Antiplatelet antibody-induced thrombocytopenia does not correlate with megakaryocyte abnormalities in murine immune thrombocytopenia.

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized by increased peripheral immune platelet destruction and megakaryocyte defects in the bone marrow. Although ITP was originally thought to be primarily due to antibody-mediated autoimmunity, it is now clear that T cells also play a significant role in the disease. However, the exact interplay between platelet destruction, megakaryocyte dysfunction and the elements of both humoral and cell-mediated immunity in ITP remains incompletely defined. While most studies have focused on immune platelet destruction in the spleen, an additional possibility is that the antiplatelet antibodies can also destroy bone marrow megakaryocytes. To address this, we negated the effects of T cells by utilizing an in vivo passive ITP model where BALB/c mice were administered various anti-αIIb, anti-ß3 or anti-GPIb antibodies or antisera and platelet counts and bone marrow megakaryocytes were enumerated. Our results show that after 24 hours, all the different antiplatelet antibodies/sera induced variable degrees of thrombocytopenia in recipient mice. Compared with naïve control mice, however, histological examination of the bone marrow revealed that only 2 antibody preparations (mouse-anti-mouse ß3 sera and an anti- αIIb monoclonal antibody (MWReg30) could affect bone marrow megakaryocyte counts. Our study shows that while most antiplatelet antibodies induce acute thrombocytopenia, the majority of them do not affect the number of megakaryocytes in the bone marrow. This suggests that other mechanisms may be responsible for megakaryocyte abnormalities seen during immune thrombocytopenia.

[Anesthesia in thoracic surgery]. / Anästhesie in der Thoraxchirurgie.

Thoracic surgery represents a special challenge for anesthesia and requires a high level of human and material resources. Accurate knowledge of the pathophysiology is essential for selection of the anesthetic procedure, the separation of the lungs, monitoring and treatment of hemodynamics as well as for postoperative follow-up care. The increasing number of thoracic interventions and patients who are often suffering from complex diseases require close interdisciplinary cooperation between surgeons, anesthesiologists and intensive care specialists. In addition to the anesthetic techniques particular attention must be paid to the prevention of perioperative complications that can have a relevant effect on patient outcome. In particular hypoxemia during one-lung ventilation influences postoperative morbidity and mortality. Protective pulmonary ventilation strategies play an important role in prevention of postoperative acute lung injury.

Thymic T cell anergy in autoimmune nonobese diabetic mice is mediated by deficient T cell receptor regulation of the pathway of p21ras activation.

Thymic T cell anergy, as manifested by thymocyte proliferative unresponsiveness to antigens expressed in the thymic environment, is commonly believed to mediate the acquisition of immunological self-tolerance. However, we previously found that thymic T cell anergy may lead to the breakdown of tolerance and predispose to autoimmunity in nonobese diabetic (NOD) mice. Here, we show that NOD thymic T cell anergy, as revealed by proliferative unresponsiveness in vitro after stimulation through the T cell receptor (TCR), is associated with defective TCR-mediated signal transduction along the PKC/p21ras/p42mapk pathway of T cell activation. PKC activity is reduced in NOD thymocytes. Activation of p21ras is deficient in quiescent and stimulated NOD T cells, and this is correlated with a significant reduction in the tyrosine phosphorylation of p42mapk, a serine/threonine kinase active downstream of p21ras. Treatment of NOD T cells with a phorbol ester not only enhances their p21ras activity and p42mapk tyrosine phosphorylation but also restores their proliferative responsiveness. Since p42mapk activity is required for progression through to S phase of the cell cycle, our data suggest that reduced tyrosine phosphorylation of p42mapk in stimulated NOD T cells may abrogate its activity and elicit the proliferative unresponsiveness of these cells.

Major histocompatibility complex class II molecules function as a template for the processing of a partially processed insulin peptide into a T-cell epitope.

Our understanding of how an autoantigen is processed and presented during the development of a major histocompatibility complex (MHC) class II-dependent and T-cell-mediated autoimmune disease, such as IDDM, is incompletely understood. We have used insulin as a model autoantigen in IDDM to address the question of whether MHC class II molecules play a role in the generation and/or preservation of an autoantigen peptide that stimulates T-cell activation. Analyses of the requirement of I-Ad class II molecules in the processing of the partially processed porcine insulin peptide A1-A14/B1-B16 demonstrate that the binding of this peptide to I-Ad is essential for it to be further processed and tailored into a T-cell epitope. Based on our observations, we propose a two-step model for insulin processing in which insulin is first processed by an enzyme(s) into an intermediate peptide that binds to class II and then class II functions as a template to guide the processing of this partially processed peptide by cathepsin D into a T-cell epitope. Our data further underscore the important realization that MHC class II-directed processing of an autoantigen (e.g., insulin) may regulate 1) the relative immunodominance of T-cell determinants in an autoantigen, 2) the self-reactivity to cryptic T-cell epitopes in autoantigens, and 3) the susceptibility to autoimmune disease.

