Lymphocyte plasma membranes. III. Composition of lymphocyte plasma membranes from normal and immunized rats

Liposomal amphotericin B inhibits in vitro T-lymphocyte response to antigen

The effects of free amphotericin B (as Fungizone) and amphotericin B (AMB) incorporated into liposomes on the proliferation of lymphocytes were determined. Freshly obtained guinea pig and rat antigen-specific lymphocytes were compared with rat T-lymphocyte cell lines cultured for a long period of time. Incorporation of AMB into multilayered vesicles significantly reduced its effect relative to that of Fungizone on cultured T-cell lines, as reported by others for mammalian cells. In contrast, the effects on freshly obtained antigen-specific lymphocytes were different. Fungizone inhibited proliferation of antigen-specific lymph node cells freshly obtained from immunized guinea pigs at fungicidal concentrations, and incorporation into multilayered lipid vesicles did not have much of a protective effect. Higher concentrations of Fungizone were required to inhibit proliferation of fresh rat lymph node cells, but incorporation into multilayered lipid vesicles still did not have much of a protective effect. Some T lymphocytes in the peripheral circulation of guinea pigs and in the lymph nodes of rats were more resistant to liposomal AMB than another more sensitive T-lymphocyte population was. Proliferation of lymphocytes in response to mitogens was inhibited less than that in response to specific antigen was. Thus, sensitivity to AMB depended on the species, the strength of the stimulus used to activate the lymphocytes, and on some other property of the lymphocytes, possibly their state of differentiation. Regardless of the reason for the difference in effects on freshly obtained lymph node lymphocytes and cultured line cells, the former may be more relevant to effects in vivo and should be considered in a complete evaluation of the in vivo toxicity of these forms of the drug. Incorporation into sonicated unilamellar vesicles had more of a protective effect, while equimolar drug-lipid complexes had even more of a protective effect. These forms of AMB might have less of an immunosuppressive potential than multilayered vesicles containing low amounts of AMB do.

Binding and incorporation of lecithin-cholesterol vesicles to lymphocytes: a spin-label study

When lecithin-cholesterol vesicles, containing the membrane-bound spin probe 3-doxyl-cholestane, were set in contact with mouse lymphocytes, the vesicles adsorbed to the cell and vesicle-membrane components were transferred to it. The spin probe was enzymatically reduced at the inside of the cell membrane. The spin-label method provided a means to determine quantitatively the extent of vesicles adsorption and vesicle-cell fusion by measuring the transfer of vesicles membrane material to the cell. This method, together with the reduction of spin label by the cell, allowed also a quantitative estimate to the extent of endocytosis during cell-liposome interaction.

Studies on the intracellular cAMP metabolism of tonsillar lymphocytes

cAMP metabolism, including the intracellular cAMP level and adenylcyclase activity, was studied in tonsillar and peripheral lymphocytes. The basal activity of adenylcyclase was significantly higher in tonsillar lymphocytes than in peripheral lymphocytes, although the basal level of intracellular cAMP did not differ. The responsiveness of the intracellular cAMP level and adenylcyclase activity stimulated by 10(-5) M isoproterenol, or 10(-5) M prostaglandin E1, which was thought to stimulate this enzyme through a specific receptor, was significantly lower in tonsillar lymphocytes than in peripheral lymphocytes. Moreover, the responsiveness of adenylcyclase activity to 10(-2) M NaF, which was thought to stimulate this enzyme directly, was also significantly lower in tonsillar lymphocytes. Tonsillar T lymphocytes represented a lower cAMP basal level than tonsillar B lymphocytes, but no difference was observed in the responsiveness of intracellular cAMP to the above agents. Tonsillar lymphocytes derived from patients with recurrent tonsillitis represented significantly lower cAMP responsiveness than those from patients of other chronic tonsillitis. Furthermore, in the tonsillar lymphocytes from patients with a recent attack of acute tonsillitis, a more depressed responsiveness of the intracellular cAMP level to the above agents was recognized. The cAMP basal level was not changed by these pathological alterations of tonsillitis.

