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Biomedical subjects

S Fong

Publications and source records attributed to S Fong.

At least 19 recordsLinked to original sources
PubMed1992

IL-10, T lymphocyte inhibitor of human blood cell production of IL-1 and tumor necrosis factor.

We have identified and purified a factor that inhibits the production of IL-1 beta and TNF by stimulated human mononuclear cells. The activity is produced by the T cell lines Hut-78 and Mo constitutively under serum-free conditions. Crude conditioned media have titers of up to 100 U/ml (one unit defined as the reciprocal of the dilution producing 50% inhibition). The activity resides mainly in a single size peak of 30 to 35 kDa and an isoelectric point around 8. Other cytokines in this size range that have been reported to be inhibitory for IL-1 and TNF production include TGF-beta, IL-4, and IL-6; these factors were excluded by lack of detection, neutralizing antibody, and low activity compared with our factor. Another factor with these size and charge properties is IL-10, which inhibits T cell cytokine production. By polymerase chain reaction analysis, Mo and HuT-78 lines contain IL-10 transcripts whereas JURKAT is negative; this correlates with inhibitor bioactivity from the three lines. Use of mAb specifically showed the inhibitor to be IL-10.

Antibodies, Monoclonal↗
PubMed1992

The plain abdominal film in intussusception: the accuracy and incidence of radiographic signs.

The incidence of four plain abdominal film features associated with intussusception was recorded by four observers in 180 films of patients with intussusception mixed with 100 films of control subjects. The crescent sign and target sign were the most accurate indicators of intussusception. The target sign was the commoner being seen in 68% of films. Signs of small bowel obstruction were not useful in the diagnosis of intussusception. The soft tissue mass was the commonest indicator of intussusception. The soft tissue mass was found more commonly, however, than small bowel obstruction in the control subjects who did not have intussusception.

Child↗
PubMed1992

Immunodominant structures of human growth hormone identified by homolog-scanning mutagenesis.

Homolog-scanning mutagenesis has been reported to be useful in elucidating the antigenic epitopes recognized by monoclonal antibodies and hGH binding to its receptor. However, little is known about which structures are recognized as immunodominant by murine serum antibodies. Therefore, the previously published series of hGH homologs and additional mutants of human placental lactogen (hPL), porcine growth hormone (pGH), and human prolactin (hPRL) were examined for their interaction with murine serum derived anti-hGH antibodies. As compared to wild-type hGH, nine of the nineteen segment substituted mutants tested showed a significant reduction in binding to anti-hGH sera. These disruptive substitutions mapped to 5 regions on a structural model of hGH: the length of helix 1 (residues 11-33), the loop between the first disulfide bond and helix 2 (residues 54-74), the beginning of helix 3 (residues 109-112), the carboxyl half of helix 4 (residues 167-182), and the final carboxyl terminus segment of the molecule (residues 184-191). In terms of the current structural model, three of the five immunodominant regions (the loop between residues 54-74, central portion of helix 4 to the carboxyl terminus and part of the amino terminus region of helix 1) closely overlaps the hGH receptor binding epitopes.

Amino Acid Sequence↗
PubMed1992

Growth hormone augments superoxide anion secretion of human neutrophils by binding to the prolactin receptor.

Recombinant human growth hormone (HuGH) and human prolactin (HuPRL), but not GH of bovine or porcine origin, prime human neutrophils for enhanced superoxide anion (O2-) secretion. Since HuGH, but not GH of other species, effectively binds to the HuPRL receptor (HuPRL-R), we used a group of HuGH variants created by site-directed mutagenesis to identify the receptor on human neutrophils responsible for HuGH priming. A monoclonal antibody (MAb) directed against the HuPRL-R completely abrogated O2- secretion by neutrophils incubated with either HuGH or HuPRL, whereas a MAb to the HuGH-R had no effect. The HuGH variant K172A/F176A, which has reduced affinity for both the HuGH-binding protein (BP) and the HuPRL-BP, was unable to prime human neutrophils. This indicates that priming is initiated by a ligand-receptor interaction, the affinity of which is near that defined for receptors for PRL and GH. Another HuGH variant, K168A/E174A, which has relatively low affinity for the HuPRL-BP but slightly increased affinity for the HuGH-BP, had much reduced ability to prime neutrophils. In contrast, HuGH variant E56D/R64M, which has a similar affinity as wild-type HuGH for the HuPRL-BP but a lower affinity for the HuGH-BP, primed neutrophils as effectively as the wild-type HuGH. Finally, binding of HuGH to the HuPRL-BP but not to the HuGH-BP has been shown to be zinc dependent, and priming of neutrophils by HuGH was also responsive to zinc. Collectively, these data directly couple the binding of HuGH to the HuPRL-R with one aspect of functional activation of human target cells.

