Biomedical subjects
H Dang
Publications and source records attributed to H Dang.
Induction of transcription factors in human T lymphocytes by aspirin-like drugs.
Aspirin-like drugs (ALD) induce calcium mobilization, an essential component of T cell activation, but do not induce the biosynthesis of IL-2. To understand the extent to which ALD may mimic mitogenic stimulation, we studied cytoplasmic and nuclear signaling steps in ALD-treated T cells. We found that ALD induce a transient activation of protein kinase (PKC) but have no effect (in comparison to anti-CD3 antibodies) on protein tyrosine phosphorylation nor on PCL gamma 1 tyrosine phosphorylation. ALD-induced calcium mobilization and PKC activation are independent of tyrosine protein kinase activity as shown by the lack of effect of herbimycin, a tyrosine-protein kinase-specific inhibitor. Although we detected no IL-2 mRNA in ALD-treated cells, the nuclei of these cells contain proteins capable of binding to three regulatory sequences in the IL-2 promoter region: NFAT, NF kappa B, and AP-1. These binding activities are expressed only in activated T cells. The expression of AP-1 depended on calcium mobilization and PKC activation. These data suggest that ALD cause transient but significant changes in T cell transmembrane signaling, although some events induced by stimulation with anti-CD3 antibodies are not induced by ALD. The signal is transmitted to the nucleus and induces DNA-binding activity by several transcription factors. However, the ALD stimulus is not capable of causing complete T cell activation.
Analysis of transforming growth factor beta and other cytokines in autoimmune exocrinopathy (Sjögren's syndrome).
Cytokines play a major role in tissue destruction caused by autoimmune dysregulation. In Sjögren's syndrome (SS) patients, salivary glands are the target organs for autoimmune tissue damage. In the present study, reverse transcriptase-polymerase chain reaction (RT-PCR) was used to look for cytokine mRNA expressed in SS salivary glands. Focus score was used to determine the severity of the lesions. Cytokine production in supernatants of the salivary gland cell culture was measured by enzyme-linked immunosorbent assay (ELISA). Immunohistochemical staining was used to identify the local presence of transforming growth factor beta (TGF-beta). Interleukin (IL)-2, IL-6, and IL-10 mRNA were expressed in moderate to severe SS salivary gland lesions. TGF-beta mRNA was constitutively expressed in normal and SS salivary glands. In SS salivary gland cell cultures, IL-6 and IL-10 proteins were produced. TGF-beta production was reduced in high focus score SS glands. Normal and minimally involved SS salivary gland ductal epithelium and acinar cells were found to produce TGF-beta by immunostaining. In conclusion, an excess production of IL-2, IL-6, and IL-10 and a reduced production of the immunosuppressive cytokine, TGF-beta, may be responsible for the progression of the salivary gland lesion in SS. Specific immunotherapy can now be designed based on mechanisms to correct this cytokine imbalance and benefit patients with autoimmune diseases, such as SS.
A comparative case study on the factors affecting infant mortality in Shanghai.
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Longitudinal exposure of human T lymphocytes to weak oxidative stress suppresses transmembrane and nuclear signal transduction.
Products of polyamine oxidase activity, at micromolar levels and during a period of 2 to 3 days, down-regulate IL-2 mRNA levels and activity in human lymphocytes. We studied whether this suppression was associated with signal transduction abnormalities. We found that polyamine oxidase activity suppresses both anti-CD3-induced IL-2 production and protein tyrosine phosphorylation. Polyamine oxidase activity also caused a reduction in intracellular calcium mobilization after mitogenic stimulation. The most distal step of CD3-mediated signal transduction is dependent upon transcription factors that regulate a set of genes, including IL-2. We found that polyamine oxidase-treated cells exhibited very low DNA binding activity of two such factors: NFAT and NF-kappa B. On the other hand, AP-1 DNA binding activity was enhanced in polyamine oxidase-treated cells, suggesting a possible role for AP-1 in the human lymphocyte stress response. In accordance with the oxidation dependence of this suppressive mechanism, N-acetylcysteine (NAC; an antioxidant) significantly reversed the polyamine oxidase effects on lymphokine production and signal transduction. These results suggest that NAC contributes, under oxidizing conditions, to the preservation of immune function. In summary, our data suggest that chronic low-level oxidative stress, via suppression of mitogen-induced transmembrane signaling (protein-tyrosine phosphorylation and calcium mobilization), causes a decrease in the DNA binding activity of transcription factors that regulate the IL-2 gene. This results in decreased IL-2 production.
Induction of lupus-associated autoantibodies by immunization with native and recombinant Ig polypeptides expressing a cross-reactive idiotype 4B4.