A marmoset T-lymphocyte protein related to defined human serum immunoglobulin and fragments

Current concepts of the antigen-specific receptor of thymus-derived (T) lymphocytes suggest that this molecule bears immunoglobulin (Ig) variable (V) regions, but does not represent a classical serum antibody. We immunized rabbits with a globulin fraction obtained from an in vitro cultured marmoset T cell lymphoma line which expressed surface components related to immunoglobulins. Quantitative immunoprecipitation and competition radioimmunoassay studies carried out using characterized monoclonal human Igs and their chains and fragments show that this rabbit antiserum, raised against a T cell product, reacts with a particular, conformational VH-determinant which is formed by interaction with lambda light chains and with two mu chain (IgM) related determinants. Neither mu chain determinant is a major isotype specific marker, and each occurs only on certain distinct subsets of serum mu chains. One is located in the Fc fragment; the location of the other mu related determinant is not known. These results show that this rabbit antiserum recognizes both variable and constant region determinants on the T cell receptor heavy chain. Rabbit antibody to the T cell product which cross-reacts with serum mu chain was isolated by immune affinity chromatography on Sepharose-derivatized covalently with one particular reactive IgM protein, the Waldenstrom macroglobulin Can (kappa mu). This antibody precipitated a biosynthetically-labelled component of approximate M.W. 70,000 as assessed by polyacrylamide gel electrophoresis in Na Dod SO4-containing buffers. These data support the conclusion that certain T cells express and synthesize a molecule related to Ig VH-regions which also has a constant region sharing antigenic markers with IgM subpopulations.

The composition and fluidity of normal and leukaemic or lymphomatous lymphocyte plasma membranes in mouse and man

The lymphocyte surface membranes from normal and leukaemic or lymphomatous cells from man and mouse were isolated, characterized, and analyzed both biochemically and by diphenyl hexatriene fluorescence polarization. The cholesterol/phospholipid molar ratio for all the pure lymphocyte plasma membranes was 0.45--0.50, and the fluorescence polarization results showed that values much higher than this were not credible. The lipid composition of all the plasma membranes was remarkably similar, except for the concentration of free fatty acids and glycerides. The latter two were particularily high in the mouse lymphoma membrane and these, rather than a low cholesterol concentration, were responsible for the increased fluidity of the cells. The most prominent protein in most of the plasma membrane preparations was actin. This is found only by some authors, and its presence probably depends on the method of lymphocyte disruption.

The binding of lectins to components of plasma membranes from porcine submaxillary lymph node lymphocytes

By sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis the plasma membranes from porcine lymphocytes contain at least 30--35 glycopolypeptides and one or more glycolipids to which one or more of 12 purified lectins bind. The specificities of binding generally followed the same pattern as those of the reaction of the lectin with intact pig lymphocytes. Some lectins (e.g., the isolectin pair, Agaricus bisporus lectins A and B and a group consisting of the Lens culinaris A and B isolectins and the closely related Pisum sativum lectins) bind to almost identical populations of plasma membrane components and compete with each other for all their binding sites. Others (e.g., Concanavalin A and the Lens culinaris-Pisum sativum group and a group consisting of phytohemagglutinin-L, Ricinus communis lectin-60 and Ricinus communis lectin-120 bind in a cross reactive manner to some common binding moieties but, in addition, to certain nonshared ones. Still others (e.g., soybean agglutinin, peanut agglutinin and wheat germ agglutinin) do not share any common binding moieties with the other lectins. The amount of lectin binding and the number of membrane components to which a lectin binds is directly related to the Ka of binding of the lectin to the intact lymphocyte. Those with high Ka (Cocanavalin A Lens culinaris lectins, Pisum sativum lectins, phytohemagglutinin-L), bind to 20-30 different components giving very complex binding patterns while those with lower Ka (Agaricus bisporus lectins, wheat germ agglutinin, peanut agglutinin, and soybean agglutinin) bind to 8--13 components with easily distinguishable patterns. Soybean agglutinin binds almost exclusively to a glycolipid fraction while for the others one or more glycopolypeptides served as the major lectin-binding molecule. The Ricinus lectins, two lymphocyte toxins, bind to essentially every plasma membrane component to which the mitogen phytohemagglutinin-L binds, in fact competing for most of those plasma membrane moieties which bind phytohemagglutinin-L.

Visualization of a guinea pig T lymphocyte surface component cross-reactive with immunoglobulin

Thymus-derived lymphocytes (T cells) show exquisite specificity in recognition of antigens, but the nature of the cell surface receptor is controversial. Although antigen recognition mediated by immunoglobulin variable (V) regions remains the minimal hypothesis, it has been extremely difficult to definitely establish the presence of immunoglobulins on these cells. Chicken antibodies, produced against the (Fab')2fragment of mouse immunoglobulin G (IgG) and purified by binding to and elution from IgG-Sepharose 4B, bind to an endogenously synthesized surface component of guinea pig T cells. The binding occurred via a cross-reaction with murine k chain and a heavy chain determinant localized in the Fd region, and was visualized by immunofluorescence and immunoelectronmicroscopy using both transmission and scanning techniques. These data provide direct evidence for the presence of a surface component related to immunoglobulin on T lymphocytes.

