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Human erythrocyte glycophorin was desialylated by mild acid hydrolysis and degalactosylated by Smith degradation. Two monoclonal antibodies (Tn5 and Tn56) obtained by immunization of mice with this 'artificial' Tn antigen were characterized and compared in some experiments with two antibodies (BRIC111 and LM225) obtained in other laboratories by immunization with Tn erythrocytes. The specific binding of the antibodies to glycophorins desialylated and degalactosylated on the nitrocellulose blot and to asialo-agalactoglycophorin-coated ELISA plates, and reactions with authentic Tn antigen served for identification of their anti-Tn specificity. The antibodies were further characterized in inhibition assay with various glycoproteins. The antibody Tn5 (similar to BRIC111) was shown to be specific for human erythrocyte Tn antigen, whereas Tn56 reacted strongly with different glycoproteins carrying O-linked GalNAc alpha- residues, and was strongly bound to the murine adenocarcinoma cell line Ta3-Ha. The antibodies Tn5, Tn56 and BRIC111 were similarly inhibited by ovine submaxillary mucin (OSM) and asialoOSM, but the antibody LM225 showed a distinct preference in reaction with OSM (sialosyl-Tn antigen). The results show that Tn antigen, obtained by chemical modifications of human glycophorin, enables the preparation and characterization of anti-Tn monoclonal antibodies, without using rare Tn erythrocytes.

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Analysis of epitopes for the three monoclonal antibodies (GPA105, GPA33, OSK4-1) against glycophorin A (GPA) was performed with the use of proteolytic fragments of GPA, the synthetic nonapeptide with the sequence of amino acid residues 35-43 of GPA, and a series of peptides synthesized on plastic pins. The antibodies were specific for a short peptide sequence RAHE (a.a. 39-42 of GPA, MAbs GPA105 and OSK4-1) or RAHEV (a.a. 39-43 of GPA, MAb GPA33). Despite recognizing the same fragment of GPA, the three antibodies showed differences in fine specificity and in response to antigen desialylation. Reactions with single replacement analogs of the RAHEV sequence showed that immunodominant (unreplaceable) residues for the MAbs GPA33 and OSK4-1 were His and Glu, respectively, whereas no such residue was found for the MAb GPA105. Desialylation of the antigen gave strong enhancement of reactivity with the MAb GPA33, moderate--with the MAb GPA105, and weak or no enhancement of reaction with the MAb OSK4-1. The results showed that monoclonal antibodies directed against the same fragment of the polypeptide chain of densely glycosylated antigen may recognize different subsites which are masked at different degree by sialic acid residues.

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Three monoclonal antibodies: 2.36.71.41, 7.60.66.55, and 18.4.40. 80 to human haptoglobin 2-1 were produced, purified and characterized. The affinity constants ranged within 0.3-2.4 x 10(8) M-1. The monoclonal antibodies 7.60.66.55 and 18.4.40.80 reacted with beta subunit of haptoglobin, showed similar epitope affinities and epitope densities on main haptoglobin types. However, the epitope on the haptoglobin molecule for the monoclonal antibody 18.4.40.80 occupied somewhat more surface than that for the antibody 7.60.66.55. The monoclonal antibody 2.36.71.41 was able to bind both alpha and beta chains of haptoglobin. In ELISA affinity reactions this antibody achieved with haptoglobin 2-2 the plateau phase at absorbance values 15% higher than with haptoglobin 2-1, and 60% higher than with haptoglobin 1-1. End-point titration of the monoclonal antibody 2.36.71.41 against three haptoglobin types showed differences in titer, indicating distinct epitope densities.

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Monoclonal IgM antibody against L1210V leukemia was coupled with ricin A-chain using N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) as a cross--linking agent. The coniugate had potent concentration--dependent cytotoxicity against L1210V, L1210 and RL male 1 cells being completely non toxic to EL-4, P388, RPC-5 and mouse bone marrow cells. The minimum time required for killing L120V leukemia cells was 30h of in vitro exposure, at a concentration 10(-6) M (as assessed by trypan blue test). However, 1h contact of L1210V cells with immunotoxin was sufficient to completely inhibit proliferation of leukemic cells subsequently inoculated into compatible mice. The toxicity could be potentiated by addition of NH4Cl, that shortened minimum exposure time to 18h and 45 min respectively.

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The Thomsen-Friedenreich (TF) antigen is a cryptic disaccharide structure on human erythrocytes which can be exposed by neuraminidase treatment and which is supposed to be expressed in an unmasked form on some carcinoma cells. For its detection in addition to auto-, allo- and heteroantisera, PNA (peanut lectin) is being applied. In the present studies the mouse monoclonal antibody (MoAb) raised to asialoglycophorin from human erythrocytes was used. The MoAb 22.19 is of mouse IgM isotype and is specifically binding to beta-D Gal-1-3 alpha-D GalNAc. The human urothelial cell lines maintained and characterized earlier were analyzed using indirect immunofluorescence assays. Among the spectrum of cell lines tested, five out of six cell lines belonging to the transformation grade III category (invasive in vitro and tumorigenic in nude mice) expressed TF antigen. The relationship between expression of TF antigen and other earlier defined biological traits related to malignant phenotype is discussed.

