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PubMed1994

Biochemical and genetic studies of Epstein-Barr virus latent membrane protein 2.

Epstein-Barr Virus (EBV) causes infectious mononucleosis in normal adolescents and malignant B lymphocyte proliferation in immune compromised patients, in marmosets, or upon transfer of infected human B lymphocytes into SCID mice. EBV is also etiologically associated with African Burkitt's lymphoma, Hodgkin's Disease, and nasopharyngeal cancer. EBV transformed, latently infected B lymphocytes contain EBV episomes and eight virus encoded proteins. Six are nuclear proteins (EBNAs) and two are the integral membrane proteins, LMP1 and LMP2. These eight proteins are presumed to mediate latent virus infection or B lymphocyte proliferation and are thus under intense scrutiny. Besides EBNA1, which is required for episome maintenance, LMP1 and LMP2, are the two transformation associated proteins that are most consistently detected in EBV related malignancies, and the LMP2 message is the only message detected in PCR analysis of B lymphocytes from individuals harboring EBV latent infections. LMP2 associates with src family tyrosine kinases, a 70 kda cell phosphoprotein, LMP1 and several other unidentified cell proteins. LMP1 is a key mediator of EBV's effects on inducing B lymphocyte activation and adhesion molecules and is a transforming oncogene in rodent fibroblasts. The association of these two EBV encoded membrane proteins could create a macromolecular complex mediating constitutive B lymphocyte activation through normal cell signal transduction pathways. LMP2 might may control activation of lytic replication or down regulate the activation state of EBV infected cells allowing persistence in the human host.

Amino Acid Sequence↗
PubMed1982

Leukocytoclastic vasculitis. A cutaneous expression of immune complex disease.

Thirty-nine patients with clinical, histologic, and immunofluorescence evidence of leukocytoclastic (necrotizing) vasculitis were studied for the presence of circulating immune complexes. These patients were selected prospectively during a three-year interval from patients seen in a dermatology clinic. Clinical and serologic data are summarized and representative cases are presented. This large series of patients with leukocytoclastic vasculitis emphasizes both the frequency of this disorder and the varied disease settings within which it may manifest. The immunopathologic data presented support an immune complex-mediated pathogenesis for this disease process.

Adolescent↗
PubMed1984

Electron-dense deposits in the renal arterioles of two patients with hypersensitivity vasculitis.

Immune complex deposition in the vessel wall is presumed to be the major pathogenetic mechanism leading to hypersensitivity vasculitis. Despite this, histologic evidence of vascular immune complex deposition such as that provided by electron-dense deposits has been reported only rarely in dermal vessels and never in visceral organs. The cases of two patients with hypersensitivity vasculitis affecting primarily the skin and the kidney are reported. Clinical renal involvement was manifested by proteinuria, hematuria, and a moderate increase in serum creatinine in one case. Renal biopsy showed minimal glomerular changes in one patient and focal necrotizing glomerulitis in the other. The arterioles appeared normal on light microscopic examination. However, obvious electron-dense deposits in the arteriolar wall could be demonstrated electron microscopically in both cases. This observation lends strong support to the theory of immune-complex-mediated vascular damage as the main pathophysiologic mechanism in vasculitis with visceral involvement.

Adult↗
PubMed1996

Detection of circulating immune complexes in dog sera by immune adherence hemagglutination method.

Circulating immune complexes (CIC) in the sera from 102 clinically healthy dogs and from 16 Dirofilaria immitis (D. immitis) infected dogs were measured by the immune adherence hemagglutination (IAHA) method. The level of CIC in the sera from healthy dogs was 28.2 +/- 29.1 micrograms/ml. There was no significant difference in the levels of CIC regarding sexes or ages. On the other hand, the level of CIC in the sera from D. immitis infected dogs was 230.3 +/- 117.1 micrograms/ml, which was significantly (p < 0.01) higher than that of healthy dogs. The results of this study confirm that IAHA method is one of the reliable means of detecting and/or diagnosing immune complex mediated diseases in dogs.

Aging↗
PubMed1991

Expression of IgG Fc receptor antigens in placenta and on endothelial cells in humans. An immunohistochemical study.

