Differences in the surface proteins of mouse B and T cells

Monoclonal antibodies to rat Na+,K+-ATPase block enzymatic activity

A panel of nine mouse monoclonal antibodies has been prepared against purified preparations of rat kidney Na+,K+-ATPase (EC 3.6.1.3). Selection for specific antibody was based upon the ability of crude hybridoma fluids to inhibit Na+-ATPase activity (using luciferase-linked ATPase assays) and upon antibody binding to both the purified kidney membrane enzyme and to glutaraldehyde-fixed hepatocytes by using standard enzyme-linked immunoadsorbent assays. After immunoaffinity purification, two of the antibodies (both of the IgG1 subclass) fully inhibit kidney and liver membrane Na+,K+-ATPase activity with Ki (apparent) values of 30 nM ("9-A5") and 600 nM ("9-B1"). Immunoblots demonstrate directly that three different 125I-labeled antibodies (6-4, 9-A5, and 9-B1) bind predominantly to a 94,000 Mr protein that comigrates in NaDodSO4/polyacrylamide gels with the fluorescein isothiocyanate-labeled alpha subunit of the Na+,K+-ATPase. Indirect immunofluorescence studies with these antibodies on paraformaldehyde-fixed liver slices reveal staining patterns congruent with bile canalicular membrane domains. These results together suggest that the antibodies exert inhibitory effects by recognizing alpha subunits of both liver and kidney Na+ pumps in their native conformations.

Complement-mediated killing of myeloma tumour cells: differences in susceptibility to lysis by antibodies and complement are independent of antigen expression and antibody binding

The susceptibility to lysis by antibodies (Ab) and complement (C) of several murine myeloma tumour sublines was studied. Significant differences in the degree of C-mediated lysis were observed and found to be independent of the expression of antigens on the cell surface and their accessibility to react with Ab. Several experiments correlate the presence and amount of a 160 kilo dalton cell-surface glycoprotein (gp160) and the diminished susceptibility to C attack observed with some of these tumour sublines. Different sources of Ab and C were tested and similar results were obtained, although the effect was most apparent when mouse Ab and rabbit C were used in the cytotoxicity assays. These results suggest that gp160, when present in large amounts on the cell surface, could be interfering with the generation of the C-induced membrane lesions.

The major histocompatibility complex-restricted antigen receptor on T cells. I. Isolation with a monoclonal antibody

An antibody-secreting B cell hybridoma, KJ1-26.1, has been prepared from mice immunized with the T cell hybridoma DO-11.10, which recognizes chicken ovalbumin in association with I-Ad (cOVA/I-Ad). KJ1-26.1 blocks I-restricted antigen recognition by DO-11.10 and a subclone of this T cell hybridoma, DO-11.10.24, which has the same specificity for cOVA/I-Ad as its parent. KJ1-26.1 does not block I-restricted antigen recognition by any other T cell hybridoma tested, including a number of T cell hybridomas closely related to DO-11.10, with similar, but not identical, specificities for antigen/I. Moreover, KJ1-26.1 binds to DO-11.10 and DO-11.10.24, but not to any other T cell hybridomas tested, including three subclones of DO-11.10 that have lost the ability to recognize cOVA/I-Ad. Thus, in every regard KJ1-26.1 appears to be binding to all or part of the receptors for antigen/I on the T cell hybridoma DO-11.10. KJ1-26.1 appears to bind to approximately 15,000 molecules/cell on the surface of DO-11.10. The antibody precipitates an 80,000 dimer from the cells, which on reduction migrates as 40-44,000 monomers. The receptor(s) for antigen/I on DO-11.10 therefore includes molecules with these properties.

Lymphocyte cell surface glycoproteins which bind to soybean and peanut lectins

In cellular immunology, peanut (Arachis hypogaea) lectin has been used to selectively agglutinate immature lymphoid cells and soybean (Glycine max-lectin to agglutinate B lymphocytes. We have used affinity chromatography to study the surface glycoproteins of rat and mouse lymphoid cells which bind to these lectins. Thymocyte and T and B lymphocyte glycoproteins were analysed either without modification (native) or after the removal of sialic acid with neuraminidase (asialo). The only native glycoprotein which was seen to bind to peanut lectin was the 95,000 mol. wt sialoglycoprotein from thymocytes. The equivalent molecules from T lymphocytes bound to peanut lectin only after neuraminidase digestion. Thus the selective agglutination of thymocytes by peanut lectin would seem to be due to a partial lack of sialic acid residues on the O-glycosidically-linked oligosaccharides of the thymocyte sialoglycoprotein. The B lymphocyte form of the leucocyte-common antigen was the only prominent native glycoprotein which was seen to bind to soybean lectin and this probably accounts for the specific binding of this lectin to B cells. The leucocyte-common antigens, in their asialo forms, from thymocytes and B and T lymphocytes differed in their binding to the lectins and this establishes that these glycoproteins which share antigenic determinants differ in their carbohydrate structures.

