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Biomedical subjects

L Ostberg

Publications and source records attributed to L Ostberg.

At least 37 records · Page 2Linked to original sources
PubMed1983

Human X (mouse X human) hybridomas stably producing human antibodies.

A method is described for constructing mouse heterohybridomas producing human monoclonal antibody with a high stability. The essence of the method is the use of a nonsecretor mouse X human hybridoma which has been made 8-azaguanine resistant as a fusion parent for construction of (mouse X human) X human hybridomas. The production of four human anti-influenza antibodies is described. The cells have now been maintained for more than 22 months in culture.

Animals↗
PubMed1979

Demonstration of a murine cell surface component with affinity for exogenous beta 2-microglobulin.

Murine and human beta 2-microglobulin (beta 2m) bind to various types of mouse cells. The binding is saturable and displays a single association constant of about 1 x 10(9) liter/mol. The binding of beta 2m to splenocytes was not affected by a variety of metabolic inhibitors but was temperature-dependent. It is suggested that the beta 2m "receptor" exhibits a temperature-dependent conformational change since the "receptor", whether integrated into the membrane or solubilized by the detergent Triton X-100, binds beta 2m poorly at low temperatures. Spleen T and B lymphocytes display more binding sites than thymocytes, kidney, liver and brain cells. The relative amounts of the beta 2m-binding "receptor" on these cell types are strongly correlated to the relative amounts of H-2 antigens. This correlation is also obvious for the teratocarcinoma cell line F9, which lacks both beta 2m "receptor" and H-2 antigens, but spermatozoa, which express very small amounts of H-2 antigens, have an appreciable amount of the beta 2m "receptor". The latter observation, together with the fact that alloantisera directed against H-2 K and D antigens do not measurably affect the binding of beta 2m to the "receptor", may argue against the notion that the beta 2m "receptor" represents H-2 antigens which have lost their endogenous beta 2m. Normal mouse serum contains a component which inhibits the binding of beta 2m to splenocytes. It is likely that this serum protein is identical to a newly discovered H-2 antigen-like glycoprotein. The beta 2m "receptor" appears to be under the control of the major histocompatibility complex as splenocytes of the H-2f haplotype bind considerably more beta 2m than splenocytes of other haplotypes.

Animals↗
PubMed1979

Non-H-2 antigens on fibroblasts and an embryocarcinoma cell line react with xenoantisera against H-2 antigens.

The murine embryocarcinoma cell line F9 lacks the classical transplantation antigens. However, rabbit anti-H-2 antigen sera, recognizing "backbone structures" of H-2 K and D antigens, react with three types of molecules manufactured by F9 cells. A 49,000- and a 25,000-dalton chain are glycoproteins located on the cell surface. The third component with an apparent molecular weight of 15,000, and the 25,000-dalton chain seem to be unrelated to the 49,000-dalton glycoprotein. The 25,000- and 15,000-dalton components are not manufactured by splenocytes, thymocytes, hepatocytes, or various lymphoma, mastocytoma, and plasmacytoma cell lines. However, fibroblasts derived from both embryos and adult animals synthesize 25,000- and 15,000-dalton molecules reactive with the rabbit anti-H-2 antigen sera. The 49,000-, 25,000-, and 15,000-dalton molecules are not recognized by a syngeneic anti-F9 cell serum.

Animals↗
PubMed1979

A rapid method for the separation of functional lymphoid cell populations of human and animal origin on PVP-silica (Percoll) density gradients.

Subclasses of lymphocytes can be separated on gradients of non-toxic polyvinylpyrrolidone-coated colloidal silica (Percoll) by virtue of differential densities. Such gradients can yield functionally active lymphocyte populations after brief centrifugation. Gradients can be generated in a discontinuous step fashion and centrifuged in standard table-top laboratory centrifuges or as self-generating gradients during ultracentrifugation. The density medium has low viscosity and can be made isotonic for virtually any use. Gradients have proved useful in both human and experimental animal studies, and high percentage yields allow for separations from small cell numbers. Methods are described for separation of whole blood and lymphoid subpopuctions. The cytoxic capability of various density fractions was evaluated for mixed lymphocyte culture-induced allogeneic killing and spontaneous, so-called "natural" killer cell activity. The lower density associated with blast transformation allows for significant enrichments of stimulated cells from in vitro cultures. Higher thymidine incorporation, restimualtion in mixed lymphocyte reactions, and greater cytotoxic capacity are associated with these "blast" fractions.

Animals↗
PubMed1978

Molecular association between transplantation antigens and cell surface antigen in adenovirus-transformed cell line.

A rat cell line (A2T2C4) transformed with adenovirus type 2 elicited cytotoxic T lymphocytes in syngeneic rats. Cytotoxicity was abolished by a rabbit antiserum directed against the major histocompatibility (AgB) antigens and by a syngeneic rat antiserum raised against the virus-transformed cell line. The syngeneic antiserum immunoprecipitated surface proteins with apparent molecular weights of 45,000, 19,000, 17,000, and 12,000 from the A2T2C4 cells but it displayed no reactivity against primary rat fibroblasts and spleen cells. The rabbit antiserum against AgB antigens precipitated a 19,000-dalton component from the A2T2C4 cells which was not observed in primary rat fibroblasts. Sequential immunoprecipitation revealed identity between the major polypeptides recognized by the two antisera. Because the rabbit anti-AgB antigen serum was specific for the transplantation antigen subunits and because the syngeneic rat antiserum against the A2T2C4 cells failed to react with the AgB antigens in normal cells, it is concluded that the 19,000-dalton component is coprecipitated with the AgB antigens. Antisera directed specifically against beta2-microglobulin and the alloantigenic AgB antigen subunit also coprecipitated the 19,000-dalton component. These results indicate that the AgB antigen subunits form a ternary complex with a virus-coded protein on the surface of the virus-transformed A2T2C4 cells. This molecular complex may be recognized by the cytoloytic T lymphocytes

Adenoviruses, Human↗
PubMed1978

Reactions and crossreactions of a rabbit anti-H2 antigen serum.

