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Biomedical subjects

S M Fu

Publications and source records attributed to S M Fu.

At least 109 records · Page 6Linked to original sources
PubMed1983

IgA specific T-cell factor produced by a human T-T hybridoma.

A human T-T hybridoma was produced, which was a fusion product between and HGPRT-deficient T-cell line, Jurkat 3, and an OKT4+ activated peripheral blood T-cell. The hybrid expressed a receptor for IgM Fc and was negative for IgA Fc. It was shown to produce a factor capable of specifically enhancing IgA production and secretion by isolated human B-cells. The factor exerts its effect directly on B-cells and appears to be different from T-cell-replacing factors previously described.

Antibody Specificity↗
PubMed1983

Neurofibrillary tangles in senile dementia of the Alzheimer type share an antigenic determinant with intermediate filaments of the vimentin class.

A monoclonal antibody produced by a hybridoma between a plasmacytoma cell and a spleen cell from a mouse immunized with human brain microtubule fraction was demonstrated to stain neurofibrillary tangles of senile dementia of the Alzheimer type (SDAT). The antibody recognized at least 50% of the tangles in neuronal perikarya isolated from SDAT brains and stained a filamentous network in HeLa cells, fibroblasts, and astrocytes. It did not stain skin epithelial cells or neurons isolated from normal brains but reacted with Z bands in skeletal muscle. The monoclonal antibody stained coils in colchicine or colcemid-treated cultured cells in a pattern characteristic of 10-nm intermediate-sized filaments. Immunoblotting of Triton-insoluble cytoskeletal proteins of cultured cells electrophoresed in SDS polyacrylamide gels showed that the antigenic determinant is present in proteins of molecular weight 58,000 which comigrates with vimentin. Thus, it appears that the neurofibrillary tangles in SDAT share an antigenic determinant with vimentin.

Aged↗
PubMed1982

Human T cell hybridomas secreting factors for IgA-specific help, polyclonal B cell activation, and B cell proliferation.

Human T-T hybridomas were established by fusion of concanavalin A-activated OKT-4+ T cells with hypoxanthine guanine phosphoribosyl transferase-deficient as well as nondeficient T cell lines. Four hybrids were selected for further study. Supernatant from hybrid clone J1.3 specifically enhanced IgA production and secretion by isolated human B cells, with increases in IgA plaque-forming cells approaching those seen with addition of autologous T cells and pokeweed mitogen. A monoclonal lymphocytic leukemia with membrane IgA also differentiated to IgA plasma cells by this supernatant. Evidence suggests that this hybrid supernatant acts on post-switch IgA-committed B cells. The other hybrids were not isotype specific; hybrid J2S1 enhanced polyclonal Ig secretion and hybrids K1 and K8 induced B cell proliferation without induction of Ig secretion.

B-Lymphocytes↗
PubMed1982

Enrichment of human marrow lymphocytes with monoclonal antibodies to murine antigens.

Two monoclonal antibodies, prepared against a murine B lymphoma and characterized as binding to a cell surface antigen represented primarily on cells of the B lineage, were found to bind to human hemopoietic cells. These antibodies recognize similar populations of cells in mice and humans. Antibodies from clones 177.17 and 83.4 bound to 6% of human bone marrow nucleated cells. This included all cells with detectable cell surface Ig (sIg+) and those that lack sIg but have detectable cytoplasmic mu (sIg-, c mu+), considered to be the immediate precursors of B lymphocytes (pre-B cells). In addition, these antibodies bound to a subpopulation of T cells and a proportion of null lymphocytes in marrow, spleen, and peripheral blood. An unexpected finding was that established pre-B cell lines were not recognized by these antibodies and possible reasons for this are considered. By using antibody-coated polystyrene plates for cell depletion and recovery, highly enriched preparations of c mu+, sIg- cells have been obtained. These antibodies and enrichment procedures should prove valuable in establishing the minimal requirements for maturation of these putative precursors in vitro, for comparative studies of immunodeficiency/autoimmune diseases in man and experimental animal models, and for monitoring the outcome of therapeutic marrow transplantation.

Animals↗
PubMed1981

J chain biosynthesis in pre-B cells and other possible precursor B cells.

