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Biomedical subjects

P A Thiem

Publications and source records attributed to P A Thiem.

14 recordsLinked to original sources
PubMed1991

Recombinant human soluble CD4 does not inhibit immune function in cynomolgus monkeys.

Recombinant soluble CD4 (sT4) has been shown to inhibit infectivity of HIV. Because of the role CD4 plays in the interaction of T-helper lymphocytes and cells bearing MHC Class II antigens, a potential adverse effect of therapy with sT4 is interference with lymphocyte function. To address this issue, we studied the effects of sT4 on mitogen-mediated blastogenesis, mixed lymphocyte reactions, and delayed type hypersensitivity reactions (DTH) in cynomolgus monkeys. We found no evidence of sT4-mediated suppression on the in vitro response to concanavalin A, phytohemagglutinin or pokeweed mitogen in 2-way mixed lymphocyte reactions, either when sT4 was added to the cultures or when cells were obtained 3 hr after drug administration from animals that received up to 100 mg/kg as an intravenous bolus. Furthermore, we also found no effect of sT4 on lymphocyte subsets or on the ability of monkeys to respond to dinitrochlorobenzene (DNCB)-mediated DTH. Because of the high degree of conservation of CD4 and MHC Class II antigens across the macaque-human barrier, these data suggest that soluble CD4-like molecules are unlikely to be immunosuppressive in humans.

Animals↗
PubMed1990

Effects of sensitization to dinitrochlorobenzene (DNCB) on clinical pathology parameters and mitogen-mediated blastogenesis in cynomolgus monkeys (Macaca fascicularis).

Immunotoxicologic testing of drug candidates and environmental contaminants is of growing importance. Cutaneous delayed type hypersensitivity (DTH) is a convenient way of testing immune function in vivo. However, DTH testing must not interfere with interpretation of other relevant parameters. We have evaluated the effects of sensitization and challenge with dinitrochlorobenzene (DNCB) on clinical parameters routinely evaluated in toxicity testing and on lectin-mediated blastogenesis. Female cynomolgus monkeys were sensitized to DNCB with 4 daily applications of DNCB in acetone to the skin of the axilla. Fifteen days later, the monkeys were challenged for DTH by applying DNCB to the antecubital skin. Skin fold thickness was measured and the macroscopic appearance of the challenge site was scored 24 and 48 hr after challenge. All 5 monkeys were successfully sensitized to DNCB. There was a significant increase in the mean skin fold thickness (compared to pre-challenge thickness) of 2 mm at 24 hr and 1 mm at 48 hr (p less than 0.001). The clinical score of the challenge site was also increased. Histologic examination of the sensitization and challenge sites from a second group of monkeys exposed to DNCB in an identical manner showed the perivascular inflammatory cell infiltrate typical of DTH. Evaluation of hematologic parameters at days 7, 14, and 21 revealed no change in the erythron at any interval and a mild decrease in total WBC, neutrophil and lymphocyte counts on day 7 in 4/5 monkeys. The WBC parameters remained within the normal range and returned to pre-sensitization values at the later intervals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Use of danazol for treatment of corticosteroid-resistant immune-mediated thrombocytopenia in a dog.

A routine health screen of a 7 1/2-year-old female Beagle participating as a control in a long-term study revealed thrombocytopenia. Immune thrombocytopenia was diagnosed on the basis of regenerative bone marrow findings (high number of megakaryocytes) and evidence of antiplatelet antibodies. Treatment with prednisone at dosages up to 1 mg/kg of body weight every 12 hours resulted in limited improvement, with relapses of severe thrombocytopenia thwarting attempts to taper the corticosteroid, and was further complicated by side effects of the drug. Addition of danazol to the treatment regimen (5 mg/kg, q 12 h) resulted in remission of the thrombocytopenia within 2 weeks and permitted the dosage of prednisone to gradually be reduced and discontinued. Associated with this response was a decrease in platelet-associated IgG to values comparable with control samples.

Animals↗
PubMed1988

Cephalosporin-induced immune cytopenia in the dog: demonstration of erythrocyte-, neutrophil-, and platelet-associated IgG following treatment with cefazedone.

