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S Fong

Publications and source records attributed to S Fong.

At least 73 records · Page 4Linked to original sources
PubMed1987

High-frequency expression of a conserved kappa light-chain variable-region gene in chronic lymphocytic leukemia.

Malignant B lymphocytes from several patients with chronic lymphocytic leukemia (CLL) were examined for reactivity with murine monoclonal antibody 17.109. This antibody, prepared against the rheumatoid factor (RF) paraprotein Sie, recognizes a crossreactive idiotype on 48% of human IgM RF paraproteins, but does not react with IgM paraproteins without RF activity or substantially with normal pooled immunoglobulin. The 17.109-reactive idiotype is a marker for a kappa III variable-region gene, designated V kappa RF, that is conserved in outbred human populations. In a limited study of 31 CLL patients, the leukemic cells from 5 of 20 patients with kappa light chain-expressing CLL were recognized by the 17.109 monoclonal antibody. Despite having malignant cells specifically reactive with this antibody, patients with 17.109-positive CLL did not have elevated serum levels of circulating antibody bearing 17.109-reactive determinants. Total RNAs isolated from the CLL B lymphocytes, or from hybridomas produced by fusing the CLL cells with the WI-L2-729-HF2 cell line, were fractionated electrophoretically and examined by blot hybridization. Under stringent hybridization conditions capable of discerning a single base-pair mismatch, RNA from the 17.109-idiotype-positive CLL cells hybridized to synthetic oligonucleotide probes corresponding to framework and complementary-determining regions in the V kappa RF gene. The high frequency of the 17.109-associated idiotype and the V kappa RF gene in CLL suggests that the disease may arise from B lymphocytes that express a restricted set of inherited immunoglobulin variable-region genes with little or no somatic mutation.

B-Lymphocytes↗
PubMed1987

Rheumatoid factor and immune networks.

Rheumatoid factors represent a normal component of the immune network. The autoantibodies promote complement fixation and clearance of immune complexes. They amplify the avidity of polyclonally induced IgG. Genes related to the primary structure of rheumatoid-factor light chains are widely distributed in the human population and have been conserved during the evolution and dispersion of the species. Products of these genes may be detected with anti-idiotypic antibodies against synthetic peptides corresponding to individual hypervariable regions on rheumatoid-factor light chains. Such anti-peptide antibodies provide unique reagents for analyzing the genetics of immunoglobulins in outbred populations. Precursors of rheumatoid factor are abundant among immature B lymphocytes. Some of these cells may tend to localize to mucosal surfaces, where they are stimulated directly by pathogenic microorganisms with polyclonal B cell-activating properties. Synthesis of rheumatoid factor regularly accompanies all secondary immune responses but is usually transient. Production of the autoantibody is T-cell dependent. The T cells may recognize antigen in an IgG-antigen immune complex that is processed and presented by B-cell precursors of rheumatoid factor. Rheumatoid factor-associated light-chain idiotypes are rare in serum IgG and on IgG myeloma proteins. They are common among monoclonal IgM proteins and on the surface of the malignant B cells from patients with chronic lymphatic leukemia. The rheumatoid factors that are produced by patients with mixed cryoglobulinemia, or primary Sjogren's syndrome can share idiotypic antigens with monoclonal rheumatoid factors. Rheumatoid factor synthesis in the diseases may reflect an abnormal proliferation of B-cells that is not antigen-driven and that can degenerate into malignancy. The rheumatoid factors in patients with rheumatoid arthritis are diverse and almost certainly represent the outcome of antigen-induced, T cell-dependent mechanisms. The antigens that drive the T cells have not been identified but could represent exogenous microorganisms, self components, or idiotypic antigens that fortuitously interact with rheumatoid factors.

Autoantibodies↗
PubMed1987

The use of defined peptides in characterizing idiotypes.

The structural correlates of idiotypes have been sought in several antibody systems. The cumulative results suggest that the hypervariable regions (or complementarity-determining regions) of the heavy and light chains are the structural basis of idiotypes. However, in most cases, it is exceedingly difficult to associate a particular idiotypic determinant with a specific amino acid sequence. Recently, synthetic peptides were used to induce antibodies specific for predefined determinants in intact proteins. These findings led us and others to use synthetic peptides corresponding to the hypervariable regions/complementarity-determining regions to induce anti-idiotypes. These novel anti-idiotypic antibodies are easy to prepare, and are ideal reagents for structural and genetic studies of antibody responses.