Adult↗
PubMed1992

Plain film diagnosis of intussusception: prevalence of the target sign.

We describe a feature of intussusception seen on plain abdominal films that to our knowledge has not been previously described. The abnormality, termed the "target sign," consists of two concentric, circular, radiolucent lines to the right of the spine superimposed on the kidney. Four observers examined 280 plain abdominal films; 180 were of 94 patients who had had 100 episodes of intussusception and 100 films were of 80 control subjects. The target sign was observed by three or four observers on plain films in 24 (26%) of 94 patients with intussusception and on 4% of radiographs of control subjects. There was no concordance between observers on false-positive findings seen in the control subjects. Our experience suggests that circular radiolucent lines superimposed on the right kidney on plain abdominal radiographs (target sign) constitute a useful diagnostic feature of intussusception.

Child↗
PubMed1991

cDNA cloning of an intracellular form of the human interleukin 1 receptor antagonist associated with epithelium.

A cDNA encoding a receptor antagonist of interleukin 1 (IL-1ra), secreted from human monocytes, has recently been isolated and sequenced [Eisenberg, S. P., Evans, R. J., Arend, W. P., Verderber, E., Brewer, M. T., Hannum, C. H. & Thompson, R. C. (1990) Nature (London) 343, 341-346]. We have identified another version of this IL-1ra, which is predominantly expressed in epithelial cells. This IL-1ra lacks a leader sequence and, thus, is probably intracellular. Both proteins are derived from the same gene through use of an alternative transcriptional start site and internal splice-acceptor site. Expression of intracellular IL-1ra cDNA in COS cells demonstrated that the intracellular product specifically inhibited exogenous interleukin 1-dependent responses. Keratinocytes were shown to contain significant amounts of nonsecreted IL-1ra protein. Constitutive expression of the intracellular IL-1ra may be an intracellular defensive mechanism in exposed epithelial cells and/or may serve to regulate autocrine interleukin 1-mediated pathways of differentiation.

Amino Acid Sequence↗
PubMed1990

Continuous multiple location body temperature measurement of infants.

This study was done to evaluate the most suitable location of skin temperature sensors to enable long term temperature measurements of infants. A high accuracy eight channel temperature monitor was developed. Linear semiconductor sensor probes were constructed in association with this. System accuracy and stability were tested. Preliminary clinical studies have shown considerable variation from the core temperature for all surface measurement locations.

Body Temperature↗
PubMed1988

Treatment of primary Sjögren's syndrome with hydroxychloroquine.

Sjögren's syndrome is an autoimmune disease characterized by lymphocytic infiltration of the salivary/lacrimal glands, autoantibody production, and polyclonal hyperglobulinemia. In view of the efficacy and relative safety of hydroxychloroquine in other autoimmune disorders, the potential benefit of hydroxychloroquine (200 mg per day for 12 months) in 10 patients with Sjögren's syndrome was evaluated. Changes in levels of total immunoglobulin, antibody against Sjögren's syndrome-associated antigen B, rheumatoid factor, and in vitro production of immunoglobulin in the serum were evaluated. For comparison, 10 patients matched according to age and sex, who did not receive hydroxychloroquine were studied. In the hydroxychloroquine-treated group, the following observations were made: (1) significantly decreased total immunoglobulin G (IgG) and IgA levels with little change in IgM levels; (2) significant decrease in IgA-rheumatoid factor with a smaller decrease in IgM-rheumatoid factor; (3) decreased IgG anti-Sjögren's syndrome-associated antigen B autoantibody; and (4) decreased erythrocyte sedimentation rate and increased hemoglobin level. Further, a specific idiotype present on their rheumatoid factor (defined by monoclonal antibody 17-109) was significantly decreased, with disappearance of detectable circulating paraprotein in two hydroxychloroquine-treated patients. Finally, rheumatoid factor production in vitro by lymphocytes from hydroxychloroquine-treated patients using a T cell-dependent mitogen was significantly decreased. These results suggest that hydroxychloroquine modulates lymphoproliferation in patients with Sjögren's syndrome and may prevent progression to extraglandular sites of neoplastic transformation.

