Coagulant and fibrinolytic activities in the leukemic cell lysates

We attempted to examine procoagulant activity (PCA), X activator activity (XAA) and plasminogen activator activity (PlgAA) of various leukemic cell lysates: 17 acute myelocytic leukemias (AML), 4 acute promyelocytic leukemias (APL), 9 acute myelomonocytic leukemias (AMMoL), 7 chronic myelocytic leukemias (CML), 4 CML with blastic crisis, 7 T cell acute lymphocytic leukemias (ALL), 8 adult T cell leukemias (ATL), 8 null cell ALL, 6 B cell lymphocytic leukemias. Among those 70 cases, 4 APL, 4 AMMoL and 5 AML were associated with overt disseminated intravascular coagulation (DIC) and 5 T cell ALL, 7 ATL and 2 null cell ALL were associated with hypofibrinogenemia not adapted for DIC. The sample used was the lysate of 10(7) cells. PCA was measured by recalcification time of normal plasma with the cell lysate, XAA and PlgAA was measured by chromogenic substrate. APL and AML, especially those associated with overt DIC, had high PCA, and lymphocytic leukemia generally had low PCA in comparison with normal controls. Total PCA (PCA multiplied by cell count/microliter) was remarkably increased in DIC and mildly increased in ALL with hypofibrinogenemia. The change in XAA and total XAA (XAA multiplied by cell count/microliter) was not remarkable in any leukemia except for T cell ALL and null cell ALL with hypofibrinogenemia. PlgAA was high in lymphocytic leukemias with hypofibrinogenemia, APL and AMMoL with DIC. Total PlgAA (PlgAA multiplied by cell count/microliter) was high especially in T cell ALL and null cell ALL with hypofibrinogenemia. Thus it is probable that PCA is the most important factor causing DIC in myelogenous leukemia and that PlgAA is the most important factor causing hypofibrinogenemia in lymphocytic leukemia. The measurement of these activities in the leukemic cells is valuable in prediction and prevention of the hemostatic disorder in leukemia.     

Increased procoagulant response of monocytes from patients with familial Mediterranean fever

Familial Mediterranean Fever (FMF) is an inherited disease of unknown etiology characterized by recurrent inflammatory episodes. Circulating fibrin was found in patients with FMF in absence of clinical manifestation of thrombosis and was statistically less frequently observed in patients treated with colchicine. These results suggest a cellular dysfunction. Therefore, we examined the procoagulant activity (PCA) of isolated mononuclear leukocytes and purified monocytes from FMF patients (n = 20). No PCA was detectable on freshly-isolated monocytes. After several hours of culture. FMF monocytes contained more PCA than control cells and the difference was more marked after endotoxin stimulation. Data obtained with coagulation factor-deficient plasma and anti-human apoprotein III antiserum indicated that the enhanced PCA in FMF monocytes is thromboplastin-like. Lysozyme and interleukin 1 production by monocytes were similar in patients and controls. The increased monocyte PCA appears to be due to an intrinsic and selective higher responsiveness of monocytes.     

Serum augments the generation of monocyte procoagulant stimulated by bacterial lipopolysaccharide or chemotactic fragments of C5

Human serum augments the ability of bacterial lipopolysaccharide (endotoxin) or partially-purified C5-derived chemotactic fragments (C5-fr) to induce the monocyte procoagulant activity (PCA) $\text{in vitro}$. Both autologous and pooled sera induced PCA in the target cell population. Dose response curves revealed a detectable response in PCA with as little as 0.1% serum (v:v) in cell suspensions incubated for 4–6 hours before assay of PCA. Heat-inactivation experiments showed that enhancing activity of serum for both endotoxin and C5-fr induced-PCA could be destroyed by heating at 56°C, with the greater part of the activity lost during the first 30 minutes of heating. The enhancing serums studied contained no endotoxin as measured by the Limulus amebocyte lysate assay and these serums failed to induce aggregation of neutrophils, a sensitive measure for the presence of complement-derived chemotactic fragments such as C5a. Serum without endotoxin or C5-fr also induced a variable increase in PCA and this inducing activity could also be abolished by heating, whereas the ability of endotoxin alone (10 μg/ml) to induce PCA was unaffected by similar heat-treatment. The procoagulant appeared to function as tissue factor in one-stage clotting assays using deficient substrate plasmas. Lymphocytes stimulated by serum and later washed failed to amplify monocyte tissue factor whereas lymphocytes exposed to endotoxin retained the ability to amplify monocyte tissue factor. These results suggest a role for serum in the modulation $\text{in vitro}$ of monocyte procoagulant.     

