Use of soybean agglutinin for the separation of mouse B and T lymphocytes

Structure-function and application of plant lectins in disease biology and immunity

Lectins are proteins with a high degree of stereospecificity to recognize various sugar structures and form reversible linkages upon interaction with glyco-conjugate complexes. These are abundantly found in plants, animals and many other species and are known to agglutinate various blood groups of erythrocytes. Further, due to the unique carbohydrate recognition property, lectins have been extensively used in many biological functions that make use of protein-carbohydrate recognition like detection, isolation and characterization of glycoconjugates, histochemistry of cells and tissues, tumor cell recognition and many more. In this review, we have summarized the immunomodulatory effects of plant lectins and their effects against diseases, including antimicrobial action. We found that many plant lectins mediate its microbicidal activity by triggering host immune responses that result in the release of several cytokines followed by activation of effector mechanism. Moreover, certain lectins also enhance the phagocytic activity of macrophages during microbial infections. Lectins along with heat killed microbes can act as vaccine to provide long term protection from deadly microbes. Hence, lectin based therapy can be used as a better substitute to fight microbial diseases efficiently in future.

Modern approaches to HLA-haploidentical blood or marrow transplantation

Allogeneic blood or bone-marrow transplantation (alloBMT) is a potentially curative treatment for a variety of haematological malignancies and nonmalignant diseases. Historically, human leukocyte antigen (HLA)-matched siblings have been the preferred source of donor cells owing to superior outcomes compared with alloBMT using other donors. Although only approximately one-third of patients have an HLA-matched sibling, nearly all patients have HLA-haploidentical related donors. Early studies using HLA-haploidentical alloBMT resulted in unacceptably high rates of graft rejection and graft-versus-host disease (GVHD), leading to high nonrelapse mortality and consequently poor survival. Several novel approaches to HLA-haploidentical alloBMT have yielded encouraging results with high rates of successful engraftment, effective GVHD control and favourable outcomes. In fact, outcomes of several retrospective comparative studies seem similar to those seen using other allograft sources, including those of HLA-matched-sibling alloBMT. In this Review, we provide an overview of the three most-developed approaches to HLA-haploidentical alloBMT: T-cell depletion with 'megadose' CD34(+) cells; granulocyte colony-stimulating factor-primed allografts combined with intensive pharmacological immunosuppression, including antithymocyte globulin; and high-dose, post-transplantation cyclophosphamide. We review the preclinical and biological data supporting each approach, results from major clinical studies, and completed or ongoing clinical studies comparing these approaches with other alloBMT platforms.

Haploidentical bone marrow transplantation in primary immune deficiency: stem cell selection and manipulation

Since the early 1980s T-cell depletion has allowed haploidentical bone marrow transplantation to be performed in patients with primary immunodeficiency for whom a matched sibling donor was not available, without causing severe graft versus host disease (GVHD). This review article presents the available data in the literature on survival, GVHD, and immune reconstitution in different categories of patients, with special emphasis on the impact of different T-cell depletion methods.

Embryonic antigens in malignancy and pregnancy: common denominators in immune regulation

There is mounting that the majority of malignant tumours of humans and rodents carry embryonic determinants (EA) associated with the cell membrane. The evolutionary and developmental purpose of these determinants seems to be related to their biochemical and structural role in the cell membrane. True EAs are uniquely expressed on germinal, embryonic and some fetal cell membranes and are not expressed in adult tissues nor in regenerating tissues. The immunological role of EA in fetal development in utero is still obscure. It is known that maternal IgG and cytotoxic T lymphocytes are produced in response to EA expressed in utero. Immunoregulatory interactions between suppressor, helper and cytotoxic T lymphocytes sensitized to EA during pregnancy have been detected in mice and hamsters bearing a variety of tumours. The same immunological events may occur in humans. The biological product of the retrogenic process that leads to the expression of EA in the emerging malignant cell clone seems to be intimately associated with the promotion of tumour-protective immune responses in the host which mimic the immune responses in pregnancy aimed at protecting the EA+ fetus from maternal immune attack. The description of the immunoregulatory perturbations generated by EA during the induction of cancer may eventually provide effective and predictable attack points for immunological intervention in the control of malignancy. This paper describes methods for detecting EA and considers some immunoregulatory traits found in response to EA expression.

Isolation and characterization of the potential receptor for wheat germ agglutinin from human neutrophils

Neutrophils participate in host protection and central to this process is the regulation of oxidative mechanisms. We purified by affinity chromatography the receptor for the GlcNAc-specific WGA from CD14+ CD16+ cell lysates (WGAr). The receptor is a 141 kDa glycoprotein constituted by two subunits of 78 and 63 kDa. It is mainly composed of Ser, Asx, and Gly, and, in a minor proportion, His, Cys, and Pro. Its glycan portion contains GlcNAc, Gal, and Man; NeuAc and GalNAc were identified in a minor proportion. The amino acid sequence of the WGA receptor was predicted from tryptic peptides by MALDI-TOF, both subunits showed homology with cytokeratin type II (26 and 29% for the 78 and 63 kDa subunits, respectively); the 78 kDa subunit showed also homology with the human transferrin receptor (24%). Antibodies against WGAr induce higher oxidative burst than WGA, determined by NBT reduction; however, this effect was inhibited (p < 0.05) with GlcNAc suggesting that WGAr participates as mediator in signal transduction in neutrophils.