Endocarditis with myocardial abscesses and pericarditis in an adult: group B Streptococcus as a cause.

Group B beta-hemolytic Streptococcus, S agalactiae, is an uncommon cause of endocarditis in adults. We present the clinical, laboratory, and postmortem findings of an adult patient with group B streptococcal endocarditis and major arterial emboli. What to our knowledge are previously unreported features are purulent pericarditis and myocardial abscesses. Twenty-five cases of endocarditis caused by group B Streptococcus that are reported in the literature are reviewed.

Randomized, prospective comparison of cefoxitin and gentamicin-clindamycin in the treatment of acute colonic diverticulitis.

In a randomized, prospective study, single-drug antibiotic therapy with cefoxitin (CFX) was compared to combination therapy with gentamicin and clindamycin (G/C) as definitive treatment for acute colonic diverticulitis. Excluding individuals requiring immediate operation, 51 patients with a clinical diagnosis of diverticulitis, who were hospitalized at five different medical centers, were randomized to receive CFX (30 patients) or G/C (21 patients). Age, sex, and the severity of diverticulitis were similar in the two groups. The cure rates of 90% and 85.7% observed for CFX and G/C, respectively, did not differ significantly. Leukocytosis resolved in a shorter time period in patients treated with CFX than in those treated with G/C (2.5 +/- 0.4 vs 4.1 +/- 0.6 days, respectively) (P = 0.03, Student's t test, unpaired data). Two cases of possibly antibiotic-related toxicity occurred in the CFX group versus three cases in the G/C group. The average cost of a course of CFX therapy was $417 compared with $488 for G/C. In this study, cefoxitin demonstrated efficacy and tolerability similar to that of gentamicin-clindamycin in the treatment of acute colonic diverticulitis and may be preferred in view of its narrower antimicrobial spectrum and lower cost.

A pilot study of pain, analgesia use, and pulmonary function after colectomy with or without a preoperative bolus of epidural morphine.

OBJECTIVE: To determine whether patients who received a preoperative bolus of epidural morphine plus postoperative parenteral analgesia had less pain and better pulmonary function over the first 2 days after a colectomy than patients who received postoperative parenteral analgesia alone. DESIGN: Repeated measures, quasi-experimental, random assignment. SETTING: Northeastern general hospital. SUBJECTS: Thirteen patients were randomized to receive parenteral with (n = 6) or without (n = 7) epidural analgesia. OUTCOME MEASURES: Indicators of pain (intensity of pain and pain-related distress, intensity of words used to describe pain, intramuscular-equivalent amount of morphine administered, duration from start of surgery to first request for analgesia) and pulmonary function (forced expiratory volume in one second FEV1], forced vital capacity [FVC], inspiratory capacity [IC], peripheral oxygen saturation [SaO2] values). MEASUREMENT: Indicators of pain and pulmonary function were obtained the day before surgery, approximately 6 hours after surgery, and the first two mornings after surgery. RESULTS: Six hours after surgery, patients in the epidural group had less pain (p = 0.0177) and related distress (p = 0.0303) and greater FVC (p = 0.0303) and FEV1 (p = 0.0025) than patients in the no-epidural group. On the first postoperative morning, patients in the epidural group had less distress related to pain (p = 0.0350) but similar respiratory rates and spirometry values. Inspiratory capacity was not statistically different but was always larger in the epidural group. Of patients who breathed room air, SaO2 was higher in the epidural group over the first two postoperative days (p = 0.0286 each occasion). Patients in the epidural group received their first on-demand analgesic an average of 30 hours after the start of surgery compared with 6 hours for patients in the no-epidural group (p = 0.0022). There were no significant differences in the total number of words used to describe the type of pain, and both groups described the pain with fewer words than expected on the first and second mornings after surgery. CONCLUSIONS: Results should be confirmed through study of a larger sample with the hypothesis that pain relief, selected aspects of pulmonary function, and peripheral oxygenation may be superior for patients who receive a preoperative bolus of epidural analgesia for abdominal surgery.