Inhibitory effect of retinoids on the generation of procoagulant activity by blood mononuclear phagocytes.

Retinoids are known to modulate several functions of mononuclear phagocytes. We have studied the effect of retinyl acetate (RAc) and retinoic acid (RA) on the production of procoagulant activity (PCA) by human peripheral blood mononuclear cells stimulated with endotoxin (1 microgram/ml, 4 or 20 h at 37 degrees C). Both compounds caused a dose-dependent reduction in the expression of cell-associated PCA (from 86 to less than 10% of control in the range of concentration comprised between 0.1 and 100 microM). This effect was also observed when the cells were exposed to retinoids for 10 min and washed before challenge with endotoxin, indicating that it is rapid and irreversible. In contrast, incubation of RAc or RA for 3 h at 37 degrees C with cells that have been already stimulated with endotoxin (20 h at 37 degrees C) remained without influence on cell PCA. The inhibitory action of retinoids was also observed when monocyte-enriched (greater than 85%) preparations or highly purified monocyte-derived macrophages (greater than 99%) were used instead of whole mononuclear cells. BW755C, an inhibitor of cyclo-oxygenase and lipoxygenase, reversed the inhibitory effect of retinoids, whereas acetylsalycilic acid, an inhibitor of cyclo-oxygenase, was inactive, suggesting the involvement of a lipoxygenase product. The inhibition of monocyte/macrophage PCA production and the subsequent reduction of cell potential for fibrin deposition might represent one of the mechanisms whereby retinoids exert their antiinflammatory and immunomodulatory activities.     

Intracranial granulocytic sarcoma in a patient with acute myeloid leukemia]

Granulocytic sarcoma (GS) is extramedullary tumor composed of immature leukemic cells. GS is presenting usually as a complication during the course of hematologic neoplasm, such as acute myeloblastic leukemia as well as myeloproliferative and myelodysplastic syndrome. The tumor was also called chroloma based on the green color of the tumorous mass. Central nervous system manifestations of GS are extremely rare. We report a 41-year-old man with acute leukemia type M7, who developed GS in the right occipital lobe after complete remission was achieved. Operative findings revealed the color of the hard tumor was greenish, which suggested the tumor was chroloma. Histological findings showed the tumor was GS. The majority of reported cases of GS in acute myeloid leukemia were M2 FAB classification and have chromosome translocation. Our patient was M7 FAB classification, not have specific chromosome translocation. GS occurrence in AML: M7 patient was extremely rare. This is the first case report of AML: M7 with GS in the central nervous system.     

Computerized morphometric analysis of human leukemic and lymphomatous cells in various histological environments of central nervous system