Different expression of Lyt differentiation antigens and cell surface glycoproteins by a murine T lymphoma line and its highly metastatic variant

Cloned lines of the methylcholanthrene-induced DBA/2 T lymphoma Eb and its highly metastatic variant line ESb were analyzed for differences in the expression of serologically detectable cell surface differentiation markers. Flow cytofluorographic analysis of cells stained with fluorescein isothiocyanate-conjugated monoclonal rate anti-mouse Thy-1, Lyt-1, Lyt-2 and complement-dependent cytotoxicity with mouse alloantisera against Lyt-3.2 and Ly-6.2 revealed, for the parental low metastasizing line, Eb, a phenotype of Thy-1+, Lyt-1-, Lyt-2+, Lyt-3+, Ly-6+, whereas the highly metastasizing variant line typed as Thy-1-, Lyt-1+, Lyt-2-, Lyt-3-, Ly-6-. Analysis of galactose oxidase/NaB3H4-labeled glycoproteins from Eb and ESb clones by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate showed further phenotypic differences. Selective binding of radiolabeled glycoproteins to Helix pomatia or Vicia villosa-Sepharose, respectively, allowed the identification of T130 to be expressed on Eb cells and T145 to be expressed on some ESb clones. The latter antigen is expressed on murine cytotoxic T lymphocytes. Immune precipitation analysis revealed that Eb and ESb bear different molecular forms of the T200 antigen. Comparisons of iodinated surface proteins derived from tumor cells either treated or untreated with tunicamycin indicated that many of the differences in membrane proteins between Eb and ESb cells could be attributed to differences in glycosylation. Our results, derived from a defined tumor system of lymphoid origin, show that the progression from a low to a high malignant tumor line can be associated with changes in the expression of various defined cell surface differentiation antigens. The question of a possible relationship between tumor progression and cell differentiation or dedifferentiation is discussed.

Partial isolation and characterization of Gp 220, the Ulex europaeus binding glycoprotein of the B-lymphocyte plasma membrane

Using affinity chromatography on Sepharose 4B coupled with Ulex europaeus lectin, a partially purified gp 220 was isolated from the RAJI cell membrane. This protein could not be isolated from the membranes of the T-cell line MOLT-4 nor from human erythrocytes. Gp 220 is composed of three subunits gp 85, 70 and 65 held together by disulfide bridges. Gp 85 contains fucosyl residues, gp 70 contains galactosyl residues, and gp 65 contains both sugars. Gp 220 is different from fibronectin and spectrin, proteins which also show binding to the Ulex europaeus lectin.

B220: a B cell-specific member of th T200 glycoprotein family

T200, a major cell-surface glycoprotein on lymphoid cells, exists in several forms with different electrophoretic mobilities. These forms have been correlated with different classes of lymphoid cell. The smaller forms, with molecular weights (MWs) of congruent to 170,000 and 180,000 are found predominantly on T cells while the 220,000 MW form is associated with B cells. The polypeptide portions of each molecule may be identical or closely related as all three forms share the same allelic variations, and all reported herologous antisera and monoclonal antibodies to T200 precipitate all three forms. We report here a monoclonal antibody specific for the 220,000 MW form of T200 and show that it is expressed only on B cells and a subset of bone marrow cells which includes B cell precursors. We suggest that this form of the molecule be designated provisionally B220.

Family of large surface proteins on human lymphocytes

Cell surface molecules of T-rosette-positive human peripheral blood lymphocytes were labelled by lactoperoxidase and examined on 5% polyacrylamide gels. Several bands, ranging in molecular weight from 220,000 to 170,000 daltons, were seen. Analysis of the tryptic and chymotryptic digests of the 187K, 200K, 210K and 220K proteins indicated that they are of similar peptide composition. Study of clones derived from this population indicated that individual cells within a population differed in expression of these proteins.

Presence of T 145 on cytolytic T cell lines and their lectin-resistant mutants

Murine cytolytic T cell lines have been analyzed for the expression of two surface glycoproteins called T145 and T130. T145, known to be expressed by activated cytolytic T cells, is also expressed by such lines, but T130, which has been described by a universal T cell marker, is not. Our results suggest a structural relationship between T145 and T130. Vicia villosa lectin, which binds selectively to T145 of activated T cells and which is cytotoxic for cytolytic T cell lines, has been used to select lectin-resistant mutants from these lines. Five independent lectin-resistant mutants have been obtained. All of them are cytolytically active, bind up to 100-fold less lectin than the parental lines, but still express T145 or a closely related glycoprotein.

Possible cell surface receptor for Friend murine leukemia virus isolated with viral envelope glycoprotein complexes

Water-soluble multimeric complexes of Friend leukemia virus envelope glycoprotein gp85 bind specifically to C57BL/6 mouse spleen leukocytes. Such complexes were used to isolate cell surface receptors for the virus, using an immunoprecipitation technique. The putative rceptor has a molecular weight of 14,000. Mouse H-2 histocompatibility antigens, which are receptors for Semliki Forest virus, are not receptors for Friend leukemia virus.

