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Biomedical subjects

S M Fu

Publications and source records attributed to S M Fu.

At least 19 recordsLinked to original sources
PubMed1992

Stimulation of tumor necrosis factor alpha production in human monocytes by inhibitors of protein phosphatase 1 and 2A.

The protein phosphatase 1 and 2A inhibitor, okadaic acid, has been shown to stimulate many cellular functions by increasing the phosphorylation state of phosphoproteins. In human monocytes, okadaic acid by itself stimulates tumor necrosis factor alpha (TNF-alpha) mRNA accumulation and TNF-alpha synthesis. Calyculin A, a more potent inhibitor of phosphatase 1, has similar effects. TNF-alpha mRNA accumulation in okadaic acid-treated monocytes is due to increased TNF-alpha mRNA stability and transcription rate. The increase in TNF-alpha mRNA stability is more remarkable in okadaic acid-treated monocytes than the mRNA stability of other cytokines, such as interleukin 1 alpha (IL-1 alpha), IL-1 beta, and IL-6. Gel retardation studies show the stimulation of AP-1, AP-2, and NF-kappa B binding activities in okadaic acid-stimulated monocytes. This increase may correlate with the increase in TNF-alpha mRNA transcription rate. In addition to the stimulation of TNF-alpha secretion by monocytes, okadaic acid appears to modulate TNF-alpha precursor processing, as indicated by a marked increase in the cell-associated 26-kD precursor. These results suggest that active basal phosphorylation/dephosphorylation occurs in monocytes, and that protein phosphatase 1 or 2A is important in regulating TNF-alpha gene transcription, translation, and posttranslational modification.

Base Sequence↗
PubMed1992

Molecular analysis of the induction of immunoglobulin E synthesis in human B cells by interleukin 4 and engagement of CD40 antigen.

The molecular events leading to immunoglobulin E (IgE) synthesis in human sIgE- B cells stimulated with interleukin 4 (IL-4) and anti-CD40 monoclonal antibody (mAb) 626.1 were analyzed. Anti-CD40 mAb increased the levels of IL-4-induced germline C epsilon transcripts and induced the production of mature C epsilon mRNA. These effects were dependent on the presence of IL-4. Nested primer PCR revealed deletional switch recombination occurring only in B cell stimulated with both IL-4 and anti-CD40 mAb. DNA sequence analysis of switch fragments showed direct S mu/S epsilon joining, without the deletions or duplications within S mu often found in B cells stimulated with IL-4 and Epstein-Barr virus. Analysis of the switch junction map sites showed "hot spots" for recombination within S mu, but not within S epsilon. These findings indicate that IL-4 provides a signal to B cells to induce germline C epsilon transcription and concurrent CD40 engagement induces S mu/S epsilon deletional switch recombination, production of mature C epsilon mRNA, and IgE synthesis.

Antigens, CD↗
PubMed1992

A rheumatoid factor from a normal individual encoded by VH2 and V kappa II gene segments.

OBJECTIVE: To gain insight into the immunoglobulin variable-region repertoire of anti-IgG antibodies (rheumatoid factors [RF]), we characterized the VH and V kappa gene segments utilized in an IgM-RF-secreting lymphoblastoid cell line (SSH23) isolated from a normal individual. METHODS: The cell line SSH23 was established by Epstein-Barr virus transformation of peripheral blood non-T mononuclear cells. First-strand complementary DNA (cDNA) was generated and used for polymerase chain reaction amplification of the heavy and light chain variable domains. The amplified variable domains were sequenced and compared with an extensive database of germline and cDNA V gene segments. RESULTS: The VH sequence was found to be identical to a previously described fetal VH2 incomplete cDNA and to differ by only 3 nucleotides from a JH proximal germline VH2 gene segment. To our knowledge, this is the first example of a VH2 rheumatoid factor. The V kappa 2-J kappa 4 light chain contains an uncommon 10-amino acid third complementarity-determining region (CDR 3). CONCLUSION: Utilization of preimmune fetal VH gene segments and unusual light chain junctional diversity appear to be features shared by many physiologic and pathologic rheumatoid factors.

