Isolation and characterization of H-2 and TL alloantigens from the surface of mouse lymphocytes

Characterization of class I bovine lymphocyte antigens (BoLA) by one-dimensional isoelectrofocusing

BoLA class I antigens were characterized in a group of British and Dutch Friesian cattle by one-dimensional isoelectric focusing (1D-IEF) and the results compared with serology using alloantisera and microcytotoxicity. For IEF analysis, non-stimulated peripheral blood mononuclear cells (PBM) were metabolically labelled with 35S methionine, detergent lysates were prepared and MHC molecules precipitated with the monoclonal antibodies (mAbs) W6/32 or B1.1G6. Staphylococcus protein A precipitated antigens were separated on a vertical slab gel under denaturing conditions. The banding patterns seen for the W6/32 precipitated molecules obtained by 1D-IEF were compared with the serological specificities. Characteristic banding patterns were observed for most serological specificities as well as workshop undefined haplotypes. These patterns were seen both in families and the outbred population. In families IEF haplotypes segregated with serotypes. Additional MHC class I products were suggested by variable banding patterns for different w10 haplotypes and when using the different mAbs. A pulse chase experiment with a w12 animal also suggested more than one expressed product. The w2 and w5 specificities were not precipitated by either W6/32 or B1.1G6 and w6.2 and w6.4 were precipitated by W6/32 but not by B1.1G6. These results show that 1D-IEF is useful for BoLA typing. For the characterization of class I antigens, however, much depends on the mAbs used.

Biosynthesis of glycophospholipid bound and secreted murine class I Qa-2 polypeptides

Murine T cells synthesize and express a cell-surface glycophospholipid anchored 40 kDa and a secreted water-soluble 39 kDa Qa-2 polypeptide. We have examined the biosynthetic pathways which lead to the production of the membrane-bound and water-soluble isoforms of the Qa-2 molecule. Using the detergent TX-114, both detergent (membrane)-bound and soluble Qa-2 polypeptides can be identified in cell lysates and can be distinguished by charge and molecular weight. Two membrane-bound forms, a 40-kDa Endo H resistant cell-surface form and a 38 kDa-Endo H sensitive form can be identified, both of which can be biosynthetically labeled with 3H-ethanolamine and can be converted to water soluble forms by digestion with a phosphatidylinositol specific phospholipase C. In addition, several water soluble polypeptides at 39, 37, 35 kDa, and a minor species at 33 kDa were identified, none of which radiolabel with 3H-ethanolamine. While the 39-kDa polypeptide was Endo H resistant, the other isoforms were sensitive to Endo H digestion. Pulse chase experiments and molecular weights of the deglycosylated core polypeptides suggest a precursor to product relationship between the intracellular water-soluble species and the mature 39-kDa secreted Qa-2 molecule. This relationship is supported by the observation that murine L cells transfected with the Qa-2 encoding class I gene Q7 fail to express membrane-bound Qa-2 molecules yet synthesize both intracellular water-soluble and secreted Qa-2 molecules. These findings argue for a pathway in which secreted soluble Qa-2 molecules are derived from intracellular precursors.

Antigens specified by the Tla locus are expressed on the surface of murine Langerhans cells

A monoclonal antibody against the murine thymus leukemia antigen TL, was employed to demonstrate the presence of the antigen on the surface of dendritic cells in murine epidermis of Tla-positive strains, B.10A and A.TH. Immunofluorescence and immunoperoxidase staining of EDTA-separated epidermal sheets demonstrated dendritic cells with a distribution pattern and density comparable to that noted for anti-IAk staining. Tla-negative mouse strains such as A.TL, C3H/HeJ, and C57BL/6 did not show any staining of dendritic epidermal cells. Epidermal cell suspensions similarly contained 2-4% cells with discrete surface staining with anti-TL antibody. Capping was noted in these cells. Once again positive results were noted only in appropriate Tla-positive strains. Control staining was carried out in all cases on frozen sections of thymii from mice. Thymocytes in the cortical zones and some dendritic cells at the corticomedullary junction were stained. TL antigen in mouse appears to be analogous to T-6 antigen previously detected on human Langerhans cells.

Polymorphism and diversity in the Tla gene system

The TL products of mouse strains carrying the Tlaa, Tlad, and Tlae haplotypes were analyzed by comparative peptide mapping. As expected from their known serologic differences, TL antigens from strain A (Tlaa), A.CA strain (Tlad) and P/J strain (Tlae) mice showed structural variation. However, comparable variations were also observed in the TL product derived from strains expressing the serologically indistinguishable Tlaa allele (A, NFS/N, SJL/J, C57BR, and C58) demonstrating additional unexpected polymorphism in the TL system. When compared with the structural diversity of the H-2 K and D gene products, the structural variation of the TL antigens was small. Taken together, the results of our analysis of the TL products suggest that Tla polymorphism is more extensive than previously thought; however, the structural diversity of the products is still low compared with K and D gene products.