Human cell lines that resemble precursors in the B cell lineage have been found to synthesize J chain. In vivo pulse labeling, together with in vitro translation of total cellular RNA in a wheat germ cell-free system, detected the synthesis of J chain in immunoglobulin-secreting cell lines, in a cell line with only surface IgM, as well as in the pre-B-like cell line Josh 4 and the round cell lines Josh 7 and KLM 2. The primary translation products of J chain from all of these cell lines were found to be indistinguishable from one another by serologic criteria, by relative mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, by charge as judged by alkaline-urea gel electrophoresis, and by peptide mapping. These findings suggest that the onset of J chain biosynthesis represents a relatively early event in B cell ontogeny, occurring before the development of immunoglobulin polymer-secreting cells. Its role may, consequently, be fundamental to the biosynthesis of all immunoglobulins, at different stages of B cell differentiation.

Animals↗
PubMed1981

Biogenesis of membrane-bound and secreted immunoglobulins. II. Two forms of the human alpha chain translated in vitro and processed in vivo as distinct polypeptide chains.

Structural differences between alpha m (ther heavy chain of membrane IgA) and alpha s (the heavy chain of secretory IgA) were investigated. Messenger RNA from the human B lymphoblastoid line 32a.1, expressing both membrane and secretory IgA, was translated in a wheat germ cell-free system, resulting in the synthesis of two primary translation products for the alpha chain, that differed in molecular weight. In vivo pulse and pulse-chase experiments demonstrated that two early biosynthetic forms of the alpha chain were subsequently modified to yield three intracellular forms. As shown by endo-beta-N-acetylglucosaminidase H (endo H) treatment, these forms represent two alpha polypeptide chains, with varying compositions of N-linked oligosaccharides. Of the two forms of the alpha chain remaining after endo H treatment, only the form with the lowest molecular weight was associated with cells after long chase periods. The possible significance of this difference from the results with mu and delta chains is discussed. These results indicate that alpha m is distinguished from an alpha s by a difference in both primary structure and intracellular processing. The functional consequences of this distinction, previously shown for the heavy chain of membrane IgM (micrometer) and heavy chain of secretory IgM (microseconds), may reflect a principle common to the secretory and membrane forms of all immunoglobulin heavy chain classes.

B-Lymphocytes↗
PubMed1981

Biogenesis of membrane-bound and secreted immunoglobulins: two primary translation products of the human delta chain, differentially N-glycosylated to four discrete forms in vivo and in vitro.

Structural differences between the heavy chain of membrane IgD (delta m) and the heavy chain of secreted IgD (delta s) were investigated by using a human lymphoblastoid cell line that expresses idiotypically identical IgM and IgD. In a wheat germ cell-free system, mRNA from this cell line was shown to encode two distinct delta chains that differed in molecular weight. When translated in vitro in the presence of dog pancreatic microsomal membranes or when synthesized in vivo, these two delta chains were processed to four discrete glycosylated forms, all of which shared idiotypic determinants, C region determinants, and light chain linkage. As shown by digestion with endo-beta-N-acetylglucosaminidase H, these four delta forms represent two delta polypeptide chains that are differentially N-glycosylated. Pulse-chase experiments demonstrated that, after endo-beta-N-acetylglucosaminidase H treatment, delta m has a higher molecular weight than delta s. After integration into dog pancreatic microsomal membranes in vitro, delta m was found not to have a large cytoplasmic domain exposed to proteolytic digestion. The finding that delta m and delta s differ in primary structure is analogous to previous work with the corresponding heavy chains of IgM (mu m and mu s) from the same cell line. Thus, this cell line produces four Ig heavy chains (mu m, mu s, delta m, and delta s), with the same idiotype. The observation of differential N-glycosylation, apparently unique for the delta class, is discussed.

B-Lymphocytes↗
PubMed1981

Ig biosynthesis in a human pre-B cell line.