The leukemic and lymphomatous cells appear within the central nervous system (CNS) in 5 different environments: in CNS vessels, perivascular spaces, meninges, nervous tissue and in CNS hemorrhages. A computerized analysis of geometric and densitometric parameters of neoplastic cells in these compartments were done for better recognition of penetration and spreading of leukemia and lymphoma within the CNS. A post-mortem neuropathological investigations were carried out on 16 patients deceased due to acute myeloblastic leukemias (M1, M2), blastic phase of chronic myelogenous leukemia, lymphoblastic lymphoma and acute lymphoblastic leukemia. Following nuclear parameters of neoplastic cells were analyzed: area, "form factor", mean, minimal and maximal density. An evident differentiation of nuclear parameters within the CNS environments was found. The nuclei within the perivascular spaces and especially in CNS hemorrhages were significantly shrunken and dense (p < 0.01), but not evidently deformed. The intracerebral infiltrates appeared to be most differentiated group (p < 0.01). Morphometric values of leukemic and lymphomatous cells show regressive changes of neoplastic cells within the CNS perivascular spaces, nervous tissue and in CNS hemorrhages. These changes depend on unfavorable factors in the mentioned CNS environments, and also on time of cell persistence in these regions. Meninges were found to be the only CNS structure facilitating the survival and proliferation of leukemic and lymphomatous cells.     

Enhanced endothelial tissue factor but normal thrombomodulin in endotoxin-treated rabbits

Exposure of cultured endothelial cells to bacterial endotoxin induces an enhancement of cell procoagulant activity (PCA) and a simultaneous reduction of thrombomodulin activity (TM). We evaluated the effect of endotoxin on the expression of both endothelial PCA and TM in vivo, in rabbits. Animals were given a single i.v. injection of endotoxin (E. coli 0111:B4 LPS, W, 10–200 μg/kg); the thoracic aorta was harvested after 2 or 4 hours and placed in an ad hoc device to expose the endothelial surface only. Endotoxin treatment resulted in a dose-dependent increase of endothelial PCA (p < 0.001, at 100 μg/kg or more), which was totally dependent on factor VII and thus identified as tissue factor. In contrast, endothelial TM activity, as measured by the rate of thrombin-induced protein C activation, was similar in control and endotoxemic rabbits, even when the animals were given two injections (50 μg/kg, 24 h apart), or a continuous infusion (40 μg/kg/h during 4 hours) of endotoxin. To explore the effect of endotoxin on TM activity at the microcirculation level, we measured the extent of protein C activation in vivo, induced by a continuous infusion of low doses of thrombin (1 NIH U/kg/min for 60 min). Again, endotoxin administration was not associated with significant changes in TM-dependent protein C activation, as assessed by the anticoagulant activity present in a barium citrate plasma eluate obtained at the end of thrombin infusion. Although reduction of TM during persistent endotoxemia cannot be definitively excluded, our data support a major role of endothelial PCA in LPS-induced coagulative changes.     

Induction of tissue factor procoagulant activity in myelomonocytic cells inoculated by the agent of human granulocytic ehrlichiosis

Human granulocytic ehrlichiosis (HGE) is a recently recognized rickettsial tick-borne febrile illness that may occasionally be complicated by coagulopathy. The agent of HGE (aHGE) is an obligate intracellular pathogen, which replicates in endosomes within neutrophils and their precursors. We hypothesized that aHGE might cause DIC via induction of monocyte tissue factor procoagulant activity (TF PCA). Peripheral blood mononuclear cells (PBMNC) and HL-60 cells were used to model the effect of aHGE infection on monocytes/macrophages. Mononuclear cells inoculated with aHGE in vitro demonstrated approximately a 12-15-fold increase in TF PCA, with peak activity occurring at 8-12 h. HL-60 cells inoculated with aHGE also manifested a 4-6 fold induction of TF PCA, with maximal activity occurring at about 8 h. By comparison, E. Coli lipopolysaccharide (LPS) also induced an increase in TF PCA of an equivalent magnitude, and with a similar time course. Induction of TF did not require inoculation of HL-60 cells with live organism, since heat-inactivated aHGE still stimulated TF PCA expression in the target cells. Furthermore, filtered supernatants from heat-inactivated organisms induced TF PCA suggesting that the effect is due to a soluble mediator produced by the organism. Although aHGE is a gram negative organism, the soluble mediator did not appear to be classic endotoxin in that the supernatants tested negative for endotoxin by the Limulus Amoebocyte assay, and polymixin had no inhibitory effect on aHGE supernatants. We conclude that aHGE induces cells of the myelo-monocytic lineage to synthesize TF, which may contribute to the clinical coagulopathy that can be observed in this condition. An atypical soluble mediator or cellular component of the organism appears to be critically important in TF induction by aHGE.     