The effects of epidural versus parenteral opioid analgesia on postoperative pain and pulmonary function in adults who have undergone thoracic and abdominal surgery: a critique of research.

Studies comparing epidural and parenteral opioid analgesia for patients experiencing thoracic or abdominal surgery are analyzed with respect to differences in postoperative pain and pulmonary function. Although most studies suggest that epidural analgesia is superior for postoperative pain relief, few clearly demonstrate an improvement in pulmonary function attributable to epidural analgesia. Recommendations for future research are proposed to improve the design, measurement, analysis, and reporting of studies. Research relevant to the nursing care of patients receiving epidural analgesia is suggested.

Separation of folic acid reductase from Streptococcus faecium (ATCC 8043).

A strain of Streptococcus faecium (ATCC 8043) which is highly resistant to the antifolic acid compound, amethopterin, was gently ruptured by exposing protoplasts of the organism to a hypotonic solution. The crude lysate resulting there-from was treated by various chemical and physical techniques designed to separate folic acid reductase from dihydrofolic acid reductase. In the process, the enzyme was purified approximately 160-fold; however, throughout the process, the enzyme preparation maintained the ability to reduce folic acid to tetrahydrofolic acid. Attempts to isolate mutants showing a deficiency in either folic acid reductase or dihydrofolic acid reductase were unsuccessful. Based on these results, it is concluded that folic acid is reduced to tetrahydrofolic acid by one enzyme in S. faecium (ATCC 8043). The crude lysate was also subjected to ultracentrifugation. An analysis of the supernatant fluid and the sediment indicated that the reductive activity is located in the soluble fraction of the cell.

Processing and presentation of insulin. III. Insulin degrading enzyme: a neutral metalloendoproteinase that is non-homologous to classical endoproteinases mediates the processing of insulin epitopes for helper T cells.

Presentation of a protein antigen to T cells generally requires that the antigen be enzymatically processed into an immunogenic peptide(s). The identification of a protease(s) and its mechanism of action in the proteolysis of such an antigen is therefore a primary goal in the study of antigen processing. We show here that insulin degrading enzyme (IDE), a neutral thiol metalloendoproteinase that is structurally non-homologous to the classical metallo, thiol, acid, or serine proteinases, is relatively specific in its proteolytic activity for insulin and digests human insulin (H(I)) into peptides that are presented by murine TA3 B cell antigen presenting cells (APCs) to HI/I-Ad-reactive T cells. These peptides are, however, not presented by fixed TA3 APCs. Anti-IDE mAbs, after their internalization by TA3 cells, significantly inhibit the presentation of H(I) by these APCs. Immunoblotting experiments demonstrate that this inhibition is mediated by the reactivity of these mAbs with a 110 kDa protein, the known M(r) of IDE. These data show that IDE is an endoproteinase that is involved in the processing of insulin and that this IDE-mediated proteolysis is necessary but not sufficient for the recognition of insulin by T cells. Furthermore, we demonstrate that reduction of the disulfide bonds of a pre-processed A-loop containing heterodimeric insulin peptide is required to further process insulin into a T cell epitope.

Naturally processed heterodimeric disulfide-linked insulin peptides bind to major histocompatibility class II molecules on thymic epithelial cells.

We determined whether disulfide-linked insulin peptides that are immunogenic in vitro for CD4+ T cells bind to major histocompatibility complex class II in vivo. Radiolabeled recombinant human insulin (rHI) was injected into BALB/c mice, and processed rHI peptides bound to I-Ad molecules on different thymic antigen-presenting cells were characterized. The A6-A11/B7-B19 and A19-A21/B14-B21 disulfide-linked I-Ad-bound rHI peptides were isolated from thymic epithelial cells but not dendritic cells. While both thymic epithelial cells and dendritic cells present rHI to HI/I-Ad-specific T cells, these antigen-presenting cells do not present the reduced or nonreduced forms of the disulfide-linked rHI peptides. Thus, a naturally processed disulfide-linked peptide can bind to major histocompatibility complex class II in vivo. The potential role of these peptides in immunological tolerance is discussed.

Indirect allorecognition of platelets by T helper cells during platelet transfusions correlates with anti-major histocompatibility complex antibody and cytotoxic T lymphocyte formation.