Lymphocyte plasma membranes. VI. Plasma membrane glycoproteins of thymic and splenic lymphocytes from inbred rats

Plasma membranes of splenic and thymic lymphocytes from ACI rats were analyzed for their protein and glycoprotein components by surface radioiodination with 125I and SDS-polyacrylamide gel electrophoresis. The glycoproteins were extracted with lithium diiodosalicylate, characterized and assayed with antisera to thymic antigen. Plasma membranes of both cell types showed more than 25 proteins of which 10--15 were glycoproteins. Both cells showed five major glycoproteins but their apparent molecular weights or intensities differed. Surface radioiodination showed a 120 000 daltons component, common to both cell types, and a 27 000 daltons thymus-specific component as the most exposed surface glycoproteins. Lithium diiodosalicylate extracts of the plasma membranes contained almost all of the glycoprotein components and comprised 5-6 percent of the total membrane protein and 40-50 percent of the total membrane carbohydrate, with sialic acid content in thymus twice that of the spleen cells. About 1 percent of the total plasma membrane protein and 7 percent of the total isolated glycoproteins from thymocytes were reactive with rabbit anti-rat thymocyte antiserum and the immune precipitates showed two components with apparent molecular weights of 72 000 and 27 000.

Molecular properties of T lymphoma immunoglobulin. I. Serological and general physicochemical properties

Immunoglobulin (Ig) released into the medium by monoclonal continuously cultured murine T lymphoma cells of the lines WEHI-22 and WEHI-7 was isolated by serological precipitation or solid-phase immunoadsorption techniques. The intact immunoglobulin had an electrophoretic mobility on sodium dodecyl-sulphate (SDS) containing polyacrylamide gels comparable to that of IgG (mass 150,000). This mobility was significantly faster than that of '7S' IgM of murine B lymphocyte surfaces. The T lymphoma immunoglobulin consisted of a pair of heavy chains linked by disulphide bonds and light chains non-covalently bound to the heavy chains. The isolated heavy chains migrated slightly faster than the mu chains of MOPC 104E IgM. Some, but not all, antisera directed against mu chains of normal mouse serum IgM bound T lymphoma immunoglobulin apparently via a cross-reaction localized to the Fd fragment. These data indicate that immunoglobulin of T lymphoma cells and, presumably normal T lymphocytes, represents an immunoglobulin isotype which is distinct from those immunoglobulins found on the B cell surface.

Lymphocyte surface immunoglobulins: detection, characterization, and occurrence in disease of the lymphoid system

Surface immunoglobulins (Igs) of lymphocytes are of considerable interest because these molecules probably function as receptors for antigen, and knowledge of their molecular properties should provide information on the mechanisms of immune differentiation. The density and types of surface Ig on a cell provide markers useful in indicating the class of a lymphocyte and its stage of maturity. Moreover, knowledge of the specificities of the surface Ig of neoplastic lymphocytes might suggest the nature of agents involved in the generation of the disease. Two broad classes of lymphocytes, bone marrow-derived lymphocytes (B cells) active in antibody secretion, and thymus-derived lymphocytes (T cells) which mediate cellular immune reactions, and their subpopulations must be considered with reference to the nature, origin, and function of their surface immunoglobulin. This article analyzes direct and indirect methods for the demonstration of surface Igs and describes certain physicochemical properties of isolated surface Ig molecules. Roles of these surface molecules in recognition of antigen, initiation of all differentiation, and cooperation among lymphocytes and accessory cells are discussed.

Binding of human hemoglobin and its polypeptide chains with haptoglobin coupled to an agarose matrix

The interactions of human haptoglobin covalently linked to agarose with human hemoglobin and with p-chloromercuribenzoic-acid-treated alpha and beta chains (alpha* and beta* chains) were studied by flow chromatography and equilibrium binding. The results indicate that in solid state, haptoglobin maintains the same binding characteristics as in solution, the order of binding affinities being: hemoglobin greater than alpha* chain greater than beta* chain. The study of the binding parameters of the alpha* chain shows an heterogeneity of binding sites on the haptoglobin and an average affinity constant Ka of 3.6 X 10(4)l/mol.

