Biomedical subjects

S Fong

Publications and source records attributed to S Fong.

At least 91 records · Page 5Linked to original sources

PubMed1985

Characterization of an epibody. An antiidiotype that reacts with both the idiotype of rheumatoid factors (RF) and the antigen recognized by RF.

Recently, an antiidiotype to human monoclonal IgM anti-IgG autoantibodies (rheumatoid factors) was found to react also with human IgG. This peculiar antiidiotype was called an 'epibody'. We describe the induction of a similar epibody by immunization with a synthetic peptide (corresponding to one hypervariable region of the IgM-RF Glo). The results confirm the existence of epibodies, and provide the possible molecular basis of the epibody phenomenon.

Animals↗

PubMed1985

Regulation of Epstein-Barr virus infection by recombinant interferons. Selected sensitivity to interferon-gamma.

Interferons (IFN) are antiviral proteins that may be important in mediating cellular defenses against Epstein-Barr virus (EBV) infection. However, the means by which IFN-alpha, -beta and -gamma modify EBV infectivity are not clear. We have evaluated the effects of purified recombinant preparations of all three classes of IFN on EBV-induced B lymphocyte proliferation and Ig secretion. When added early after EBV infection, all three recombinant IFN reduced B cell outgrowth and Ig secretion. IFN-gamma exerted a 7-10-fold more potent antiviral effect than IFN-alpha or -beta. All three types of IFN act directly on B cells. Monocytes and natural killer cells are not necessary for the anti-EBV activity. Of the three recombinant IFN, only IFN-gamma reduced EBV-induced proliferation and Ig secretion when added 3-4 days after virus infection; IFN-alpha/beta were only effective up to 24 h. B lymphoblastoid lines already transformed by EBV are insensitive to the anti-proliferative actions of all three types of IFN. On the basis of these findings, we propose three phases of regulation during EBV infection. In the early phase, EBV-infected cells can be regulated by all IFN. Subsequently, there is an intermediate period where only IFN-gamma is capable of directly affecting EBV-induced B cell responses. In the third phase, B lymphocytes become insensitive to direct actions of all IFN and are now subject to regulation only by cytotoxic cells.

B-Lymphocytes↗

PubMed1985

Possible involvement of human D minigenes in the first complementarity-determining region of kappa light chains.

The nucleotide sequences of the complementary strands of two human diversity region (D) minigenes, D2 and D4, show stretches of homology with two human variable region kappa chain (V kappa) genes, NG9 and HK101, respectively, in the first complementarity-determining region. In one V kappa sequence, the homology includes the 5' flanking region of D minigenes, which may comprise a recombinase recognition signal. It is thus conceivable that gene conversions involving D minigenes may contribute to V kappa diversity.

Antibody Diversity↗

PubMed1985

Origin and age-associated changes in the expression of a physiologic autoantibody.

Aging is accompanied by increased prevalence of serum autoantibodies. One commonly detected autoantibody, IgM rheumatoid factor, is also found associated with rheumatoid arthritis and other autoimmune disorders. Much evidence indicates that this autoantibody plays a physiologic role in the immune response. The potential of human subjects to secrete this autoantibody and the age-related changes in its expression by human peripheral blood and bone marrow lymphocytes have been investigated. The size of this self-reactive B cell pool increases with advancing age. The lymphocytes expressing this potential are found predominantly in an early B cell subset in elderly individuals as compared to a more mature B cell subset in individuals with rheumatoid arthritis. Preliminary data show that IgM rheumatoid factors share idiotypes implying a common origin, possible from a single light chain gene or a closely related family of light chain genes.

Adolescent↗

PubMed1985

The majority of human monoclonal IgM rheumatoid factors express a "primary structure-dependent" cross-reactive idiotype.