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The mouse hybridoma monoclonal antibody BIII.136 of the IgG2a class is specific for human erythrocyte band-3 protein. It was shown by means of immunoblotting and immunoprecipitation assays that the antibody recognized an epitope located in the cytoplasmic pole of the band-3 molecule within approximately 20 kDa from the N-terminal end. The N-terminal fragments of band-3 protein, migrating in SDS/polyacrylamide gel electrophoresis in the 60-kDa, 40-kDa and 20-kDa regions, were detected with the antibody in untreated red-cell membranes as products of autolysis of band-3 protein. A correlation was found between the amount of these fragments and erythrocyte age, which suggests that partial degradation of band 3 proceeds in vivo during senescence of erythrocytes. The further degradation of band-3 protein in vitro was not observed in intact erythrocytes stored at 4 degrees C, but progressed distinctly after hemolysis of red cells, during washing and storing the membranes.

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Monoclonal antibody to purified prostatic acid phosphatase from seminal plasma was produced by fusion of spleen cells from immunized mice with the Sp2/O-Ag 14 cell line. This hybridoma-derived antibody, designated MAb-14, was classified as IgG1 immunoglobulin. The apparent affinity constant of phosphatase.MAb-14 complex formation calculated by using the Langmuir isotherm is 2.4 x 10(-8) M. The molecular weight of the complex formed under the condition of antibody excess was found to be 350K, which suggests that 2 molecules of prostatic phosphatase bind to 1 molecule of the antibody. The MAb-14 antibody bound to phosphatase had a negligible effect on the catalytic activity of the enzyme. All isoenzymatic forms of catalytically active prostatic phosphatase, resolved by isoelectric focusing or by chromatofocusing in different pH gradients, reacted with the monoclonal antibody. Several peptides of Mr 25K to 76K and of 13K to 76K were adsorbed from the prostatic tissue extract and from seminal fluid, respectively, on an MAb-14-Sepharose column. The MAb-14 monoclonal antibody was applied to the immunohistochemical investigation of prostatic phosphatase distribution in normal human prostate gland, in nodular hyperplasia, and in adenocarcinoma of the prostate. Immunostaining was observed in prostatic secretory epithelium, within the luminal content of prostatic glands, and in the neighborhood of prostatic cancer cells. Metastatic prostatic carcinoma was also strongly immunoreactive with the antibody. There was no cross-reactivity with leukocytes, kidney, liver, pancreas, spleen, breast, stomach mucosal, and colon tissues.

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Two monoclonal antibodies, N/61 (IgG2b) and N/92 (IgG2a), reacting preferentially with blood group N antigen, were obtained by immunization of BALB/c mice with human red cell membrane glycophorins. The antibodies showed distinctly different specificities. N/61 reacted with an epitope with NH2-terminal Leu residue, its free amino group, and sialic acid residues as essential components. The antibody N/92 reacted equally well with untreated and desialylated N glycoprotein, but did not react with de-O-glycosylated antigen. It seemed to recognize an epitope including both blood group N-characteristic amino acid residues, namely the 1st Leu and 5th Glu. The antibodies also differed in pH-dependence. N/61 showed maximal activity at pH 6-7 with tendency to decrease at higher pH values, whereas N/92 was not or weakly active up to pH 7, and showed a strong increase of activity at pH range 7-8.

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Prostatic acid phosphatase (EC 3.1.3.2) was fragmented by trypsin and papain in the presence of sodium dodecyl sulphate. Trypsin-catalysed cleavage gave a peptide of 33 kDa which was subsequently trimmed to 18 kDa, 15 kDa and 13 kDa peptides. Even the small tryptic fragments reacted with antiphosphatase antibodies from rabbit serum and with monoclonal antibody mAb-14. Papain treatment under these conditions resulted in the release of a 40 kDa peptide which was gradually reduced to a 18 kDa peptide. The monoclonal antibody mAb-14 to the prostatic phosphatase was bound exclusively to the 50 kDa subunit of the phosphatase and to the 40 kDa peptide. The results suggest that the monoclonal antibody mAb-14 binding site represents a "local" sequence rather than a "conformational" one and does not require an extensive tertiary folding of the antigen molecule.

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Seven inbred mouse strains, AKR, CBA, C3H, C57BL/6, C57BR/cd, DBA/2 and Swiss, maintained at the Bhabha Atomic Research Centre, Bombay (designated Bh) were monitored for compatibility with standard strains as well as for genetical homogeneity. For this purpose, five individual mice from each strain were typed serologically for H-2 class I and class II antigens and for lymphocyte differentiation markers, Thy-2, Lyt-1, Lyt-2, TL and Ly-10. In this latter testing, 15 inbred strains from the Institute of Immunology and Experimental Therapy, Wroclaw (designated Iiw) were included. Results revealed that none of the tested strains deviated from the reactivity pattern of standard strains described in the literature. No evidence of genetic contamination was found in any strain. In the course of these studies, several interesting observations were made: (1) Swiss/Bh strain is an intra H-2 recombinant, probably KdAbEbDbTlab, (2) C3H/Bh and C3H/Iiw are Ly-10a and Ly-10b, respectively (3) some (CBA, C3H, DBA/2 and GR/S) but not C58/Ly-2a strains cross reacted with high concentration of anti Lyt-2.2 monoclonal antibody HO.2.2.