Immunochemical detection of the Thomsen-Friedenreich antigen (T-antigen) on the pig lymphocyte plasma membrane

A method for the isolation of lymphocytes from pig peripheral blood and preparation of plasma membranes was developed. The method resulted in a ten-fold increase in 5'-nucleotidase activity and neuraminic acid, relative to protein. A cholesterol/phospholipid ratio of 0.93 was obtained. Alkaline borohydride treatment of isolated plasma membrane, after desialylation, released the disaccharide beta-D-galactosyl-(1 leads to 3)-N-acetyl-D-galactosaminitol (the immunodominant group of the T-antigen), which was identified by gas chromatography using a crystalline standard. The disaccharide was not found without prior desialylation, indicating that all the disaccharide units were substituted by neuraminic acid. Serological evidence using the agglutinins from Arachis hypogoea and Helix pomatia confirmed the presence of this disaccharide (T-antigen) in the lymphocyte membrane and indicated that it was the major alkali-labile oligosaccharide of the pig lymphocyte membrane.

Surface immunoglobulin on activated human peripheral blood thymus-derived cells

Human peripheral blood lymphocytes grown in vitro were stimulated with nonspecific mitogens and in mixed lymphocyte culture. The presence of IgM and thymus (T) surface markers on large and small lymphocytes was investigated by immunofluorescence and correlated with spontaneous rosette formation. All stimulated large lymphocytes formed spontaneous rosettes and all except pokeweed mitogen (PWM)-stimulated large lymphocytes had IgM and T markers. IgG, IgA, and light chain determinants were only detected on PWM-induced large lymphocytes. Thus, surface markers expressed on activated human lymphocytes may differ for different mitogens. IgM was always present on large cells which had the T markers, and it cannot be used to identify a lymphocyte as a bone marrow-derived (B) cell. Due to the overlap of surface markers, the classification into B and thymus-derived (T) cells ought to be restricted to functional phenomena of antibody-production or cell-mediated immunity.

Lymphocyte surface immunoglobulins

Immunoglobulins have been isolated from the surface of B (bone marrow-derived) and T (thymus-derived) lymphocytes. Two types of membrane immunoglobulin occur on B lymphocytes; one type resembles the 200,000-dalton subunit of IgM, the second possesses a heavy chain electrophoretically distinct from mu chain and does not correspond to any of the known classes of mouse immunoglobulins. It might correspond to human sigma chain. T lymphocytes possess only one type of surface immunoglobulin. This molecule has a mass of approximately 200,000 daltons and contains light chains and heavy chains similar to, but not identical to, mu chains. Evidence now exists that surface IgM-like immunoglobulins of B lymphocytes and T lymphocytes activated to certain antigens can bind specifically to antigen. These observations suggest that surface immunoglobulin functions as a receptor for antigen on B cells and at least on some T cells. The mechanisms by which combination of antigen with surface immunoglobulin initiate differentiation remain to be determined.

Biochemical and enzymatic characterization of thymic and splenic lymphocyte plasma membranes from inbred rats

Purified splenic and thymic lymphocytes from the ACI and F344 strains of inbred rats were disrupted by controlled hypotonic treatment, and their plasma membranes were prepared by sucrose density gradient centrifugation. The plasma membrane preparations were highly purified as judged by the structural appearance of the smooth membrane vesicles, by the 10- to 15-fold enrichment of 5'-nucleotidase, which cytochemically localized exclusively in the plasma membranes of intact lymphocytes, by the high cholesterol to phospholipid molar ratio (0.7-1.0), and by the very low specific activities of the enzymes associated predominantly with mitochondria, lysosomes, and endoplasmic reticulum. The protein and the lipid contents of the membranes were 48-55 and 37-48%, respectively. The total lipid content of plasma membranes was characteristically higher in thymic than splenic lymphocytes from both ACI and F344 strains. The specific activity of 5'-nucleotidase was similar in splenic lymphocyte membranes of the ACI strain, and in both the thymic and splenic lymphocyte membranes of the F344 strain. In contrast, the thymic lymphocyte membranes in the ACI strain showed half as much 5'-nucleotidase specific activity. Cytochemical results indicated that the 5'-nucleotidase is located on the outside surface of the lymphocyte plasma membranes.