Biomedical subjects
P H Plotz
Publications and source records attributed to P H Plotz.
An efficient method for enrichment of histidyl-tRNA synthetase (Jo-1 antigen) from HeLa cells.
A rapid method has been developed for enrichment of Jo-1 antigen (histidyl-tRNA synthetase) from HeLa cells. The enzyme has been prepared from post-ribosomal supernatant by successive chromatography with Blue Sepharose and Poly-U-Sepharose, followed by DEAE-high performance liquid chromatography (HPLC). By this method, enzyme could be obtained within 4 days of HeLa cell harvesting, with 40% recovery of the enzymatic activity. The apparent native molecular size of the enzyme as determined by HPLC-size exclusion column chromatography was approximately 120 kDa. Under denaturing conditions using SDS-polyacrylamide gel electrophoresis the enzyme subunit size was approximately 55 kDa. The antigen preparation, although not homogeneous, was found to react only with anti-Jo-1 positive antisera when tested by immunoblotting with many patient sera of defined autoantibody specificities, making the preparation useful for immunologic studies of anti-Jo-1 antibodies.
An enzyme-linked immunosorbent assay for the detection and quantitation of anti-Jo-1 antibody in human serum.
We have developed an enzyme-linked immunosorbent assay (ELISA) specific for autoantibodies directed against the autoantigen Jo-1 (histidyl-tRNA synthetase) using antigen prepared biochemically from HeLa cells. No other patient sera, including those containing antibodies directed at threonyl-tRNA synthetase or alanyl-tRNA synthetase, reacted in the assay. Screening of sera from 169 patients with a variety of autoimmune and neuromuscular diseases confirmed that anti-Jo-1 antibodies are confined to a subgroup of patients with pure polymyositis, pure dermatomyositis, or myositis associated with another rheumatic disease.
Viral and host genetic factors influence encephalomyocarditis virus-induced polymyositis in adult mice.
Recent research findings implicate picornaviruses in the etiology of human polymyositis/dermatomyositis and suggest that genetic factors play a role in susceptibility to these diseases. We compared 2 variants of encephalomyocarditis (EMC) virus for their ability to induce polymyositis in adult mice, and evaluated what role the genetic background of the host plays in the degree of myositis induced. While BALB/c mice developed minimal myositis when infected with a diabetogenic variant (EMC-D), the same strain inoculated with a newly isolated myopathic variant (EMC-221A) developed viral dose-dependent elevations in muscle-associated enzymes, bilateral limb muscle weakness, and the histopathologic changes of severe polymyositis. Mice with different genetic backgrounds showed significantly different susceptibilities to EMC-221A. These data suggest that the severity of polymyositis induced by EMC virus is influenced by both the viral and host genomes.
Soluble immune complexes in lupus mice: clearance from blood and estimation of formation rates.
Elevated levels of circulating immune complexes (IC) occur in patients with systemic lupus erythematosus (SLE) and in several strains of mice that spontaneously develop a lupus-like illness. An increase in circulating IC might occur as a result of increased IC formation or decreased IC clearance. Previous work with one murine lupus strain, NZB/W, demonstrated normal clearance of soluble IC. We studied the in vivo behavior of stable model IgG IC in two murine lupus strains. MRL/l and BXSB, and in two normal strains, C3H/HeN and BALB/c. IC were injected intravenously, and blood radioactivity was measured over 3 hr. A clearance curve was derived for each mouse using the Marquardt-Levenberg curve-fitting method. A formula is derived which predicts the formation rate of IC in each animal from the blood level of IC and the clearance curve parameters. All mice exhibited biphasic exponential clearance of IC over 3 hr. Clearance of IC was significantly slower in MRL/l mice than in normal strains (P less than 0.02), and clearance in BXSB mice was significantly faster than in normals (P less than 0.02). However, the derived formula suggests that the observed differences in IC clearance have only a small effect on the blood levels of IC in the mice studied, and therefore suggests that the major factor which accounts for increased blood levels of IC in lupus mice is an increase in the IC formation rate.
Studies of immunosuppressive drugs in the treatment of lupus nephritis.
Long-term, controlled trials to evaluate the efficacy and toxicities of immunosuppressive drug therapies compared to treatment with corticosteroids alone in the management of patients with lupus nephritis have been performed. The studies demonstrate that immunosuppressive drug regimens, particularly intravenous cyclophosphamide, reduce the likelihood of end-stage renal failure. However, toxicities such as herpes zoster and ovarian failure were found to be increased in patients with cyclophosphamide.
Therapy of lupus nephritis. Controlled trial of prednisone and cytotoxic drugs.