A monoclonal antibody recognizing a human thymus leukemia-like antigen associated with beta 2-microglobulin

A monoclonal antibody, M241, was produced which binds to a human cell surface molecule with properties similar to the murine thymus leukemia (TL) antigen. This human TL-like antigen was found on thymocytes and some T cell lines derived from patients with acute lymphocytic leukemia, but was not found on peripheral blood lymphocytes or B cell lines. The monoclonal antibody M241 was used to immunoprecipitate a molecule from lysates of 125I surface-labeled MOLT 4 cells which had two subunits, a 43-kDa chain and a 12-kDa chain. The small subunit was shown to be beta 2-microglobulin (beta 2m) by immunoprecipitation with a monoclonal antibody, BBM.1, which recognizes human beta 2 m. The TL-like molecule recognized by M241 was shown to be serologically distinct from the HLA-A,B,C molecules recognized by three monoclonal antibodies W6/32, PA2.6 and BB7.8, and distinct from another human thymocyte antigen, the 49 kDa HTA 1 molecule, recognized by the monoclonal antibody NA1/34. Following removal of the HLA-A,B,C molecules, the HTA 1 molecules, and the M241-defined TL-like molecules from MOLT 4 lysates, additional beta 2m-associated molecules were immunoprecipitated with BBM.1. These molecules contained a 45-kDa subunit attached to beta 2m.

Rapid semi-quantitative isolation of beta-2-microglobulin from urine

A rapid semi-quantitative purification of beta 2-microglobulin from transplant urine relies on a batch absorption using hydroxylapatite-cellulose. Stepwise elution is followed by Sephadex G-150 gel permeation chromatography. Using this methodology, it is possible to process quickly and conveniently many liters of urine at bench scale, with yields exceeding 95% and overall purity greater than 97% beta 2-microglobulin.

A public antigenic determinant in the HLA-B5 cross-reacting group--a basis for cross-reactivity and a possible link with Behcet's disease

Serologic cross-reactivity among allelic gene products commonly occurs in the HLA complex, but the molecular basis of these serologic phenomena is incompletely characterized. Because of strong cross-reactivity among antigens comprising the B5 cross-reactive group (i.e., HLA-B5, B15, B18, and Bw35), we initiated a study of the chemical basis of cross-reactivity among this group of antigens. Using classic serologic procedures, an 125I-Protein A binding assay, and chemical immunoprecipitation techniques, we have defined a new antigenic determinant, tentatively designated "Y," which is present on certain HLA-B molecules. By a series of sequential immuno-precipitation experiments, Y was shown to be a "public" antigenic determinant distinct from the "private" determinants B5, B15, B18, and Bw35, but present on the same 44,000 dalton glycoprotein molecules. Although B5 is most highly associated with Behcet's disease, other members of the B5 cross-reactive group have also been associated with Behcet's, albeit to a lesser extent. These associations suggest that determinant Y may play a role in predisposition to Behcet's disease.

Use of immobilized lactoperoxidase to label L cell proteins involved in adhesion to polystyrene

Proteins involved in the attachment of murine L cells to polystyrene have been identified by a technique designed to iodinate only those macromolecules coming into closet apposition to the substratum. Whereas soluble lactoperoxidase (LPO) catalyzes the radioiodination of a broad spectrum of polypeptides, the same enzyme immobilized on polystyrene tissue culture flasks discriminately labels 55,000 and 42,000 mol wt polypeptides that adhere tightly to the substratum after the cells are removed. One-dimensional peptide mapping following limited proteolysis showed that the labeled 55,000 mol wt polypeptide is similar to a component of comparable molecular weight present in the detergent-extracted cytoskeleton. The functional association of two cytoskeletal structures, presumably 10-nm filaments and actin, is discussed, and alternative explanations for their susceptibility to iodination by immobilized LPO are presented.

Plasma membrane polypeptides of resident and activated mouse peritoneal macrophages

With the lactoperoxidase/glucose oxidase-catalyzed iodination method, we have identified at least 19 exteriorly disposed plasma membrane polypeptides on mouse peritoneal macrophages, with molecular weights ranging from 12,000 to 290,000. Resident and inflammatory macrophages could be distinguished by qualitative and quantitative differences in the display of selected polypeptides, although the overall banding patterns were similar. Some of the labeled polypeptides were identified by immunoprecipitation.