Human homologue of murine T200 glycoprotein

We report the identification of the human homologue of murine T200 glycoprotein. Peptide-mapping experiments suggest that the structure of the glycoprotein is highly conserved between the two species. Many of the properties of human T200 homologue are similar to those of murine T200 glycoprotein: it is broadly distributed within the hematopoietic system but is not detectable on nonhematopoietic cells; there are also structural differences between the forms of the glycoprotein found on T and B lymphoblastoid cell lines. These results suggest the homologous glycoproteins may play similar functional roles in both species.

Human cell-surface glycoprotein with unusual properties

We report here the identification of human cell-surface glycoprotein with unusual and interesting properties. We initially detected this glycoprotein on the surface of cultured human haematopoietic cell lines by means of a monoclonal antibody. Although it is expressed on all cultured human haematopoietic cell lines tested, including the inducible promyelocytic tumour cell line HL-60 (ref. 1), it is not present in readily detectable amounts on most normal or leukaemic human haematopoietic cells. HL-60 cells, on exposure in vitro to appropriate chemical inducers, undergo morphological and functional differentiation along the granulocytic pathway or into macrophage-like cells. One consequence of in vitro induction in the specific loss of the glycoprotein from the surface of HL-60 cells. The molecule does not, however, seem to be a highly tissue-specific differentiation antigen because it is also found on human tumour cell lines derived from non-haematopoietic tissues. Rather, its expression seems to be related to cell proliferation. Preliminary chemical characterization suggests that the glycoprotein maybe identical to the abnormal glycoprotein previously reported by Bramwell and Harris to be associated with malignancy.

T cell subsets defined by expression of Lyt-1,2,3 and Thy-1 antigens. Two-parameter immunofluorescence and cytotoxicity analysis with monoclonal antibodies modifies current views

Using monoclonal antibodies and multiparameter fluorescence analyses, we show that the expression of Lyt-1, Lyt-2, and Lyt-3 on T cell subpopulations is more complex than was originally recognized by the cytotoxic depletion studies with conventional reagents that defined the Lyt-1+2+3+, Lyt-1+2-3-, and Lyt-1-2+3+ populations. We detect at least some Lyt-1 on all T (Thy-1-bearing) lymphocytes; however, in agreement with previous studies, we find that Lyt-2+3+ cells are more difficult to depelete with anti-Lyt-1 than Lyt-1+2-3- cells. Surprisingly, we found a small subpopulation of cells carrying relatively large amounts of Lyt-1 and no Thy-1 detectable by fluorescence-activated cell sorter analysis. We also detect cells with this phenotype histologically in B cell zones (primary follicles) and germinal centers in spleen and lymph nodes. In general, the Lyt-1 only population represents approximately 2% of spleen cells. The relative quantitative expression of Thy-1, Lyt-1, Lyt-2, and Lyt-3 changes systematically during T cell maturation. Among Lyt-1+2+3+ cells in the thymus, Thy-1 and Lyt-2 are high, whereas Lyt-1 is low. Among splenic T cells, in contrast, Thy-1 is low, Lyt-1 is high, and Lyt-2 and Lyt-3 are a little higher than in thymus. In general, Thy-1 expression is negatively correlated with Lyt-1. Thus, even among splenic and lymph node T cells subpopulations exist that tend to be either high Thy-1 and low Lyt-1 or vice versa. Lyt-2+3+ cells represent approximately 85% of thymocytes but only approximately 35% of splenic or lymph node T cells. The Lyt-2+3+ cells are found predominantly in the low Lyt-1, high Thy-1 subpopulation.

Direct evidence for a two-signal mechanism of cytotoxic T-lymphocyte activation

The cellular requirements for the activation of cytotoxic T lymphocytes to alloantigens are complex. In addition to cytotoxic precursors (CLPs), metabolically active stimulator cells, adherent accessory (A) cells and antigen-specific helper T cells are also required. However, the requirement for A cells, metabolically active stimulator cells or helper T cells can be replaced by soluble factors or co-stimulator (CoS), a lymphokine obtained by stimulation of murine spleen cells with concanavalin A (Con A). We show here that in the presence of CoS, cultures containing on average one lymph node lymphocyte (LNL) and Con A can be activated to produce single cytotoxic clones. This observation strongly suggests that one of the target cells of CoS is the CLP and provides more direct evidence for a two-signal mechanism for cytotoxic T lymphocyte activation.

T200 cell surface glycoprotein of the mouse. Polymorphism defined by the Ly-5 system of alloantigens

The cell line BW5147, and a mutant T200-negative cell line derived from BW5147, were studed by immunoprecipitation and peptide mapping, with xenogeneic monoclonal anti-T200 serum and with Ly-5 alloantiserum. It appears that the Ly-5 system defines a structural polymorphism of the cell surface glycoprotein T200, and that the monoclonal anti-T200 serum defines a feature of T200 that is common to mice of both Ly-5a and Ly-5b genotypes and may be invariable in the species.