Genetic studies of human immunoglobulin variable regions have been hampered by the lack of anti-idiotypic antibodies that recognize specific heavy and light chain variable region sequences. Sixty percent of human monoclonal IgM anti-IgG autoantibodies (rheumatoid factors [RF]) from unrelated individuals share a cross-reactive idiotype (CRI) termed Wa. In previous experiments in which we used an enzyme-linked immunosorbent assay, we reported that a synthetic peptide (PSL2), corresponding to the second hypervariable region in the kappa light chain of a monoclonal IgM-RF (Sie), induced rabbit antibodies reactive with several RF paraproteins. In the present experiments, to avoid interference due to the human IgM-RF binding toward rabbit IgG, the reactivity of the anti-PSL2 antibody to the separated heavy and light chains of multiple IgM proteins and Bence-Jones proteins was assessed by the Western blot technique. The PSL2-induced anti-CRI reacted well with the separated kappa chains from 10 out of 12 IgM-RF, zero out of four light chains from IgM proteins lacking anti-IgG activity, and one out of six kappa Bence-Jones proteins. The results show that the PSL2-CRI is associated with RF and is not a kappa subgroup marker. Furthermore, a comparison of the reported light chain sequences of the PSL2-CRI-positive IgM-RF suggests that the majority of human IgM-RF light chains derive from a single germ-line VK gene or from a family of closely related VK genes that is highly conserved in the human population. Synthetic peptide-induced anti-CRI provide a potent tool for analyzing the genetic basis of CRI and abnormal autoantibody production in humans.

Amino Acid Sequence↗

PubMed1985

Comparison of the biological activities of human recombinant interleukin-2(125) and native interleukin-2.

Human interleukin-2 proteins (IL-2), purified to homogeneity from both the Jurkat cell line and from genetically engineered Escherichia coli, were compared in a variety of biological systems. The gene coding for the recombinant IL-2 protein used in these studies contained a site-specific modification resulting in the replacement of a cysteine residue with a serine residue at position 125 in the encoded polypeptide. The specific activity was 2-4 X 10(6) units/mg for both the recombinant IL-2(125) and the native IL-2 molecules when measured by DNA synthesis in the murine HT2 cell line. The abilities of these two molecules to support the short-term proliferation and the long-term growth of mitogen- and alloantigen-activated peripheral blood mononuclear cells (PBMC) from humans and of mitogen-activated PBMC from cats, cows, sheep, and horses were equivalent. In addition, both molecules were directly mitogenic for human PBMC and induced the production of interferon-gamma. Human PBMC treated with IL-2 generated enhanced levels of cytotoxic cells against both natural killer (NK)-sensitive and NK-resistant targets. In all of these systems and assays, recombinant IL-2(125) had the same range of biological activity and potency as homogeneous native IL-2.

Animals↗

PubMed1985

Structural similarities in the kappa light chains of human rheumatoid factor paraproteins and serum immunoglobulins bearing a cross-reactive idiotype.

The monoclonal antibody (MoAb) 17.109 recognizes a cross-reactive idiotype (CRI) associated with the light chains of Waldenstrom's macroglobulins with rheumatoid factor (RF) activity. The MoAb also reacts with a proportion of IgM-RF molecules from the sera of rheumatoid arthritis and primary Sjogren's syndrome patients, and from the sera of seropositive normal human subjects. In the present experiments, we used affinity chromatography to purify the 17.109 CRI-positive immunoglobulin from serum and have analyzed the isolated material by Western blotting. The purified 17.109 CRI-positive material from the sera of rheumatoid arthritis patients, Sjogren's syndrome patients, and normal subjects contained exclusively kappa light chains, and had demonstrated RF activity. In every case the 17.109 CRI-positive isolates reacted with antibodies against synthetic peptides corresponding to both the conserved second and third complementarity-determining regions (CDR) of the monoclonal kappa IgM-RF paraprotein Sie. The binding was inhibited specifically by the free peptides in solution. The antipeptide antibodies did not react appreciably with unfractionated human immunoglobulin. The data establish that the 17.109 CRI-positive immunoglobulin from diverse human sera have similar or identical second and third light chain CDR. These results suggest i) that the MoAb 17.109 identifies the protein product of a single or a very few V kappa genes, ii) that the ability to make kappa light chains with the 17.109-associated variable region is widespread in the human population, and iii) that the 17.109-defined kappa variable region segment is associated with IgM-RF autoantibodies.

Amino Acid Sequence↗

PubMed1985

Carcinoembryonic antigen fraction in digestive cancer.