Amino Acid Sequence↗
PubMed1992

Studies of the effect of cyclosporine in psoriasis in vivo: combined effects on activated T lymphocytes and epidermal regenerative maturation.

Cyclosporine (CSA) decreases lymphokine synthesis and keratinocyte proliferation in vitro, but its in vivo mechanism of action in treating recalcitrant psoriasis is incompletely understood. Ten psoriasis patients were treated with CSA (2-7.5 mg/kg/d) with clinical improvement in nine of 10 patients. Skin biopsies before and after 1-3 months of CSA treatment were studied for evidence of immune and keratinocyte activation using immunoperoxidase and Northern blotting analysis. The number of activated, IL-2 receptor+ T cells in plaques after CSA treatment was reduced in all patients by a mean of 60%. Seven of 10 patients showed a decrease in keratinocyte HLA-DR expression; five of seven showed a decrease in gamma-IP-10 immunoreactivity, suggesting a decline in gamma interferon levels in plaques after CSA therapy. We studied the effect of CSA treatment in vivo on TGF-alpha, IL-6, and keratin K16 expression, three markers of keratinocyte growth activation. Expression of keratinocyte TGF-alpha and IL-6, which are elevated in active psoriatic epidermis, did not change in these patients after CSA treatment. The majority of patients (five of eight) continued to express the hyperproliferative keratin K16 after CSA treatment. Our results suggest that the predominant direct mechanism of action of Cyclosporine in vivo is a diminution of T-cell activation in plaques, with attendant decreased lymphokine production.

Cyclosporine↗
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↗
PubMed1979

Induction of polyclonal antibody synthesis by human allogeneic and autologous helper factors.

Human helper factors were obtained from supernates of 48 h unidirectional allogeneic and autologous mixed lymphocyte reactions. These supernates were shown to induce the production of large amounts of immunoglobulin by tonsillar and peripheral blood mononuclear cells. Abundant polyclonal activation to antibody production occurred in these cultures in the absence of antigenic challenge which was similar in degree to that produced by pokeweed mitogen. This was documented by quantitating plasma cells, specific plaque-forming cells, and secreted immunoglobulin. In addition, the supplementation of companion cultures with sheep erythrocytes resulted in a significant enhancement of the specific plaque-forming cell response without an appreciable change in plasma cell number of secreted Ig.

Antibody Formation↗
PubMed1979

Human cell lines containing Epstein-Barr virus but distinct from the common B cell lymphoblastoid lines.

A group of very similar cell lines was established from peripheral blood or bone marrow of 12 patients with a variety of disorders. The cells in these cell lines were uniform and round in shape. They grew as single-cell suspensions or as aggregates of small numbers of cells in stationary culture. The most striking characteristic of these lines was the lack of cells with surface immunoglobulin or with demonstrable immunoglobulin synthesis. This lack of immunoglobulin synthesis and their special growth characteristics distinguished them from the lymphoblastoid B cell lines previously described. The cells of these unusual cell lines had strong Fc receptors and C3 receptors and expressed Ia antigens. They did not form rosettes with sheep erythrocytes and did not have detectable levels of terminal deoxynucleotidyltransferase. They did not secrete lysozyme and failed to stain for peroxidase. The presence of the Epstein-Barr virus nuclear antigen in the cells indicated the presence of Epstein-Barr viral genome. The possibility that these cells represent some type of precursor cell in the B cell lineage is discussed, but the exact cellular origin remains to be ascertained.

Antigens, Viral↗
PubMed1979

Induction of human antibody responses in vitro with emphasis on allogeneic helper factors.