Cephalosporin treatment in man has been associated with a low incidence of hemolytic anemia, thrombocytopenia, and neutropenia; some cases have been shown to be immune-mediated. This triad of blood dyscrasias was also demonstrated in our laboratory in a series of toxicity studies in dogs of two cephalosporin compounds, cefonicid and cefazedone; these studies provided evidence for drug-associated immune hemolytic anemia, based on conventional laboratory tests. To further investigate possible immune mechanisms of the cephalosporin-induced cytopenias, we measured erythrocyte-associated, platelet-associated (PAIgG), and serum antineutrophil IgG over the course of cephalosporin treatment, using highly sensitive 125I-staphylococcal protein A (SPA) assays, as well as the direct antiglobulin test; we compared these findings with the hematologic changes. Intravenous treatment with high doses of cefazedone (540 mg/kg/day, increased to a maximum of 840 mg/kg/day for 4 months or until hematologic effects were evident) resulted in a high incidence of anemia (7/14), thrombocytopenia (11/14), and neutropenia (7/14). Of the affected dogs examined, 6/7 with anemia, 9/9 with thrombocytopenia, and 7/7 with neutropenia showed increased levels of the respective cell-associated antibody, compared with untreated controls. Unaffected dosed animals generally did not show these changes. In 3/3 dogs examined following remission of thrombocytopenia, PAIgG returned to levels comparable with controls; as one of these dogs suffered a relapse, increased PAIgG was again observed. Animals sacrificed during cytopenic episodes showed cytologic and histologic evidence of increased hemophagocytosis. We conclude that antibody-mediated blood cell destruction contributes to all three cephalosporin-induced cytopenias in the dog.

Anemia, Hemolytic↗
PubMed1988

Techniques for assessing canine mononuclear phagocyte function as part of an immunotoxicologic evaluation.

Although the dog is used extensively as a model for toxicologic investigation, few practical techniques for assessing immunotoxicity in this species have been reported. We have adapted techniques for assessing peripheral blood monocyte (PBM) function in the dog. Methods for isolating PBM were compared; a technique employing hypertonic conditioning followed by density gradient centrifugation, which resulted in greater than 90% purity and a greater yield of PBM than that obtained with other previously reported methods is described, along with methods for measuring antibody-dependent cellular cytotoxicity (ADCC) and the production of prostaglandin E2 (PGE2) and superoxide anion (O2-). An assay for the measurement of interleukin-1 (IL-1), based on its ability to induce interleukin-2 (IL-2) production by the EL-4 mouse thymoma line in the presence of the calcium ionophore A23187, was examined. Together, these assays provide the tools to better define drug or chemical effects on the mononuclear phagocyte system (MPS) of this important animal model.

Animals↗
PubMed1988

The effect of longterm treatment with auranofin and gold sodium thiomalate on immune function in the dog.

Although gold compounds are recognized as effective immunomodulatory agents in the treatment of rheumatoid arthritis (RA), their mechanism of action is controversial. We examined the effect of longterm treatment with 0.6-3.6 mg/kg auranofin (AF) per os q24h, or intramuscular injections of 0.5-2.0 mg/kg gold sodium thiomalate (GSTM) q3d, on 13 variables of immune function in normal dogs. None of the changes in these variables previously attributed to treatment with AF or GSTM could be demonstrated after 6-7 years' dosing. As gold compounds are effective in treating spontaneous RA in dogs, these proposed actions may not be responsible for the remittive effects of chrysotherapy in this disease.

Animals↗
PubMed1987

The role of conventional pathology and toxicology in evaluating the immunotoxic potential of xenobiotics.

Investigating the immunotoxic potential of candidate drugs as part of a preclinical safety evaluation poses several problems. These include the need for practical, validated tests, the difficulty in establishing the toxicologic significance of positive findings, and a poor understanding of the predictive value such findings hold for drug effects in man. A key component of this investigation is the toxicologic profile generated through preclinical toxicity and safety studies. As this "routine" assessment becomes increasingly comprehensive and sophisticated, most toxicologically significant drug-associated effects are revealed. Such findings may serve as "triggers" for investigating possible immune mechanisms. Decisions to test specifically for immunotoxicity may also be influenced by the molecular structure and pharmacologic profile of the compound, as well as the intended use of the drug. Examples of such indications and follow-up studies are discussed in this review. We are presently poorly equipped to effectively screen drugs indiscriminately for an immunotoxic potential. We are better prepared, however, to investigate whether a drug-associated change is due to an adverse effect on the immune system. This problem-oriented approach to immunotoxicology challenges us as diagnosticians and immunopathologists, and requires a close working relationship among the toxicologic pathologist, the basic immunologist, the immunopharmacologist, and the clinician.