A human mAb designated 4B4 with anti-Sm activity was derived from a patient with systemic lupus erythematosus. This antibody expressed a lupus-associated cross-reactive Id, partially related to the monoclonal murine anti-Sm (Y2) from MRL/lpr mice. Studies were performed to investigate the ability of 4B4 to induce lupus in nonautoimmune-prone mice. BALB/c mice immunized with 4B4 produced antibodies to dsDNA, ssDNA, Sm ribonucleoprotein, and mouse Fc fragment. There was no antibody activity against SSA/Ro, SSB/La, and hen egg lysozyme. Ag inhibition studies show that the autoantibodies were not polyreactive. Mice were also immunized with r4B4 polypeptides representing the H/L heterodimer, H chain and L chain. Autoantibodies were induced in mice immunized against the H/L and H polypeptides. No autoantibodies were induced in mice immunized with recombinant L chain. Furthermore, from 20 to 68% of antibody activity to Sm or dsDNA could be inhibited with anti-Id antiserum (either anti-4B4 or Y2). The autoantibody was initially IgM and then underwent an isotype switch to IgG. These results show that lupus-associated autoantibodies can be induced by immunization with 4B4 and that the 4B4 VH region is important in this induction process. The finding of murine IgG autoantibody expressing a cross-reactive Id similar to the immunizing 4B4 suggests a role for anti-idiotypic Th cells in this autoimmune response.
Two inactive fragments derived from the yeast mitochondrial ribosomal protein MrpS28 function in trans to support ribosome assembly and respiratory growth.
The mitochondrial ribosomal protein MrpS28 of Saccharomyces cerevisiae is one of several mitochondrial ribosomal proteins homologous to Escherichia coli ribosomal proteins within the context of a larger protein. Relative to a region of homology with E. coli ribosomal protein S15, the mature MrpS28 protein has unique sequence domains of 117 and 48 amino acids at its amino and carboxyl terminus, respectively. To better understand the role of the various sequence domains of the MrpS28 protein in vivo, truncated derivatives were expressed under conditions where they were the only potential source of functional MrpS28 protein. The results shown here demonstrate that the amino-terminal domain and the S15-like domain are both essential for respiratory growth. Interestingly an inactive amino-terminal fragment can be complemented in trans by a second inactive fragment comprising the S15-like domain and the carboxyl-terminal 48 amino acids. Consequently, the assembly of these fragments into ribosomal subunits can be examined when they are expressed individually or together. Results from these studies indicate that each of the MrpS28-derived fragments facilitates the incorporation of the other into 37 S ribosomal subunits.
Cloning of a human IgM autoantibody bearing a cross-reactive idiotype in a lambda expression vector: a new approach to studying autoantibodies.
The monoclonal antibody 4B4 is a human IgM,kappa which expresses a cross-reactive lupus-associated idiotype and has anti-Sm binding activity. We find that the VL nucleotide sequence of 4B4, like the 4B4 VH region, is encoded by unmutated germline genes. The 4B4 VH and VL were cloned into the ImmunoZap lambda expression vector to produce three recombinant immunoglobulin polypeptides. These recombinant polypeptides expressed, respectively, either the 4B4 VH or VL alone or a VH/VL heterodimer. ELISA showed that the VH/VL heterodimer retained anti-Sm antibody activity. The 4B4 idiotype was found predominantly on the VH. This report describes: (i) a method for producing recombinant immunoglobulin molecules from an IgM-secreting B cell line and (ii) the ability of recombinant antibody fragments expressed in Escherichia coli to retain the structural and antigenic properties of the native molecule.
Characterization of a cross-reactive idiotype on two human autoantibodies associated with systemic autoimmune disease.
A human-human hybridoma was derived from a patient with primary Sjogren's Syndrome. The monoclonal antibody from this hybridoma, P36, was found to be polyreactive. P36 shared idiotypic cross-reactivity with a lupus-associated monoclonal antibody called 4B4. There was a strong correlation between P36 and 4B4 idiotype levels in systemic lupus erythematosus sera. Western blot studies showed that this shared idiotype was found on the heavy chain of both antibodies. This study shows that the heavy chain is important in the expression of this idiotype and provides another immunologic link between these two rheumatic diseases.
Summary evaluations of risk factors related to infant mortality.
The authors discuss risk factors related to infant mortality. "The size and magnitude of these risk factors vary across different countries and regions. In order to more accurately describe the relationship between risk factors and infant mortality, risk factors should be quantified, making it possible to estimate the degree of risk associated with infant deaths. This article introduces some risk factors and their evaluation method."
[1-stage repair of congenital blepharostenosis].
Nine cases of congenital blepharostenosis have been corrected by operation. The procedure included shortening of the ligaments of the inner canthus, correcting epicanthus, incision of the external canthus, and rectifying drooping of the upper lid in one stage. After operation, incision scar is not noticeable.
Human kappa chain expression in a lambda phage vector: methods of isolating amplified cDNA affects cloning efficiency.