Isolation of the receptor for the Amaranthus leucocarpus lectin from human T lymphocytes

Amaranthus leucocarpus lectin (ALL) is specific for GalNAc, and recognizes human T cells. The receptor for ALL was purified from T cells using biotin-labeled lectin and avidin-agarose as affinity matrix. It is a 70-kDa glycoprotein, constituted mainly by serine, glycine, and glutamic acid; its glycosidic portion contains mainly GalNAc; galactose, sialic acid, mannose, and GlcNAc were identified at a lower proportion. By ionic strength chromatography, as well as double dimension electrophoresis, we identified four isoforms of the ALL-receptor. N-terminal amino acid was blocked both in the ALL-receptor and its isoforms, therefore, tryptic peptides of ALL-receptor, analyzed through MALDI-TOF, were compared with the relative values obtained from the NCBInr (ProFound 2004/06/01) database. Our results indicated that the tryptic peptides obtained showed 54% homology with a DnaK-core molecular chaperone, 47% with human KIAA protein, and 44% with heat shock protein 8. The most frequent phenotype of the CD4 or CD8 ALL+ T cells was CD45RA+ CD27+; 26% of ALL+ T cells were CD25+ and 13% were CD69+, indicating that the glycoprotein recognized by ALL is present mainly on naive or quiescent T cells.

How proteins bind carbohydrates: lessons from legume lectins

The pioneering studies of Irvin Liener on soybean agglutinin (SBA) in the early 1950s served as the starting point of our involvement in lectin research during the past four decades. Initially we characterized SBA extensively as a glycoprotein and showed that its covalently linked glycan is an oligomannoside commonly present in animal glycoproteins. We have also introduced the use of the lectin to the study of normal and malignant cells and to the purging of bone marrow for transplantation. Our recent work focuses on the combining site of Erythrina corallodendron lectin, closely related to SBA. In this legume lectin, as in essentially all other members of the same protein family, irrespective of their sugar specificity, interactions with a constellation of three invariant residues (aspartic acid, asparagine, and an aromatic residue) are essential for ligand binding. Lectins from other families, whether of plants or animals, also combine with carbohydrates by H-bonds and hydrophobic interactions, but the amino acids involved may differ even if the specificity of the lectins is the same. Therefore, nature finds diverse solutions for the design of binding sites for structurally similar ligands, such as mono- or oligosaccharides. This diversity strongly suggests that lectins are products of convergent evolution.

Isolation of the receptor for Amaranthus leucocarpus lectin from murine naive thymocytes

From murine medullary thymocytes we purified the receptor for the Amaranthus leucocarpus lectin (ALL) using a complex with the biotin-labeled lectin and avidin-agarose as the affinity matrix. Most ALL(+)thymocytes (83%) are naive cells with the CD4(+)CD8(-)CD45RB(+)phenotype. The receptor for this lectin is a 70 kDa glycoprotein that contains 20% of sugar by mass. It is constituted mainly by aspartic and glutamic acids, serine, proline, and glycine; its glycosidic portion contains mainly O-glycosidically linked glycans with Gal, GalNAc and NeuAc residues as well as one N-glycosidically linked glycan per molecule. Ionic strength chromatography revealed that the ALL-thymocyte receptor (ALLTr) is made up by three isoforms, which possess similar amino acid composition but show slight differences in their sugar composition. The N-terminal amino acid residues are blocked both in the receptor and its purified isoforms. Analyses of the receptor's peptides, obtained by trypsin digestion with MALDI-TOF (matrix assisted laser desorption ionization-time of flight), were compared with the relative values obtained from the NCBInr (Swiss-Prot 10/01/99) database. Our results indicate that the peptides of ALLTr show low homology (<17%) with the human KIIA protein, the Fas-associated death domain protein, and the transforming growth factor-beta type II receptor. Our results suggest that the ALL thymocyte receptor could be considered a novel phenotypic marker specific for naive T cells.

The use of soybean agglutinin (SBA) for bone marrow (BM) purging and hematopoietic progenitor cell enrichment in clinical bone-marrow transplantation

Soybean agglutin (SBA) is a plant lectin that has been used to fractionate bone marrow cells. It binds bone marrow mononuclear cells, including mature myeloid, erythroid, and lymphoid cells, but has very low binding affinity and no toxic effect to the human hematopoietic cells. In this article we describe the possibilities of enriching bone-marrow-derived CD34+ hematopoietic progenitor cells using SBA. As the method is simple and elegant. SBA is of vast importance to the field of clinical bone marrow transplantation.

Fractionation of feline bone marrow with the soybean agglutinin lectin yields populations enriched for erythroid and myeloid elements: transplantation of soybean agglutinin-negative cells into lethally irradiated recipients

Feline bone marrow cells treated with the soybean agglutinin (SBA) lectin are separated into two populations, the agglutinated SBA(+) fraction containing predominantly cells of myeloid origin and the nonagglutinated SBA(-) fraction consisting of cells primarily of the erythroid lineage. FACScan analyses revealed a clear distinction of the cells based on their light scattering properties, i.e., large cells and cells with high granularity were found in the SBA(+) fraction, whereas cells having a low forward light scatter and side light scatter were found in the SBA(-) fraction. Colony-forming assays showed colony-forming unit-granulocyte/monocyte (CFU-GM) cells to have a strong affinity for SBA because these were found almost entirely in the SBA(+) fraction; in contrast, burst-forming unit-erythroid (BFU-E)-forming cells were concentrated in the SBA(-) fraction. When the marrow was fractionated by counterflow centrifugal elutriation (CCE), a differential binding to SBA among the CFU-GM forming cells was found. The SBA(-) fractions of cells collected at 21 and 25 ml/min contained primarily BFU-E forming cells, similar to that observed with whole marrow; the later CCE fractions, those collected at 32 ml/min and the rotor off fraction, when treated with SBA showed a small but significant number of CFU-GM cells in the SBA(-) fraction. T lymphocytes were found predominantly in the SBA(+) fractions of whole bone marrow and the CCE fractions. Successful autologous marrow transplants were performed with the early CCE SBA(-) fractions. The latter cells were used for our initial transplant attempts because ongoing studies in our laboratory had shown these cells to be free of any viral-containing cells when the marrow had been obtained from animals infected with the feline immunodeficiency virus. In summary, although SBA treatment of feline marrow yields a marked separation of CFU-GM and BFU-E progenitors, select CCE SBA(-) fractions contain stem cells capable of providing hematopoietic reconstitution of lethally irradiated animals.