A clinical study in a group of patients with digestive cancers was done with a radioimmunoassay technique employing a carcinoembryonic antigen (CEA) fraction. Among 45 patients with colorectal carcinomas, 51% showed CEA levels in the pathologic range before therapy, those with metastatic disease from well differentiated adenocarcinomas showed the higher values. Measurement of the circulating levels of this CEA fraction proved to be more useful in the monitoring of the course of disease during and after antineoplastic treatment. Sensitivity of the radioimmunoassay technique for the remaining digestive cancers was over 50%, but pathologic CEA values are not exclusive for malignant digestive disease, since 22% of patients with benign diseases also showed raised serum levels of CEA.

Carcinoembryonic Antigen↗

PubMed1984

Delineation of a cross-reactive idiotype on human autoantibodies with antibody against a synthetic peptide.

Antibody against a cross-reactive idiotype (CRI) on human IgM-rheumatoid factor (RF) antibodies was induced by immunization of rabbits with a synthetic peptide ( PSL2 ) corresponding to the second complementarity-determining region (CDR), and adjacent amino acid residues of the kappa light chain of the IgM-RF Sie . The anti-peptide antibody bound efficiently to IgM-RF proteins known to share a cross-reactive idiotype, and to their isolated kappa chains. The anti-CRI was absorbed by, and eluted from, a peptide-Sepharose affinity column. The antibody activity was inhibited by the free peptide in solution. The anti-peptide antibody thus identifies a public idiotype on human IgM-RF, that is largely dependent on the primary sequence of the second CDR of the light chain. Such peptide-induced antiidiotypes of predefined specificity may facilitate studies of the molecular basis of idiotypic cross-reactions, the inheritance and somatic diversification of antibody molecules, and the regulation of the idiotype network.

Animals↗

PubMed1984

Cystamine augments the stimulation of DNA synthesis by peptide growth factors and microtubule-disrupting agents in cultures of 3T3 mouse fibroblasts.

Cystamine together with colchicine markedly enhanced the uptake of [3H]-thymidine into DNA of quiescent cultures of insulin-stimulated Swiss 3T3 mouse fibroblasts. Flow cytofluorometric analyses showed an increased rate of transition of cells from G0/G1----S + G2 in response to combinations of insulin, colchicine, and cystamine. Cystamine, the most effective of several thiol compounds, gave maximal augmentation at 200 microM and was toxic at 300-500 microM. Amplification of DNA synthesis by cystamine was also obtained with epidermal growth factor, vasopressin, and 0.5% fetal bovine serum. Combinations of cystamine and other microtubule-disrupting agents such as nocodazole, maytansine, and podophyllotoxin enhanced DNA synthesis in insulin-stimulated cells. In experiments involving sequential addition of agents, significant enhancement of DNA synthesis was observed when the addition of colchicine to cystamine-treated cells was delayed or conversely when the addition of cystamine to colchicine-treated cultures was delayed. This reciprocal interaction between cystamine and colchicine suggests that a prereplicative intermediate accumulates in response to the action of these dissimilar compounds. We consider the possibility that cystamine may act by forming mixed disulfides with thiol groups of unknown protein(s) that regulate DNA replication.

Animals↗

PubMed1984

Anti-hypervariable region antibody induced by a defined peptide: an approach for studying the structural correlates of idiotypes.

The structural correlates of idiotypes have been sought in several antibody systems. However, the precise molecular basis of idiotypes are exceedingly difficult to define. Antibodies of predetermined specificity can be induced by immunization with synthetic peptides. In the present experiments, a synthetic peptide corresponding to a hypervariable region on a monoclonal human IgM rheumatoid factor (Sie) has been used to induce specific anti-hypervariable region antibodies. The antibodies bound to the intact Ig molecule and to its isolated heavy chains but not to other IgM paraproteins nor to pooled human IgG. The binding of the antibody to the intact IgM was inhibited specifically by the free peptide, and the antibody activity was removed by a peptide-coupled affinity column. These results clearly demonstrate that specific anti-idiotypic antibody of predefined specificity can be induced by a hypervariable region peptide. Antibodies of this class may provide a new tool for defining the structural correlates of idiotypes.

Animals↗

PubMed1984

Modulation of human rheumatoid factor-specific lymphocyte responses with a cross-reactive anti-idiotype bearing the internal image of antigen.