Isolated Recurrence of Intracranial Granulocytic Sarcoma Mimicking a Falx Meningioma in Acute Myeloblastic Leukemia

Intracranial granulocytic sarcomas are rare tumors, which are composed of immature granulocytic cells. Although it has been well known that these tumors are associated with acute myeloblastic leukemia (AML), they have been almost always related to bone marrow relapse. However, isolated recurrence of granulocytic sarcoma following complete remission from prior AML is extremely rare, especially in the central nervous system. A 44-year-old male presented with isolated recurrence of granulocytic sarcoma mimicking a falx meningioma two years after complete remission by allogenic peripheral blood stem cell transfusion (PBSCT) in the acute myelomonoblastic leukemia (FAB, M4). Because of depressed mental state and mass effect, total surgical resection was performed. Pathological findings were compatible with the granulocytic sarcoma. There was no evidence of leukemic relapse in the peripheral blood. We suggest that this phenomenon can be explained by the hypothesis that a certain barrier effect such as blood brain barrier might lead to the proliferation of intracranial leukemic cells which metastasized before PBSCT.     

Monocyte procoagulant activity and membrane-associated D dimer after knee replacement surgery

We have recently shown that monocyte membrane-associated cross-linked fibrin derivatives (D dimer) can be evidenced by immunogold staining. Using this method, the procoagulant activity (PCA) expressed in vitro by endotoxin-stimulated monocytes has been found to correlate significantly with the number of D dimer-positive monocytes. The incidence of postoperative thrombosis in patients undergoing total knee replacement has been reported by Stulberg et al to be 57%. Since monocytes can play a role, via increased PCA, in the activation of intravascular coagulation, we sought to determine the level of monocyte PCA ex vivo after knee replacement surgery and its possible correlation with the number of D dimer-positive monocytes. Finally, we examined the possible link between these modifications and the occurrence of postoperative deep vein thrombosis (DVT). The PCA expressed by monocytes with or without suboptimal stimulation, the number of D dimer-positive monocytes and the plasma level of D dimer were measured pre- and post-operatively in 11 patients undergoing total knee replacement. Phlebography was performed on day 10 after surgery. A significant increase in the PCA of stimulated monocytes was observed on day 10 after surgery. Moreover, both the number of D dimer-positive monocytes and the plasma level of D dimer increased significantly post-operatively. The number of D dimer-positive monocytes correlated with both monocyte PCA and the plasma D dimer level. The relation between these parameters is discussed. However, neither monocyte PCA nor the number of D dimer-positive monocytes was found to correlate with the occurrence of deep vein thrombosis.     

Lymphocyte collaboration is not required for the induction of murine macrophage procoagulant by endotoxin

The putative requirement for lymphocytes as instructor cells in the induction of macrophage procoagulant (PCA) by endotoxin (LPS) was tested on elicited mouse peritoneal macrophages and on bone marrow-derived macrophages. Percoll purification of thioglycollate macrophages to at least 99.8 percent failed to diminish PCA induction by LPS. Bone marrow macrophages synthesized most PCA in response to LPS when they constituted more than 95 percent of the cells. In addition, PCA synthesis by these cells was not enhanced by the addition of splenic lymphocytes in a ratio of four to one. Exudate macrophages from endotoxin unresponsive C3H/HeJ mice failed to increase PCA synthesis in the presence of LPS. The addition of responsive C3H/HeN splenic lymphocytes to non-responsive HeJ macrophages did not permit LPS to induce the synthesis of PCA, suggesting the absence of unidirectional lymphocyte-instructed pathway. These data provide no evidence for lymphocyte collaboration in the LPS induction of murine macrophage PCA. LPS appears to induce PCA by acting directly on the macrophage.     