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IgG1 monoclonal antibody to purified seminal fluid phosphatase was raised by fusion of spleen cells from immunized mice with cell line Sp2/O-Ag 14 using simple method of screening for antiphosphatase antibody secreting clones. All molecular forms of catalytically active seminal fluid phosphatase and prostatic tissue phosphatase, resolved by chromatofocusing in pH gradient, react with this monoclonal antibody and with rabbit antiserum to purified seminal fluid phosphatase. Peptides of Mr 25,000 to 76,000 and of Mr 13,000 to 76,000 were adsorbed from the prostatic tissue extract and from seminal plasma on the monoclonal antibody-Sepharose column.

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Tissue distribution of non-Lyt1.1 ("Ly10-like") antigen or antigens encoded by short chromosomal segment differentiating B6-Ly-1a congenic strain from B6 strain of mice was studied by quantitative absorption of (BALB/c X B6)F1 anti B6-Ly-1a antiserum and by direct cytotoxicity of Ly-10-132-12-26 monoclonal antibody on lymphoid cell populations. Identical strain but not tissue distribution pattern does not allow to conclude whether antiserum and monoclonal antibody detect the same or closely linked antigens. Absorption experiments revealed the highest antigen content in the brain tissue, lower in testis and kidney, still lower in lymphoid organs and the lowest in liver and lung. Among lymphoid cells, bone marrow cells had highest absorbing capacity, followed by thymus, spleen and lymph nodes. Monoclonal antibody lysed almost 100% of thymocytes, 30% bone marrow cells and 10-20% of spleen and lymph node cells (both T-cell and B-cell enriched populations contained the same proportion of positive cells). Cortisone resistant thymocytes showed the same sensitivity as cortical thymocytes to Ly-10-132-12-26 antibody which is distinguishable characteristics of medullary thymocytes from peripheral T cells. Mitogen activated lymphocytes exhibited significantly higher expression of Ly10-like antigen than resting peripheral lymphocytes.

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We obtained a monoclonal anti-TL antibody-producing hybridoma by fusion of Sp2/0 hybrid cells with spleen cells from (B6 X A-Tlab) F1 mice immunized with ASL1 leukemia cells. The antibody, TL-22-27-17, reacts in complement-dependent cytotoxicity assay with ASL1 cells as well as with normal thymocytes of TL+ mouse strains (B6-Tlaa, A, BALB/c, DBA/2 and 129) but not with thymocytes from TL- mice (B6--Ly-1a). In addition, it did not react with lymph node cells or Concanavalin A-induced spleen blasts from B6-Tlaa mice; this result shows that TL-22-27-17 recognizes TL and not Qa-1 antigen. The positive reactions with BALB/c (TL.1-2+3-5-6-7+) and 129 (TL.1-2+3-5-6-7-) thymocytes suggest that antibody TL-22-27-17 reacts with TL.2 or TL.2-like antigenic determinant.

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Conventional antisera to L-1210 leukemia were being prepared in our laboratory for nearly a decade and consistently the only specificity detectable was anti Mammary Leukemia antigen (ML). Serological analysis of five monoclonal antibodies obtained following the same immunization schedule showed more diverse pattern of reactivity. Two antigens detected belong to oncofetal category. The third one is differentiation antigen Ly-6 and the nature of two others, expressed on leukemic cells only, remains at present unclear. Thus none of the clones analysed produces antibodies to ML antigen. Our previous analysis of cell surface antigens of L-1210 leukemia with the use of conventional antisera has already been described. This paper presents the results of applying monoclonal antibodies in a comparable studies.

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Allogenic, semisyngeneic and syngeneic sera of animals immunized with ML-positive leukemia L1210 cells, besides anti-ML antibodies, contain antibodies which react with Gross cellular surface antigen. ML antigen and Gross cellular surface antigen were shown by the immunoferritin test in electron microscopy, and by the blocking test, to be situated on different parts of the cell surface. No budding viral particles were found on the areas occupied by these antigens. By distinguishing the ML antigen identified on the surface of leukemia L1210 cells from the Gross cellular antigen, it was shown that the MTV present in leukemias of DBA/2 mice has no leukemogenic properties. Demonstration of core and envelope antigens of the MTV and Gross MuLV, besides C particles and intracytoplasmatic A particles, which are precursors of B particles, is proof of existence of genomes of both viruses in leukemia L1210 cells. The ability of leukemia L1210 cells to absorb activity from the anti-ML sera and reaction between anti-ML sera and isolated B particles of the MTV in immunoprecipitation, indicate probable existence of an antigenic component of the MTV within the ML antigen.

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