Some structural properties of thymus leukemia antigen (TL) solubilized with detergent

Plasma membranes were isolated from the leukemia cell line ASL1w and extracted with detergent (DOC). DOC solubilized more TL activity than could be detected on isolated membranes. However, extraction of membranes with LDS or EDTA solubilized only 17% and 4%, respectively, of the activity. This indicated that TL was not loosely associated with the membrane but rather was integrated into the lipid bilayer. At low concentrations of DOC (0.05%), TL was found to be largely aggregated and was also prone to autolysis. Neither aggregation nor autolysis was observed at a higher DOC concentration (0.5%). The apparent molecular weight of TL in 0.5% DOC was determined by Sephadex G-200 chromatography to be about 65,000-70,000. Digestion of a 0.5% DOC extract of TL with either papain or trypsin produced a fragment of TL of about 35,000 molecular weight. These fragments were similar in size to a fragment produced by autolysis. These data suggested that a region of the TL molecule was very prone to proteolytic attack. The 35,000 molecular weight proteolytic fragments bound specifically to lentil lectin affinity columns, which indicated that they retained at least part of the carbohydrate present on the native molecule.

beta 2-Microglobulin: methods and clinical applications

beta 2-Microglobulin is a low molecular weight protein that is found in most biological fluids. It was originally isolated from urine of cadmium-poisoned patients. Its amino acid sequence was established and shown to be structurally related to immunoglobulin constant domains. With the aid of antibodies specific against beta 2-microglobulin, the protein was detected on the membranes of all nucleated cells, normal and neoplastic. Measuring the quantity of beta 2-microglobulin showed that high levels are present in patients with renal tubular deficiencies and several other pathological conditions including neoplastic diseases. Extremely high levels were detected in seminal fluid and colostrum. Despite the structural relationship to immunoglobulins, no immunological relationship was demonstrated with these proteins using antibodies specific for beta 2-microglobulin. However, such antibodies are cytotoxic to all cells carrying beta 2-microglobulin on their surfaces. The discovery that beta 2-microglobulin is an integral part of the histocompatibility antigens of human and murine origin stimulated further research and interest in this molecule. Several groups of investigators have shown that beta 2-microglobulin is the low molecular weight chain and is noncovalently bound to a high molecular weight chain which carries the histocompatibility antigens. The structure of the histocompatibility antigens of lymphocytes (HLA) was shown by immunochemical as well as biological methods, and it is now well accepted. The antibodies against beta 2-microglobulin are extremely useful in the isolation of the histocompatibility antigens for sequence studies. Furthermore, the antibody to beta 2-microglobulin revealed that other structures may be bound to beta 2-microglobulin such as phytohemoagglutimin (PHA) receptors, mixed lymphocyte culture (MLC) antigens, etc. Murine thymus leukemia (TL) antigen also contains beta 2-microglobulin as an integral part of its structure; other tumor antigens may have a similar structure. Through all these studies, beta 2-microglobulin emerged as the best known membrane protein that can serve as a model for study of the arrangement and the function of the cell membrane.

The effect of specific antiserum on the metabolism of three membrane-associated antigens of ASL-1 x LM(TK)- hybrid cells

Fusion of ASL-1 cells, a murine leukemia forming thymus leukemia (TL) antigens, with LM(TK)- cells, a TL(--) murine cell line, resulted in a stable hybrid forming TL antigens. The hybrids failed to undergo modulation, the reversible dissappearance of TL antigens from the surfaces of the cells, stimulated by TL antiserum. Unlike ASL-1 cells, the rate of disappearance of the antigens from modulation negative hydrid cells was unaffected by TL antiserum. The t 1/2 of TL antigens of the hybrid was approximately 30 h. The t 1/2 of TL antigens of ASL-1 cells was 10 h in the presence of TL antiserum, 18 h in the absence of TL antiserum. The rate of metabolism of a putative tumor-associated antigen of ASL-1 cells formed by the hybrid was unaffected by exposure to specific antiserum, as was the metabolism of H-2 antigens formed by the cell types.

Non-lytic, non-ionic detergent extraction of plasma membrane constituents from normal and transformed fibroblasts

A technique has been developed for the selective extraction of plasma membrane protein constituents from normal and transformed cell employing non-ionic detergents. The extraction procedure does not damage cells as judged by cell viability, 51Cr release, and trypan blue staining. Lactoperoxidase-catalyzed iodination followed by detergent extraction permits demonstration of a 100,000 dalton protein which is found on the surface of normal but not transformed hamster and mouse fibroblasts.