Autoantibodies↗
PubMed1988

Incidence of three cross-reactive idiotypes on human rheumatoid factor paraproteins.

The basis for rheumatoid factor (RF) production in autoimmune or lymphoproliferative diseases cannot be understood without defining the molecular factors that dictate RF structure and specificity. Recently three different mAb (6B6.6, 17.109, and G6) have been developed that define cross-reactive idiotypes (CRI) on intact L or H chains of human monoclonal RF cryoglobulins. However, the true incidence of these CRI among RF and their relationship to each other have not been delineated. In the present experiments, a panel of 163 randomly selected IgM paraproteins was evaluated for the expression of the two kappa L chain CRI, 6B6.6 and 17.109, and the H chain CRI, G6. Among the paraproteins with kappa L chains, 14% expressed the 17.109 CRI, and 9% expressed the 6B6.6 CRI. Both ELISA and Western immunoblotting experiments showed that the two L chain CRI were mutually exclusive. Anti-IgG activity was documented in 22 of the IgM-kappa paraproteins, among which mAb 6B6.6 reacted with 7 (32%) and mAb 17.109 with 6 (27%). Both CRI were expressed exclusively by L chains within the kappaIII variable gene subgroup. Although 17.109 CRI+ paraproteins had kappaIIIb L chains, none of the 6B6.6 CRI+ paraproteins possessed L chains with this kappa sub-subgroup specific Ag. The G6 CRI was found predominantly among RF paraproteins and was frequently yet not exclusively associated with the 17.109 CRI+ L chains. Additional experiments were performed on a panel of normal adult human sera and documented the presence of 6B6.6 and 17.109 CRI on a small percentage (0.1 to 2.0%) of IgM from most individuals. These data indicate that 1) the mAb 6B6.6 and 17.109 identify two major and distinct CRI among IgM-RF paraproteins, 2) both CRI are associated exclusively with kappaIII L chains, 3) kappaIIIb and kappaIII non-b L chains are equally prevalent among IgM-RF, 4) the G6 H chain CRI is frequently associated with 17.109 CRI+ L chains, but not with 6B6.6 CRI+ L chains, and 5) although the ability to make 6B6.6 and 17.109 CRI+ kappa L chains is common in humans, these CRI are present in low concentrations in normal IgM.

Adolescent↗
PubMed1988

The long-term stability of recombinant (serine-17) human interferon-beta.

Escherichia coli-derived (Serine 17) human interferon-beta (HuIFN-beta SER) was formulated with SDS and placed at multiple isothermal temperatures (-70 degrees C to 37 degrees C). Three stability-indicating test methods (bioassay, SDS-PAGE, RP-HPLC) were used to evaluate the long-term stability of this preparation. No change was observed when stored for nearly a year at either -70 degrees C or 4 degrees C. At the elevated temperatures, proteolytic cleavage, noncovalent oligomer formation, and loss of antiviral activity were observed. The absence of a carrier protein makes this stable IFN-beta frozen reference preparation useful as a standard in both biological assays and protein chemical methods of analysis.

Biological Assay↗
PubMed1988

Idiotypic and subgroup analysis of human monoclonal rheumatoid factors. Implications for structural and genetic basis of autoantibodies in humans.