Cell surface polypeptides of murine T-cell clones expressing cytolytic or amplifier activity

Murine cytolytic T-cell and amplifier T-cell clones derived from secondary unidirectional mixed leukocyte cultures were labeled with 125I by the lactoperoxidase method and their polypeptide profiles were analyzed by NaDodSO4/polyacrylamide gel electrophoresis. All cytolytic T-cell clones derived from the same mouse strain yeilded similar cell surface polypeptide profiles. However, profiles obtained with three amplifier T-cell clones were strikingly different from each other as well as from those of cytolytic T-cell clones. Comparison of these profiles with those obtained from mixed leukocyte culture cells, whole spleen cells, glass wool/nylon wool-purified splenic T-cells, and thymocytes indicates that cytolytic T-cell clones have a characteristic cell surface polypeptide profile that distinguishes this type of lymphocyte from most other lymphocytes.

Radio-iodinated surface proteins of electrophoretically separated rat lymphocytes

Rat thymocytes and lymph node cells were separated into three T and one B subpopulation by means of free flow electrophoresis. The surface proteins of the separated cells were labeled by lactoperoxidase catalysed radioiodination. Most of the label was demonstrated to be at the cell surface. The labelled cells were either lysed in sodium dodecyl sulphate or treated with Nonidet P-40 to extract cell proteins. The radioiodinated proteins were analysed on sodium dodecyl sulphate polyacrylamide gel electrophoresis followed by autoradiography. In contrast to sodium dodecyl sulphate Nonidet P-40 did not extract cell proteins completely. Furthermore the degree of extraction varied considerably in the different cell populations. 58% of protein bound radioactivity was extracted from thymocytes, 67% from peripheral T cells and 81% from B cells. Gel electrophoresis revealed that four proteins were not extracted at all, whereas five components were better soluble in Nonidet P-40 than all other proteins. One protein was extracted from B cells only although it was present in all cells. Although the surface protein patterns of the four lymphocyte subpopulations were rather similar, distinctive differences could be found. B cells had six labelled proteins which seemed to be absent in the other cells, In the T cell group, three protein bands were identified, each with specificity for peripheral T cells, thymocytes and all T cells respectively. Four other proteins were found which showed quantitative differences between the four cell groups.

Biochemical analysis of ligand-induced receptor patching and capping using a novel immunolactoperoxidase iodination technique

A novel approach for the analysis of membrane proteins involved in ligand-induced surface receptor patching and capping is described. The technique is based on the use of immunolactoperoxidase (immuno-LPO) conjugates which catalyze the iodination of those surface proteins with available tyrosine groups that are located in the immediate vicinity of the patch or cap of a particular antigen. We have used the patching and capping of the H-2 (histocompatibility) antigen on mouse thymocytes to illustrate this method. However, this technique should be generally applicable to any cell surface proteins which can be induced to form patches or caps by a specific ligand. Cytochemical analysis indicates that the immuno-LPO conjugates induce the same patching and capping of the H-2 antigen as does the unconjugated antibody. Biochemical analysis of the 125I-labeled proteins by SDS polyacrylamide gel electrophoresis indicates that a large membrane protein (mol wt of approximately 200,000 daltons) is closely associated with H-2 patches and caps. Since a number of other prominent membrane proteins are not labeled by this procedure, selective redistribution of certain surface proteins must be occurring during H-2 antibody-induced patching and capping.

Surface glycoproteins of resting and activated human T lymphocytes

This review summarizes some recent studies on the surface glycoproteins of human thymocytes and T lymphocytes. Purified cells were surface labeled by the galactose oxidase-NaB3H4 or periodate-NaB3H4 techniques. The radioactive membrane glycoproteins were separated by polyacrylamide slab gel electrophoresis and visualized by fluorography. Thymocytes and T lymphocytes show characteristic surface glycoprotein profiles which are easily distinguishable from those of the other main groups of human leukocytes. We observed specific changes in the surface glycoprotein patterns which correlate with the degree of maturation and functional activation of T cells. Surface molecules carrying T cell specific antigens were identified by immune-precipitation from lysates of surface labeled thymocytes and T lymphocytes using rabbit anti-human T cell antibodies. Finally we describe a leukocyte membrane glycoprotein which is a precursor of serum alpha 1 acid glycoprotein (orosomucoid).