Amino Acid Sequence↗
PubMed1987

Rheumatoid factor.

Many human RF-associated crossreactive idiotypes (CRIs) have been defined. Since these CRIs probably are the phenotypic markers of Ig variable region genes, the data suggest that human RFs employ several Ig variable region genes which are common among outbred human populations. There are at least four types of stimuli which can trigger RF production. They are aggregated IgG in the form of antigen-antibody complexes, exogenous antigens bearing cross-reactive determinants to human IgG, autologous antibodies which mimic the Fc region of human IgG, and polyclonal B cell activators. Transient RF secretion is regularly induced by antigen-antibody complexes during secondary immune responses. In normal human subjects, RFs may be produced primarily by the B cells which bind mouse red cells, or express Leu l markers on their surface. Leu l is the human homolog of Ly l in mice. Upon polyclonal stimulation, these Ly l B cells secrete IgM autoantibodies. Combined protein and DNA sequencing studies reveal that human RFs utilize a small number of light chain variable region genes, together with several heavy chain variable regions genes. In contrast, by mRNA sequencing, murine RFs were found to employ many heavy and light chain variable region genes which belong to various gene families. Two human RF-related light chain variable region genes have been cloned and characterized. One germ-line Vk gene (designated Humkv325) is identical to four RF light chain sequences from unrelated individuals, and differs from the other eight RF light chains by one to seven amino acid residues. These results demonstrate that this RF-related Vk gene is both widely distributed and conserved among outbred human populations.

Amino Acid Sequence↗
PubMed1986

Human kappa light chain subgroup analysis with synthetic peptide-induced antisera.

All human kappa light chains belong to one of four subgroups, classified according to their amino acid sequences or by reactivity with adsorbed heteroantisera. The structural basis for the subgroup distinction by antisera is unknown. Therefore, to create anti-kappa subgroup antibodies with predefined specificity, we immunized rabbits with synthetic peptides which correspond to sequences within the first framework region of prototype kappa I, II, III, and IV light chains. The peptide-induced antisera recognized primary sequence-dependent kappa subgroup determinants. They correctly predicted the amino acid sequence in the first framework region of two kappa light chains. By Western immunoblotting and enzyme-linked immunoassay the antisera also identified previously typed, monoclonal light chains of different subgroups with complete specificity. These reagents, define a site of kappa subgroup distinction and represent a potent tool for the characterization of light chain heterogeneity.

Amino Acid Sequence↗
PubMed1986

Expression of three cross-reactive idiotypes on rheumatoid factor autoantibodies from patients with autoimmune diseases and seropositive adults.

Approximately one-half of human monoclonal IgM anti-IgG autoantibodies (rheumatoid factors (RF] from unrelated individuals with cryoglobulinemia coordinately express three cross-reactive idiotypic antigens (CRI). The CRI are detected with: 1) monoclonal antibody 17.109, which recognizes a conformation-dependent CRI on K-light chains; and 2) two rabbit anti-peptide antibodies that react with primary sequence-dependent CRI (PSL2 and PSL3) corresponding to the conserved second and third K-chain complementarity-determining regions, respectively. In the present experiments, the structural features of polyclonal RF autoantibodies from diverse patients with rheumatoid arthritis and from those with primary Sjögren's syndrome, and from seropositive elderly subjects without overt autoimmune diseases, were investigated with these three defined anti-CRI reagents. The pattern of expression of the CRI differed among patient groups. Only the RF autoantibodies from Sjögren's syndrome patients frequently displayed all three CRI. However, the RF from nearly every subject tested, including patients with rheumatoid arthritis, were enriched in the primary sequence-dependent PSL2-CRI as compared to RF-depleted Ig from the same subjects. Amino acid sequence analysis of monoclonal IgM-RF indicates that PSL2-CRI-positive light chains probably represent the products of a single Vk gene. Therefore, a proportion of the polyclonal RF from different autoimmune states may represent somatic variants of this germ-line RF Vk gene which retain the PSL2 sequence as a common element.

Adult↗
PubMed1986

Release of lymphokines after Epstein Barr virus infection in vitro. I. Sources of and kinetics of production of interferons and interleukins in normal humans.