Separation of lectin-binding cells using polystyrene culture devices with covalently immobilized soybean agglutinin

The plant lectin, soybean agglutinin (SBA), has been widely used to separate heterogeneous populations of cells. In the field of bone marrow transplantation, SBA has been used for partial depletion of T cells from bone marrow allografts to reduce graft-vs.-host disease. SBA's high affinity for many different tumor cells has also indicated its use as a tumor purging agent for autologous bone marrow transplants. We have compared two methods of cell separation using either soluble SBA agglutination, or SBA covalently attached to an activated polystyrene surface. The nonbinding SBA-cell populations generated by these two procedures were very similar in terms of cell recovery, light scatter properties, and phenotypic profile. Notably, both SBA- fractions were enriched in cells with the known progenitor markers, CD34, CD33, and HLA-DR, and were relatively depleted of SBA binding cells. In addition, the activity of each SBA- cell population was measured in vitro in short-term progenitor assays. Here, both SBA- populations were significantly enriched for CFU-GM. When device-separated SBA- cell populations were seeded into long-term bone marrow culture, they produced both increased progenitor activity and cell proliferation compared to unseparated BMMCs. The polystyrene technology described here could reduce or eliminate many of the drawbacks of soluble SBA agglutination, making SBA cell separation a viable and convenient technique for clinical application.

Surface glycoprotein of human natural killer cells recognized by wheat germ agglutinin

We analyzed surface glycoproteins of human natural killer (NK) cells by utilizing lectins. Among the lectins tested, wheat germ agglutinin (WGA) was found to bind preferentially to CD16(Leu11)-positive lymphocytes as determined by two-colour flow cytometry. Analysis of glycoproteins in the lysate prepared from NK cells with sodium dodecyl sulfate (SDS) gel electrophoresis followed by Western blotting and 125I labeled WGA staining revealed that a glycoprotein with an M(r) of 65 kDa was strongly bound to the lectin, but no corresponding glycoprotein was detected in the lysate of T lymphocytes. This glycoprotein (GP65) gave several spots in the pI range 4.1-4.6 on 2-dimensional gel electrophoresis. Sialidase treatment of GP65 resulted in a single spot on the 2-dimensional gel, suggesting that GP65 is heterogeneous in the degree of sialylation. GP65 was shown to be exposed on the cell surface, since it was radiolabeled with 125I by the lactoperoxidase-catalyzed method. We next isolated GP65 from human peripheral blood lymphocytes by a combination of chromatography on a cation-exchange column and a WGA-agarose column and preparative SDS gel electrophoresis. It is suggested that GP65 is a novel surface glycoprotein on human NK cells.

Pregnancy-associated suppressor cells in mice: functional characteristics of CD3+4-8-45R+ T cells with natural suppressor activity

Natural suppressor (NS) cells are MHC-unrestricted regulatory cells with non-specific inhibitory activity for immune responses. In adult mice, NS cells are characteristically found in bone marrow and in splenic tissue following total lymphoid irradiation and cyclophosphamide treatments. Recently, we have shown that the spleens of pregnant mice harbour a population of lymphocytes which resemble NS cells in terms of phenotype and inhibitory activity. In this study, we use positive and negative selection techniques to further characterize splenic pregnancy-associated NS (SPANS) cells as predominantly 'double negative' T cells (CD3+4-8-) bearing receptors for the lectins wheat germ agglutinin and soybean agglutinin, as well as expressing CD45R and the heat-stable J11d.2 antigen. Taken together, these findings lead us to conclude that SPANS cells belong to an immature T cell lineage. In keeping with their T cell phenotype, SPANS cells do not express the natural killer (NK) cell-specific markers NK2.1 and asialoGM1 and do not mediate lytic activity against NK-sensitive YAC-1 cells, although natural cytotoxic activity against WEHI-164 cells was found to co-purify with SPANS cells. Suppressive activity of SPANS cells in mixed lymphocyte reactions (MLR) is abolished by treatment with mitomycin C, suggesting that natural suppression in this system is a proliferation-dependent phenomenon. Preincubation of SPANS cells with conditioned medium from Con A-stimulated T cell cultures results in augmented NS activity, indicating that SPANS cells respond to T cell signals. Our data suggest that SPANS cells mediate suppression via the elaboration of a soluble suppressor factor since SPANS cells do not require cell-cell contact to mediate suppression and supernatants from short-term cultures of SPANS cell-enriched SBA+ pregnancy spleen cells inhibit MLR. We believe that SPANS cell may be important in regulating hematopoiesis and maternal anti-fetal immunity during murine pregnancy.

Lectin-binding receptors, Na+,K(+)-ATPase, and acetylcholinesterase on immunocyte plasma membrane of Limulus polyphemus

Plasma membrane receptors are crucial for nonself tissue recognition. Using concanavalin A (Con A), wheat germ agglutinin, peanut agglutinin, soybean agglutinin (SBA), and winged pea agglutinin, five lectin-binding receptor molecules have been recognized on the plasma membrane of the granulocyte (immunocyte) of the horseshoe crab, Limulus polyphemus. Only Con A and SBA caused capping of surface receptors. On the basis of the known functions of these lectin-binding receptor molecules in other invertebrates and vertebrates, their roles in phagocytosis, encapsulation, signaling, and possibly in complement pathway activation are postulated. In addition to lectin-binding receptors, Na+,K(+)-ATPase and acetylcholinesterase were detected on the plasma membrane. Because Limulus dates back to some 200 million years, the antiquity of these molecules is suggested. Furthermore, some of the lectin-binding surface receptors have the potential to be used as markers to separate different kinds of hemocytes in higher arthropods and to distinguish between normal and neoplastic cells in humans.

