on T lymphocyte subpopulations

Heteroantisera were raised in rabbits to thymocytes, HSB2 cells, and Sezary cells. Following absorption with Ia-positive leukemia cells, these sera appeared to be specific for different T cell antigens. Both the anti-HSB2 and the anti-Sezary sera reacted with approximately 50% and the antihymocyte serum with 100% of normal peripheral blood T lymphocytes. None of the sera reacted with B cells. The apparent molecular weights of the antigens being derected were determined by immunoprecipitation followed by SDS polyacrylamide gel eletrophoresis. A dimer of 170,000 daltons consisting of two similar 85,000-dalton polypeptide chains was immunoprecipitated by the anti-HSB2 serum whereas single polypeptides of 53,000 and 64,000 daltons were immunoprecipitated by the anti-Sezary and antithymocyte sera, respectively.     

Identification of an Anti-Human Osteogenic Sarcoma Monoclonal-Antibody-Defined Antigen on Mitogen-Stimulated Peripheral Blood Mononuclear Cells

An anti-human osteogenic sarcoma monoclonal antibody (mouse IgG2b) termed 791T/36 was found to exert complement-dependent cytotoxicity against phytohaemagglutinin (PHA)-stimulated peripheral blood mononuclear (PBMN) cells. This reaction was examined by flow cytofluorimetry using indirect membrane immunofluorescence to detect cell-bound antibody and by measurement of the binding of fluorescein-isothiocyanate-conjugated 791T/36 antibody to cells. The antibody reacted strongly with peripheral blood blast cells induced by PHA, and there was negligible reactivity with resting lymphocytes. Maximum binding was observed after 3 days' culture with PHA, coinciding with maximum DNA synthesis, and this represented of the order of 2 X 10(5) antibody molecules bound per cell. After cell surface radioiodination of PHA-stimulated PBMN cells, detergent lysis and immunoprecipitation of antigen with 791T/36 antibody and Sepharose-protein A, the apparent molecular weight of this antigen was determined to be 72,000 by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. This is identical to that of the 791T/36-defined antigen expressed on various osteogenic sarcoma cell lines [3, 17], and by this criterion the antigen is distinguishable from other cell surface markers of activated human lymphocytes.     

The lipid raft microdomain-associated protein reggie-1/flotillin-2 is expressed in human B cells and localized at the plasma membrane and centrosome in PBMCs

Reggie-1/flotillin-2 is a plasma membrane-associated cytoplasmic protein, which defines non-caveolar raft microdomains. Reggie-1/flotillin-2 is enriched in detergent insoluble (TX100) membrane fractions (DIG), co-localizes with activated GPI-linked proteins and the fyn-kinase in neurons and T cells, and thus apparently participates in the assembly of protein complexes essential for signal transduction. In T cells activated by crosslinking the GPI-linked protein Thy-1 or by crosslinking the ganglioside GM1, reggie-1/flotillin-2 co-localizes with the T cell receptor. To determine whether reggie-1/flotillin-2 is also expressed in B cells, primary B cells from human blood and cell lines representing the developmental stages of pro, pre, mature and plasma B cells were analyzed by Western blotting, RT-PCR and immunofluorescence. Here, we show that reggie-1/flotillin-2 is expressed throughout B cell development, as well as in primary B cells, purified by cell sorting. On non-activated mature B cell Raji cell line we found reggie-1/flotillin-2 are exclusively in the detergent (TX100) insoluble membrane fractions that are staining positive for the raft marker GM1. Immunofluorescence microscopy showed that reggie-1/flotillin-2 is localized at the plasma membrane and marks intracellular spots in PBMCs. Confocal co-localization studies showed that reggie-1/flotillin-2 is associated with the plasma membrane, and the centrosomes (microtubule organizing centers) in these PBMCs. Comparison of reggie-1/flotillin-2 cDNA sequences with the genomic sequence database allowed us to determine the exon/intron structures in mouse and human. The gene organizations are highly conserved suggesting an important function of reggie-1/flotillin-2. Since reggie/flotillin proteins co-cluster with the T cell receptor and fyn kinases upon T cell stimulation, our findings of reggie-1/flotillin-2 in B cells suggest a similar role in B cell function.     

