Membrane Ig-cytoskeletal interactions. I. Flow cytofluorometric and biochemical analysis of membrane IgM-cytoskeletal interactions

Membrane IgM (mIgM) and mIgD are the receptors for Ag on the surface of B lymphocytes, mIg is soluble in detergent; however, when mIg is cross-linked with anti-Ig, the mIg becomes associated with the cytoskeletal matrix and is rendered detergent-insoluble. By a novel flow cytofluorometric assay and by biochemical analysis, it has been shown that anti-isotype-specific antibodies induce mIgM and mIgD to associate with the cytoskeleton of B lymphocytes in an isotype-specific fashion. The detergent solubility of other prominent B lymphocyte surface proteins, such as class I and class II MHC proteins were unaffected by cross-linking of mIg. A panel of mu-specific mAb was analyzed for their ability to induce mIgM-cytoskeletal association. Although all mAb bound mIgM, only three out of seven rendered mIgM cytoskeletally associated. Further analysis revealed a strict correlation in the capacity of mu-specific mAb to induce capping and to induce the association of mIgM with the cytoskeleton.

Heterogeneity of a murine B cell lymphoma. Isolation and characterization of idiotypic variants

mAb directed toward the idiotype of the 38C13 murine B cell lymphoma can be used to treat and cure a high percentage of mice challenged previously with an otherwise lethal dose of tumor cells. Tumors developing in animals despite antibody therapy were examined by immunofluorescence and found to demonstrate either loss of surface Ig, or expression of an altered idiotype that no longer bound the antibody used for treatment. Further immunofluorescence analysis of the variant tumors revealed individual patterns of cross-reactivity with anti-38C13 idiotype mAb other than that used for therapy. The variant tumor cells were fused to myeloma cells and hybrids were isolated which secreted large quantities of the altered idiotype proteins. Polyclonal antibodies and mAb prepared against the mutant proteins demonstrated cross-reactivity with the original 38C13 protein and its other variants. But the variants and wild type cells could be distinguished from each other by their patterns of reactivity with the panels of anti-idiotype antibodies. Differences in apparent m.w. were demonstrated in the L chains of each of the mutant proteins. Southern blot analysis of the H chain locus of these mutants established that they were all clonally related; however, the L chain loci were grossly different. Thus, rare cells with alteration in their Ig L chain genes and expressed proteins can give rise to idiotype variants in this B cell tumor.

Membrane IgM: interactions with the cortical cytoskeleton in the human lymphoblastoid cell line WiL2

Cell-surface IgM (antigen receptor) sediments with the membrane fraction following osmotic lysis and homogenization of cells of the human lymphoblastoid cell line WiL2. In nonreducing buffers, SDS PAGE analysis of membrane pellets demonstrates that "native" membrane IgM exists as a dimer. In contrast to osmotic lysis, lysis of cells with the nonionic detergent Triton X-100 releases approximately 90% of the membrane-bound IgM into the supernatant; approximately 10% of the IgM pellets with the cytoskeletal fraction on centrifugation. Ligand challenge with either mu-chain-specific antibodies or concanavalin A induces a change in the state of membrane IgM making it refractory to detergent extraction, such that 43% of the IgM pellets during centrifugation. This ligand-induced retention of IgM is significantly diminished by the microfilament-disrupting agent cytochalasin D, whereas pretreatment of cells with sodium azide or colchicine results in no significant change in the percentage of membrane IgM retained by Triton X-100 residues. These results indicate that retention of IgM involves an association with the cortical actin-based cytoskeleton. Investigation of the structural basis for ligand-induced Triton X-100 retention of membrane IgM by using ferritin-conjugated antibodies, myosin subfragment S1, and stereo-imaging electron microscopy has revealed linkages between ligand-receptor (antigen-IgM) complexes and elements of the cortical actin-based cytoskeleton.