Differences between the carbohydrate units of cell-surface glycoproteins of moust B- and T-lymphocytes

Carbohydrate units of cell-surface glycoproteins of mouse B- and T-lymphocytes, labelled in their sialic acid residues by the periodate/NaB3H4 method and in their galactose residues by the galactose oxidase/NaB3H4 method after neuraminidase treatment, have been studied. Glycopeptides were prepared from the labelled cells by Pronase digestion and fractionated by concanavalin A affinity chromatography into two fractions (A and B). Alkali-labile oligosaccharides were isolated after mild NaOH/NaBH4 treatment by gel filtration. The alkali-labile oligosaccharides were further analysed by t.l.c. To study the relative proportion of neutral mannose-rich carbohydrate units (fraction C) in lymphocyte glycoproteins, glycopeptides were also prepared from unlabelled cells and subjected to concanavalin A affinity chromatography after N-[3H]acetylation of their peptide moiety. The major alkali-labile oligosaccharide component of both cell types was identified as galactosyl-(beta 1 leads to 3)-N-acetylgalactosaminitol. T-Lymphocytes were characterized by a high proportion of this oligosaccharide and a lower proportion of alkali-stable fraction A glycopeptides, whereas the opposite was observed for B-lymphocytes. The relative proportions of the concanavalin A-binding fractions B and C were similar in both cell types. The differences observed may correlate with the different surface properties of B- and T-lymphocytes.

Cell surface sialylation of glycoproteins and glycosphingolipids in cultured metastatic variant RNA-virus transformed non-producer BALB/c 3T3 cell lines

The sialic acid composition and the display of cell surface sialyl components of several metastatic variant RNA-virus-transformed non-producer BALB/c 3T3 have been studied in culture. The following observations have been made concerning the sialyl components in these lines: (1) the compositions of whole-cell total, protein-bound and lipid-bound sialic acid were not appreciably different; (2) the surface sialic acid studied using the neuraminidase-galactose oxidase method and metabolic labelling followed by neuraminidase hydrolysis showed a positive correlation with the metastatic properties of these lines; (3) the degree of surface sialylation determined by galactose oxidase--sodium borotritide labelling of neuraminidase-treated and untreated cells revealed that 44--89% of exposed galactose and/or N-acetyl galactosamine residues of total cell-surface saccharides were sialylated in highly and intermediately metastatic lines as compared with 11-30% in the poorly and non-metastatic lines; (4) the cell surface glycoproteins and glycosphingolipids contributed equally well in their degree of sialylation and there was a positive correlation with the metastatic properties of the cells in vivo; (5) the cell surface proteins labelled by the lactoperoxidase-catalyzed iodination technique, followed by gel electrophoresis, showed some minor differences between metastatic variant lines. However, glycoproteins detected by the galactose oxidase labelling of neuraminidase-treated and untreated cells showed major differences in composition between the metastatic variant lines. The study of four highly metastatic lines has shown that the cells of these lines were enriched in several sialyl-glycoproteins, whereas three non tumorigenic lines and two poorly metastatic or non-metastatic lines contained unsialylated glycoproteins. The results indicate an enhancement of the degree of sialylation of surface glycoconjugates accompanying the metastatic process in RNA-virus-transformed mouse lines.

Further characterization of a human T lymphocyte associated antigen

A human T lymphocyte associated antigen (TLAA), defined with appropriately absorbed antisera to the lymphoblastoid cell line HSB, was originally characterized as a 150,000 mol. wt antigen using sodium deoxycholate solubilized, 125I Bolton-Hunter labelled membranes of HSB, thymus and peripheral blood lymphocytes. The TLAA, which appears to be the major membrane protein labelled with either the Bolton-Hunter, or galactose oxidase-sodium 3H borohydride methods, is weakly labelled in vitro with a 3H amino acid mixture and appears to be a minor membrane component by Coomassie blue staining of detergent solubilized HSB membranes. The antigen is trypsin-sensitive and not extractable with 3 M KCl. The glycoprotein nature of the antigen is suggested by its binding to a Lens culinaris column and its labelling by the galactose oxidase-sodium 3H borohydride and 3H glucosamine methods. Both gel filtration chromatography and sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis studies on 4% SDS gels indicate that the mol. wt. of the antigen is approximately 170,000 Daltons.

Metabolic carbohydrate-labelling of glycolipids from mouse splenocytes. Mitogen-stimulated B and T cells show different labelling patterns

Splenic lymphocytes from CBA/J, AKR/A/J, BALB/c/A, C57/BL/6J, C3H/HeJ and C3H/Tif nu/nu mice and B lymphocyte or T lymphocyte preparations derived from CBA/J mouse spleen were cultivated in the presence of either concanavalin A, phytohemagglutinin, Salmonella minnesota R595 lipopolysaccharide or Proteus mirabilis soluble lipoprotein. The mitogens stimulated the incorporation of [14C]galactose into acid-insoluble cell material with the same specificity for B or T cells as that known for thymidine incorporation. The glycolipids extracted from mitogen-activated, carbohydrate-labelled B or T cells were compared by thin-layer chromatography and characteristic differences between B and T cells were noted in the ganglioside as well as in the neutral glycolipid fractions. In addition, subsets of B or T cells, namely lipopolysaccharide-responsive or lipoprotein-responsive B-cell populations or nylon-purified T cells may be recognized by characteristic neutral glycolipid bands.