Expression of the fibronectin receptor VLA-5 is regulated during human B cell differentiation and activation.

We examined the expression of VLA-5, a fibronectin receptor, during human B cell development and activation. VLA-5 is a member of the integrin supergene family; VLAs are heterodimers of at least six unique alpha chains sharing a common beta chain; most are involved in cell attachment to extracellular matrix (ECM). A hypothesis of haematopoietic development is that maturing cells leave the bone marrow because of the loss of VLA-5 during differentiation. However, mature B cells are not primarily circulating cells, and the role of ECM receptors in homing to peripheral lymphoid tissue and inflammatory sites is unknown. To examine the expression of VLA-5 during B cell development, cell lines blocked at specific stages of differentiation were evaluated for their synthesis and surface expression of VLA-5 using VLA-5-specific antibody and cDNA probes. VLA-5 mRNA and surface expression were found in the pre-B cell lines, REH and Nall 1, but not in more differentiated Raji cells or in several EBV-transformed peripheral B cell lines. Circulating peripheral B lymphocytes and resting tonsillar and splenic B lymphocytes expressed no VLA-5 by FACS analysis. Interestingly, mRNA and surface expression of VLA-5 were found in SKW, a highly differentiated, IgM-secreting line. In addition, low levels of staining for VLA-5 expression could be demonstrated when tonsillar or peripheral blood B lymphocytes were stimulated by Staphylococcus aureus Cowan (SAC). All cell lines expressed VLA-3 and VLA-4, two other receptors reported to mediate fibronectin binding in some cell types. Thus, our studies provided no evidence for developmental or inflammatory regulation of these receptors. Binding studies, however, demonstrated that adherence of both pre-B REH cells and SKW cells to fibronectin was almost completely inhibited by a monoclonal antibody to VLA-5 alpha. In addition, Raji cells, which lack VLA-5 but express VLA-3 and VLA-4, showed very low level binding to fibronectin. This demonstrates that for some B lymphocytes VLA-5, rather than other possible fibronectin receptors, primarily mediates attachment to fibronectin. These data also suggest that human VLA-5 expression is regulated during B cell development, with expression at a very early stage and then again after activation. This pattern of loss and reacquisition of an ECM receptor may be relevant to normal B cell maturation and to function during immunologic injury.     

Expression of the CD2 molecule on human B lymphoid progenitors.

CD2 expression on human B lymphoid progenitor cells was examined. By immunofluorescence analysis, a small fraction of bone marrow B cells was found to express CD2 on their surface. CD2 expression was not demonstrated on peripheral B cells. Epstein-Barr virus-transformed B cell lines derived from fetal liver at 8 weeks of gestation were analyzed to delineate the expression and function of CD2 at the early stage of human B cell development. Characterization of surface and genomic phenotypes of cell lines revealed that the established cell lines represent at least three different phenotypic characteristics of early B lineage cell: B progenitor, pre B, or early B cell. None of the 18 cell lines and 13 subclones with the phenotype of the early B lymphoid cells initially expressed CD2 antigen. However, CD2 expression was induced by the successive cultivation of some cloned B progenitor cell lines. In spite of the expression of CD2, these clones cell lines were unable to form rosettes with sheep red blood cells. By immunoprecipitation analysis, an identical 50 kDa protein was precipitated with anti-CD2 antibody from the lysates of the radioiodinated CD2+B progenitor cell line and peripheral blood T cells. Anti-CD2 antibody induced significant enhancement of proliferation of the CD2+B progenitor subline. These data indicate that human CD2 is expressed on a fraction of B lineage cells at a very early differentiation stage and may play a role in B lymphopoiesis.     