Alterations in the electrical properties of T and B lymphocyte membranes induced by mitogenic stimulation. Activation monitored by electro-rotation of single cells

Stimulation of either B or T lymphocytes using specific mitogens results in changes in the passive electrical properties of the cell surface. These effects can be related to growth and secretion. This was possible because the high resolution of the contra-field electro-rotation method, combined with the use of very low conductivity media, allowed accurate and analytically-derived values for the cell surface properties. Increases in effective CM (membrane capacity) and changes in apparent membrane conductivity (reflecting the additive effects of true membrane conductivity GM and surface conductance KS) were measured. After 72 h treatment with concanavalin A, thymocyte CM had increased from 0.76 muF/cm2 to 1.24-1.46 muF/cm2 (7.6 to 12.4-14.6 mF/m2). Allowing for the stimulation-induced size increase (cell radius increased from 2.8 to 4.4 micron) these data imply that the plasma membrane area per cell increases 5-fold during stimulation. Stimulation of B cells (by 3 days incubation with bacterial lipopolysaccharide) increased CM from 0.93 to 1.6-1.7 muF/cm2 (9.3 to 16-17 mF/m2). Incubation without mitogen gave no significant increase in CM or in radius. Control cells of different sizes showed no difference in membrane properties. The increases in effective CM are argued to reflect an increase in membrane ramification (microvilli, folding, etc.). The apparent membrane conductivity of T cells also increased during stimulation, from 5 to 21 mS/cm2 (50 to 210 S/m2). This increase is proportionately much greater than that in CM or in membrane area. It seems to be due to a real increase in GM, but a small increase in KS may also occur. The earliest changes in apparent membrane conductivity were evident between 3 and 5 h after stimulation, before the cells increased in size. This response parallels increases in transmembrane transport reported to follow mitogenic stimulation.

Altered immune response patterns in murine syngeneic pregnancy: presence of natural null suppressor cells in maternal spleen identifiable by monoclonal antibodies

Expression of certain autologous lymphocyte-activating antigenic determinants on the developing embryo is known to provide a stimulus for maternal anti-fetal autoproliferative responses. If left unregulated these responses could exert negative influences on the reproductive process by converting to autoaggressive forms of immune reactivity. In normal circumstances, immunological reactions of this nature are therefore likely to be under the control of pregnancy-associated immunoregulatory elements found within the maternal/fetal environment. In the present investigation we describe a naturally occurring splenic inhibitory cell type devoid of conventional T, B, and macrophage surface markers associated with syngeneic murine pregnancy that is capable of exerting potent immunosuppressive effects on an in vitro expression of fetal/newborn T cell autoreactivity, namely the autologous mixed lymphocyte reaction (AMLR). Maternal spleen cells inhibitory for AMLR were found to be highly resistant to cytotoxic pretreatment with a panel of conventional antisera directed against T cell-specific antigenic determinants. The non-T nature of the natural splenic suppressor cell was further indicated by experiments showing that purified spleen T cells had no inhibitory activity. Pregnancy spleen cell populations that were effectively depleted of macrophages retained full ability to inhibit AMLR. Maternal suppressor activity could be localized to the spleen cell population bearing receptors for the B cell-specific lectin, soybean agglutinin (SBA). A panel of monoclonal antibodies prepared against enriched populations of suppressor cells was screened and selected for specific reactivity using an ELISA against glutaraldehyde-fixed SBA+ spleen cell subpopulations from pregnant versus virgin animals. Several of the monoclonals developed against suppressor-enriched spleen cell populations from isopregnant as well as allopregnant animals were effective in reducing or eliminating suppressor cell activity following cytotoxic pretreatment in the presence of complement. The novel set of anti-suppressor monoclonal antibodies described here should prove useful in furthering the isolation and characterization of pregnancy-associated suppressor cells and in determining their relationship to natural suppressor cell populations described in other systems.

Sialic acids in human lymphocytes. Qualitative and quantitative alterations in cancer cases

Sialic acids, hydrolyzed from human lymphocytes, were determined, in the nanomole range, with a modified form of the periodic acid-thiobarbituric acid assay and liquid chromatography. The l.c. separations were carried out with two different systems, firstly an Aminex HPX-72 S anion-exchange resin and a 0.15M ammonium sulfate mobile phase, and secondly an amine phase (5 microns) and an acetonitrile-phosphate buffer as mobile phase. The lymphocytes of cancer-stricken persons showed an evident rise of the sialic acid content, combined with a shift of the sialic acid distribution to higher O-acetylated derivatives, as compared to the controls.

Analysis of differentiation and transformation of cells by lectins

During differentiation cells are known to change their biological behavior according to their genotype. This is thought to be accompanied by a modulation of cell surface determinants expressed on the outer cell membrane. Vice versa, cell surface molecules are suggested to mediate extracellular signals to the genome. Most of these molecules integrated in the cell membrane have been proven to be glycoconjugates. The carbohydrate moieties of these molecules can be detected by means of lectins that are characterized by their ability to react specifically with distinct terminal sugar sequences. Thus, lectins have been used as appropriate tools for studying the modulation of functionally important membrane-associated molecules during the differentiation of cells, in particular of B- and T-lymphocytes. Moreover, lectins have been proven to distinguish between differentiated cells and malignant cell clones, according to the hypothesis that transformed cells possess a glycoconjugate profile that corresponds to the stage of differentiation at which they are arrested. Since lectins, like monoclonal antibodies, make it possible to study functionally important molecules that are associated with differentiation and malignancy, they might be of value for diagnostic purposes and, moreover, for analyzing malignant transformation.