Tissue factor reduction and tissue factor pathway inhibitor release after heparin administration

Elevated plasma levels of tissue factor (TF) and tissue factor pathway inhibitor (TFPI) and large amounts of monocyte procoagulant activity (PCA) have been documented in unstable angina (UA) patients. In in vitro experiments heparin is able to blunt monocyte TF production by inhibiting TF and cytokine gene expression by stimulated cells and after in vivo administration it reduces adverse ischemic outcomes in UA patients. TF and TFPI plasma levels and monocyte PCA have been investigated in 28 refractory UA patients before and during anticoagulant subcutaneous heparin administration (thrice daily weight- and PTT-adjusted for 3 days) followed by 5000 IU X 3 for 5 days. After 2-day treatment, immediately prior to the heparin injection, TF and TFPI plasma levels [(median and range): 239 pg/ml, 130-385 pg/ ml and 120 ng/ml, 80-287 ng/ml] were lower in comparison to baseline samples (254.5 pg/ml, 134.6-380 pg/ml and 135.5 ng/ml, 74-306 ng/ml). Four h after the heparin injection TF furtherly decreased (176.5 pg/ml, 87.5-321 pg/ml; -32.5%. p<0.001) and TFPI increased (240.5 ng/ml, 140-450 ng/ml; +67%, p<0.0001). After 7-day treatment, before the injection of heparin, TF and TFPI plasma levels (200 pg/ml, 128-325 pg/ml and 115 ng/ml, 70-252 ng/ml) significantly decreased (p<0.05) in comparison to the pre-treatment values. On the morning of the 8th day, 4 h after the injection of heparin TF plasma levels and monocytes PCA significantly decreased (156.5 pg/ml, 74-259 pg/ml and from 180 U/105 monocytes, 109-582 U/10(5) monocytes to 86.1 U/10(5) monocytes, 28-320 U/10(5) monocytes; - 38% and -55% respectively) and TFPI increased (235.6 ng/ml, 152-423 ng/ ml; +70%, p<0.001). In conclusion, heparin treatment is associated with a decrease of high TF plasma levels and monocyte procoagulant activity in UA patients. These actions of heparin may play a role in determining the antithrombotic and antiinflammatory properties of this drug.     

Brain cytokine synthesis induced by an intraparenchymal injection of LPS is reduced in MCP-1-deficient mice prior to leucocyte recruitment

We have previously shown that ischaemic lesions are smaller in monocyte chemoattractant protein-1-deficient (MCP-1(-/-)) mice than in wild-type (wt) controls. In addition to its role as a monocyte chemoattractant, monocyte chemoattractant protein-1 (MCP-1) has been proposed to contribute to lesion progression after focal ischaemia by driving local cytokine synthesis by resident glia. To investigate this hypothesis we injected lipopolysaccharide (LPS) into the brain parenchyma of MCP-1(-/-) mice and compared the resulting inflammatory response and production of proinflammatory cytokines to those in wt mice. Microglial and astrocyte morphological activation was the same in the two strains, but MCP-1(-/-) mice showed significantly lower levels of proinflammatory cytokine synthesis; interleukin-1beta (IL-1beta) and tumour necrosis factor-alpha (TNF-alpha) levels were up to 50% lower than in wt controls after 6 h. This reduced synthesis of proinflammatory cytokines occurred well before leucocyte recruitment to the central nervous system (CNS) is observed in this model of acute inflammation and thus cannot be attributed to lower numbers of recruited monocytes at the site of injury. We propose that MCP-1 contributes to acute CNS inflammation by pleiotropic mechanisms. In addition to being a potent chemoattractant for monocytes, we provide evidence here that MCP-1 can modify the responsiveness of CNS glia to acute inflammatory stimuli prior to leucocyte recruitment, thereby acting as a priming stimulus for cytokine synthesis in cells such as microglia.     