We evaluated renal function in 107 patients with active lupus nephritis who participated in long-term randomized therapeutic trials (median follow-up, seven years). For patients taking oral prednisone alone, the probability of renal failure began to increase substantially after five years of observation. Renal function was better preserved in patients who received various cytotoxic-drug therapies, but the difference was statistically significant only for intravenous cyclophosphamide plus low-dose prednisone as compared with high-dose prednisone alone (P = 0.027). The advantage of treatment with intravenous cyclophosphamide over oral prednisone alone was particularly apparent in the high-risk subgroup of patients who had chronic histologic changes on renal biopsy at study entry. Patients treated with intravenous cyclophosphamide have not experienced hemorrhagic cystitis, cancer, or a disproportionate number of major infections. We conclude that, as compared with high-dose oral prednisone alone, treatment of lupus glomerulonephritis with intravenous cyclophosphamide reduces the risk of end-stage renal failure with few serious complications.
Bacterial cell wall composition, lysozyme resistance, and the induction of chronic arthritis in rats.
Bacterial cell wall induced arthritis is an experimental model of chronic erosive synovitis in which arthritis is induced in rats by a single injection of an aqueous suspension of cell wall fragments from selected Gram-positive bacteria. To understand better the Gram-positive bacterial cell wall characteristics necessary for the induction of chronic arthritis we tested the arthritogenicity of five Gram-positive bacteria which were (1) lysozyme resistant and contained a polyrhamnose peptidoglycan side chain moiety, (2) lysozyme resistant, but had little or no rhamnose in the peptidoglycan, polysaccharide, or (3) neither lysozyme resistant, nor contained rhamnose in their peptidoglycan, polysaccharide. All of the lysozyme resistant cell walls tested induced acute arthritis, but only those cell walls which were both lysozyme resistant and contained rhamnose in their polysaccharide side chain were able to induce chronic arthritis. Cell walls which were neither lysozyme resistant nor contained rhamnose were not arthritogenic. These data suggest that both lysozyme resistance and the rhamnose moiety in the peptidoglycan, polysaccharide side chain play an important role in the induction of chronic arthritis by Gram-positive bacterial cell walls in aqueous suspension.
Failure of methotrexate and methylprednisolone to alter the clearance of model immune complexes.
We evaluated the effect of methotrexate (MTX) and methylprednisolone (MP) on reticuloendothelial system (RES) clearance of soluble model immune complexes (IC) in BALB/C mice. MTX was administered by intraperitoneal route either as a single dose (0.5 mg/kg) or as 10 alternate day doses (0.1 or 0.5 mg/kg), MP as a single intravenous (IV) bolus (50 mg/kg) with normal saline used as a control. Mice were then injected IV with radiolabelled IgG anti-DNP covalently crosslinked IC. Blood radioactivity was measured over a 3 h period at which time organ uptake, corrected for blood contamination, was determined. Clearance curves for each mouse were derived using the Marquardt-Levenberg curve fitting method. No significant differences in IC clearance or organ uptake were found between drug and control groups at any drug dose or time period. Our findings argue against an influence of MP and MTX on immunospecific clearance of soluble IC.
Effect of treatment on the evolution of renal abnormalities in lupus nephritis.
We retrospectively studied the evolution of histopathologic features in successive renal biopsies in patients with lupus nephritis, to evaluate the effects of various treatment regimens. Repeat renal biopsies had been performed in 62 patients after more than 18 months of observation (median interval, 44 months) in randomized therapeutic trials comparing prednisone with cytotoxic drugs. Renal histopathologic features were graded individually, and a composite score reflecting the number and severity of irreversible lesions was defined as a chronicity index. The chronicity index for patients treated with conventional high-dose prednisone increased linearly with the interval between biopsies, whereas the index in the group receiving cytotoxic-drug treatments did not increase over time. After statistical adjustment for important prognostic factors (age and initial chronicity index) identified by multiple linear regression, the difference in the slopes between the group receiving prednisone and the group receiving cytotoxic drugs was significant (P less than 0.0001). We conclude that cytotoxic-drug treatment reduces the likelihood of progressive renal scarring in lupus nephritis.
Lactobacillus casei cell wall-induced arthritis in rats: cell wall fragment distribution and persistence in chronic arthritis-susceptible LEW/N and -resistant F344/N rats.
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Severe, acute pulmonary disease in patients with systemic lupus erythematosus: ten years of experience at the National Institutes of Health.