Expression of leukocyte IgG Fc receptor (Fc gamma R) antigens by placenta, endothelial cells (EC) of normal tissues, and ECs of kidney and skin from subjects with immune complex diseases was studied immunohistochemically using anti-Fc gamma R monoclonal antibodies (MAb). Monoclonal antibodies against all three leukocyte Fc gamma R classes stained placental villous macrophages. Placental villous trophoblasts were stained intensely by anti-Fc gamma RIII MAb 3G8, while both anti-Fc gamma RI (MAb 32) and anti-Fc gamma RII MAbs IV3, KU79, CIKM5, 2E1, KB61, and 41H16) antibodies did not react with these cells. Anti-Fc gamma RII MAbs IV3, KU79, CIKM5, 2E1, KB61, and 41H16 immunostained placental villous capillary EC, in contrast to anti-Fc gamma RI MAb 32 and anti-Fc gamma RIII MAb 3G8, CLB-Granl, and B73.1, which did not bind. Anti-Fc gamma RI MAb 32, anti-Fc gamma RII MAb IV3 and CIKM5, and anti-Fc gamma RIII MAb 3G8 did not react with the ECs of tonsil, liver, kidney, spleen, intestine, lung, or uterus. Similarly no EC staining was seen with these four MAbs in 14 skin and 14 kidney biopsies from subjects with immune-complex diseases. Fc gamma R antigens are expressed constitutively only by placental villous ECs and are not induced on nonplacental ECs by immune-complex-mediated diseases.

Antibodies, Monoclonal↗
PubMed1993

The role of the 70 kDa subunit of human DNA polymerase alpha in DNA replication.

DNA polymerase alpha is the only enzyme in eukaryotic cells capable of starting DNA chains de novo and is required for the initiation of SV40 DNA replication in vitro. We have cloned the 70 kDa subunit of human DNA polymerase alpha (hereafter referred to as the B subunit) and expressed it as a fusion protein in bacteria. The purified fusion protein forms a stable complex with SV40 T antigen, both in solution and when T antigen is bound to the SV40 origin of DNA replication. Analysis of mutant forms of the B subunit indicates that the N-terminal 240 amino acids are sufficient to mediate complex formation. The B subunit fusion protein promotes formation of a complex containing T antigen and the catalytic subunit (subunit A) of DNA polymerase alpha, suggesting that it serves to tether the two proteins. These physical interactions are functionally significant, since the ability of T antigen to stimulate the activity of the catalytic subunit of DNA polymerase alpha is highly dependent upon the B subunit. We suggest that the interactions mediated by the B subunit play an important role in SV40 DNA replication by promoting DNA chain initiation at the origin and/or facilitating the subsequent priming and synthesis of DNA chains on the lagging strand template. The protein may play similar roles in cellular DNA replication.

Amino Acid Sequence↗
PubMed1990

Differences between C4A and C4B in the handling of immune complexes: the enhancement of CR1 binding is more important than the inhibition of immunoprecipitation.

There are two isotypes of C4--C4A and C4B--, encoded within the major histocompatibility complex with quite different properties. In this study we have compared purified C4A and C4B with regard to their ability to prevent immune complex precipitation and to enhance the binding of both preformed and nascent immune complexes to the receptor CR1 on red cells. C4A was modestly more effective than C4B at inhibiting immunoprecipitation, particularly in antibody excess. In the CR1 binding assay C4A was markedly more effective than C4B in enhancing binding to CR1. This difference was seen with both preformed and nascent immune complexes at equivalence and antibody excess. Thus the major differences between C4A and C4B in regard to immune complex handling is at the level of CR1 binding. Given the strong association of C4A* QO alleles with immune complex-mediated diseases like systemic lupus erythematosus, these findings have important pathogenetic implications.

Antigen-Antibody Complex↗
PubMed1991

Enhancement by fatty acids of the rectal absorption of propranolol: in vitro evaluation in the rat.