Central impairment of renal nerve response to stimulation of medullary pressor area in rabbit endotoxic hypotension

The present study was designed to determine if there is a central abnormality in the sympathetic efferent outflow through the brainstem in endotoxic hypotension. Mean blood pressure (MBP), heart rate (HR) and renal nerve activity (NA) were recorded simultaneously following intravenous injection of endotoxin (1 mg/kg). MBP fell significantly so that 30 min and 60 min after the injection, MBP were 76 +/- 11 mm Hg and 56 +/- 10 mm Hg respectively. Simultaneously with decreases in MBP, NA and HR also decreased significantly. Peak responses in MBP and NA to repetitive stimulation of medullary pressor area (MPA) were attenuated significantly after endotoxin. Onset and peak latencies of renal nerve discharges (RNDe) evoked by the electrical stimulation of the MPA at 5 min after endotoxin were significantly shorter than that before endotoxin, followed by a recovery to the pre-endotoxin level. Peak and total activities of RNDe were reduced significantly so that 30 min after endotoxin activities were 53 +/- 9% and 53 +/- 11% of pre-endotoxin levels respectively. However, responses in MBP, NA and RNDe to the stimulation of the thoracic sympathetic chain did not differ significantly between before and after injection of endotoxin. These data confirm the presence of a central neural abnormality in central sympathetic outflow in the hypotension induced by E. coli endotoxin.     

Cancer procoagulant in acute non lymphoid leukemia: relationship of enzyme detection to disease activity

Blast cell extracts from patients with acute non lymphoid leukemia (ANLL) express cancer procoagulant (CP). This factor X (FX) activator is distinct from tissue factor (TF) in that it does not require factor VII (FVII) to trigger blood coagulation, it acts as a cysteine proteinase and is not present in normal mononuclear cells. To assess whether there is any relationship between the presence of CP and the status of the disease, ANLL patients have been studied at diagnosis, during remission, at relapse. The procoagulant activity in either the presence or absence of F VII and sensitivity to cysteine proteinase inhibitors were tested on cell extracts. Immunoreactivity was explored with an anti-CP polyclonal antibody. Data obtained in 91 newly-diagnosed ANLL patients (subtypes M1 to M5, FAB classification) confirmed the presence of CP in M1 to M4 groups (mean +/- SE FVII-independent activity: M1 = 2.1 +/- 0.7 unit/mg; M2 = 5.7 +/- 1.7 unit/mg; M3 = 31.5 +/- 8 unit/mg; M4 = 1.6 +/- 1.2 unit/mg); CP was absent in the M5 type. In eight patients analyzed in a subsequent phase of partial remission, specific activity had dropped from 26.9 +/- 7.8 to 10.5 +/- 4.0 unit/mg. Activity was virtually absent (0-0.05 unit/mg) in the bone marrow of 37 patients studied at complete remission. Bone marrow samples from six subjects tested at different intervals after complete remission were repeatedly negative for CP but became positive 2 to 5 months before relapse. Upon relapse, the FVII independent activity rose to 24.2 +/- 8.2 unit/mg.(ABSTRACT TRUNCATED AT 250 WORDS)     

Induction of endothelial cell/macrophage procoagulant activity: synergistic stimulation by gamma interferon and granulocyte-macrophage colony stimulating factor

Inflammatory mediators such as endotoxin can stimulate the expression of procoagulant activity on both endothelial cells and macrophages while the monokines Interleukin 1, IL-1, and Tumor Necrosis Factor, TNF, induce procoagulant activity on endothelial cells. Incubation of murine peritoneal macrophages with suboptimal concentrations of endotoxin results in a two fold increase in procoagulant activity. Macrophages incubated with gamma interferon, IFN gamma, or Granulocyte-Macrophage Colony Stimulating Factor, GM-CSF, for 16 hours prior to endotoxin stimulation demonstrated a synergistic increase in procoagulant activity. A synergistic increase in procoagulant activity was also observed with primary cultures of human umbilical cord endothelial cells incubated with recombinant human IFN gamma for 16 hours prior to endotoxin, TNF, or IL-1 stimulation. Human GM-CSF had no stimulatory effect on endotoxin or monokine induced endothelial cell procoagulant activity. The augmentation of macrophage and endothelial cell procoagulant activity by IFN gamma and GM-CSF may provide a novel explanation for the role of these cytokines in acute and chronic inflammation.     