Infection of human lymphocytes with Epstein Barr virus (EBV) activates the release of lymphokines. Previous experiments have emphasized the ability of interferon-gamma (IFN-gamma) to prevent EBV-induced B cell transformation. However, the factors that regulate IFN-gamma synthesis and release during in vitro EBV infection are controversial. In the present investigation we have systematically evaluated the kinetics of production, cellular origins, and accessory cell requirements for IFN-alpha and IFN-gamma and for IL 1 and IL 2, after EBV infection. Our data indicate that IFN-alpha is released entirely by natural killer (NK) cells and B cells, in the absence of accessory cells, independently of the other lymphokines and within 24 hr of infection. In contradistinction, IFN-gamma secretion is exclusively of T cell origin, is absolutely dependent on the prior elaboration of IL 1 and IL 2, and is maximal 8 days after EBV infection. IL 2 secretion by T cells peaks on day 5 and requires the earlier release of IL 1. Both NK cells and monocytes are a source of IL 1. Secretion of IL 2 and IFN-gamma occurs in the presence of either one of these cell types but not in the absence of both. Antibody against IL 1 blocks EBV-induced IL 2 and IFN-gamma generation, and antibody against IL 2 decreases production of IFN-gamma. Thus, the production of IFN-gamma, the lymphokine that prevents EBV-induced B cell transformation, is the final outcome of a cascade of lymphokine-mediated events that involve interactions between virus-infected B lymphocytes that serve as antigen-presenting cells, NK cells and monocytes as sources of IL 1, and T lymphoblasts. Dysfunctions of any or all of these cell types would be expected to impair the regulation of EBV transformation.

Adult↗
PubMed1986

Release of lymphokines after infection with Epstein Barr virus in vitro. II. A monocyte-dependent inhibitor of interleukin 1 downregulates the production of interleukin 2 and interferon-gamma in rheumatoid arthritis.

Epstein Barr virus (EBV)-infection of normal peripheral blood mononuclear cells (PBMC) in vitro induces IFN-alpha secretion from B cell and natural killer (NK) cell populations, and IFN-gamma secretion from T cells. IFN-gamma depends on prior elaboration of IL 2 and IL 1 that originates from monocytes and NK cells. PBMC from rheumatoid arthritis (RA) patients released moderately elevated levels of IFN-alpha (236 +/- 62 U/ml vs 168 +/- 34 in normals). In contrast, IFN-gamma was significantly lower in RA (88 +/- 34 U/ml vs 209 +/- 32) with an associated deficit in IL 2. A monocyte-dependent factor was shown to be responsible for this deficit, since monocyte depletion of RA cultures normalized the levels of IL 2 and IFN-gamma. Significantly lower levels of IL 1 activity were present in the supernatants of RA PBMC cultures as compared with normal cultures, and this was shown to be associated with presence of a nondialyzable IL 1 inhibitor. This inhibitor was capable of preventing the IL 1-dependent synthesis of IL 2 and IFN-gamma by normal PBMC. Exogenous IL 1 or IL 2 restored the deficient IFN-gamma secretion in RA PBMC. Thus, the deficient ability of RA lymphocytes to control EBV infection may be secondary to impairment of a monocyte-T cell interaction at the level of IL 1.

Adult↗
PubMed1986

Response of bovine and porcine peripheral blood mononuclear cells to human recombinant interleukin 2(125).

Bovine and porcine peripheral blood mononuclear cells (PBMC) were tested for their response to human recombinant interleukin 2(125) (rIL 2(125)). The rIL 2(125) used in these experiments was purified to homogeneity from Escherichia coli, contained a site-specific modification at amino acid #125 replacing a cysteine with a serine residue and had a specific activity of 4 X 10(6) units/mg. Human rIL 2(125) was shown to be directly mitogenic for bovine and porcine PBMC and was able to maintain the long-term growth of mitogen-activated PBMC of both species. Long-term cultures were highly sensitive to low levels of rIL 2(125) and showed dose-dependent responses when used in short-term IL 2 assays. Bovine and porcine PBMC preincubated with human rIL 2(125) for 1 and 5 days demonstrated enhanced levels of cell-mediated cytotoxicity against both allogeneic and xenogeneic cell lines.

Animals↗
PubMed1986

Cloning and sequence determination of a human rheumatoid factor light-chain gene.