The effects of a series of fatty acids on the rectal absorption of propranolol (PL) were examined in vitro, using macrogol 1500 base and rat rectal tissue. Lauric acid, at a fatty acid: PL molar ratio of 1:1, produced the largest increase in permeation rate (Js), penetration coefficient and partition coefficient of PL. PL flux was increased 2.5-fold in the presence of lauric acid compared to that without the fatty acid. However, the Js value of PL was decreased at increased molar ratios (e.g., 3:1) of lauric acid. The permeation rate of lauric acid across the rectal membrane was much larger than that of PL. Furthermore, the apparent partition coefficient of PL in an n-octanol/buffer system was significantly increased at a 1:1 molar ratio to lauric acid compared with that of PL alone. These results suggest that a complex-mediated mechanism facilitates PL transport, thereby partially contributing to the enhancement of PL rectal absorption. A similar mechanism is applicable to percutaneous drug absorption, as reported previously. Thus, a portion of PL, after first forming a complex with fatty acids, may rapidly permeate across rectal membranes.

Animals↗
PubMed1976

Immunology of Allergy.

Immune reactions, presumably developed to rid organisms of troublesome invaders, are rather frequently associated with responses that result in injury to host tissue. Such responses are manifestations of allergy or hypersensitivity, and involve antibodies of certain immunoglobulin classes, complement components, mast cells and basophils, lymphocytes, macrophages, and various pharmacologic mediators and other soluble substances in an exuberant array of possible combinations. An understanding of clinical hypersensitivity diseases is aided by classifying basic allergic mechanisms into four main types: anaphylactic (Type I), cytotoxic (Type II), complex-mediated (Type III), and cell-mediated (Type IV), which may participate in various combinations in disease states.

Allergens↗
PubMed1982

Immune complexes: characteristics, clinical correlations, and interpretive approaches in the clinical laboratory.

Immune-complex-mediated injury is thought to play a role in diseases such as rheumatoid arthritis, systemic lupus erythematosus, serum sickness, various infectious diseases, and malignancies. With increased appreciation of the biological and pathological significance of circulating immune complexes has come efforts to develop appropriate techniques for identifying and measuring them. Common approaches exploit such phenomena as the attachment of complement components to antigen-antibody complexes, the presence of specialized receptors for immune complexes at the surface of cells, and the ability of rheumatoid factor to bind with immune complexes. This variety of assay systems for immune complexes has yielded abstruse results in numerous human pathological conditions. Unfortunately, these results seldom correlate with one another in a given disease. Thus, use of a panel of immune complex assays has been recommended. Indirect consequences of immune complex disease may still be appraised and evaluated with some confidence in clinical medicine: measurements of C3 and C4, cryoglobulins, serum viscosity, and turbidity of serum samples. Measurement of immune complexes may be useful in diagnosis, prognosis, and therapeutic monitoring, but it is the characterization of immune complexes that holds the greatest potential for better understanding of disease mechanisms.

Antigen-Antibody Complex↗
PubMed1989

The biogenesis of the cyanellae of Cyanophora paradoxa. I. Polypeptide composition of the cyanellae.

Based on polypeptide separation, protein purification and immunoblotting techniques using heterologous antibodies, we have been able to identify several photosynthetically important polypeptide components of the cyanellae of Cyanophora paradoxa. Cytochrome c-552 and ferredoxin have been purified to electrophoretic homogeneity and exhibit apparent molecular masses of 10.5 and 9.0 kDa, respectively. Cytochrome c-552 has an isoelectric point of pH 4.2 +/- 0.1. Plastocyanin was immunologically and spectrally undetectable even in cells grown in the presence of Cu2+. Polypeptides for cytochromes f, b-6 and c-552 have been located in electrophoretically resolved thylakoid samples by using the TMBZ-staining procedure. Intact phycobilisomes have been purified and characterized with respect to polypeptide composition and absorption and emission spectra. Photosystems I and II have been isolated and characterized with respect to their photochemical activities, spectral characteristics and polypeptide composition. Photochemically active PS I complexes fluoresce maximally at 720 nm at 77 K and comprise five polypeptide subunits resolved under denaturing conditions with apparent molecular masses of 66, 21, 18, 14 and 11 kDa. PS II core complexes mediate light-dependent 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU)-sensitive electron transfer between 1,5-diphenylcarbazide (DPC) and 2,6-dichlorophenolindophenol (DPIP) at rates of 140-200 mumol h-1 mg-1 chlorophyll. These complexes exhibit absorption maxima at 436 and 673 nm and show fluorescence emission maxima at 685 and 695 nm at 77 K. Rubisco was separated by two-dimensional electrophoresis and immunologically characterized.