Expression of Thy-1 glycoprotein on lectin-resistant lymphoma cell lines

Lectin-resistant mutants with specific defects in glycosylation have been selected from the mouse lymphoma cell line, BW5147 (Thy-1+). The quantitative expression of cell surface glycoproteins on the mutant cells has been studied. The results show that some glycosylation defects that confer resistance to the cytotoxic effects of concanavalin A block the expression of Thy-1 glycoprotein on the cell surface. However, some changes in the oligosaccharides of Thy-1 glycoprotein generated by glycosylation defects found in PHAR mutant cells and restricted to the termini of complex-type oligosaccharides have no effect on the ability of Thy-1 to reach the cell surface. No glycosylation defects were found that interfered with the expression of either gp 69, 71 or H-2 on the surface of the mutant cells. It is concluded that aberrant biosynthesis of Thy-1 oligosaccharides can interfere with its expression on the cell surface, but that specific changes in oligosaccharide structure are necessary to block transport to the cell surface and integration into the plasma membrane.

Actin may be present on the lymphocyte surface

Lymphocytes were assessed for the presence of surface actin and myosin by lactoperoxidase-catalyzed iodination and indirect immunofluorescence using antisera against purified pig skeletal muscle actin and pig smooth muscle myosin. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis of 125I-labeled pig, mouse, and human B lymphocytes revealed an intense radioactive band of 43,000 molecular weight, whereas pig and mouse T lymphocytes gave a much less intense band. This band comigrated with actin, was nonglycosylated as judged by lack of binding to lentil lectin-Sepharose, was bound specifically by myosin fibers, and could be distinguished from a polypeptide of similar mobility derived from the major histocompatibility antigens. These results suggest that actin is present on the surface of B lymphocytes and, to a lesser extent, on T lymphocytes. Pig, mouse, and human Ig-bearing cells were stained by antiactin and antimyosin antisera, as judged by indirect immunofluorescence, whereas non-Ig-bearing cells were not stained. Antibody binding, however, was depleted by adsorbing the antisera with Ig-Sepharose. It was concluded that the immunofluorescence results are misleading and reflect the presence of antibodies that crossreact with Ig.

Interspecies spleen-myeloma hybrid producing monoclonal antibodies against mouse lymphocyte surface glycoprotein, T200

A cell hybrid has been selected from fusion of a mouse myeloma and rat spleen cells immunized against mouse lymphoma cells that produces monoclonal antibody against the mouse lymphocyte surface glycoprotein, T200. Antibody binding assays employing the monoclonal antibody show that there are about 50,000-100,000 molecules of T200 glycoprotein on mouse thymocytes and that similar antigens are present on spleen and bone marrow but not detected on nonlymphoid tissues. Examination of the labeled molecules precipitated from detergent extracts of spleen cells and thymocytes iodinated by the lactoperoxidase technique by SDS-PAGE confirm that there are structural differences between the antigens found on B and T lymphocytes. The B-cell glycoprotein consists of at least one component of apparent mol wt 220,000 on SDS-PAGE, while the T-cell glycoprotein has an apparent mol wt of about 190,000.

Identification and characterization of normal and malignant human blood leukocytes by surface glycoprotein patterns

We have labeled surface glycoproteins of normal and malignant human blood leukocytes by the galactose oxidase-NaB3H4 and periodate-NaB3H4 labeling techniques. The labeled glycoproteins were separated by slab gel electrophoresis in the presence of sodium dodecyl sulfate and visualized by fluorography. The different types of normal blood cells could be distinguished by their surface glycoprotein patterns. The surface glycoproteins of cells from patients with acute lymphoblastic, myeloid, or monoblastic leukemia were different from those of normal cells. The leukemic cells could be classified by their surface glycoprotein patterns with respect to their relationships to normal blood cells, and an estimation of their degree of differentiation was obtained.

The lymphocyte surface: differences in the surface chemistry of murine spleen T lymphocytes of varying major histocompatibility haplotypes

Spleen lymphocytes and erythrocytes from congenic mice of different m. h. c. haplotypes were characterized on a biophysical basis (the anodic electrophoretic mobility, e. p. m.) to correlate any subtle differences in the cell surface topochemistry with the H-2 specificity. Spleen Tlymphocytesfrom A. CA (H-2 f ) and A.SW (H-2 s ) mice exhibited high values of e. p. m., which were significantly different. In contrast, significant differences in the e. p. ms of B cells and erythrocytes of the two m. h. c. haplotypes were not observed. Cell electrophoresis of live, intact T lymphocytes of spleen (without the ‘contaminating’ B cells), before and after the chemical modification of the cell surface by treatment with small, non-toxic concentrations of maleic anhydride (MA), showed the number of lysine side chain amino groups of surface membrane proteins of cells with H-2 f specificity to be about twice that on cells with H-2 S specificity. Such a difference was ob­served both in the case of T lymphocytes from cyclophosphamidetreated mice, and the effluent from nylon wool columns. The difference in the number of the cationogenic amino groups (-NH 2 + H + ⇌ -NH 3 + ) in the cell periphery (within about 1 nm of the cell surface in physio­logical saline), contributing a positive charge, would explain the observed difference in the e. p. ms of H-2 f and H-2 S spleen T lymphocytes. An interpretation of the data is that the macromolecules coded by the H-2 genes or other genes under H-2 control might be responsible for delicate differences in the chemical composition of the surface membranes of cells of the two m. h. c. haplotypes, detectable only on high e. p. m. lympho­cytes of spleen (T or T-like cells). The possibilities of other factors influencing the observed differences in the surface chemistry are discussed.