Properties of a specific interleukin 1 (IL 1) receptor on human Epstein Barr virus-transformed B lymphocytes: identity of the receptor for IL 1-alpha and IL 1-beta

The properties of specific human interleukin 1 (IL 1) receptors on human Epstein Barr virus-transformed B lymphocytes (EBV-B) were studied. Purified human IL 1-beta from a myelomonocytic cell line (THP-1) was labeled with 125I by the Bolton-Hunter method without detectable loss of biological activity. Among four EBV-B cell lines tested, a pre-B cell type (VDS-O) specifically bound the highest amount of 125I-IL 1-beta. Maximal binding was reached within 20 min at 4 degrees C. Scatchard plot analysis of the binding of 125I-IL 1-beta to VDS-O cells yielded a Kd (dissociation constant) of 2.4 to 5.9 X 10(-10) M with 110 to 220 binding (receptor) sites/cell. The binding of 125I-IL 1-beta to VDS-O cells was also inhibited by F(ab)'2 fragments of anti-human IL 1 and recombinant human IL 1-alpha, as well as by unlabeled human IL 1-beta but not by recombinant lymphotoxin, recombinant tumor necrosis factor, or phorbol myristic acid, suggesting that IL 1-alpha and IL 1-beta bind specifically to the same receptor. The m.w. of IL 1 receptor on human EBV-B cells was estimated to be 60,000 by both the chemical cross-linking method and high pressure liquid chromatography (HPLC) gel filtration analysis of receptor extracted from membrane enriched fraction by a non-ionic detergent (CHAPS). The isoelectric point of solubilized human IL 1 receptor was 7.3 on HPLC chromatofocusing. The evidence of existence of IL 1 receptor on human EBV-B cells additionally supports the hypothesis that IL 1 may be an autocrine signal for these cells.

Mesenteric lymph nodes: cells with surface and sytoplasmic immunoglobulins

The distribution and morphology of cells with surface and cytoplasmic immunoglobulins were investigated in mesenteric lymph nodes (MLN) from rats, using both frozen and (fixed) paraffin sections, with a two-step immunoperoxidase technique. Anti-IgA, -IgE, -IgG and -IgM sera were used. Surface Ig-cells (sIg) of all four isotypes studied were found in MLN, mainly localized in the interfollicular area and within the follicle corona. The percentages of sIgA, IgE, IgG and IgM were about 15, 5, 45 and 35%, respectively. In addition, sIgM- and sIgG-cells were found around high endothelial venules. The percentages of cells containing IgA, IgG or IgM (cIg-cells) were about 60, 25 and 15%, respectively; only a few cIgE-cells were found. cIg-cells were not only present in the interfollicular areas and the medulla but also within the germinal centers of the follicles. These results are discussed with regard to the interaction between Peyer's patches (PP) and MLN.

Ultrastructural localization of immunoglobulins in hairy cell leukemia

Neoplastic cells from 13 cases of hairy cell leukemia were investigated for immunoglobulin production and lysozyme activity by an electron-immunoperoxidase technique. In 10 cases cytoplasmic immunoglobulins were found, but lysozyme activity was absent in all cases. Immunoglobulins were detected in the perinuclear space and endoplasmic reticulum and at the surface of hairy cells. Of the cases in which immunoglobulins were detected in hairy cells, nine were positive with IgM antiserum and one with IgG antiserum. The immunoglobulins were monoclonal in all cases; six were positive with lambda antiserum and three with kappa antiserum. The class and type of surface immunoglobulins were identical to those of cytoplasmic immunoglobulins in the hairy cells. These results support the conclusion that hairy cells are commonly derived from immunoglobulin-producing B cells at an earlier stage of differentiation than plasma cells.