The separation of immunocyte subpopulations by use of various lectins

The use of lectins for the enrichment of various lymphocyte subpopulations was investigated. Bauhinia purpurea lectin (BPA) was found to be effective for the enrichment of B cells, and the B cells thus obtained were further fractionated with lentil lectin into subsets showing high and low responses to dextran sulfate. The ability of various lectins to selectively induce suppressor T cell activity or helper T cell activity was also examined. The suppressor T cells thus induced were enriched peanut lectin and, conversely, the helper T cells were enriched with Limulus polyhemus lectin. This method was applied to analysis of age-dependent changes in the levels of suppressor and helper T cells in autoimmune-prone mice. Cytotoxic T cells induced in an allogeneic mixed lymphocyte culture were enriched with Dolichos biflorus lectin (DBA). These cytotoxic T cells showed a specific killing effect in vitro. However, when spleen cells of tumor-bearing mice were fractionated by use of DBA, the DBA- cells mediated the regression of the tumors in vivo. BPA was also found to be effective for the enrichment of the interleukin-2-producing T cell subset and macrophage precursor cells. Using this technique, bone marrow cells of autoimmune-prone MRL/1 mice were found to be rich in macrophage precursor cells.

The application of lectins to the characterization and isolation of mammalian cell populations

Mammalian cells invariably contain a vast array of glycosylated moieties, both inside the cell and on the cell surface. There is an increasing awareness of the utility of these carbohydrates in delineating the phenotype or function of many populations of cells. To this end lectins are extremely useful reagents. Lectins are carbohydrate-binding proteins and glycoproteins of non-immune origin derived from numerous plants and animals. A wide variety of lectins with many distinct carbohydrate specificities have been isolated. Historically the most common laboratory techniques utilizing lectins have been agglutination, mitogen stimulation, and fluorescence techniques. Recent advances in the development and conjugation procedure for labels and matrices have led to the creation of numerous novel lectin-based assays. Lectins are currently used not only to identify cells with specified carbohydrate groups, but also to quantitate the carbohydrate groups or to isolate the carbohydrate-bearing cells or structures.

A shared B-T cell phenotype in autoimmune mice bearing the lpr gene

MRL-lpr mice and MRL-+/+ mice are identical except for the presence of an autosomal recessive lymphoproliferation gene (designated lpr) in the former. Mice bearing the lpr gene develop autoimmune and lymphoproliferative abnormalities. An antigenic marker designated 14D10, characteristically expressed on the surface of Lyt-2+ T cells and B cells of normal mice, is expressed in unusually high levels on Thy-1+ cells of lpr mice which are Lyt-2-. In younger lpr animals, 14D10+ cells are a minor subpopulation of Ia+ cells which, when expanded in diseased animals, continue to express Ia. 14D10+ cells from lpr mice are elevated in fetal spleen and adult bone marrow (BM) but are absent on pre-B cells in the BM. Medullary thymocytes of lpr mice are enriched in 14D10+ cells compared to congenic (+/+) controls. Although 14D10 appears to be present on the activated, proliferating T-cell population, coculture of lpr cells with IL-2 leads to minimal proliferation. 14D10+ Lyt-2- T cells can be isolated from normal spleens, indicating the lpr gene may be responsible for the disregulated proliferation of a minor cell subset. The functional significance of this molecular complex is still undetermined.

The separation of lymphocyte subpopulations with lectins

Wistaria floribunda agglutinin (WFA), Sophora japonica agglutinin (SJA) and Maclura pomifera lectin (MPL) were employed as immunofluorescent and leucoagglutinating reagents to study murine lymphocytes. WFA, which labels 90% of thymocytes, binds to only 57% of the splenocyte population. The latter subset corresponds to surface immunoglobulin bearing cells. Differential agglutination of splenocytes with this lectin results in the isolation of a WFA negative population which exhibits T-lymphocyte surface markers. The agglutinable splenocytes bind only 2.5 times more WFA than non-agglutinable cells suggesting that the preferential agglutination of B-splenocytes is due to a combination of reduced cell surface negative charge and increased number of lectin binding sites on these cells as compared to T-lymphocytes. Forty percent of splenocytes are positive for SJA and differential agglutination of splenocytes yields a population of SJA non-agglutinable cells that are not labeled by this lectin. The two populations fractionated by SJA are unrelated to T- and B-lymphocyte subsets. Differential agglutination of thymocytes by SJA yields a non-agglutinable group representing 42% of total thymocytes. Although the nature of the two thymocyte subsets discriminated by SJA remains unknown, this lectin appears useful in identifying and separating unique thymocyte and splenocyte populations.

Murine neonatal spleen contains natural T and non-T suppressor cells capable of inhibiting adult alloreactive and newborn autoreactive T-cell proliferation

The spleen of neonatal mice is known to be a rich source of cells capable of suppressing a variety of immune functions of adult lymphocytes in vitro. From such observations has emerged the concept that the gradual development in ability to express immune functions after birth is due in part to the parallel normal physiological decay of naturally occurring regulatory suppressor cells. There is, however, some confusion in the literature as to the exact nature of the newborn of the newborn inhibitory cell type(s). In contrast to most previous reports which detect only a single type of neonatal suppressor cell, usually a T cell, we show here that newborn spleen harbors both T and non-T inhibitory cells. Both types of suppressor cells could be shown to suppress the proliferative response of adult spleen to alloantigens as well as newborn T cells reacting against self-Ia antigen in the autologous mixed lymphocyte reaction (AMLR). Newborn suppressor T cells were characterized as being non-adherent to Ig-anti-Ig affinity columns, soybean agglutinin receptor negative (SBA-), and susceptible to lysis by anti-T-cell specific antiserum plus complement. Non-T suppressor cells were identified as non-phagocytic, SBA receptor positive (SBA+), and resistant to cytotoxic treatment with anti-T-cell antibodies and complement. The apparent controversy surrounding previous reports as to the T versus non-T nature of newborn suppressor cells can be reconciled by the present observation that both types of inhibitory cells coexist in the spleen. Furthermore, the demonstration that newborn suppressor cells can effectively regulate T-cell proliferative activity mediated by other newborn cells provides more direct support for the contention that such inhibitory cells play a physiological role in controlling immune responsiveness during early ontogeny.