Three common methods of isolating amplified DNA were evaluated for their effects on cloning efficiency in a phage vector designed to express human kappa chain. The "glass milk" technique gave higher cloning efficiency and protein expression than phenol-chloroform extraction or microfiltration. This shows that the quality of amplified cDNA should be considered when studying the human antibody repertoire using this vector system.
Sjögren's syndrome and retroviral protein reactivity: reply.
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Cross-reactivity of the B/B' subunit of the Sm ribonucleoprotein autoantigen with proline-rich polypeptides.
Using recombinant fusion proteins representing different regions of the human Sm B/B' polypeptide, the 4B4 monoclonal anti-Sm antibody was found to bind a C-terminus epitope that is proline-rich. 4B4 cross-reacted with the p24 gag protein of HIV-1 and with other polypeptides rich in proline residues, including collagen. BALB/c mice immunized with human collagen not only produced antibodies to the immunizing antigen but also antibodies to Sm. This immune mouse serum also recognized C-terminus B/B' fusion proteins. These data suggest that the Sm B/B' antigen contains a poly-Pro epitope that is shared by several autoantigens and retroviral proteins. These sites may be important in the induction of autoantibodies through molecular mimicry.
Are endogenous retroviruses involved in human autoimmune disease?
A role for viruses in the etiopathogenesis of human autoimmune diseases has long been suspected but has not yet been proven. In Sjögren's syndrome (SS), there is continuing experimental support for the possible involvement of Epstein-Barr virus. Since the advent of AIDS, there is also great interest in retroviruses and autoimmune disease. We previously reported that 30% of SS patients and 36% of systemic lupus erythematosus (SLE) patients have serum antibodies to the p24 gag protein of HIV-1. We now report that two mechanisms classic for retroviruses (molecular mimicry and immunosuppression) may be operative in SS and SLE. The p24 gag protein shares a proline-rich epitope with the Sm nucleoprotein to which many SLE patients have antibodies. The impaired lymphocyte activation seen in peripheral blood T cells in SS patients is also seen in a human T cell line infected with an A-type retroviral particle linked to SS. Many studies suggest that endogenous retroviral sequences are important in immunoregulation. We now suggest that endogenous retroviral sequences may also be important in the etiology and pathogenesis of SS and SLE.
Spatial frequency evoked visuograms in multiple sclerosis.
We obtained steady-state visual evoked potentials (VEPs) to sinusoidal gratings alternating at 4 Hz with spatial frequencies varying from 0.5 to 8 cpd in 21 normal controls and 21 patients with multiple sclerosis (MS), and analyzed responses by fast Fourier transform. Amplitude- and phase-spatial frequency functions were obtained and referred to as amplitude and phase "visuograms." We observed two types of abnormalities in the phase visuograms of MS patients: (1) abnormal responses at all spatial frequencies tested (37%), and (2) abnormal responses only at selective spatial frequencies (52%). Some patients had phase lag limited to low, middle, or high spatial frequencies. Steady-state and transient VEPs to 2 and 4 cpd showed a similar percent of abnormalities. The use of more than one spatial frequency stimulus increased the diagnostic yield by 17%. Our data confirm that MS may selectively affect specific neuronal channels within the visual pathways.
Evidence for possible retroviral involvement in autoimmune diseases.
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Salivary and serum IgA antibodies to the Epstein-Barr virus glycoprotein gp340: incidence and potential for virus neutralization.
Human antibody responses to the Epstein-Barr virus (EBV) glycoprotein gp340 have been measured using purified preparations of the native molecule as the substrate in ELISAs. This glycoprotein is the dominant component of the EBV envelope and a major target for the virus-neutralizing antibody response. Healthy virus carriers (both Caucasian and Chinese) regularly show detectable anti-gp340 IgG in serum and, unexpectedly, 21-30% of these individuals are also serum anti-gp340 IgA positive. Chinese patients with the EBV-genome-positive malignancy nasopharyngeal carcinoma (NPC) show elevated serum IgA antibodies to gp340 but, given the background of responses amongst healthy virus carriers, anti-gp340 IgA titres are a poorer diagnostic indicator of NPC than serum IgA antibodies detectable by immunofluorescence against the multicomponent EBV early antigen (EA). Salivary IgA antibody responses to gp340 are potentially important as a means of neutralizing orally-transmitted virus. We detected salivary IgA (but not IgG) to gp340 in a minority (12-19%) of healthy virus carriers and in a higher proportion (49%) of NPC patients. Even saliva samples chosen for their relatively high anti-gp340 IgA titres showed only weak neutralizing activity against transforming EBV preparations whether from B95.8 cell culture supernatant or from the throat washing of an infectious mononucleosis patient. We conclude that in healthy virus carriers, salivary IgA responses to gp340 are unlikely to provide effective local immunity against re-infection with a second EBV strain.