Expression of C3d receptors during human B cell differentiation: immunofluorescence analysis with the HB-5 monoclonal antibody

We have examined human B lymphocytes at different stages of differentiation for the expression of surface receptors for the C3d fragment of complement. C3d receptors (C3dR) were identified by indirect immunofluorescence using the HB-5 monoclonal antibody, which recognizes a 145,000 m.w. C3dR molecule on B lymphocytes. Pre-B and immature B cells from fetal bone marrow and liver did not express C3dR, whereas a small subpopulation (25%) of B cells in fetal spleen were C3dR+. Approximately 50% of the B cells in adult bone marrow were C3dR+, whereas the more mature B cells in the blood of newborns and adults and in peripheral lymphoid tissue of adults uniformly expressed the C3dR. Activated B cells responsive to T cell-derived differentiation factors were C3dR+, whereas plasma cells rarely expressed C3dR. T cells, NK cells, erythrocytes, and myelomonocytic cells did not express detectable surface C3dR. These results suggest that in hematopoietic and lymphoid tissues, the expression of C3dR is a specific feature of relatively mature lymphoid cells of B lineage.

A phosphatidylethanolamine-containing complex on human B cells that mediates rosette formation with mouse erythrocytes

The maturation-associated human B cell rosette receptor (MER) for mouse erythrocytes has been solubilized from B cells by mild trypsinization. It specifically agglutinates mouse red cells. Material with hemagglutinating activity partitioned into the lipid-soluble phase of a Folch partition of the trypsin extract was sensitive to phospholipase C and alkali, and on two-dimensional thin layer chromatography, it co-migrated principally with phosphatidylethanolamine (PE). Phosphatidylcholine, the major lipid present, was inactive. The relationship of phospholipid structure to hemagglutinating activity has been described. PE in the crude trypsin extract was associated with unidentified glycoprotein and albumin. Material containing hemagglutinating lipid bound to a wheat germ lectin-Sepharose column and was released by N-acetylglucosamine, indicating that the PE was complexed with glycoprotein. When the crude trypsin extract or eluate from the lectin column was extracted with aqueous phenol, hemagglutinin in the aqueous phase no longer bound to wheat germ lectin-Sepharose; however, albumin was greatly enriched, indicating that some of the PE exists in a complex with albumin. The molar ratio of PE to albumin was approximately 200:1. After delipidation, this albumin (in molar excess) inhibited hemagglutination by PE in the same way as a recently described subclass of serum albumin. Studies with phospholipase-treated B cells were also consistent with PE being the MER. We conclude that MER is PE, existing in a complex containing glycoprotein and a subclass of albumin. The capacity to form rosettes can be transferred to nonrosetting Raji B cells by the complex, but not pure PE, indicating that the proteins may be involved in orienting PE correctly for it to function as the MER.

The murine lymphocyte receptor for IgE. I. Isolation and characterization of the murine B cell Fc epsilon receptor and comparison with Fc epsilon receptors from rat and human

The Fc receptor for IgE (Fc epsilon R) on murine B lymphocytes was studied by using BALB/c mice infected 12 to 18 days previously with Nippostrongylus brasiliensis. B cells were enriched in the Sephadex G-10-passed lymphocytes by treating with anti-Thy-1.2 and complement (C). After stripping any cytophilic Ig with low pH, the B cells were 125I surface labeled; subsequently the membranes were solubilized with nonionic detergent, and putative Fc epsilon R components were allowed to bind to IgE-coated adsorbents. Bound radiolabel was eluted with low pH, and when examined by SDS-PAGE, was found to consist primarily of a relatively broad band centered at 49,000 m.w. (49K). Fluid-phase IgE could prevent the binding of the 49K component to the IgE solid-phase adsorbents. Rebinding studies further indicated that the 49K component exhibited a specificity for IgE, thus confirming that the 49K component was the murine B lymphocyte Fc receptor for IgE (Fc epsilon R). Some rebinding to rabbit IgG was observed, and by using 2.4G2, the monoclonal anti-Fc gamma 2b receptor (Fc gamma 2bR) antibody to isolate the IgG2b receptor, a clear distinction between the FC gamma 2bR and the 49K IgE receptor was demonstrated by SDS-PAGE analysis. Rabbit IgG was thus found to interact with both the 49K Fc epsilon R and the 59K FC gamma 2bR. The murine B lymphocyte Fc epsilon R was compared with the human B cell Fc epsilon R from the RPMI 8866 cell line and with the high affinity Fc epsilon R on rat basophilic leukemia cells by one- and two-dimensional gel analyses. The lymphocyte Fc epsilon R from mouse and human was found to be quite similar with respect to m.w. (45 to 50K) and isoelectric point (pI 4.5 to 5.0), whereas the basophil Fc epsilon R differed in both aspects.