Characterization of Monoclonal Antihuman-B-Cell Antibody BL13 as an Anti-C3d-Receptor (CR2) Antibody

BL13, a mouse monoclonal IgG1 antibody raised against human B cells, blocked the function of the C3d receptor (CR2) and bound with high affinity (5 X 10(8) L M-1) to CR2 on B lymphoma cells. Following capping with the second antibody, BL13 inhibited C3d-dependent rosette formation of Daudi and Raji cells and C3b-dependent CR2-mediated rosette formation with B lymphoma cells, but did not inhibit CR1-mediated rosettes between C3b-bearing cells and peripheral blood lymphocytes. Competitive binding experiments between biotinylated BL13 or anti-CR2 antibody HB-5 and unlabelled antibodies demonstrated that BL13 bound to an epitope that is distinct from that recognized by HB-5, and closely associated with that recognized by monoclonal antibody anti-B2. BL13 only reacted with some B cells and follicular dendritic cells in germinal centres in human lymph nodes, whereas HB-5 strongly reacted with circulating B cells and bound to most cells in the follicles. These results demonstrate the heterogeneity of antigenically defined CR2.     

A monoclonal antibody reactive with a second epitope of the 67,000-dalton human T cell antigen

Hybridomas were produced against the T-cell CLL derived-cell line, SKW3, by the fusion of hyperimmune spleen cells with P3 myeloma cells. One clone, designated DU-SKW3-1, was shown to produce a murine IgG2b antibody reactive with an antigen expressed on normal thymocytes and peripheral blood T cells. This antigen was not detected on human B cells, erythrocytes, monocytes, granulocytes, or platelets. D-SKW3-1 also reacted with T-ALL, T-CLL, and B-CLL cells, but did not react with common ALL or acute myelocytic or monocytic leukemias. Immunoprecipitation of lactoperoxidase-iodinated, detergent-solubilized PBL demonstrated that DU-SKW3-1 reacted with a protein with an apparent mass of 67,000 daltons (p67), which had identical mobility to the antigen precipitated by L17F12, Cocapping experiments suggested that DU-SKW3-1 and L17F12 detected the same molecule: however, DU-SKW3-1 was unable to block the binding of L17F12. In addition, DU-SKW3-1 reacted with the T lymphocytes of both the great apes and old world monkeys, in contrast to L17F12 and two other p67 monoclonals, T101 and 10.2, which reacted only with the cells of the great apes. This data suggests that DU-SKW3-1 may react with a second, less phylogenetically restricted epitope on the p67 T cell-/CLL-associated molecule.     

Identical forms of the CD2 antigen expressed by mouse T and B lymphocytes

A monoclonal antibody (12-15) reactive with the mouse CD2 was used to study the expression of the antigen in different lymphoid cell subsets. By two-color immunofluorescence using B or T cell-specific reagents and cell sorting in combination with biochemical analysis we provide evidence that the CD2 antigen is present on mouse B and T cells. The antigen is expressed by both subsets at similar density and appears to be biochemically indistinguishable.     

Monoclonal antibodies define the characteristics and cellular distribution of an Ia-associated protein

In a recent report we described the identification of physical associations between Major Histocompatibility Complex (MHC) Class II (Ia) antigens and other structures of Mr 67,000, which were significantly enhanced following brief T-B cell co-culture (1). To further investigate this 67K Ia-associated product, monoclonal antibodies (MAb) were produced against isolated 67K material and their reactivity examined. Cell surface binding by these MAb was detected only after perturbation of the membrane by cellular adherence or following aldehyde fixation, which indicates that the determinant recognized by these mAb is retained in the plasma membrane in a covert fashion. All lymphoid cells tested showed reactivity with the MAb as determined by immunofluorescence and by ELISA, but no binding was detected on bone marrow or peritoneal macrophages. Expression of the antigen reactive with these antibodies followed a similar pattern with established murine cell lines, with T and B cell lines and a pre-B cell line showing reactivity, while no antigen was detected on macrophage-like and fibroblast cell lines. The intensity of antigen expression by normal lymphoid cells was ordered: thymocytes greater than splenic T cells greater than or equal to bone marrow lymphocytes greater than splenic B cells. No correlation was observed between expression of Ia antigens by non-lymphoid cells and expression of the 67K molecule. These observations suggest that this antigen is primarily a marker of lymphoid cells, with the highest expression on cells of the T lymphocyte lineage. Finally, inhibition of antigen-specific, MHC-restricted T-cell activation by the MAb directed against the 67K structure suggests an important functional role for this interesting molecule originally identified by its physical association with Ia following T-B cell interactions.     