Cell surface glycoproteins of murine cytotoxic T lymphocytes. I. T 145, a new cell surface glycoprotein selectively expressed on Ly 1-2+ cytotoxic T lymphocytes

T lymphocytes at various stages of maturation and differentiation have been isolated by cellular fractionation procedures and characterized by cell surface markers and functional assays, The cell surface glycoproteins of the various T-cell preparations have been selectively radiolabeled by the galactose oxidase-tritiated sodium borohydride technique and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Details are presented on the appearance of a new cell surface glycoprotein (T 145), present on immunocompetent T lymphocytes after activation by either major histocompatibility complex alloantigens or by concanavalin A. The intensity of T 145 expression on T lymphoblasts is shown to be directly correlated in time and extent to the levels of cytotoxicity generated in a variety of T-cell activations. Specific enrichment procedures of purified populations of mixed leukocyte culture blasts have shown Ly 1(+)2(-) blasts to be T 145(-) and Ly 1(-)2(+) blasts to be strongly T 145(+). Similar enrichment procedures on normal peripheral T cells have failed to reveal any significant expression of T 145 on a highly enriched population of Ly 1(-)2(+) T cells, Further studies on the stability of T 145 expression after induction have shown it to be a more permanent-type differentiation structure whose expression is clearly not linked to the blast stage of activation. T 145 would thus appear to represent a membrane glycoprotein whose exclusive expression on T lymphoblasts is further restricted to a defined group of cells endowed with cytolytic activity and bearing the Ly phenotype Ly 1(-)2(+).

Phenotypic expression in T-lymphocyte x "fibroblast" cell hybrids

The effects of pulsatile motion on MR imaging of spinal CSF were quantitatively evaluated with a spine phantom that simulated spinal CSF pulsation. Two fundamental interdependent pulsation flow phenomena were observed: variable reductions in signal intensity of pulsatile CSF (signal loss) and spatial mismapping of this signal beyond the confines of the subarachnoid space (phase-shift images). Phase-shift images were observed as multiple regions of signal intensity conforming morphologically to the subarachnoid space but displaced symmetrically from it along the phase-encoding axis, either added to or subtracted from stationary signal intensity. Both CSF pulsation flow phenomena occurred secondary to harmonic modulation of proton precessional phase (temporal phase shift) by the unique pulsatile motion of spinal CSF when the repetition time was not an integral multiple of the pulsation period. Each flow phenomenon was analyzed with the spine phantom independently to control individual imaging and physiologic parameters including imaging plane, repetition time, echo time, slice thickness, number of echoes, number of excitations, CSF pulsation amplitude, and CSF pulsation period. In the axial plane, signal loss was present on both first- and second-echo images and was more pronounced with larger pulsation amplitudes and smaller slice thicknesses. A quantitative relationship between these two parameters allowed the prediction of CSF pulsation amplitude when the slice thickness was known and the CSF signal intensity was measured. In the sagittal plane, signal loss was present on first-echo images, was more pronounced with larger pulsation amplitudes, and under-went incomplete even-echo rephasing on second-echo images. Phase-shift images were influenced by the relationship between repetition time and CSF pulsation period. They were partly eliminated on sagittal but not on axial second-echo images because of incomplete even-echo rephasing. Both signal loss and phase-shift images were completely eliminated with CSF gating or pseudogating, indicating the rationale for gating during clinical spinal MR. The clinical significance of these findings is that awareness of the existence of spinal CSF pulsation flow phenomena avoids diagnostic confusion, whereas understanding their etiology provides a rational approach, such as CSF gating, to eliminate them.

Human B cell line deficient in the expression of B cell-specific glycoproteins (GP 27,35)

A human B lymphoid cell line, P3HR-1, expresses only low levels of the 27 000 and 35 000 mol.wt. B cell-specific glycoproteins (GP 27,35). Indirect antibody-binding and quantitative absorption tests with a xenoantiserum against the antigens showed that P3HR-1 cells have on their surface about 1% of the amount found on other human B lymphoblastoid cell lines. The deficit of the glycoproteins on the surface of P3HR-1 cells could be accounted for by a reduced rate of synthesis in these cells. A simple relationship between the reduced expression of GP 27,35 on P3HR-1 cells and their inability to bind Epstein-Barr virus (EBV) or express complement receptors was excluded because other B lymphoid cells which expressed neither virus-binding sites nor complement receptor had normal amounts of GP 27,35 on their surface. However, antibodies against GP 27,35 could block the absorption of EBV by EBV receptor-positive B cells.