Animals↗
PubMed1983

Beta-adrenergic receptors of human leukocytes. Studies with intact mononuclear and polymorphonuclear cells and membranes comparing two radioligands in the presence and absence of chloroquine.

Owing to the large differences in reported values for beta-adrenergic receptor numbers and binding affinity in normal leukocytes, we undertook a systematic re-examination of the binding of two widely used beta antagonists, (-)-[3H]dihydroalprenolol (DHA) and (+/-)-[125I]iodohydroxybenzylpindolol (HYP), to intact normal mononuclear (MN) leukocytes and polymorphonuclear (PMN) leukocytes and membrane preparations. Assays were conducted in the presence and absence of chloroquine, which has been proposed recently to eliminate ligand uptake into a non-receptor cell compartment such as lysosomes. The binding curves relating radioligand concentration to specific sitesper intact cell were biphasic. At high (10-24 nM) (-)-DHA ligand concentration in the absence of chloroquine, a large number (20,000-60,000 sites/cell) of low affinity (Kd 12-15 nM) stereospecific binding sites were detected in both cell types. This class of binding sites was eliminated by 10 microM chloroquine not only in PMN cells but also in the lysome-poor MN cells (greater than or equal to 90% lymphocytes), leaving 2000-3000 specific high affinity (-)-DHA sites/cell. In the absence of chloroquine, comparably low numbers of specific high affinity binding sites/cell were also obtained by the use of appropriately low concentrations of (-)-DHA or (+/-)-HYP (800 pM or less). However, even at these low radioligand concentrations chosen to measure high affinity specific binding, the addition of 10 microM chloroquine produced a moderate reduction in the number of sites/cell, without a detectable change in the apparent Kd. Mean (+/- S.E.M.) site numbers obtained in the presence of chloroquine were: 1331 +/- 100 sites/MN cell and 1135 +/- 129 sites/PMN cell (Kd 143-153 pM) using (-)-DHA; and 1487 +/- 210 sites/MN cell and 1065 +/- 69 sites/PMN cell [avg. Kd(+/-) 224-274 pM] using (+/-)-HYP. Chloroquine had no effect on agonist-stimulated cAMP production but produced an apparent increase in the effectiveness of (-)-propranolol as an inhibitor of DHA binding. Competition studies on the binding of DHA and HYP with zinterol and practolol confirmed that the receptor was of the beta 2-subtype for both MN and PMN cells. The detection of a moderately larger number of high affinity binding sites at saturation (Scatchard analysis) by (+/-)-HYP than by (-)-DHA was a consistent finding with either intact cells or membranes, with or without chloroquine. The possible overestimation of receptor numbers by a racemic ligand such as (+/-)-HYP is discussed and leads us to favor the use of a pure stereoisomer such as (-)-DHA. A system employing 800 pM (-)-[3H]DHA, 1 microM (-)-propranolol and 10 microM chloroquine with intact MN and PMN cells yielded reproducible and plausible results. Our values for beta-adrenergic receptor numbers of intact MN and PMN cells and membranes are compared to others in the literature.

Adult↗
PubMed1983

Non-centrifugal plasma collection using cross-flow membrane plasmapheresis.

A prototype of a cross-flow membrane plasmapheresis system was tested for its safety and efficacy in normal donors. 550 ml of plasma can be harvested in less than 1 h. The procedure appears to be safe for the donor. No significant alterations in donor hematological, coagulation, or biochemical values were obtained after the procedure compared to the predonation levels. Changes in the classical and alternate complement pathways were studied serially by analysis of functional hemolytic titers, C3 and C4 levels, and C3 and factor B cleavage products. No firm evidence of complement activation by the polysulfone filtration cell membrane was found.

Adult↗
PubMed1979

Complement lysis of human erythrocytes. Differeing susceptibility of two types of paroxysmal nocturnal hemoglobinuria cells to C5b-9.