Systems have been developed for the reproducible production of antigen-specific plaque forming cells for both tonsillar and peripheral blood B cells. Allogeneic helper activity was an essential supplement and monocyte removal was important, especially in the peripheral blood situation. Highly active allogeneic helper factors could be obtained from undirectional MLC supernatants which aided the proeuction of antigen-driven plaques. These factors also caused a polyclonal activation of B lymphocytes. A number of clinical applications of the above system were described. A defect in the T cells of patients with chronic lymphocytic leukemia with respect to the generation of helper activities was delineated.

Antibody Formation↗
PubMed1979

Poor mixed lymphocyte reaction stimulatory capacity of leukemic B cells of chronic lymphocytic leukemia patients despite the presence of Ia antigens.

The human Ia-like antigens, selectively expressed on B lymphocytes, are now recognized to be closely associated with, or identical to, the gene products of the major histocompatibility complex responsible for stimulation in the mixed lymphocyte reaction. The leukemic B lymphocytes of patients with chronic lymphocytic leukemia express these antigens very well. In the present study they were readily detected by several techniques utilizing both allo- and heteroantisera. However, the leukemic B cells from most patients were found to be extremely poor stimulating cells in the mixed lymphocyte reaction. This was particularly apparent when comparisons were made on a B-cell basis with isolated normal B lymphocytes. Leukemic cell death, abnormal kinetics of leukemic cell-mediated stimulation, and serum or cellular suppressor factors do not appear to explain these findings. Studies comparing cells from a leukemic patient with those of her HLA identical sibling and results of mixed lymphocyte reactions between normal and leukemic subjects discordant for D-region-associated Ia antigens ruled out genetic explanations for the differences observed. Experiments with normal peripheral blood mononuclear cells depleted of T cells and monocytes exclude the quantitative deficiency of monocytes which is found in the peripheral blood of most leukemic patients as an explanation. The present results with chronic lymphocytic leukemia cells indicate that the mere expression of the Ia-like antigens by cell populations does not render them effective stimulators. The accumulated evidence obtained indicate that abnormalities, particularly of membrane function and metabolism, known to occur in chronic lymphocytic leukemia lymphocytes may be involved in the poor stimulatory capacity of the leukemic B cells.

Animals↗
PubMed1979

T cell helper defect in patients with chronic lymphocytic leukemia.

Purified peripheral blood T lymphocytes from normal donors were shown to help allogeneic tonsillar B cells to differentiate and secrete specific anti-SRBC antibody in vitro in a plaque-forming assay. Utilizing this system, a comparison was made between the allogeneic helper activity generated by the T cells of normal individuals and patients with various disease states. Allogeneic helper activity was absent when T lymphocytes from patients with CLL were used. Conversely, relatively normal allogeneic helper function was provided by T cells of patients with a variety of other disorders studied. Thus, a functional deficiency was identified in CLL patients in the subpopulation of regulatory T cells responsible for providing helper activity in allogeneic interactions.

B-Lymphocytes↗
PubMed1978

Induction of in vitro differentiation and immunoglobulin synthesis of human leukemic B lymphocytes.

Successful induction of in vitro differentiation and immunoglobulin synthesis of the leukemic lymphocytes was carried out in two cases of chronic lymphocytic leukemia. Few plasma cells and little specific Ig secretion were detected in the cultures of isolated leukemic B cells in either the presence or the absence of autologous T cells. Up to 30% of the leukemic B cells matured to plasma cells, and a 32-fold increase in specific Ig synthesis was observed when T cells from normal individuals were added to the cultures of these leukemic B cells. In one of the two cases, autologous T cells were able to induce greater than 50% of the leukemic B cells to differentiate further to plasma cells in the presence of pokeweed mitogen. This markedly accelerated in vitro differentiation was only achieved with leukemic cells from cases in which there was evidence of slight differentiation in vivo. No evidence could be obtained for excessive suppressor T cells in these patients. However, a T-cell defect in the generation of allogeneic effect helper factors was identified. This defect may be responsible for the reduced rate of leukemic maturation in vivo.