Cell Fractionation↗
PubMed1977

Nephritis associated with a diphtheroid-infected cerebrospinal fluid shunt.

Hypocomplementemic proliferative glomerulonephritis occurred during diphtheroid infection of a ventricular decompression shunt for cerebrospinal fluid diversion (cerebrospinal fluid shunt) in a young man. Granular deposits of immunoglobulin M (IgM) and the third component of complement (C3) were found along the glomerular basement membrane. This report provides supportive evidence for immune complex-mediated glomerular injury due to diphtheroid infection in a cerebrospinal fluid shunt.

Adult↗
PubMed1987

Composition of immune complexes and their relation to plasma fibronectin in chronic myeloproliferative disorders.

High concentrations of circulating immune complexes were detected by polyethylene glycol precipitation in 11 of 20 patients with myelofibrosis secondary to chronic myeloproliferative disease. Circulating immune complexes showed a positive correlation with plasma IgG concentrations both in patients and controls. Covariance analysis of the two groups showed significantly increased polyethylene glycol precipitable IgG in patients when adjusted for plasma IgG concentrations, indicating that the patients had significantly increased concentrations of complexed IgG. The immune complexes contained IgG, C3, and fibronectin and were inversely correlated with plasma fibronectin concentrations, suggesting that this major non-specific opsonin is important for the normal clearance of immune complexes. Therapeutic plasmapheresis efficiently removed circulating complexes and produced an increase in plasma fibronectin. This suggests that plasmapheresis may be useful for controlling immune complex mediated complications of these disorders.

Aged↗
PubMed2007

The C. elegans RSA complex localizes protein phosphatase 2A to centrosomes and regulates mitotic spindle assembly.

Microtubule behavior changes during the cell cycle and during spindle assembly. However, it remains unclear how these changes are regulated and coordinated. We describe a complex that targets the Protein Phosphatase 2A holoenzyme (PP2A) to centrosomes in C. elegans embryos. This complex includes Regulator of Spindle Assembly 1 (RSA-1), a targeting subunit for PP2A, and RSA-2, a protein that binds and recruits RSA-1 to centrosomes. In contrast to the multiple functions of the PP2A catalytic subunit, RSA-1 and RSA-2 are specifically required for microtubule outgrowth from centrosomes and for spindle assembly. The centrosomally localized RSA-PP2A complex mediates these functions in part by regulating two critical mitotic effectors: the microtubule destabilizer KLP-7 and the C. elegans regulator of spindle assembly TPXL-1. By regulating a subset of PP2A functions at the centrosome, the RSA complex could therefore provide a means of coordinating microtubule outgrowth from centrosomes and kinetochore microtubule stability during mitotic spindle assembly.

Animals↗
PubMed1994

p53-dependent G1 arrest involves pRB-related proteins and is disrupted by the human papillomavirus 16 E7 oncoprotein.

The cell cycle regulatory tumor suppressor proteins p53 and pRB are targeted for inactivation by several tumor viruses, including the high-risk types of human papillomaviruses (HPVs) via interactions of the HPV E6 and E7 oncoproteins with p53 and pRB, respectively. p53 plays a central role in a signal transduction pathway that mediates G1 arrest after DNA damage, though the mechanism by which G1 arrest occurs has not been elucidated. The cyclin-associated protein p21waf1/cip1 has recently been shown to be induced by p53 and to inhibit cyclin complex-mediated phosphorylation of pRB in vitro. Thus, we investigated a possible role for pRB in the p53-mediated DNA damage response. After gamma-irradiation, cells expressing wild-type p53 arrested in G1, contained increased levels of WAF1/CIP1 mRNA, and demonstrated accumulation of hypophosphorylated pRB. In contrast, cell lines with abnormal p53 genes or with p53 functionally inactivated by the E6 oncoprotein of HPV16 (a high-risk HPV) failed to arrest in G1, did not elevate WAF1/CIP1 mRNA, and did not accumulate hypophosphorylated pRB. Despite apparently normal elevation of p53 protein and WAF1/CIP1 mRNA after irradiation, cells expressing HPV16 E7 also failed to arrest in G1 and did not accumulate hypophosphorylated pRB. Disruption of RB genes alone did not totally abrogate this G1 arrest. Our results suggest that p53 indirectly regulates phosphorylation of pRB and that pRB and/or other pRB-like molecules that bind to HPV16 E7 participate in the DNA damage-mediated G1 arrest signal. In the process of HPV infection, the HPV E6 and E7 oncoproteins may undermine this cell cycle checkpoint, contributing to the accumulation of genetic alterations during tumorigenesis.