Quantitative isolation of mouse thymus leukemia antigen, TL

This report describes the purification of TL from papain digests of a tumor line (ASL1) and of an established cell line (L251A). Through the use of gel filtration and ion-exchange chromatography, the TL was purified approximately 100-fold with respect to the original digest. It was noted that the TL isolated from ASL1 had a specific activity 1.4 times higher than that isolated from L251A. The reason for this anomaly is unexplained. However, this work indicates that classical methods of protein chemistry can be used in the purification of these membrane components which are present in only small amounts on the cell surface.

Distribution of transplantation antigens on cell surfaces

Significant advances have been made over the past few years in elucidating the genetics, the chemical composition, and, more recently, the in situ relation of the major histocompatibility antigens of the mouse and man. Attempts to map the arrangement of individual antigens on the surface of cells have revealed that some antigens specified by a given subregion of both the H-2 and HL-A systems are in close proximity on the cell membrane and that attachment of antibody to one site to a certain degree blocks or inhibits the binding of antibody to the adjacent site. Allelic antigens in the H-2 system tend to inhibit binding. H-2D and H-2K antigens show either inhibition or noninteraction, possibly reflecting a cis-trans effect. Unlike with the H-2, inhibition of binding occurs only between HL-A antigens specified by homologous chromosomes. Also, a number of instances have been noted where inhibition of binding is unidirectional, possibly reflecting a polymeric nature of antigen or stratification of moieties at cell surface. Inhibition of antibody attachment between several alloantigenic systems on thymocytes in mice and also a variation in the mobility of the histocompatibility antigens suggest that the moieties bearing histocompatibility antigens are comprised of several gene products. Further work is needed to establish the validity of this assumption and to fully define the composition of these units. Ample data have been obtained from both biological and biophysical experiments to support the suggestion that single or multiple complexes of glycoproteins can move in the plane of the membrane. Although the composition of these cell membrane components remains a question, direct visualization by fluorescence and electron microscopy indicates that these moieties are small and, under natural conditions, distributed uniformly over the cell surface. Direct and indirect labeling techniques have shown that the complexes have no fixed position in the cell membrane and can be displaced laterally in the plane of the membrane without affecting the distribution of other surface molecules, such as sIg and species-specific antigens. Additional evidence suggests that H-2D and H-2K antigen complexes, as well as their gene products specified by different parent chromosomes, may be displaced separately. These observations are especially interesting and must be reconciled and data obtained by proximity analysis which indicate an association of some allelic products and possibly certain combinations of D and K antigens. Whether the differences noted in reactivity of the various surface antigens following attachment of antibodies are attributable to difference in size or to differences in the manner of their intercalation in the cell membrane remains to be elucidated. The rapid advances in elucidation of the molecular structure of biological membranes suggest that experimental work should be done on the biophysics of the structure of the antigenic sites and the mechanism of migration...

The subunit structure of thymus leukemia antigens

EDTA-containing buffer solubilizes thymus leukemia antigens (TLa) from crude thymocyte membrane fractions. The TL antigens consist mainly of molecules of a size similar to immunoglobulin G when gel chromatography analyses were performed under physiological conditions. A single component of TLa was apparent on sucrose density gradient ultracentrifugation of solubilized thymocyte membrane macromolecules as monitored by indirect immunoprecipitation. The sedimentation constant for the TL antigens (5.8 S) was considerably less than that for immunoglobulin G. The gel chromatography and ultracentrifugation data suggest an apparent molecular weight for TLa of about 120000. TLa isolated by indirect immunoprecipitation is composed of two types of polypeptide chains. The smaller subunit was identified as beta2-microglobulin. The larger polypeptide chain carried the alloantigenic determinants and displayed a molecular weight of about 50000 after reduction and alkylation. TLa subjected to molecular weight determination under denaturing conditions was composed of two components. The smaller component was beta2-microglobulin which evidently is linked to the larger polypeptide chain by noncovalent interactions only. The larger component had a size greater than reduced and alkylated immunoglobulin G heavy chains. Upon reduction and alkylation of the latter component its size was reduced and it appeared to have a molecular weight of about 50000. Consequently, TLa is composed of two disulfide linked heavy polypeptide chains and two beta2-microglobulin molecules. TLa solubilized by papain digestion comprises two polypeptide chains, one of which is beta2-microglobulin. The larger 37000-dalton subunit is a fragment of the heavy polypeptide chain. This was demonstrated by digesting solubilized 120000-dalton TLa with papain. The proteolytic fragments obtained were indistinguishable from those directly released from the cell surface by proteolysis. The papain-derived TLa fragment exhibited most if not all the alloantigenic determinants.