Sheep erythrocyte rosette formation by B chronic lymphocytic leukemia cells as a consequence of monoclonal surface immunoglobulin with "Forssman-like" antibody activity

Peripheral blood and splenic lymphocytes from an elderly man with chronic lymphocytic leukemia (Rai stage 4) were shown to have monoclonal surface immunoglobulin (IgM+, IgD+, kappa+), Ia-like antigen and receptors for unsensitized sheep red blood cells. The sheep red blood cell receptor was not blocked by monoclonal antibodies that bind to the classic T lymphocyte rosette receptor (OKT-11 and Lyt-3) or by anti-human IgG or antilambda antibodies. However, the sheep red blood cell receptor was blocked by antihuman IgM and kappa antisera and by soluble guinea pig kidney antigen (Forssman antigen). It is concluded from these and other observations that our patient has a B-cell lymphoproliferative disorder expressing monoclonal surface immunoglobulin with anti-"Forssman-like" antibody activity.

Determination of dissociation constants and ligand specificity of detergent solubilized surface membrane immunoglobulin A from MOPC-315

Surface membrane immunoglobulin from MOPC-315 plasmacytoma cells (smM315) was isolated by nonionic detergent lysis of radioiodinated cells and affinity chromatography on Dnp-aminohexyl-Sepharose 4B. Verification of the solubilized molecule as an integral membrane protein, distinct from secreted MOPC-315 IgA (M315) was accomplished by NaDodSO4-PAGE, charge-shift electrophoresis and molecular sieve gel filtration with NP-40 and deoxycholate. smM315 was compared to reduced and alkylated monomeric secreted immunoglobulins from MOPC-315, MOPC-460, and XRPC-25 by quantitative affinity chromatography (QAC) using two differently substituted Dnp-aminohexyl-Sepharose 4B resins. Unique patterns of cross-reactivity of all secreted myeloma proteins were independently established with a competitive hapten inhibition assay using 125I-Dnp26BSA as the precipitating probe. After derivation with dinitrobenzylsulfonate, Dnp-aminohexyl-Sepharose 4B was modified with succinic anhydride which, with the inclusion of 0.03% Doc in a PBS and 0.1% NP-40 buffer, prevented nonhapten specific protein-matrix interactions during QAC. Dissociation constants determined by QAC for three ligands, (dinitrophenyl-glycine, trinitrophenyl-amino-caproate and tetramethylrhodamine) were essentially the same for smM315 and M315. Both of the other nitrophenyl binding IgA myelomas had distinct and significant differences in dissociation constants. Thus, for a differentiated antibody secreting cell which has undergone a heavy chain class switch, such as MOPC-315, the cell surface immunoglobulin has an identical ligand binding active-site as the secreted immunoglobulin.

"Membrane-associated" immunoglobulins in cyst and ascites fluids of ovarian cancer patients

A new column chromatography technique, utilizing peroxidase-labeled antihuman immunoglobulins, is described, which can measure the binding of specific antibodies to membrane fragments containing relevant antigens. Using this assay, the presence of bound immunoglobulin is demonstrated on membrane fragments isolated from ascites fluids, but not from tumor tissues. In this study, two populations of immunoglobulins were examined: 'free' immunoglobulins and immunoglobulins bound to ascites fluid-derived membrane fragments. Immunoglobulins eluted from membrane fragments of the ascites fluids were capable of binding to the tumor. These were specific for binding to tumor membrane preparations, in that there was two orders of magnitude greater binding of these immunoglobulins at a given concentration than 'free' immunoglobulins at the same concentration.