Preliminary characterization of two thymus-dependent xenoantigens from mouse lymphocytes

Preliminary characterization of two mouse thymus-dependent (T) lymphocyte xenoantigens, T25 and T200, which are selectively labelled by lactoperoxidase-catalysed iodination of T-cells, is described. Both molecules are membrane-bound glycoproteins. Fractionation of membrane vesicles prepared from BW5147 lymphoma cells by sedimentation through sucrose density gradients show that antigens T25 and T200 are in fractions enriched with plasma membrane. Moreover antigen T200 is partially degraded when viable cells are treated briefly with low concentrations of trypsin. Both molecules are efficiently solubilized in buffers containing sodium deoxycholate or Nonidet P-40, as measured by failure to sediment at 100000g for 60min. However, gel filtration on Sepharose 6B showed the presence of aggregated material in Nonidet P-40 extracts which was not found in deoxycholate-solubilized membranes. After solubilization in detergent, antigens T25 and T200 bind to, and may be specifically eluted from, columns of pea lectin--Sepharose or concanavalin A--Sepharose. Both molecules are heterogeneous when examined by polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. As judged by its binding to columns of pea lectin, at least part of the heterogeneity of mouse thymocyte antigen T25 resides in its carbohydrate moiety.

Evidence that MuLV-induced thymic lymphoma cells possess specific cell membrane binding sites for MuLV

Cell-surface binding sites specific for thymotropic murine leukemia viruses were found in high concentrations on thymic lymphoma cell lines induced by this class of virus, but were detectable in much lower concentrations (if at all) in several non-T leukemias, plasmacytomas, and normal thymocytes or spleen cells. By specific comparison, Moloney leukemia virus (M-MuLV) binds to a lymphoma induced by M-MuLV, but not to a thymic lymphoma induced by Gross leukemia virus (G-MuLV); and G-MuLV binds to an AKR lymphoma but not to the M-MuLV-induced lymphoma. The material which binds to these T-lymphoma membrane sites is input virus, rather than a contaminant which copurifies with virus. Autoradiographic analysis demonstrates that a high proportion of T-lymphoma cells possess binding sites, whereas only a rare cell in the thymus binds murine leukemia virus to the same degree. We raise and discuss the hypothesis that each T lymphoma induced by thymotropic leukemia viruses may represent the clonal descendants of the few rate cells in the normal thymocyte population which also bind these viruses.

Differentiation antigens of the lymphocyte cell surface

Many alloantigens and xenoantigens of lymphocytes are not found generally on other tissues, and this suggests that much of the lymphocyte cell surface is differentiated in comparison with other cell membranes. These differentiation antigens are probably molecules that mediate lymphocyte-specific functions, and are also of interest in that they provide markers for different lymphoid cell types and may be important as target antigens for immunosuppressive anti-(lymphocyte) sera. The purification of differentiation antigens will be important in allowing their molecular properties to be discovered, and will also lead to the production of strong, specific antisera that can be used in functional studies. Radioimmunoassays have been developed for the analysis of anti-(lymphocyte) sera, and these assays provide advantages in purification studies over other techniques. The features of these assays are discussed, and studies of differentiation antigens of rat lymphocytes are described. These include the purification and characterization of the rat Thy-1 antigen, and preliminary studies on two other rat lymphocyte differentiation antigens.

Analysis of the envelope of Rauscher murine oncornavirus: in vitro labeling of glycopeptides

The identity and localization of the oligosaccharides of Rauscher murine type C viral glycoproteins have been examined by techniques of in vitro labeling. Terminal sialic acid was labeled with tritium by borohydride reduction after selective periodate oxidation, and galactose was labeled by borohydride reduction after specific enzymatic oxidation of the nonreducing terminal of the sugar. The results were compared with those of protein surface labeling with pyridoxal phosphate or lactoperoxidase catalyzed radioiodination. Examination of the labeled reaction products by polyacrylamide gel electrophoresis in sodium dodecyl sulfate showed that in every case the major component labeled was a glycoprotein of about 70,000 daltons. The identity of this glycoprotein as the virion envelope component was confirmed by immunoprecipitation with mono-specific antiserum prepared against purified Rauscher virus glycopeptides of 69,000 and 71,000 daltons. No other protein or glycoprotein on the surface of the virion was detected, and disruption of virions-before labeling did not reveal additional distinctive glycoproteins. There was minor labeling of sugar residues of other components, but these remain to be characterized and are not now identified as other viral proteins. Studies of the structural organization of virion proteins using the cross-linking reagent methyl-4-mercaptobutyrimidate showed only linkage of the virion envelope or core proteins to themselves. These results indicate that most, if not all, of the oligosaccharides at the surface of Rauscher virus are entities of the 69,000- and 71,000-dalton glycopeptides and that they contain a terminal sialic acid and galactose and a subterminal galactose.