A rabbit antiserum raised against highly purified, papain-solubilized H-2d antigens contained two sets of non-crossreacting antibodies directed against each one of the two H-2 antigen subunits. The antiserum recognized only 12,000 and 47,000 dalton polypeptide chains when splenocyte membrane glycoproteins were analysed. Among the molecules precipitated with the rabbit antiserum all H-2K and D antigens were present. In addition to regular H-2K and D antigens minor amounts of material with the typical H-2 antigen subnit structure, but lacking alloantigenic determinants, were precipitated by the antiserum. These 'non-H-2 antigens' were produced in relatively greater amounts by T-cells than by B-cells. Both sets of antibodies in the rabbit antiserum reacted with the TL antigens demonstrating that there is an immunological crossreactivity between the classical alloantigenic H-2 antigen chain and the alloantigenic TL antigen chain. The F9 cell line, believed to represent cells at the morula stage, display H-2 antigen-like structures as revealed by the rabbit antiserum.

Animals↗
PubMed1976

Formation and properties of retinylphosphate galactose.

Crude cell membrane fractions from a number of tissues can form acidic glycolipids. The formation of acidic galactose lipid and mannose lipid was greatly reduced in vitamin A deficiency, primarily in tissues known to be mucus-producing. Mouse mastocytoma tissue was active in forming acidic galactose lipids with UDP-galactose as substrate. One of the products was identified as retinylphosphate galactose. The synthetase reaction producing this compound exhibited an apparent pH optimum at 6.3. The presence of detergent and retinol stimulated the synthetase reaction, which exhibited an absolute requirement for Mn2+ or Mg2+. The synthetase reaction was readily reversible. Incubation of particulate enzyme with retinylphosphate galactose and UDP yielded UDP-galactose and a compound tentatively identified as retinylphosphate. The galactose lipid was isolated by column chromatography on DEAE-cellulose and silica gel. The retinylphosphate galactose was homogeneous when examined by thin layer chromatography. Mild acid hydrolysis of labeled retinylphosphate galactose yields [14C]galactose, whereas alkaline hydrolysis and hydrogenolysis produced [14C]galactose 1-phosphate. Retinylphosphate galactose bound to vitamin A-depleted, retinol-binding protein.

Animals↗
PubMed1976

Independent expression of the two HL-A antigen polypeptide chains.

It is now well established that beta2-microglobulin constitutes one of the two HL-A antigen subunits. In this study support was obtained for the previous notion that the human lymphoma Daudi does not produce beta2-microglobulin (beta2m). Papain-solubilized as well as Nonidet P-40-solubilized Daudi HL-A antigens do not contain any beta2m or any detectable structural analogue of this protein. The chemical and physico-chemical characteristics of highly purified HL-A antigens derived from Daudi cells are indistinguishable from those of the HL-A antigen-carrying polypeptide chain isolated from the P3HRIK cell line. Like P3HRIK-derived HL-A antigens, the HL-A antigens derived from Daudi cells are composed of two identical heavy, alloantigenic polypeptide chains with a molecular weight of about 50 000 each, which are held together by disulfide bridge(s). The HL-A antigens of P3HRIK cells contain, in contrast to Daudi HL-A antigens, two molecules of beta2m. Although no evidence was obtained suggesting any beta2m synthesis in Daudi cells it was apparent that these cells express the HL-A alloantigenic polypeptide chain in amounts similar to those of other cell lines which produce beta2m. The present data suggest [1] that beta2m and the alloantigenic HL-A polypeptide chain are under separate genetic regulation [2], that the cell surface integration of the HL-A antigen-carrying polypeptide chain is independent of the presence of beta2m and [3] that beta2m does not constitute a membrane component absolutely necessary to the integrity of the cell membrane.

Beta-Globulins↗
PubMed1976

Beta2-microglobulin on the cell surface. Specificity of inhibition of the mixed leukocyte reaction and mitogenic properties of antibodies against the two HLA antigen polypeptide chains.

Intact antibodies, and F(ab')2, and Fab' fragments thereof directed against beta2-microglobulin (beta2m) and the HLA alloantigenic polypeptide chain impede the mixed leukocyte culture reaction (MLR). The Fab' fragments are effective only when bound to the responder cell population. The kinetics of their inhibiting action suggest that they interfere with the recognition phase of the MLR. Thus, it seems possible that beta2m may be part of or closely associated with those structures on the responding cells which recognize the stimulatory alloantigens. Antibodies against beta2m or the other HLA antigen polypeptide chain are mitogenic for peripheral blood lymphocytes. The antibodies against beta2m caused greater stimulation than those against the HLA alloantigenic polypeptide chain. Only bivalent antibodies against beta2m were mitogenic and promoted blast transformation of 1 to 2% of the lymphocytes. Although only B lymphocytes were triggered, the mitogenic response of cultures containing various proportions of B and T cells suggests that cooperation of the two cell types is necessary to obtain optimal mitogenic stimulation.

Antigen-Antibody Reactions↗
PubMed1975

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.

Animals↗