Alterations in plasma membrane lipid organization during lymphocyte differentiation

The fluorescent probe merocyanine 540, which binds preferentially to bilayers in which the lipids are loosely packed, was used to investigate changes in the organization of the lipids of the lymphocyte plasma membrane during primary and secondary lymphopoiesis. When mouse thymocytes were incubated with the dye, most immature cells stained, while most mature cells, about to enter the peripheral circulation, did not. Similarly, mature lymphocytes from both mouse and human peripheral blood did not stain, but these same cells did when activated by in vitro mitogenic stimulation. Freshly isolated splenic lymphocytes, presumably activated in vivo by antigen, also bound merocyanine 540, but after 48 hours of culture in the absence of stimulus they displayed only a low affinity for the dye, a phenotype that reverted to a high affinity upon mitogenic stimulation. These results suggest that changes in the organization of the lipids of the plasma membrane take place during lymphocyte differentiation: viz., immature cells possess a disordered membrane that becomes increasingly ordered as the cells mature and enter the peripheral circulation; then, upon antigen-induced differentiation, the plasma membrane again becomes disordered. These lipid organization changes are discussed in the context of their possible role in the regulation of lymphocyte circulation via intercellular interactions between lymphocytes and cells of the reticuloendothelial system.

Binding of Griffonia simplicifolia I lectin to rat pulmonary alveolar macrophages and its use in purifying type II alveolar epithelial cells

We report that the isolectin Griffonia simplicifolia I-B4 isolated from G. simplicifolia seeds binds to rat alveolar macrophages present in frozen sections of lung tissue or bronchoalveolar lavage fluid. G. simplicifolia I-B4 does not bind to alveolar epithelial cells. We established that G. simplicifolia I-B4 binds to the macrophages via interaction with terminal alpha-D-galactopyranosyl residues present on these cells. This was substantiated by demonstrating that binding is inhibited either by the haptenic sugar alpha-D-galactopyranoside or by treating the cells with coffee bean alpha-galactosidase. Because murine laminin is known to contain terminal alpha-D-galactopyranosyl end-groups, and because we found that an anti-laminin antiserum binds to rat alveolar macrophages, we suspect that G. simplicifolia I-B4 may be binding to laminin present on the macrophages. To isolate alveolar type II epithelial cells from rat lungs, we developed a method that utilizes the lectin G. simplicifolia I. When proteinase-derived suspensions of pulmonary cells are incubated with G. simplicifolia I, the macrophages agglutinate and can be removed by filtration through nylon mesh. After incubating the resulting cellular suspension in tissue culture, the adherent cells are 94 +/- 2% (S.D.) type II cells. When compared to cells isolated by repeated differential adherence, the lectin-prepared type II cells have similar morphology and staining characteristics, form domes in monolayers and incorporate similar amounts of palmitate into disaturated phosphatidylcholine. We believe that the procedure outlined in this report provides a simple and effective method to isolate type II alveolar epithelial cells from rat lungs.

Topical application of a tumor promoter induces proliferation of an adherent cell population in murine spleen

The tumor-promoting phorbol esters have proven to be potent immunomodulatory agents in vitro. It has not been possible to assess the role of phorbol ester-induced alterations of immune function in tumor promotion however, due to a lack of in vivo studies. Studies were therefore designed to assess proliferative responses of murine leukocytes after in vivo exposure to these agents. Topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA) was found to cause an increase in division of murine spleen cells. The effect was dose-related up to 14 micrograms per application and generally reached a peak two days after TPA application. Cell separation experiments suggested TPA was acting on an adherent cell population distinct from splenic lymphocytes. Inflammatory reactions to TPA followed a similar time-course to that observed for spleen cell proliferation. The increased levels of proliferation observed could, therefore, be due to increased division of neutrophil and/or macrophage precursors residing in the murine spleen and appeared also to be associated with the inflammatory reaction induced by TPA.

In vitro activation of bone marrow-derived T-and non-T-cell subsets by alpha-fetoprotein

Alpha-Fetoprotein (AFP) is a major serum glycoprotein during embryonic and early postnatal life. A number of diverse biologic functions have been attributed to AFP, including osmotic and carrier function and immunosuppressive activity. In this study we demonstrate that AFP selectively stimulates in vitro proliferation of two distinct subsets of adult murine bone marrow cells. One population of AFP-reactive bone marrow cells expresses surface receptors for soybean agglutinin (SBA) lectin. SBA+ bone marrow cells are resistant to cytotoxic pretreatment with T-cell-specific antisera and are not retained on Ig-anti-Ig affinity columns. The absence of conventional T- and B-cell markers, coupled with the presence of SBA receptors, suggests that AFP-activated non-T bone marrow cells may belong to an immature set of B lymphocytes. A second population of AFP-responsive bone marrow cells expresses the Thy-1+ Lyt 1+2- phenotype characteristic of conventional mature adult T helper cells. The potential physiological relevance of the mitogenic effects of AFP on bone marrow cells with respect to immunoregulatory processes in the fetal/newborn environments is discussed.

Different populations of herpes simplex virus glycoprotein C discriminated by the carbohydrate-binding characteristics of N-acetylgalactosamine specific lectins (soybean and Helix pomatia). Brief report

From the herpes simplex virus specified glycoprotein C two fractions were isolated with affinity either for Helix pomatia lectin (HPA) or soybean lectin (SBA). The data indicated that HPA and SBA, despite their mutual main specificity for N-acetylgalactosamine, recognize structurally different gC populations.

