Molecular pathways of CTL-mediated cytotoxicity.
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Animals↗
Biomedical subjects
C M Walsh
Publications and source records attributed to C M Walsh.
Cell-mediated cytotoxicity in perforin-less mice.
We have used a perforin-less (PO) mouse to explore alternate CTL-mediated lytic pathways. PO mice are unable to overcome an infection with LCMV in vivo. Nevertheless, splenocytes from infected mice show vigorous, antigen-specific cytotoxicity that requires the presence of the Fas antigen on target cells. The Fas lytic pathway is virtually indistinguishable, in terms of kinetics and magnitude of cytotoxicity, from perforin/granzyme-mediated lysis. It is rapidly induced in CTL upon occupation of the TcR, and requires protein synthesis for full expression. Upon removal of the activating signal, the capacity for fas-mediated lysis rapidly disappears. PO mice infected with LCMV also undergo what appears to be a CD8-mediated immunopathology, and rarely live beyond one month. The precise basis of this pathology is unknown at present. Given the widespread distribution of Fas in mice, particularly on inflamed tissues, the complete failure to clear virus from any tissue or organ is surprising.
Animals↗
Immune function in mice lacking the perforin gene.
Mice lacking the perforin gene were generated by using targeted gene disruption in embryonal stem cells. When infected with lymphocytic choriomeningitis virus (LCMV), perforin-less (-/-) mice showed clear signs of having mounted an immune response based on activation of CD8 T cells but were unable to clear the LCMV infection. This failure to eliminate virus was accompanied by a failure to generate spleen cells capable of lysing LCMV-infected fibroblasts in vitro. Spleen cells from LCMV-infected -/- mice were able to lyse hematopoietic target cells after exposure to phorbol 12-myristate 13-acetate and ionomycin, provided the target cells expressed the Fas antigen. Spleen cells from -/- mice also responded to alloantigen in mixed leukocyte culture by blastogenesis and proliferation. The resulting cells were able to lyse hematopoietic target cells, although not as well as spleen cells from +/+ littermates sensitized in the same manner. However, lysis by -/- cells was again seen only if the target cells expressed Fas antigen. We conclude that perforin-less -/- mice retain and express the Fas lytic pathway as expressed in vitro but that this pathway is insufficient to clear an LCMV infection in vivo.
Animals↗
The role of the Fas lytic pathway in a perforin-less CTL hybridoma.
The murine CTL hybridoma PMMI has been shown by the most sensitive techniques to be devoid of perforin. We thus used PMMI activated with PMA and ionomycin, to investigate possible alternate lytic pathways in CTLs in the absence of perforin. We found that PMMI is equipped with membrane TNF-alpha as a potential lytic mechanism, but TNF-alpha is unlikely to be involved in acute (4 h) lytic reactions. On the other hand, PMMI readily lyses target cells expressing the gene for the Fas Ag, but does not lyse target cells expressing fas antisense DNA. The generation of fas-dependent lysis required protein synthesis in PMMI, but target cell protein synthesis was not required for lysis. Lysis of Fas-positive target cells by PMMI was accompanied by DNA fragmentation, and both lysis and DNA fragmentation were blocked by inhibition of protein synthesis in the effector cell. We find the relative extent and kinetics of fas-dependent lysis and DNA fragmentation indistinguishable from that seen in "classical" CTL lytic assays. Both fas- and perforin-dependent lysis were blocked by inhibitors of poly(ADP) ribosylation. We found very little difference in the sequence of events in target cells lysed by the fas pathway compared with the classical (probably perforin) lytic pathway. Given the widespread distribution of fas, particularly in hematopoietic target cells, caution may be required in interpreting the relationship between parameters such as DNA fragmentation and 51Cr-release solely on the basis of the granule exocytosis model.
Animals↗
Recurrent hairy cell leukemia during pregnancy: a case report.
Recurrent hairy cell leukemia was diagnosed during the second trimester of pregnancy, which was subsequently terminated because of therapeutic considerations. Treatment issues are discussed.
Adult↗
Enhanced length of stay management through monitoring of discharge planning parameters.