To study the cellular immunology of platelet-induced alloimmunization, a murine transfusion model was developed. BALB/c (H-2d) recipient mice were transfused weekly with 2 x 10(8) platelets or 10(3) leukocytes from C57BL/6 (H-2b) donor mice. Recipient antidonor major histocompatibility complex (MHC) class I alloantibodies could be detected in flow cytometric assays by the fifth platelet transfusion. In contrast, when leukocytes only were transfused, alloantibodies were not detected. In vitro assays demonstrated that murine H-2b platelets were positive for MHC class I expression but lacked MHC class II molecules on their membranes and were unable to stimulate proliferation or cytokine production when incubated with naive H-2d spleen cells. In vivo, however, platelet transfusions induced two distinct patterns of cell-mediated reactivity. First, during the initial transfusions and before alloantibody formation, there was induction of T-cell anergy, characterized by the inability of recipient T cells to respond to Concanavalin A (ConA) or to proliferate in an antidonor mixed lymphocyte reaction (MLR), together with suppressed natural killer (NK) cell activity. This unresponsiveness was associated with a transient increase in nitric oxide (NO)-dependent cytotoxicity and interleukin-1 (IL-1) production. Second, once alloantibodies developed, significantly increased antidonor CD8+ cytotoxic T lymphocyte (CTL) and NK cell responses were observed. At this time, when recipient spleen cells were depleted of CD8+ T cells and incubated with only donor platelets in 7-day antigen-presenting cell (APC) assays, enhanced proliferation and IL-2 production occurred. These cellular responses were not seen when 10(3) allogeneic leukocytes were transfused. Thus, the results suggest that leukoreduced platelet transfusions induce antidonor MHC antibodies and CD8+ CTL responses in recipient mice. At the same time, the transfusions induced recipient CD4+ T-cell activation when incubated with donor platelets in the presence of syngeneic APCs, an indirect recognition pathway that correlates with the time of alloantibody production.

Unique processing pathways within recipient antigen-presenting cells determine IgG immunity against donor platelet MHC antigens.

Recipient IgG immunity against leukoreduced donor platelets is dependent on indirect T-cell allorecognition and is suppressed in vivo by inhibitors (aminoguanidine, AMG) of inducible nitric oxide synthase (iNOS). To examine recipient processing pathways of donor platelet antigens, enriched macrophages (antigen-presenting cells [APC]) from BALB/c (H-2(d)) mice were pulsed with allogeneic C57BL/6 (H-2(b)) platelets and transfused weekly into naive BALB/c mice. Platelet-pulsed APC stimulated IgG antidonor antibody production in 45% of recipients by the second transfusion and in 100% by the sixth transfusion; this response was enhanced by pulsing in the presence of interferon-gamma. By the sixth transfusion, high-titer IgG1 (mean titer 4990) and IgG2a (1933) isotypes specific for donor major histocompatibility complex (MHC) class I antigens were detected. Platelet pulsing in the presence of AMG or colchicine significantly inhibited the ability of APC to stimulate IgG alloantibodies; only 50% (P <.005) and 20% (P <.0001) of recipients, respectively, produced antibodies by the sixth transfusion. AMG inhibition was reversed by the addition of L-arginine, the substrate for iNOS. In contrast, pulsing in the presence of chloroquine, the proteasome inhibitory peptide MG115, or Brefeldin A enhanced APC immunity (70-100% of recipients antibody positive by the second transfusion [P <.05]); these agents allowed the pulsed APC to stimulate IgG2a but inhibited IgG1 production and this correlated with a reduction in serum interleukin (IL)-4 levels. The results suggest that for donor platelet antigens to stimulate IgG alloantibodies, recipient APC use the essential generation of nitric oxide and a noncytosolic, pH-independent processing pathway, which can be exploited as an effective immunotherapy target to further inhibit alloimmunization against leukoreduced platelets. (Blood. 2000;95:1735-1742)

Recipient humoral immunity against leukoreduced allogeneic platelets is suppressed by aminoguanidine, a selective inhibitor of inducible nitric oxide synthase.