Ig synthesis was investigated in a human Epstein-barr virus transformed pre-B-like lymphoblastoid line, Josh 4. Translation of total extracted cellular RNA in a wheat germ cellfree system showed that the transcripts for both micrometer (the heavy chain of membrane IgM) and micros (the heavy chain of secreted IgM) were present in approximately equal proportions. Pulse-labeling of cells with 35S-methionine in culture followed by immunoprecipitation and endo-N-acetylglucosaminidase digestion of the precipitates demonstrated that each of these chains were synthesized and glycosylated intracellularly. No light chain synthesis was detected in either system. In addition, both mu-chains were found to be secreted. Hybrids formed between Josh 4 and 2 light chain-producing lymphoblastoid lines, RPMI-8866P (IgG kappa) and 32a1 (IgA lambda), were found to express surface IgM. Thus the provision of light chains permitted membrane expression of chains which might otherwise be degraded. These findings were discussed in relation to normal B cell development.

B-Lymphocytes↗
PubMed1980

Pre-B cells and other possible precursor lymphoid cell lines derived from patients with X-linked agammaglobulinemia.

A group of unique Epstein-Barr virus-containing cell lines was derived from the bone marrow of three patients with X-linked agammaglobulinemia. Efforts to obtain cell lines from the peripheral blood of these patients were uniformly unsuccessful. Immunofluorescence analyses as well as biosynthetic studies with [(35)S]methionine indicated unusual patterns of Ig synthesis in many of these bone marrow derived lines. Seven of the lines were of particular interest in that two produced no Ig of any type; two others showed no Ig by fluorescence but small amounts by [(35)S]methionine labeling; one expressed only cytoplasmic mu chains without any evidence of light chain synthesis, and two produced primarily mu chains with only slight amounts of light chains. One of the lines without membrane or cytoplasmic Ig studied in detail grew like a typical lymphoid line and was carried in intermittent culture over a period of 2 yr without Ig expression. One line grew quite differently and resembled the round cell type described previously, which has been obtained from a variety of sources. The cell line with cytoplasmic mu chains and no light-chain expression had the characteristic properties of pre-B cells. Three normal type Ig-producing cell lines also were obtained from the patients. The accumulated evidence obtained in the present study indicates that these unusual cell lines represent normal precursor cells of the B-cell lineage; these grew out in these cases because of the virtual absence of mature B cells that ordinarily overgrow the culture system. However, the possibility that in certain instances they reflect abnormal Ig synthesis characteristic of the disease has not been ruled out.

Agammaglobulinemia↗
PubMed1980

Biogenesis of membrane-bound and secreted immunoglobulins. I. Two distinct translation products of human mu-chain, with identical N-termini and different C-termini.

Structural differences between the heavy chain of membrane-bound IgM (mu m) and the heavy chain of secreted IgM (mu s) were investigated. The primary translation products of the mu-chain, free of posttranslational modifications, were synthesized in a wheat-germ cell-free system, programmed with messenger RNA derived from human lymphoblastoid cell lines positive for both membrane-bound and secreted IgM. Encoded in this sytem were two mu-chains, which shared N-terminal signal peptides and which differed both in molecular weight and in C-terminal amino acid sequence. In vivo pulse labeling of cells confirmed that, as intermediates in the rough endoplasmic reticulum, these two forms expressed the same idiotype and maintained their difference in molecular weight and in C-terminal sequence. By correlation with pulse-chase kinetics and with immunofluorescence, one form of mu-chain represents mu m, and the other, mu s. Because the molecular weight difference between the two is manifest at the level of their primary translation products, these studies demonstrate that mu m is distinguished from mu s by a difference in primary structure, at least in part at the C-terminus.

Amino Acid Sequence↗
PubMed1980

Two types of Ia-positive T cells. Synthesis and exchange of Ia antigens.

Two distinct types of Ia-positive T cells have been described. One type represents a blastoid T cell responding from stimulation by mitogens, antigens, and in allogeneic and autologous mixed lymphocyte culture reactions. This is a large cell that is strongly positive for Ia antigens as measured by a variety of different antisera. The other general type is a smaller cell with a lower expression of Ia antigens that is found at low levels in normal peripheral blood and is markedly elevated in various pathological states. It also rises rapidly after inoculation with tetanus toxoid and PPD in sensitized individuals. This cell does not incorporate thymidine and is enriched in the Tgamma fraction; it can be markedly concentrated from normal lymphocytes, and current evidence indicates that it is a T cell. The marked elevation of this cell in the blood of patients with rheumatoid arthritis is of special interest. Considerable evidence indicates that, at least in certain instances, the Ia antigens are synthetized by the cells that carry them. Incorporation of labeled amino acid experiments and the in vitro translation results presented above indicate this. However, the ready exchange of Ia antigens between cells in the experiments described indicates that uptake from other cells may be a significant source.