The contribution of germ-line variable regions to autoantibody formation in humans is poorly understood. To study the gene structure of a human autoantibody, chronic lymphatic leukemia (CLL) cells from a patient with an IgM anti-IgG (rheumatoid factor, RF) paraprotein were utilized. The rearranged immunoglobulin gene encoding the kappa light chain for the RF was cloned, and the nucleic acid sequence of its variable region was determined. As demonstrated by Southern blot analysis using a kappa joining-region probe, the CLL cells, stable CLL-WIL2-729-HF2 RF-secreting hybridomas, and the cloned light-chain gene all had an identical restriction fragment containing the rearranged light-chain gene. The CLL RF light chains reacted weakly with an antipeptide antibody against a primary structure-dependent idiotype present on the light chains of the majority of IgM RF paraproteins. The nucleotide and predicted amino acid sequences of the CLL light-chain gene place it in the kappa III variable-region subgroup, and a comparison to known RF paraproteins reveals marked homology to the light-chain amino acid sequence of the IgM RF paraprotein Pom. Both Pom and the CLL light chain appear to identify a second kappa III gene or gene group that is able to encode RF paraprotein light chains.

Amino Acid Sequence↗
PubMed1986

Expression of a cross-reactive idiotype on rheumatoid factor in patients with Sjogren's syndrome.

Primary Sjogren's syndrome (SS) is a systemic autoimmune disorder characterized by lymphocytic infiltration of salivary and lacrimal glands. These patients have evidence of marked B cell hyperactivity, including the production of autoantibodies such as rheumatoid factor (RF) and an increased frequency of non-Hodgkin's lymphoma. We now demonstrate that RF from 12/15 SS patients contains a cross-reactive idiotype (CRI) on their kappa light chain defined by a monoclonal antibody (MoAb 17-109) and immunoblotting. This CRI was associated with immunoglobulin (Ig) A-RF, and to a lesser extent with IgM-RF molecules on the basis of direct binding studies. With the use of immunoperoxidase techniques to stain frozen tissue sections, B cells containing cytoplasmic Ig reactive with MoAb 17-109 were detected in the salivary gland biopsies from 11/12 SS patients at high frequencies, and in the blood from the same patients at much lower frequencies. One patient with pre-existant SS developed non-Hodgkin's lymphoma with tumor cells and RF paraprotein reactive with MoAb 17-109. Evaluation of serial biopsies over a 4-yr period showed a progressive increase in the proportion of B cells bearing the CRI. In contrast, synovial membrane biopsies from RA patients lacking sicca symptoms did not contain B cells expressing the CRI. Because previous studies have demonstrated that MoAb 17-109 detects a CRI on RF paraproteins from patients with lymphoma, B cells bearing this CRI may have increased frequency of neoplastic transformation. SS patients provide an opportunity to study the expression of this CRI and to understand the transition of B cell clones from autoimmune proliferation to neoplastic transformation.

Adolescent↗
PubMed1986

Characterization of a crossreactive idiotype in Sjögren's syndrome.

Sjögren's syndrome (SS) is characterized by lymphoid infiltration of the salivary glands and autoantibody production. Rheumatoid factor (RF) in patients with primary SS (1 degree SS) contains a crossreactive idiotype (CRI) defined by a monoclonal antibody (MoAb 17-109). This CRI was located on the kappa light chain by immunoblotting methods. A high frequency of CRI+ B cells was found in SS salivary gland biopsies, suggesting this tissue as the site of production for this autoantibody. Further characterization of CRI+ RF from SS patients was performed using antibodies prepared against synthetic peptides corresponding to the hypervariable region of RF paraproteins from patients with Waldenström's macroglobulinemia (WM). These results demonstrate a close structural relationship between RF in SS and WM patients. To analyze the genes that encode these RF in SS patients, B cell hybridomas that secreted CRI+ immunoglobulin were created and their DNA analyzed by Southern blot techniques. These hybridomas will allow us to determine the DNA sequence of kappa genes encoding the CRI and to identify adjacent regulatory genes that may promote high levels of CRI expression.

Cross Reactions↗
PubMed1986

The common occurrence of internal image type anti-idiotypic antibodies in rabbits immunized with monoclonal and polyclonal human IgM rheumatoid factors.