Rabbit anti-idiotypic antibodies to human rheumatoid factor (RF) autoantibodies were isolated by affinity chromatography on rabbit anti-human IgG Fc Sepharose 4B. The anti-idiotypic antibodies bore the "internal image" of the antigen, human IgG. They reacted specifically with multiple human monoclonal and polyclonal IgM-RF, independent of any particular light or heavy chain amino acid sequence. The anti-idiotypes did not react with IgM or IgG proteins lacking RF activity. The present experiments determined the potential of the "internal image" antibodies to modulate in vitro lymphocyte functions. The addition of anti-idiotypic antibody to peripheral blood mononuclear cell cultures from patients with rheumatoid arthritis elicited lymphocyte proliferation, but not RF synthesis. The antibody did not induce the proliferation of lymphocytes from a normal individual. Moreover, the anti-idiotype specifically suppressed IgM-RF secretory responses when preincubated with B cells before co-culture with autologous pokeweed mitogen-activated T cells. The data show that the anti-idiotypic antibodies with the "internal image" of antigen are capable of interacting with B cell receptors in an antigen-restricted manner, and possess specific immunomodulatory properties.

Animals↗

PubMed1984

Characterization of recirculating lymphocytes in rheumatoid arthritis patients: selective deficiency of natural killer cells in thoracic duct lymph.

Five patients with rheumatoid arthritis (RA), who were treated by lymphocyte depletion by using thoracic duct drainage (TDD), provided an opportunity to characterize the phenotype and function of their recirculating lymphocytes. We found that: a) thoracic duct lymphocytes (TDL) were similar in their proportion of T cells (83% +/- 6 OKT3+), OKT4+ subset (65% +/- 8), and OKT8+ subset (22% +/- 6) to peripheral blood lymphocytes (PBL): b) fewer natural killer-like cells were present in TDL (5% +/- 4 Leu-7+; 2% +/- 2 Leu-11+: 8% +/- 2 OKM -1+) than in PBL (20% +/- 10 Leu-7+: 11% +/- 6 Leu-11+; 18% +/- 5 OKM -1) (p less than 0.01); c) TDL differed from synovial fluid lymphocytes ( SFL ) and synovial membrane lymphocytes ( SML ) in that TDL lacked a high percentage of activated lymphocytes (T cells bearing Ia antigen, OKT10 , and transferrin receptor): d) immature T cells (expressing either OKT6 antigen or reactive with peanut agglutinin) were not found in TDL even late in the course of TDD: and e) in vitro functional studies demonstrated that TDL were similar to PBL in their ability to synthesize immunoglobulin after mitogen stimulation and to generate cytotoxic T lymphocytes capable of lysing autologous EBV-transformed B cells. However, natural killer activity, as measured by lysis of K562 cells was significantly lower in TDL than PBL (p less than 0.05). These results demonstrate that natural killer cells defined by phenotype and function are excluded from thoracic duct lymph and thus have a circulation pattern different from most T cells.

Adult↗

PubMed1983

A common idiotope on human rheumatoid factors identified by a hybridoma antibody.

Human monoclonal and polyclonal anti-IgG autoantibodies [rheumatoid factors (RFs)] are composed primarily of kappa light chains, and may display cross-reactive idiotypes. However, the nature of the shared idiotope(s) has remained unclear. We have prepared a murine hybridoma antibody (17-109) that recognizes an idiotope present on 30% (3/10) of human IgM-RF paraproteins, and absent on immunoglobulins without RF activity. The idiotope was measurable on isolated, intact kappa light chains, but not on light-chain tryptic peptides, nor on isolated heavy chains. A comparison of the binding to 17-109 of five IgM-RF paraproteins, with known kappa chain amino acid sequences, suggested a relationship between the idiotope recognized by the hybridoma and the complementarity-determining regions. The serum of patients with rheumatoid arthritis contained idiotope positive material that bound specifically to a 17-109 immunoadsorbent column. Moreover, the 17-109 anti-idiotope antibody partially inhibited the binding to IgG of IgM-RF and IgA-RF in serum, but did not effect the binding to antigen of IgM and IgA anti-tetanus toxoid antibodies. These results suggest that a significant proportion of IgM-RF paraproteins share an idiotope located at or near the complementarity-determining regions of the kappa light chain. Human serum RFs include a kappa light chain family that is idiotopically related to the kappa chains on IgM-RF paraproteins.

Animals↗

PubMed1983

Lymphocyte phenotype and function in pseudolymphoma associated with Sjögren's syndrome.