Although enhanced sensitivity of erythrocytes to complement-mediated lysis is a hallmark of paroxysmal nocturnal hemoglobinuria (PNH), subpopulations of erythrocytes in such patients vary significantly in this respect. One PNH erythrocyte subpopulation (termed type III) comprises exquisitely sensitive cells, whereas type II PNH erythrocytes are intermediate in complement sensitivity between PNH type III and normal human erythrocytes. Differences in the action of the terminal complement components that would account for the differing lytic behavior of types II and III PNH erythrocytes have been proposed but not directly demonstrated. The present studies, making use of carefully selected cases with pure populations of type II or type III erythrocytes, confirm a prior observation that antibody-coated PNH erythrocytes of both types II and III display comparably supranormal C3 binding in whole human serum. However, when lysis was induced by the isolated C5b-9 membrane attack mechanism, bypassing the requirement for C3 binding, only type III PNH cells exhibited greater than normal lysis. This finding suggests that type III PNH erythrocytes have an additional membrane abnormality not present in type II cells. Thus, the differing lytic behavior of these two cell types in whole serum may reflect the additive effects on type III cells of both exaggerated C3 binding and enhanced sensitivity to C5b-9, whereas the more moderate lysis of type II PNH cells may be determined mainly or entirely by the earlier-acting mechanism producing augmented C3 binding. The failure of guinea pig C8 and C9, as opposed to human C8 and C9, to reveal the true lytic sensitivity of PNH-III E in our earlier study is illustrated, and its implications briefly discussed.

Animals↗
PubMed1975

Studies with human leukocyte lysosomes. Evidence for antilysosome antibodies in lupus erythematosus and for the presence of lysosomal antigen in inflammatory diseases.

Human lysosomes were isolated from normal peripheral blood leukoyctes and characterized by electron microscopy, enzyme analysis, and assays for DNA and RNA. Stored sera from 37 unselected patients with systemic lupus erythematosus (SLE), including active and inactive, treated and untreated cases, were tested in complement fixation (CF) reactions with these lysosome preparations. 23 SLE sera exhibited positive CR reactions, as did sera from two patients with "lupoid" hepatitis. The seven SLE sera with strongest CF reactivity also demonstrated gel precipitin reactions with lysosomes. Neither CF nor precipitin reactions with lysosomes were observed with normal sera or with sera of patients with drug-induced lupus syndrome, rheumatoid arthritis (RA), polymyositis, or autoimmune hemolytic anemia. By several criteria the antilysosome CF and precipitin reactions of SLE sera cound not be attributed to antibody to DNA, RNA, or other intracellular organelles. The lysosomal component reactive with SLE sera in CF assays was sedimentable at high speed and is presumably membrane associated. The CF activity of two representative SLE sera was associated with IgG globulins by Sephadex filtration. A search for lysosomal antigen in SLE and related disorders was also made. By employing rabbit antiserum to human lysosomes in immunodiffusion, a soluble lysosomal component, apparently distinct from the sedimentable (membrane-associated) antigen described above, was identified in serum, synovial fluid, or pleural fluid from patients with SLE, RA, ankylosing spondylitis, and leukemoid reaction. An antigenically identical soluble component reactive with the rabbit antiserum could be released in vitro from intact lysosomes by repeated freeze-thaw cycles..

Anemia, Hemolytic, Autoimmune↗
PubMedDate not supplied

Induction of suppressor cell activity in vivo and suppression of lymphoproliferative responses in vitro by SK&F 105.685 in the dog.

SK&F 105.685 (N,N-dimethyl-8,8-dipropyl-2-azaspiro[4.5]decane-2-propanamine+ ++ dihydrochloride) is a novel azaspirane with beneficial activity in rat models of adjuvant-induced arthritis and experimental autoimmune encephalomyelitis as well as in the murine lupus model. The mechanism of action in these models appears to be the induction of non-specific suppressor cell activity which is measured by the ability of cells from treated animals to partially inhibit the proliferative response of lymphocytes from control animals to concanavalin A (ConA) in a co-culture assay. In this study we have shown that oral administration of 0.1-3 mg/kg/day of SK&F 105.685 to purebred beagle dogs induced suppressor cell activity in the spleen and bone marrow but not in the peripheral blood. In vitro, SK&F 105.685 partially suppressed the proliferative response of dog splenocytes to the mitogens phytohemagglutinin (PHA), ConA and, to a lesser extent, pokeweed mitogen (PWM). Peripheral blood lymphocytes (PBLs) differed from spleen cells in their susceptibility to suppression by SK&F 105.685. While the PWM and ConA responses of PBLs and spleen cells showed similar levels of inhibition, the PHA response of PBLs, in marked contrast to spleen cells, was resistant to suppression by the compound. Our results show that the immunoregulatory effects of SK&F 105,685 are not limited to rodents and that suppressor cell activity in dogs is induced quickly and by relatively low doses of the compound.

Adjuvants, Immunologic↗