Traditional data collection in discharge planning programs has been largely retrospective, measuring the patient's length of stay and unnecessary hospital days at the point of discharge. Although the data collection is useful, it does not lend itself to corrective actions on a concurrent basis. Carney Hospital has developed a data base that monitors patient status daily in order to identify when a length of stay problem is developing and when corrective actions are succeeding. The Patient Tracking System is an interactive computer report utilized by Continuing Care staff, Utilization Review staff, and clinical managers on the patient care units. It is a caseload register that operates from the admission transfer discharge (A/T/D) system of the hospital and sorts inpatients by discharge planning status, length of stay, discharge planning worker, and nursing unit. It is the basis for a weekly management review that identifies numbers of patients and average length of stay to date of key groups of patients proven to impact the overall length of stay in the hospital. Carney Hospital has successfully utilized this system to alert managers to any length of stay "creep," to identify the sources of the length-of-stay problem, and to mobilize key personnel to take corrective actions. The system is easy to use and is an effective length-of-stay management tool.
Boston↗
Modulation of monocyte functions by muramyl tripeptide phosphatidylethanolamine in a phase II study in patients with metastatic melanoma.
BACKGROUND: Muramyl tripeptide phosphatidylethanolamine (MTP-PE) is a synthetic analogue of muramyl dipeptide (MDP), a component of bacterial cell walls that has potent in vitro monocyte-activating properties. We conducted a phase II clinical trial of MTP-PE in 30 patients with metastatic melanoma. PURPOSE: Our purpose was to define a clinical response rate for this agent in patients with advanced melanoma and to evaluate the agent's immunomodulatory properties. METHODS: Patients were randomly assigned to 1- or 4-mg dose levels of MTP-PE and received the drug intravenously once a week for 12-24 weeks. Immunological monitoring consisted of measurement of plasma tumor necrosis factor-alpha (TNF-alpha), neopterin, interleukin-1-beta, interleukin-6 (IL-6), and beta 2-microglobulin levels; phenotyping analysis of expression of human HLA-DR, CD-14 on mononuclear cells; and measurement of in vitro monocyte cytotoxicity against SKMel28 targets cells. RESULTS: MTP-PE was well tolerated; fever and chills were the major toxic effects. Plasma TNF-alpha levels increased 16-fold 2 hours after the first MTP-PE treatment. Increases in TNF-alpha levels after MTP-PE administration continued through week 12, but changes were of a lower magnitude after week 1. Plasma neopterin levels were significantly increased 24 hours after treatment at weeks 1, 6, and 12. A marked increase in IL-6 and a modest rise in beta 2-microglobulin levels were also seen at week 1. No significant changes from baseline IL-1 beta were observed. In the cytotoxicity assay, monocyte cytotoxic activity was significantly increased at weeks 4 and 6. Surface immuno-phenotyping revealed a consistent transient reduction in the number of circulating monocytes 2 hours after MTP-PE was administered. In addition, we observed a down-regulation (i.e., a decrease) in the expression of Leu M3 and HLA-DR on monocytes, 2 hours after MTP-PE treatment, followed by a recovery 24 hours after treatment. No objective clinical responses were seen in this advanced disease population. CONCLUSIONS: We conclude that MTP-PE has pleiotropic and potentially beneficial biologic effects and that further clinical investigations of MTP-PE are justified. IMPLICATIONS: In view of the clear immunomodulatory actions seen in our study and in earlier clinical trials, we believe that MTP-PE deserves further study in the adjuvant setting.
Acetylmuramyl-Alanyl-Isoglutamine↗
Thrombocytopenia and human immunodeficiency virus-1 infection.
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Acquired Immunodeficiency Syndrome↗
Risk for the acquired immunodeficiency syndrome among thrombocytopenic and nonthrombocytopenic homosexual men seropositive for the human immunodeficiency virus.
A group of 44 homosexual patients with immune thrombocytopenia and serologic evidence of infection with the human immunodeficiency virus (HIV) was observed for a total of 844 person-months. The risk of developing the acquired immunodeficiency syndrome (AIDS), an actuarial incidence of 36.5% in 37 months, was no different than that reported for seropositive homosexual men from New York who are nonthrombocytopenic and asymptomatic. A statistical analysis comparing the hazard function with a constant-risk model showed that the hazard of developing AIDS was not constant but increased with duration of seropositivity.
Acquired Immunodeficiency Syndrome↗
Onset of pancuronium and d-tubocurarine blockade with priming.