Cell Cycle↗
PubMed1999

Interaction of the U1 snRNP with nonconserved intronic sequences affects 5' splice site selection.

Intron definition and splice site selection occur at an early stage during assembly of the spliceosome, the complex mediating pre-mRNA splicing. Association of U1 snRNP with the pre-mRNA is required for these early steps. We report here that the yeast U1 snRNP-specific protein Nam8p is a component of the commitment complexes, the first stable complexes assembled on pre-mRNA. In vitro and in vivo, Nam8p becomes indispensable for efficient 5' splice site recognition when this process is impaired as a result of the presence of noncanonical 5' splice sites or the absence of a cap structure. Nam8p stabilizes commitment complexes in the latter conditions. Consistent with this, Nam8p interacts with the pre-mRNA downstream of the 5' splice site, in a region of nonconserved sequence. Substitutions in this region affect splicing efficiency and alternative splice site choice in a Nam8p-dependent manner. Therefore, Nam8p is involved in a novel mechanism by which a snRNP component can affect splice site choice and regulate intron removal through its interaction with a nonconserved sequence. This supports a model where early 5' splice recognition results from a network of interactions established by the splicing machinery with various regions of the pre-mRNA.

5' Untranslated Regions↗
PubMed1985

Report of a case with fulminant hepatitis A associated with acute renal failure.

A 34-year-old male presented with fulminant hepatitis A associated with acute renal failure. The patient was admitted four days after flu-like symptoms developed. Physical examination was unremarkable except for icteric sclerae. Laboratory studies showed SGOT 10719 U/l, SGPT 5780 U/l, prothrombin time 22%, BUN 25.5 mg/dl, and creatinine 2 mg/dl. Serum complements were within normal ranges, and circulating immune complexes were not detected. Anti-HAV IgM was positive. He developed hepatic coma on the fourth hospital day, and his renal function deteriorated progressively. He was treated with hemodialysis, but there was no improvement in consciousness. Although acute liver failure improved, he died on the 74th hospital day of subendocardial infarction. Autopsy examination showed acute renal tubular necrosis. The liver was enlarged and was in the residual stage of acute hepatitis without submassive necrosis. The development of fulminant hepatitis in hepatitis A has been rare, but in recent years acute renal failure in hepatitis A has been reported. Although the mechanisms responsible for renal failure in liver diseases are uncertain but could be multifactorial, immune complex-mediated nephritis and/or endotoxemia have been considered.

Acute Kidney Injury↗
PubMed1984

Correlation of histopathologic evidence of disease activity with the presence of immunoglobulin-containing cells in the colons of patients with inflammatory bowel disease.

Immunofluorescence of formalin-fixed, paraffin-embedded tissues was performed to study the plasma cell population in 114 colonic specimens from 58 patients. Correlation of the histopathologic stage of disease activity with the isotypes and numbers of immunoglobulin-containing cells in the lamina propria demonstrated highly significant (P less than 0.001) increases in the mean numbers of IgG- (18-fold), IgA- (twofold) and IgM- (sixfold) containing cells in specimens from patients with active inflammatory bowel disease as compared with control specimens. Increased numbers of immunoglobulin-containing cells were uncommon in inactive inflammatory bowel disease and in reactive mucosa. No deposition of immunoglobulin-containing immune complexes was found at any stage of disease activity. These findings suggest that immune complex-mediated damage does not play a major role in the epithelial damage in inflammatory bowel disease. In future studies, it will be of importance to determine whether the antibody from immunoglobulin-containing cells seen in patients with inflammatory bowel disease can effect damage via an antibody-dependent cell-mediated cytotoxicity mechanism.

Antigen-Antibody Complex↗