以人B淋巴细胞株Raji、人早幼粒白血病细胞株HL60为底物检测抗细胞膜DNA抗体在系统性红斑狼疮中的诊断价值

目的 比较以人B淋巴细胞株Raji、人早幼粒白血病细胞株HL60为底物检测抗细胞膜DNA抗体(抗cmDNA抗体)在系统性红斑狼疮(SLE)中的诊断价值.方法 分别以人B淋巴细胞株Raji、人早幼粒白血病细胞株HL60为底物,用间接免疫荧光法(IIF)检测306例SLE患者、192例疾病对照组患者、50例健康对照组血清中的抗cmDNA抗体.结果 以人B淋巴细胞株Raji为底物检测抗cmDNA抗体在306例SLE患者中阳性率为72.5%.而在脊柱关节病、类风湿关节炎、原发干燥综合征和其他结缔组织病中的阳性率分别为5.8%、10.0%、13.3%、15.0%.以人早幼粒白血病细胞株HL60为底物检测抗cmDNA抗体在306例SLE患者中阳性率为76.1%.而在脊柱关节病、类风湿关节炎、原发干燥综合征和其他结缔组织病中的阳性率分别为9.6%、11.1%、20.0%、22.5%.两种细胞为底物检测抗cmDNA抗体在健康对照组中阳性率均为0.抗cmDNA抗体阳性率在SLE组明显高于疾病对照组及健康对照组(P<0.01).以Raji及HL60两种细胞株为底物检测SLE患者抗cmDNA抗体,敏感性分别为72.5%和76.1%,特异性分别为91.7%和86.8%,差异均无统计学意义(P>0.05).Raji及HL60细胞培养、冻存及复苏方法相似,但Raji细胞较HL60细胞更易复苏.在荧光显微镜下观察,Raji细胞比HL60细胞表达效果更好.结论 抗cmDNA抗体是一种诊断阳性率较高的SLE血清学标记物之一.选择Raji细胞株为底物检测SLE患者的抗cmDNA抗体较HL60细胞株更有优势.

Abstract：

Objective To compare the significance of DNA-associated autoantibodies to cell membrane(cmDNA)in systemic lupus erythematosus(SLE)detected with indirect immunofluorescence on human B lymphoma cell line Raji and pmmyelocytic line HL60.Methods Indirect immunofluorescence assay both on cell line Raji and HL60 was used to measure anti-cmDNA antibodies in sera of 306 SLE patients.192 patients with other rheumatic diseases and 50 healthy controls.Results Indirect immunofluorescence assay on cell line Raji was used to measure anti-cmDNA antibodies.72.5% SLE and 10.4% other rheumatic diseases were positive for anti-cmDNA,but negative in 50 blood donors(P<0.01).Indirect immunofluorescence assay on cell line HL60 was used to measure anti-cmDNA antibodies,76.1% SLE and 16.7% other rheumatic diseases were positive for anti-cmDNA,but negative in 50 blood donors(P<0.01).The sensitivity of anti-cmDNA were 72.5%and 76.1%,respectively.The specificity of anti-cmDNA was 91.7% and 86.8%,respectively.There was no significant difference in sensitivity and spocificity(P>0.05).The methods of culture,freeze and resuscitation on the two cells were similar.but cell line Raji was easier to resuscitate than cell line HL60.Observing with fluorescence microscope.we find that cmDNA was expressed on the both cells and the staining was stronger on cellline Raji than HL60.Conclusion Anti-cmDNA antibody has high positivity which is one of the most valuable marker in the diagnosis of SLE.We recommend to measure anti-cmDNA antibodies with indirect immunofluorescence assay on cell line Raji rather than HL60.