Rheumatoid factors (RFs) in humans have been studied intensively because of their association with autoimmune and lymphoproliferative diseases. Many human IgM-RFs express cross-reactive idiotypes (CRIs) and have homologous light chains, some of which are encoded by a single V kappa gene, termed V kappa 325. However, although antibody activity generally requires the interaction between heavy and light chain variable regions, much less is known about structural relationships among RF heavy chains. To delineate further the structural and genetic basis of RF autoantibody synthesis, we generated "sequence-dependent" reagents specific for the human heavy and kappa light chain subgroups, and used them to analyze a panel of 27 monoclonal RFs. In addition, these proteins were tested for the expression of a heavy chain-associated CRI (G6), and a light chain-associated CRI (17.109). The results showed that most 17.109-reactive RFs contain heavy chains of the VHI subgroup, which bear the G6 idiotypic marker. However, among the 14 17.109-reactive RFs, two have heavy chains of the VHII subgroup, and another two contain heavy chains of the VHIII subgroup. Previously, we have shown that 17.109 is a phenotypic marker of the human V kappa 325 gene. Accordingly, these results demonstrate that the same human V kappa gene can combine with several VH genes from different VH gene subgroups to generate RF activity.

Amino Acid Sequence↗
PubMed1988

Idiotypic characteristics of rheumatoid factors.

We have used monoclonal anti-idiotypic antibodies and "sequence-dependent" heterologous anti-peptide antibodies of predefined specificities against either the complementarity determining or framework regions of the human immunoglobulin molecules to delineate the structural and genetic basis of human IgM rheumatoid factor (RF) paraprotein formation. Human IgM RF paraproteins were found to be most commonly reactive with anti-kappa III subgroup anti-sera (88%). These RFs could be subdivided into two major light chain cross reactive idiotype (CRI) groups with the monoclonal antibodies 17.109 and 6B6.6. The two CRI positive light chains are likely encoded by two distinct V kappa germline genes, designated respectively Humkv325 (VkRF) and Humkv328. These CRIs are also associated with specificities other than RFs. Heavy chain analysis of RFs revealed that the product of the Humkv325 gene frequently assemble with heavy chains of the VHI subgroup, but will assemble with the heavy chains of other subgroups less frequently. The VHI heavy chains RFs were found to carry frequently the G6 CRI marker.

Antibodies, Monoclonal↗
PubMed1988

Parameters for the evaluation of long-term stability of tumour necrosis factor preparations.

Escherichia coli-derived Tumour Necrosis Factor (TNF) was formulated in the absence of a protein-carrier, both as a solution and as a lyophilized preparation. By means of three stability-indicating test methods (bioassay, SDS-PAGE, IEF), the long-term stability of these TNF preparations was evaluated. Both preparations showed no change upon storage for 9 months at -70 degrees C and -20 degrees C. Depending upon the test method, different rates of change were detected at elevated temperature. The analysis presented will assist in the design of future TNF reference standards.

Amino Acid Sequence↗
PubMed1987

Genetic analysis of human B cell hybridomas expressing a cross-reactive idiotype.

We have examined the genetic basis for the expression of a human cross-reactive idiotype (CRI) commonly found on monoclonal IgM rheumatoid factors. The CRI was identified with a monoclonal antibody (17.109) and has been localized previously to the kappa-variable region. By using the human lymphoblastoid cell line WI-L2-729-HF2, and mononuclear cells from several sources, a panel of hybridomas was generated that produced 17.109 CRI-positive Ig. A recently cloned human germ-line V kappa III gene, Humkv305, served as a probe to identify genes which were rearranged and expressed in 17.109 CRI-positive and -negative hybridomas. This probe, when hybridized to human genomic DNA under stringent conditions, identified only two to five germ-line bands. In 10 separate 17.109 CRI-positive hybridoma clones, an additional rearranged V kappa band was identified. The probe did not anneal to rearranged V kappa bands in hybridoma clones that produced kappa-chains lacking the CRI. RNA dot-blot studies provided evidence for expression of genes hybridizing to the Humkv305 probe. The results indicate that the 17.109 CRI is a serologic marker for a single V kappa gene, or a small family of closely related V kappa genes, which is identified by the Humkv305 probe.

B-Lymphocytes↗