Lymph node (LNL) and salivary gland lymphocytes (SGL) from three patients with pseudolymphoma and primary Sjögren's syndrome (1(0)SS) were characterized with monoclonal antibodies to demonstrate (a) a predominance of T cells (greater than 80%) reactive with anti-T cell antibodies OKT4 (greater than 70%) and OKT8 (less than 20%); (b) a high prevalence of activation antigens (greater than 50% of cells reactive with antibody OKT10 and anti-Ia antibody); (c) polyclonal B cells (8-15% of all cells expressing kappa or lambda); and (d) a specific B cell subset defined by reactivity with antibody B532 that was not present in their peripheral blood. In vitro functional studies showed that both SGL and LNL provided T helper activity for immunoglobulin synthesis and that this activity could be abolished by treatment with antibody OKT4 plus complement. The SGL and LNL exhibited little natural killer, antibody-dependent cellular cytotoxicity, or cytotoxic T cell activity. Normal karyotype was observed in SGL, LNL, and peripheral blood lymphocytes (PBL) from these patients. These findings indicate that pseudolymphoma in 1(0)SS results from the infiltration of salivary glands and extraglandular tissues by nonneoplastic T helper cells. Monoclonal antibodies provide an important tool to distinguish pseudolymphoma from non-Hodgkins (B cell) lymphomas that have a markedly elevated incidence in 1(0)SS patients. Our finding of T helper cells in pseudolymphoma tissues supports the hypothesis that chronic stimulation of B cells by helper T cells leads to eventual escape of a malignant B cell clone.

Aged↗

PubMed1983

Characterization of the phenotype and function of lymphocytes infiltrating the salivary gland in patients with primary Sjogren syndrome.

Monoclonal antibodies directed against T-cell subsets, B-cell subsets, and monocytes were used to characterize the cells infiltrating the salivary glands of patients with primary Sjogren syndrome (1 degree SS). Analysis of stained frozen tissue sections and lymphocyte suspensions derived from salivary glands revealed the majority of infiltrating cells to be T cells (reactive with antibodies SC1 and Leu 4) of the Leu 3a+ subset (greater than 70% reactive). Of particular interest, a high frequency of Ia+ T cells (up to 50% of T cells) and B cells reactive with antibody B532 (5-15% of infiltrating cells) were found in salivary gland lymphocytes (SGL) but not in peripheral blood lymphocytes (PBL) of the same patients. Our finding that the phenotype of SGL was significantly different from PBL emphasizes the need to characterize lymphocytes at the site of tissue destruction. In vitro functional assays demonstrated that the OKT4+ SGL exhibited T-helper activity but not natural killer, antibody-dependent cellular cytotoxicity, or cytotoxic T-lymphocyte activity. Of note, rheumatoid factor (IgM anti-IgG) was produced by SGL but not by the corresponding PBL. Our studies on SG-lymphocyte function represent an early step in elucidating the cellular and subcellular events responsible for this autoimmune disease.

Antibodies, Monoclonal↗

PubMed1983

Two different rheumatoid factor-producing cell populations distinguished by the mouse erythrocyte receptor and responsiveness to polyclonal B cell activators.

The subsets of human peripheral blood B lymphocytes from which Epstein Barr virus- (EBV) and pokeweed mitogen- (PWM) induced IgM anti-IgG autoantibody-producing B cells arise have been compared. EBV-induced IgM anti-IgG autoantibodies preferentially derive from a subset of B cells that forms rosettes with mouse erythrocytes. In contrast, PWM-induced IgM anti-IgG antibodies preferentially arise from a B cell subset lacking the mouse erythrocyte receptor.

Antibody Formation↗

PubMed1983

Carcinoembryonic antigen fraction in lung cancer.

Serum levels of a carcinoembryonic antigen fraction were measured in 195 patients with lung diseases by means of a radioimmunoassay technique. Overall sensitivity for lung cancer was 54.6% and specificity was 71.4%, but the carcinoembryonic antigen fraction was more frequently raised among patients with lung adenocarcinoma than in those bearing epidermoid or undifferentiated carcinomas. It is concluded that this radioimmunoassay technique is an useful adjunct in the diagnosis of lung adenocarcinoma and shows a good correlation with its clinical stage.

Adenocarcinoma↗