B-Lymphocytes↗
PubMed1978

Ia-bearing T lymphocytes in man. Their identification and role in the generation of allogeneic helper activity.

The presence of Ia-like antigens was demonstrated on a small population (2-6%) of highly purified human circulating T lymphocytes by immunofluorescence with a rabbit anti-Ia serum raised against the isolated bimolecular Ia structure. The Ia+ T lymphocytes have no surface or intracellular immunoglobulins. The expansion of this Ia+ T-cell population was encountered in certain patients. Ia antigens were also found on T blasts grown in long-term cultures with conditioned medium generated by phytohemagglutinin-stimulated lymphocytes. In addition, leukemia blasts which stained for Ia antigens and formed E rosettes were identified in the peripheral blood of two leukemic patients. This evidence further supports the existence of Ia-bearing T cells in man. The Ia+ T-lymphocyte population was shown to contain cells responsible for the generation of allogeneic helper activity. Elimination of Ia+ lymphocytes from a purified T-cell population by the anti-Ia antiserum and complement abolished its ability to help an allogeneic B-cell preparation to generate plaque-forming cells against sheep erythrocytes in vitro in the presence of the antigen.

Antigens, Surface↗
PubMed1978

Lymphoblastoid cell lines from patients with chronic lymphocytic leukemia: identification of tumor origin by idiotypic analysis.

Multiple lymphoblastoid cell lines have been derived from two patients with chronic lymphocytic leukemia with an associated monoclonal immunoglobulin (Ig) band. Idiotypic antisera raised against the monoclonal serum Ig bands were shown to be specific for the membrane Ig of the patients' leukemic cells. The idiotypic determinants in these patients thereby constitute tumor-specific antigens. Surface and intracellular immunofluorescence studies utilizing these idiotypic antisera were used to identify the cell lines of leukemic origin. These studies showed that certain cell lines from each patient were derived from the leukemic cells while other cell lines were derived from residual normal B lymphocytes. The leukemic cell lines were variable and contained different percentages of lymphoid cells with the idiotype-specific membrane Ig and, in addition, different percentages of plasma cells with intracellular Ig of the same specificity. Specific Ig synthesis was also demonstrated by hemagglutination-inhibition analysis of cell line supernatants. Aside from Ig specificity, no differences have been found between the leukemic cell lines and those derived from normal cells. One of the leukemic cell lines was cloned in soft agarose. All the clones were shown to be of leukemic origin.

Aged↗
PubMed1978

Patterns of expression of human "Ia-like" antigens during the terminal stages of B cell development.

The "Ia-like" antigens characteristically present on the membrane of B lymphocytes were shown to be absent in most terminally differentiated Ig-producing plasma cells. This was most evident in analyses of myeloma plasma cells that uniformly lacked the Ia-antigens. Also, in B lymphoid cell lines, the lymphoblasts were uniformly Ia-positive but the plasma cells were negative. In contrast, however, the majority of plasma cells produced after pokeweed mitogen stimulation remained positive. Plasma cells in tonsil and in the tissue of peripheral blood of patients with Wladenström's macroglobulinemia were also sometimes Ia-positive although the majority were negative. Studies of membrane IgM and IgD indicated a similar loss in some instances. However, the SIg and Ia antigens were not invariably associated. These results lead to the conclusion that Ia-antigens are differentiation antigens for B cells and are usually lost by the end stage cells in this series.

B-Lymphocytes↗
PubMed1977

An unusual kappa immunoglobulin antigen present on the membrane of T and B lymphocytes.

Several K immunoglobulin antisera out of a large number studied showed the unique property of reacting with a membrane structure present on all T and B lymphocytes examined. This antigen was detected on lymphocytes by indirect fluorescence, direct fluorescence, and by cytotoxic analysis. Absorption of the antiserum by all K myeloma proteins, K Bence-Jones proteins, and kappa light chains removed the activity; L proteins had no effect. The possibility that the cross-reacting membrane antigen is part of the HL-A system was discussed.

Antibody Specificity↗