Structural similarities between a product of the T/t-locus isolated from sperm and teratoma cells, and H-2 antigens isolated from splenocytes

Molecules specified by the H-2-linked T/t locus in the mouse are expressed on H-2-negative cells such as early embryos, sperm, and teratoma cells. By means of enzymatic radioiodination of cells and immunoprecipitation of lysates with congenic antiserum, one of these molecules, known as F9, has been obtained from sperm and teratoma cells and compared to H-2 isolated from murine splenocytes. Our studies indicate that both H-2 and F9 have identical molecular weights and subunit structure, including the presence of a B2-microglobulin-like subunit. These findings, taken together with previous studies of TL alloantigens, suggest that a number of gene products of the 9th linkage group show structural homology with each other and, in addition, with immunoglobulin. The genes in question may therefore have arisen from a primitive gene concerned with cellular recognition.

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

Isolated plasma membranes of thymic and splenic lymphocytes from unimmunized and immunized rats of the inbred ACI and F344 strains were analyzed for chemical and enzymatic composition, for membrane protein patterns by polyacrylamide gel electrophoresis and for membrane-associated immunoglobulins. After immunization, the thymic and splenic lymphocyte membranes from F344 rat contained less carbohydrate and higher phospholipid contents than control animals. In both ACI and F344 inbred rat strains the membrane phospholipid to cholesterol weight ratio increased significantly after immunization. The electrophoretic patterns of solubilized membrane proteins and of iodinated external membrane proteins were similar in unimmunized and immunized animals. When thymic and splenic lymphocytes of normal or immunized animals were surface radioidinated, solubilized in Triton X-100, NP-40 or 10 M urea in 1.5 M acetic acid and analyzed by immunoprecipitation, labeled IgM immunoglobulin was recovered from thymic lymphocytes but both labeled IgG and IgM were recovered from splenic lymphocytes. However, when unlabeled isolated plasma membranes were solubilized in 1 percent Triton X-100 and analyzed by immunodiffusion in agarose gels both IgG and IgM were identified in thymic and splenic cells.

Synthesis, intracellular distribution, and secretion of immunoglobulin and H-2 antigen in muring splenocytes

A/J spleen cells were labeled with [(3)H]leucine and at intervals thereafter were homogenized and separated into microsomes and cell sap. Ig and H-2 antigens were assayed in the cell fractions and cell supernatants using immunoprecipitation. In addition, cells labeled by enzymatic radioiodination were incubated to determine the rates of release of Ig and H-2 antigens from the surface. The results indicate that the majority of Ig and H-2 antigens remain membrane bound throughout their intracellular life. In contrast to Ig, H-2 antigens are neither secreted nor shed from the cell surface. It is suggested that Ig is a peripheral protein of the cell membrane, whereas H-2 antigens are integral ones. The release of Ig on a fragment of plasma membrane could occur at fixed cell surface areas that contain no H-2 antigens or from which they have migrated before release.

Some biochemical properties of thymus leukemia antigens solubilized from cell membranes by papain digestion

Thymus leukemia (TL) alloantigenic activity was solubilized by papain proteolytic digestion from intact RADA1 tumor cells. If the cells were labeled with amino acids and fucose, the TL alloantigen could be isolated as a doubly labeled glycoprotein fragment by indirect precipitation from the papain digest. This TL glycoprotein fragment was approximately the same mol wt as the papain-digested H-2.4 alloantigen fragment as judged by chromatography on Sephadex G-150 in sodium dodecyl sulfate. The carbohydrate chain of the TL glycoprotein obtained by exhaustive pronase digestion behaved as a glycopeptide of approximately 4,500 mol wt, as compared with the glycopeptide of the H-2.4 alloantigen that had a mol wt of about 3,500. Thus, the TL alloantigen can be solubilized by papain digestion as a glycoprotein fragment similar in mol wt to the H-2 alloantigen glycoprotein fragment. The carbohydrate chain of the TL glycoprotein is larger than the H-2 carbohydrate chain.

Cell surface immunoglobulin. V. Release from murine splenic lymphocytes

Turnover and release of cell surface Ig and secretion of total intracellular Ig has been studied in small lymphocytes from normal mouse spleen. The major findings to emerge are: (a) small lymphocytes secrete 8S IgM and IgG. A small portion of the 8S IgM, but virtually none of the IgG appears to have a cell surface phase. (b) Cell surface IgM is actively turned over with a half-life of 6-8 hr, and turnover can be accounted for by release into the incubation medium. Release is temperature dependent. (c) Released cell surface Ig is noncovalently bound to a fragment of plasma membrane. (d) H-2 antigens are not released during short-term incubation. Based on the above findings, we propose a model for the transport and release of both cell surface and conventionally secreted Ig.