Histocompatibility Antigens Class II↗
PubMed1980

Peripheral blood Ia-positive T cells. Increases in certain diseases and after immunization.

The Ia antigens, usually expressed primarily on B lymphocytes, are found on a small percentage of normal peripheral blood T cells (average 2.6% by fluorescence and 10.8% by rosette assay). Elevated levels up to 40% by both assays were observed in a high proportion of patients with rheumatoid arthritis. Increases also were found in patients with systemic lupus erythematosus and various types of infections. The increases were evident with a specific heteroantiserum, a hybridoma reagent, and DR specific alloantisera. Normal levels were present in multiple sclerosis and an assortment of metabolic and other disorders. A rise in similarly positive T cells occurred in normal individuals after immunization with tetanus toxoid or PPD. The cells primarily involved in all of these instances were small lymphocytes, which stained relatively weakly with the fluorescent reagents and were readily distinguishable from T-cell blasts. They were found to be enriched in isolated T gamma fractions but were also found in other T cells. The accumulated evidence indicated that these cells represent an expansion of one or more subsets of T cells found in normal individuals, and that their level in the peripheral blood may serve as an index of immunological stimulation.

Arthritis, Rheumatoid↗
PubMed1979

Ia determinants on stimulated human T lymphocytes. Occurrence on mitogen- and antigen-activated T cells.

Human T-cell blasts were generated by stimulation with mitogens and antigens. A proportion of these blasts expressed Ia antigens detectable by immunofluorescence with both allo- and hetero-antiserums. The maximal expression of Ia antigens was delayed and usually occurred after the peak of blastogenesis. Among the three mitogens used, pokeweed mitogen (PWM) was most effective in giving a high percentage and intense Ia staining of T-cell blasts. Phytohemagglutinin and concanavalin A blasts gave weaker and lower percentages of Ia staining. Activation by alloantigens and soluble antigens such as tetanus toxoid and purified protein derivative resulted in Ia expression on T cells comparable to PWM stimulation. Depletion of Ia+ cells from freshly isolated T cells with anti-Ia and complement decreased subsequent Ia expression, suggesting that a proportion of Ia+ blasts were derived from Ia-bearing peripheral blood T cells. When the specificities of the Ia antigens on T-cell blasts were examined with alloantiserums, it was evident that the T blasts expressed similar HLA-DR determinants to those on B cells from the same donor; occasional minor differences between stimulated T cells and autologous B-cell lines or fresh B cells were encountered.

Cells, Cultured↗
PubMed1979

Isolation and immunological characterization of a major surface glycoprotein (gp54) preferentially expressed on certain human B cells.

A major membrane glycoprotein with mol wt of approximately 54,000 has been isolated from membrane preparations of B-type lymphoid cell lines. Antiserum prepared against the isolated material specifically precipitated this glycoprotein from membranes labeled by surface radioiodination or by metabolic labeling. This antiserum was shown by complement-mediated cytotoxicity assay, membrane immunofluorescent staining, and by quantitative absorption analysis to react preferentially with certain B-lymphoblastoid cell lines, with a minor population of peripheral blood B lymphocytes, and a major population of tonsillar B lymphocytes. Certain B-cell leukemias also expressed the antigen, whereas others did not. Considerable variability was observed among positive B cells in the intensity of fluorescent staining even among the leukemic cells from a single individual. Although T cells, including T cells, were negative by direct immunofluorescent and cytotoxicity assay, evidence for low levels of the antigen on the cells of T cell lines was obtained. The whole specific antiserum and its F(ab')2 fragments stimulated B lymphocytes to proliferate. This proliferation did not produce differentiation to plasma cells and was T-cell independent. The monovalent Fab fragments had no effect. None of these preparations timulated T cells. The possibility that this antigen, termed gp54, may play some role in B-cell activation is discussed.

Antigens, Surface↗