Lectin separation of nonlymphoid suppressor cells induced by total lymphoid irradiation

Suppression of the mixed lymphocyte reaction (MLR) exerted by splenocytes derived from mice treated with fractionated total lymphoid irradiation (TLI, 200 rds x 8) was analyzed by various criteria in order to characterize the phenotype of the cell type(s) responsible for suppression. TLI-induced suppressor cells could not be eliminated by removal of cells bearing surface immunoglobulin, Thy-1, Lyt-2 and TL, and thus could not be ascribed to lymphocytes of the B or T cell lineage. Suppressor cells were large, and nonadherent to nylon wool, Sephadex G-10 and plastic surfaces. Suppressor activity of TLI splenocytes was predominantly located in fractions of cells bearing receptors for soybean agglutinin (SBA), peanut agglutinin (PNA) or both lectins. SBA+, PNA+, sequentially agglutinated (SBA followed by PNA) SBA+PNA+ and (PNA followed by SBA) PNA+SBA+ suppressor cells were radioresistant upon exposure to 1000 rds in vitro. Cells bearing the receptor for PNA but lacking that for SBA (PNA+SBA-) had sharply reduced suppressor activity. However, a radiosensitive PNA- suppressor cell subset was also documented in the spleen of TLI-treated mice. Thus, suppressor cells could best be physically separated from nonsuppressors by the SBA lectin. SBA+ suppressor cells were found, by scatter analysis, to include the population of large cells characteristic of TLI splenocytes, whereas SBA- cells were much smaller and almost exclusively devoid of suppressive capacity. The PNA receptor was found to further dissect the SBA+ suppressor cells into two distinct subpopulations: radioresistant SBA+PNA+ cells and radiosensitive SBA+PNA- cells. In summary, we suggest here the presence of at least two suppressive populations induced by TLI: radioresistant SBA+, PNA+, SBA+PNA+ or PNA+SBA+ cells, and radiosensitive PNA- and SBA+PNA- cells. Similar subsets of MLR suppressor cells can be isolated from normal bone marrow cells and splenocytes of nude mice, suggesting that suppression is mediated by large, immature, nonlymphoid cells which might migrate from shielded bone marrow compartments into the spleen of TLI-treated mice.

Characterization of peanut agglutinin receptors of murine thymocytes

Murine thymocytes can be separated on the basis of their agglutinability by peanut agglutinin (PNA) into two broad subpopulations assimilated to immunoincompetent agglutinated PNA+ cells and immunocompetent nonagglutinated PNA- cells. Seven surface membrane components have been isolated by immunoprecipitation using rabbit anti-PNA IgG and Staphylococcus aureus bearing protein A, from PNA-coated radiolabeled immature cells. These components (apparent molecular weights of 180, 175, 130, 115, 65, 26, and 23 kDa) labeled by the galactose oxidase/tritiated sodium borohydride method and by 125I-iodination are glycoproteins which are PNA-receptor sites normally exposed on the surface membrane of PNA+ thymocytes. The nonagglutinated PNA- cells also possess on their surface unmasked receptors for the lectin (175-180 kDa) but in lower amounts. Neuraminidase treatment prior to galactose oxidase/tritiated sodium borohydride labeling shows that the majority of PNA receptors is present on the PNA-thymocyte surface but are masked by sialic acid residues on the terminal position of the oligosaccharidic chains.

Epidermal fucosylation of cell surface glycoprotein

When Ulex europeus agglutinin I (UEA) conjugated with fluorescein isothiocyanate is applied to tissue sections from the cutaneous epidermis of the newborn rat, the lectin binds to the surfaces of cells in the layer immediately above the basal layer but not to the cells in the basal layer itself. The latter cells bind the isolectin I-B4, from Griffonia simplicifolia (GS I-B4). The addition of a fucosyl residue to the oligosaccharide of the glycoprotein found on the surface of the basal cell can account for the change in lectin-binding specificity which occurs as the basal cell moves toward the cutaneous surface and becomes a spinous cell. The epidermis of the newborn rat has the necessary transferase to convert a glycoprotein with binding-specificity for GS I-B4 to binding specificity for UEA by adding a fucosyl residue from GDP-L-fucose.

Molecular analysis of the lymphocyte membrane

Methods for the molecular analysis of lymphocyte membranes are reviewed briefly, and wherever possible presented in a manner relevant to comparative studies. The specific areas reviewed include the bulk isolation of lymphocyte membranes, the use of radioisotopes to covalently label lymphocyte membrane molecules, the use of lectins to characterize membrane glycoconjugates, and our current understanding of lymphocyte membrane immunoglobulins.

Differential binding characteristics and applications of DGal beta 1----3DGalNAc specific lectins

The binding properties of Arachis hypogaea (PNA), Bauhinia purpurea alba (BPL), Maclura pomifera ( MPL ) and Sophora japonica (SJL) lectins were studied by quantitative precipitin and precipitin inhibition assays, demonstrating them to be most specific for DGal beta 1---- 3DGalNAc residues. Additionally, each lectin had its own binding characteristic such as different binding activities to DGal beta 1---- 4DGlcNAc or DGal beta 1---- 3DGlcNAc beta 1----linked oligosaccharides, and/or DGalNAc alpha 1----linked to the Ser or Thr of the protein moiety. These differential binding characteristics can be used for investigating fine differences of the carbohydrate structure of the glycoconjugates, especially those having DGal beta 1---- 3DGalNAc residues as terminal non-reducing ends.