Leukoreduced allogeneic platelet transfusions have been previously shown to initially stimulate an in vitro cellular cytotoxicity and subsequently Induce the formation of immunoglobulin G (IgG) antidonor alloantibodies. To further characterize these responses and determine if they are related, recipient BALB/c H-2d mice were treated with aminoguanidine (AMG), a selective inhibitor of inducible nitric oxide synthase (iNOS), and transfused weekly with 2 x 10(8) C57BL/6 H2b platelets. In control, non-AMG-treated mice, transfusion significantly (P < .01) increased serum levels of interferon-gamma (IFN-gamma) by day 1 posttransfusion (PT). IFN-gamma returned to pretransfusion levels by day 3 PT, and its production was not affected by AMG treatment. Serum interleukin-4 (IL-4), on the other hand, was undetectable before and during the transfusion protocol. By day 3 PT, recipient spleen cells could mediate in vitro anti-P815 (auto), anti-EL4 (allo), and anti-R1.1 (third-party MHC) cytotoxicity, and these responses were maximal by day 7 PT. Concurrently, a significant reduction in the vitro ability of recipient splenocytes to respond to Concanavalin A (ConA) was observed; this was not seen with lipopolysaccharide (LPS) stimulation. Elevated levels of NO2- were found in the ConA culture supernatants from transfused mice at day 3 PT. Serum antidonor alloantibodies were detected by the fifth platelet transfusion. AMG treatment of recipient mice significantly inhibited the transfusion. Induced cytotoxicity and ConA-stimulated NO2- production, and restored ConA-induced proliferation to normal levels. AMG appeared to selectively inhibit platelet-induced alloantibody production in that it did not affect antibody production induced by transfusions with 10(5) allogeneic leukocytes or by immunization with a foreign protein antigen, human gamma globulin, in adjuvant therapy. These results indicate that an in vivo AMG-sensitive mechanism is essential for recipients to initiate a humoral IgG immune response against allogeneic platelets.

Extreme leukoreduction of major histocompatibility complex class II positive B cells enhances allogeneic platelet immunity.

In a murine model of platelet alloimmunization, we examined the definitive role that mononuclear cells (MC) have in modulating platelet immunity by using platelets from severe combined immunodeficient (SCID) mice. CB.17 (H-2(d)) SCID or BALB/c (H-2(d)) mouse platelets were transfused weekly into fully allogeneic CBA (H-2(k)) mice and antidonor antibodies measured by flow cytometry. MC levels in BALB/c platelets were 1.1 +/- 0.6/microL and SCID mouse platelets could be prepared to have significantly lower (<0. 05/microL) MC numbers. Transfusions with 10(8) BALB/c platelets (containing approximately 100 MC/transfusion) stimulated IgG antidonor antibodies in 100% of the recipients by the fifth transfusion, whereas 10(8) SCID mouse platelets (containing approximately 5 MC/transfusion) stimulated higher-titered IgG alloantibodies by the second transfusion. When titrations of BALB/c peripheral blood MC were added to the SCID mouse platelets, levels approaching 1 MC/microL reduced SCID platelet immunity to levels similar to BALB/c platelets. Characterization of the alloantibodies showed that the low levels of MC significantly influenced the isotype of the antidonor IgG; the presence of 1 MC/microL was associated with induction of noncomplement fixing IgG1 antidonor antibodies, whereas platelet transfusions, devoid of MC (<0. 05/microL), were responsible for complement-fixing IgG2a production. When magnetically sorted defined subpopulations of MC were added to the SCID platelets, major histocompatability complex (MHC) class II positive populations, particularly B cells, were found to be primarily responsible for the reduced SCID mouse platelet immunity. The presence of low numbers of MC within the platelets was also associated with an age-dependent reduction in platelet immunogenicity; this relationship however, was not observed with SCID mouse platelets devoid of MC. The results suggest that a residual number of MHC class II positive B cells within allogeneic platelets are required for maximally reducing alloimmunization.

Melatonin in postmenopausal females.

There is little information about the interaction between melatonin, sexual steroids and neuroendocrine system in postmenopausal females, even if former research showed that melatonin is clearly involved in human physiology and pathophysiology. We evaluated the overnight urinary excretion of 6-sulfatoxymelatonin (6-SMT) using a radioimmunoassay in 60 postmenopausal women. The group has been divided into patients with insomnia (10), hyperprolactinemia (7), depression (9), obesity (7) and controls (27). Compared to controls 6-SMT values were significantly higher in depressive females. Patients with hyperprolactinemia showed a trend toward a significantly elevated average nocturnal melatonin concentration. Melatonin levels were significantly lower in patients with insomnia and obese postmenopausal females than in controls. Since previous studies described lower melatonin levels in postmenopausal than in premenopausal women, the indication of melatonin therapy, especially for sleep disorders in this collective, can be handled more generously. Melatonin should be prescribed restrictively in patients with depression and in those with hyperprolactinemia. The role of melatonin in obese females remains unclear.