The synergistic effect of pancuronium bromide (PCB) and d-tubocurarine (DTC) on the onset time of neuromuscular blockade was tested in 108 ASA physical status I and II adults anaesthetized with thiopentone, nitrous oxide and halothane. Either saline or a small (priming) dose (DTC, 0.04 mg X kg-1, or PCB, 0.007 mg X kg-1) was administered 3 min before a paralyzing dose of either DTC or PCB. The total dose of relaxant was equivalent to DTC, 0.4 mg X kg-1, or PCB, 0.07 mg X kg-1. Neuromuscular activity was measured using train-of-four stimulation applied every 12 s. Time to 50 per cent first twitch blockade was 63 +/- 4.6 s (mean +/- SEM) with DTC and 88 +/- 5.2 s with PCB (p less than 0.002). Times to 90 per cent blockade were not different between the two drugs (161 +/- 20 s and 141 +/- 21 s respectively). Priming a DTC blockade with either DTC or PCB or priming a PCB blockade with PCB produced an acceleration of less than 10 s at all levels of blockade. Compared with PCB alone, priming PCB blockade with DTC reduced the time to 50 per cent blockade to 71 +/- 4.5 s (p less than 0.02) and to 90 per cent blockade to 111 +/- 8 s (p less than 0.05). Priming did not affect the duration of action significantly, except in the case of PCB priming of DTC, where duration was increased from 39 +/- 4.4 to 57 +/- 4 min (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Effect of seat position on maximal linear velocity in wheelchair sprinting.
The purpose of this study was to investigate the relationship between seat position and linear velocity in wheelchair sprinting. Nine male subjects with various physical disabilities participated in the experiment. Linear velocity was determined by analyzing the filmed performance of subjects wheeling at maximum speed on a wheelchair ergometer. The results revealed no significant differences between the maximal linear velocities at each of the nine seat positions chosen for investigation. These findings suggest that given a limited variability in seat positions, maximal linear velocity will be minimally affected. Simple correlation procedures revealed a significant negative correlation between the length of push and linear velocity. This is in opposition to current findings and suggests that pushing frequency may be more critical than the length of push in generating maximum speed in wheelchair sprinting.
Adult↗
On the mechanism of thrombocytopenic purpura in sexually active homosexual men.
Thrombocytopenic purpura has recently been noted in sexually active homosexual men. To elucidate the pathogenesis of thrombocytopenic purpura in this population, we compared the disorder in 33 homosexual men with that in 23 patients (15 women and 8 men) thought to have classic autoimmune thrombocytopenic purpura. The homosexual group had 3.8-fold higher levels of platelet-bound IgG and 4.2-fold higher levels of platelet-bound complement than the patients with autoimmune thrombocytopenic purpura. Eluates from the platelets of only 1 of 10 homosexual patients reacted in vitro with normal platelets, as compared with those from the platelets of 12 of 15 patients with autoimmune thrombocytopenic purpura. Twenty-one of 24 homosexual patients (88 per cent) had elevated serum levels of immune complexes that were capable of binding to platelets, whereas none of 5 patients with autoimmune thrombocytopenic purpura had circulating immune complexes. The IgG fraction of positive serum samples from three homosexual patients did not bind to normal platelets, whereas that from the positive serum of two patients with autoimmune thrombocytopenic purpura and one woman in whom isoimmune antiplatelet antibody developed during pregnancy (studied as a positive control) did bind to normal platelets. We conclude that, whereas classic autoimmune thrombocytopenic purpura involves antiplatelet IgG directed against platelet antigenic determinants, the thrombocytopenic purpura that occurs in sexually active homosexual men is usually caused not by antiplatelet IgG but probably by the nonspecific deposition of complement and immune complexes on platelets.
Acquired Immunodeficiency Syndrome↗
Controlled supplemental oxygenation during tracheobronchial hygiene.
The effect of controlled supplemental oxygenation without bag ventilation on transcutaneous partial pressure of oxygen (TcPO2) measurements during tracheobronchial hygiene was evaluated. Procedure A, no supplemental oxygenation, was compared to Procedure B, in which controlled supplemental oxygenation was used. For controlled supplemental oxygenation, the FiO2 was increased until TcPO2 measurements rose to levels between 90 and 100 torr. Sixteen premature infants who required mechanical ventilation were studied in the neonatal center. Both procedures were performed on each patient in random order. In both procedures, a precipitous decrease in TcPO2 was observed during chest vibration, and further decrease in TcPO2 was noted with endotracheal suctioning. Except for baseline readings, throughout the tracheobronchial hygiene TcPO2 measurements were significantly higher and more subjects maintained TcPO2 values greater than 40 torr in Procedure B. In Procedure A corresponding TcPO2 measurements were 40 torr or less. Mean recovery time was shorter in Procedure B, 2.1 +/- 2.3 minutes, than in Procedure A, 4.9 +/- 2.8 minutes, p less than .003. Thus, in most patients, controlled supplemental oxygenation without manual bag ventilation seems sufficient to prevent hypoxia during tracheobronchial hygiene; it also shortens recovery time from hypoxemia as a result of the bronchopulmonary hygiene procedure.
Blood Gas Monitoring, Transcutaneous↗