Cell-mediated immunity following experimental vaccinations with Candida albicans ribosomes

The aim of the present study was to ascertain whether cell-mediated immunity (CMI) is induced in animals by vaccination with Candida albicans ribosomes. Delayed type hypersensitivity (DTH) was detected in vivo in ribosome-vaccinated mice and guinea pigs by the footpad swelling and skin tests, respectively. The observed DTH was similar to that induced by live C. albicans organisms. A lymphocyte transformation assay was used for in vitro detection of CMI. The tritiated thymidine incorporation assays revealed that spleen lymphocytes from mice immunized with C. albicans ribosomes were stimulated by the ribosomal antigen. The findings establish that C. albicans ribosomes are able to induce CMI in experimental animals.

Activation of murine B lymphocytes by Neisseria meningitidis and isolated meningococcal surface antigens

Heat-killed Neisseria meningitidis was found to be a potent mitogen for mouse splenic lymphocytes. Results obtained with different cell separation techniques indicated that the bacteria acted to selectively induce proliferation of B lymphocytes. First, partial or total depletion of T lymphocytes by treatment with various anti-T-cell antisera plus complement did not affect the ability of the remaining spleen cells to proliferate in response to N. meningitidis. Second, T lymphocytes purified by affinity chromatography through an immunoglobulin-antiimmunoglobulin-coated glass bead column were unresponsive to meningococcal stimulation, even when provided with a source of macrophages (irradiated or mitomycin C-treated spleen cells). Finally, treatment of spleen cells with soy bean agglutinin showed that, whereas the soy bean agglutinin-positive population (B-enriched lymphocytes) was highly responsive to stimulation by N. meningitidis, the soy bean agglutinin-negative population (T-enriched lymphocytes) displayed only a background level of proliferation when exposed to the bacteria. Isolated meningococcal surface antigens such as lipopolysaccharide (LPS) and outer membranes also possessed mitogenic activity and induced proliferation of B lymphocytes in a dose-dependent manner. Both LPS and non-LPS components contributed to the mitogenicity of outer membranes since the addition of outer membrane preparations to spleen cells from the low LPS responder C3H/HeJ mouse strain gave rise to a high level of proliferative activity.

Enrichment of IL-2-producer T cells from mouse spleen by use of Bauhinia purpurea lectin

Bauhinia purpurea agglutinin (BpA) was used to enrich the interleukin 2 (IL 2)-producing T-cell subset from mouse spleen. IL 2 was found to be produced by the BpA-non-agglutinated (BpA-) T cells of mouse spleen on stimulation with concanavalin A (Con A). The degree of IL 2 production by BpA-agglutinated (BpA+) T cells was significantly low. The proliferative response to Con A of BpA- T cells was not influenced by the addition of exogenous IL 2, whereas BpA+ T cells were partially dependent on the exogenous addition of IL 2 in the proliferative response.

Thymus cell differentiation and in vivo T-cell migration. I. Migration of lectin-selected thymocytes

The in vivo quantitative distribution and tissue positioning of mouse thymocytes selected in vitro by Lyt phenotype and lectin binding properties were examined. Lyt 1+2- thymocytes were selected for by cytotoxic elimination; peanut agglutinin (PNA) and soybean agglutinin (SBA) binding and nonbinding thymocyte fractions were separated by an agglutinin technique. Selected cell suspensions were labelled in vitro with 51chromium (51Cr) or [3H]adenosine. Labeled washed cells were injected intravenously into syngeneic recipients which were killed at 1, 24 or 48 hr. In recipients of 51Cr-labeled cells, tissues were collected for gamma counting, and the overall percentage recovery of injected radiolabel from the various tissues was assessed. Tissues collected from recipients of [3H]adenosine-labeled cells were fixed, sectioned, and processed for autoradiography; the positioning of labeled cells within the tissues was determined. Selected Lyt 1+2-, PNA-, and SBA- sets all showed significantly enhanced entry into lymph nodes and intestinal lymphoid tissues. Entry of SBA+ cells into these tissues was comparable to that of peripheral T cells. PNA- and SBA- selected sets, but not Lyt 1+2- selected cells, also showed increased localization to the spleen and lungs, and decreased localization to the liver. By autoradiography, PNA- cells entered lymphoid tissues much more than PNA+ cells, and at 1 hr fewer PNA+ cells in spleen were associated with lymphoid follicles. At 24 and 48 hr almost all labeled cells in lymphoid tissues were positioned in T-dependent areas. These results suggest that enrichment for thymocyte subpopulations described as "mature" also enriches for cells with the ability to enter lymphoid tissue. They also suggest that interactions at other tissue sites are important in the determination of in vivo migration, and that surface carbohydrate composition is an important factor in this determination.

Naturally occurring non-T suppressor cells in pregnant and neonatal mice: some functional and phenotypic characteristics

The mammalian fetus thrives in the presence of a maternal immune system which is considered capable of initiating an aggressive reaction against alloantigens expressed on fetal cells. The control of harmful immunological reactions during pregnancy may be due in part to the combined action of soluble immunoregulatory factors and suppressor cells in the maternal/fetal environments. In the present investigation, a comparison has been made between naturally occurring splenic suppressor cells isolated from neonatal and pregnant adult CBA/J mice. Functional analysis of inhibitory activity was carried out using conventional one-way allogeneic mixed lymphocyte reactions (MLR) consisting of adult CBA/J spleen cells responding against mitomycin C-inactivated BALB/cJ spleen cells. Suppressor cells in the spleen of pregnant animals as well as a population of inhibitory cells in newborn spleen could be shown to be highly resistant to cytotoxic pretreatment with anti-T cell serum plus complement. Both newborn and pregnant non-T suppressor cells were shown to be agglutinated by the B cell-specific lectin soybean agglutinin. The densities of these two populations of non-T inhibitory cells, as determined by Percoll gradient centrifugation, were demonstrated to be very similar (ie, within the range of 1.067 to 1.043 g/ml). The striking parallels in the functional and phenotypic characteristics of the non-T suppressor lymphocytes found in the spleen of pregnant and neonatal animals suggest a common mechanism for their induction.