We have previously reported that rabbits immunized with a polyclonal human rheumatoid factor (RF) autoantibody preparation could induce anti-idiotypic antibodies bearing the 'internal image' of the Fc fragments of human IgG. The 'internal image' anti-idiotype have been shown to react with both the RF molecules as well as with the RF receptors on B lymphocytes. Under what conditions these anti-idiotypes occur is not known. Presently, we report that these anti-idiotypic antibodies occur more frequently than previously thought and could be isolated in sera of rabbits immunized with either monoclonal paraproteins with RF activity or other purified human polyclonal serum RFs. Immunization of rabbits with a peptide corresponding to the second complementarity-determining regions of a monoclonal RF did not induce this anti-idiotype. Immunization of goats with human RF similarly did not result in induction of such anti-idiotype. Induction of these anti-idiotypes thus depended upon immunization with the intact RF antigen as well as the species of animal immunized. The repeated isolation of 'internal image' anti-idiotypic antibodies from RF immunized rabbits suggests that the antigenic conformations recognized by human RF autoantibodies are restricted, and that 'internal image' anti-idiotypic species to RF may pre-exist within the rabbit immune network. Such broadly cross-reactive anti-idiotypic reagents provide unique reagents for studying the regulation of RF autoantibody synthesis.

Animals↗
PubMed1985

IgM rheumatoid factor autoantibody and immunoglobulin-producing precursor cells in the bone marrow of humans.

The natures of the IgM rheumatoid factor (RF)-, IgM-, and IgG-secreting cells in the human bone marrow as compared to the peripheral blood, have been investigated by (1) response to the polyclonal B-cell activator, the Epstein-Barr virus (EBV), (2) sensitivity to the S-phase specific antimetabolite hydroxyurea, (3) presence of the BA-1 and Ia antigens on the cell surface, and (4) cell size, as determined by counter flow elutriation. The EBV-inducible bone marrow IgM-RF precursors derived from medium to large B cells that were inhibited by hydroxyurea pretreatment. The marrow total IgM response derived from small to medium size cells, and was only partially inhibited by hydroxyurea. Hydroxyurea had no effect on IgM-RF or IgM synthesis by peripheral blood cells. These results indicate that the marrow EBV-induced IgM-RF response is not representative of the response by peripheral blood cells, moreover; the marrow RF secreting response arises from a dividing cell pool that may represent newly generated autoreactive B cells.

Aging↗
PubMed1985

Characterization of human rheumatoid factors with seven antiidiotypes induced by synthetic hypervariable region peptides.

Recently, we have used synthetic peptides corresponding to the complementarity-determining regions (CDR) of Ig molecules to induce antiidiotypic antisera. Peptide PSH3, representing the third CDR of the IgM rheumatoid factor (RF) Sie heavy (H) chain, induced a private antiidiotype that reacted with only one out of five IgM-RF. Peptide PSL2, corresponding to the second CDR of Sie light (L) chain, induced an antibody against a crossreactive idiotype (CRI), expressed by 10 out of 12 human IgM-RF analyzed. Herein, we report that five additional antiidiotypic antibodies were generated by immunization with synthetic peptides identical to the third L chain CDR of IgM-RF Sie (PSL3), the second and third H chain CDR of IgM-RF Wol, and the second and third CDR of IgM-RF Pom. As analyzed by immunoblot assay, both anti-PSL3 and anti-PSL2 reacted with the majority of 16 IgM-RF. In contrast, all five antiidiotypes induced by the H chain peptides reacted only with the parent proteins, except anti-PSH3, which reacted weakly with one additional RF. These results suggest that one (or very few) VL gene(s), but a larger number of VH genes, are used to encode IgM-RF autoantibodies.

Antibodies, Anti-Idiotypic↗
PubMed1985

Synthetic peptides corresponding to third hypervariable region of human monoclonal IgM rheumatoid factor heavy chains define an immunodominant idiotype.

Synthetic peptides corresponding to eight individual heavy chain complementarity-determining regions (CDR) of three human monoclonal IgM anti-IgG (rheumatoid factor [RF]) paraproteins elicited rabbit antibodies with markedly different properties. All antisera recognized the immunizing peptide, and several reacted with the isolated IgM heavy chain on immunoblots. However, only the antisera against peptides representing the third CDR bound consistently and specifically to the intact IgM-RF molecule. These data indicate that the third CDR of human mu chains comprises an immunodominant idiotype, and suggest that the D gene segment may be especially important in creating idiotypic diversity. Synthetic peptides corresponding to the third heavy chain CDR of human paraproteins may be clinically useful for the specific induction of antiidiotypic antibodies.

Amino Acid Sequence↗