Relation between actin-associated proteins and membrane immunoglobulin in B-cells

The myosin-affinity technique, along with conventional immunoaffinity chromatography of membrane immunoglobulin (mIg), was used to study the relation between proteins that bind to actin, and those that co-isolate with the mIg of normal chicken B-cells. In the case of biosynthetically-labeled cells, we found approximately 13 actin-associated polypeptides. Of this group, eight could be labeled with 125I surface labeling. When the actin-associated proteins were compared to proteins that co-isolate with mIg during immunoaffinity chromatography, we found that two of them (mol. wts 55,000 and 34,000) co-isolate with mIg. The 55,000 mol. wt polypeptide can be labeled with 125I surface labeling techniques, while the 34,000 mol. wt protein cannot, suggesting that only the 55,000 mol. wt protein is exposed on the outer surface of the plasma membrane. It is speculated that the function of these proteins may be involved in linking mIg to actin and perhaps to the cytoskeleton.

Cell sorting using a universally applicable affinity chromatography matrix: solid-phase anti-fluorescein isothiocyanate antibody

Procedures are described for fractionating cells utilizing a universally applicable cellular affinity chromatography matrix. The affinity matrix consists of immunoabsorption purified goat anti-fluorescein isothiocyanate antibody coupled to large derivatized polyacrylamide beads. This matrix may, in principle, be used to isolate any cell subpopulation provided it has a fluorescein-labeled ligand on its surface. In this report the matrix was used to isolate viable purified fractions of mouse surface Ig-positive cells, Lyt1 cells, and mouse lymphocytes that bind the lectin soybean agglutinin. A preliminary experiment using the anti-FITC beads suggested that this technique can provide a fraction of cells enriched in antigen binding cells. Cell populations isolated by this technique retain their ability to respond to in vitro mitogen stimulation, as well as their ability to be maintained in cell culture following fractionation. Additional experiments using a column consisting of goat anti-rabbit Ig antibody coupled to the same support material are also reported.

Multiple sclerosis: capping of surface immunoglobulin G on macrophages engaged in myelin breakdown

Macrophages were examined for immunoglobulin G (IgG) and albumin in actively demyelinating lesions in two patients with multiple sclerosis (MS) using the peroxidase-antiperoxidase immunocytochemical technique. In both cases, macrophages were present that stained for cytoplasmic or surface IgG or both. In one case, in which the tissue was rapidly fixed in chilled fixative, macrophages located among myelinated nerve fibers at plaque margins, but not elsewhere in the plaque, revealed surface IgG in the form of caps restricted to one or both poles of the cell. These caps were absent in sections stained for albumin. Because capping implies the presence of a multivalent ligand close to the cell surface and because cap formation was observed only in macrophages contacting myelin sheaths, we suggest that antimyelin antibody cytophilic for macrophages may be present in the central nervous system in MS, and that immune ligand-mediated phagocytosis may play a role in myelin breakdown in the disease. This study provides the first direct evidence that IgG participates locally in myelin breakdown in MS.

T lymphoreceptopathy in systemic lupus erythematosus

Decreases in numbers and functions of SLE T lymphocytes as a form of lymphoreceptopathy were investigated using T lymphocytes and sera obtained from both SLE patients and healthy subjects with respect to the effects of suppressor T cells and Con A induced suppressor factor against antibody formation, changes in the membrane microviscosity and the ultrastructure of membrane associated particles (MAPs) of T lymphocytes. The lymphoreceptopathy of SLE T lymphocytes was induced by decreased microviscosity and abnormalities of distribution, size and density of MAPs on the T lymphocyte membrane which can be modulated by serum factors consisting mainly of IgG as T cell membrane binding antibody and partially of IgM as cytotoxic antibody.

Murine cell surface immunoglobulin: two native IgD structures

Murine spleen cell surface IgD is found in two forms upon SDS-polyacrylamide gel electrophoresis under nonreducing conditions. Both IgDI and IgDII are present on the surface of intact cells and appear to be native structures. Neither form could be accounted for by proteolytic degradation or disulfide bond rearrangement. IgDII has an apparent m.w. of 96,000, suggesting an HL structure. IgDI has an apparent m.w. of 150,000, approximately 33,000 daltons lower than that expected for an H2L2 structure. Significant variation in the relative amounts of IgDI and IgDII was found when mice of different strains were examined.