The sudden development of diffuse pulmonary infiltration in a patient with SLE presents difficult diagnostic and therapeutic problems to the clinician. In the past ten years, we have seen eight patients with this problem. Neither roentgenograms nor clinical findings were specific. In six patients, pulmonary hemorrhage was found, but in only two of them did it exist alone. In the other four, heart failure, uremia, and coagulopathy complicated the findings. In one patient, P carinii was the cause; in one congestive heart failure, which was not obvious clinically or radiologically, was the cause. Three patients died: one of uncomplicated pulmonary hemorrhage, one with pulmonary hemorrhage occurring during the treatment of pneumonia due to L bozemanii, and one with pulmonary hemorrhage and multiple complications including sepsis due to Candida. On the basis of this experience, we have recommended a plan of action for physicians facing this problem.
NIH conference. Systemic lupus erythematosus: insights from animal models.
Systemic lupus erythematosus is a multisystem, antibody-mediated, autoimmune disorder that occurs spontaneously in humans and mice. Genetic factors appear to play an important predisposing role in the disorder: The presence of certain genes may produce a generalized immune abnormality, whereas others may lead to specific autoantibodies. Environmental triggers increase autoantibody production and augment the expression of illness. Bacterial and viral illnesses can provide stimulation by activating macrophages and T cells that, in turn, stimulate B cells. In the absence of normal control mechanisms, the stimulatory process is not suppressed, and excessive stem cell proliferation results in abnormal B-cell proliferation. A trigger for the disease is the signaling of the proliferating B cells to differentiate into antibody-forming cells. Most autoantibody-producing B cells can be eliminated from mice with lupus erythematosus by virtue of the presence of the gene, xid. In addition, administration of an analog of arachidonic acid is an effective treatment for murine lupus erythematosus.
Monocyte receptors for the Fc portion of IgG are increased in systemic lupus erythematosus.
Defective clearance of IgG-sensitized particles has been documented in systemic lupus erythematosus (SLE). This defect may be of pathogenetic significance because it allows the prolonged circulation of endogenous immune complexes with subsequent tissue deposition. To assess the possible contribution of a genetically determined defect in phagocyte Fc-IgG receptor expression or immune complex saturation of Fc-IgG receptors to impaired clearance, we used a well-characterized monomer binding assay to quantitate monocyte Fc-IgG receptors in normal controls and in 26 patients with SLE. Mean monocyte Fc-IgG receptor numbers were increased in both male and female SLE patients relative to normal controls. Increasing receptor numbers correlated positively with increasing clinical disease activity and increasing titers of antibody to native, double-stranded DNA. No significant correlation was found between any single disease symptom, organ system involvement, drug therapy, antigenic C3 levels, or immune complex levels and receptor number. A negative correlation was noted between Fc-IgG receptor binding affinity constants in SLE patients and clinical disease activity, but none of the observed affinity constants fell outside the 95% confidence normal range, and the mean affinity constants for patients both with and without active disease were not significantly different from controls. Our results are inconsistent with a genetically determined defect in Fc-IgG receptor elaboration by mononuclear phagocytes, and suggest that simple immune complex saturation does not underlie abnormal Fc-IgG-mediated clearance in SLE.
Autoantibodies are anti-idiotype antibodies to antiviral antibodies.
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Analgesic nephropathy. For this time and for this place.
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Low-dose D-penicillamine therapy in rheumatoid arthritis. A controlled, double-blind clinical trial.
Two hundred twenty-five patients with active severe rheumatoid arthritis were admitted to a multiclinic, controlled, double-blind trial comparing the use of 500 mg D-penicillamine per day, 125 mg D-penicillamine per day, and placebo. One hundred seventy-one patients completed at least 30 weeks of therapy. The 500 mg D-penicillamine group demonstrated statistically significant improvement over the placebo group in grip strength, average circumference of swollen proximal interphalangeal joints, and patient assessment. While the trend was for greater improvement with the larger dose of D-penicillamine, there was no statistically significant difference among the 3 groups in duration of morning stiffness, walking time, physician's assessment, number of swollen joints, or scores for tender and swollen joints. The slight increase in efficacy of higher dose D-penicillamine was associated with increased toxicity.
Polyarthritis in rats following the systemic injection of Lactobacillus casei cell walls in aqueous suspension.
Postdysenteric Reiter's syndrome and the arthritis associated with jejunal bypass surgery for obesity suggest that the gastrointestinal tract is a possible source of bacterial products capable of initiating chronic inflammatory arthritis. Lactobacillus casei, a common component of the enteric flora, has a cell wall structure similar to that of arthritogenic streptococci. In this study we have demonstrated that a single intraperitoneal injection of an aqueous suspension of the cell walls of Lactobacillus casei induces a dose-dependent, chronic, symmetric, erosive, peripheral polyarthritis in inbred LEW/N female rats. This model suggests that bacteria in the "normal enteric flora" may be a source of inflammatory products capable of inducing chronic erosive polyarthritis.