Procoagulant activity of T lymphoblastoid cells in extrinsic and intrinsic coagulation systems

We have measured the procoagulant activity (PCA) of four T lymphoblastoid cell lines (Jurkat, CEM, HSB-2 and Molt 4) as well as normal peripheral blood T lymphocytes, before and after stimulation with phytohaemagglutinin (PHA), using clotting and amidolytic methods. Of the four cell lines only one, Jurkat, gave enhanced PCA after stimulation with PHA. This activity was shown to be tissue factor-like by its dependence on factor VII in plasma and in an amidolytic assay with purified factors VII and X. Jurkat was also the only one of the four cell lines to secrete interleukin-2. All four cell lines promoted the generation of large amounts of thrombin in platelet-free plasma in glass tubes. This activity was dependent on the presence of plasma factor VIII, and was probably due to phospholipids in the cell membranes. Normal T lymphocytes gave intrinsic PCA in the thrombin generation test which was only 15% of that of the lymphoma cells. These results show that some T lymphocytes can develop PCA in both intrinsic and extrinsic systems and this should be taken into account in studies of the PCA of mixed leukocyte populations.     

The Unique Characteristics of Inflammatory Responses in Mouse Brain are Acquired During Postnatal Development

The kinetics of leukocyte recruitment during acute inflammation in adult mouse brain differ from the stereotyped response occurring in non-CNS tissues; neutrophil recruitment is minimal and monocyte recruitment occurs after a 48 h delay. One aspect of the CNS microenvironment which may contribute to restricted leukocyte recruitment is the highly differentiated nature of resident CNS macrophages, the microglia. Thus we studied the inflammatory response to intracerebral injections of endotoxin in neonates in which microglia are less differentiated and resemble more closely macrophages of non-CNS tissues. Mice injected with endotoxin on the day of birth exhibited both neutrophil and monocyte recruitment to the parenchyma, but the response differed from that occurring in non-CNS tissues such as skin. Leukocyte recruitment was very slow, the mononuclear phagocyte response peaking 14 days after endotoxin injection. This sluggish inflammatory response was reminiscent of that previously described in fetal wounds. However, when endotoxin was injected into brains of 7-day-old neonates the inflammatory response resembled that seen in non-CNS tissues; i.e. prolific neutrophil recruitment and a brisk mononuclear phagocyte response. Thus the unusual inflammatory cell kinetics are a property of the mature CNS microenvironment; all signals necessary to support typical leukocyte recruitment are present in the brain by 7 days of age but the brain becomes able to restrict leukocyte immigration during subsequent postnatal development. Developmental changes in the host response to identical inflammatory challenges suggest a window during which the brain may be particularly vulnerable to inflammatory bystander damage.     

Tissue factor released from leukemic cells

Using clotting assay and radioimmunoassay (RIA), tissue factor activity (TFA) and TF related antigen (TFR:AG) were determined in an extracellular culture medium of HL-60 cells. After 12 h incubation, TFA and TFR:AG in the medium with endotoxin (EDX: 1 microgram/ml) reached maximums which were 1.8 and 2.1 times greater than those in the medium without EDX, respectively. In the leukemic cells of 10 patients with acute nonlymphoid leukemia (ANLL), TFR:AG showed a significant correlation with TFA (p less than 0.01). On day 1 of the induction chemotherapy, TFR:AG in the 7 patients with DIC significantly increased to 288.9 +/- 153.1 ng/ml (p less than 0.01), whereas no increase in TFR:AG was recognized in the 3 patients without DIC. These results suggest that TF may be released from leukemic cells into the culture medium or blood stream, and that this may correlate with the development of DIC.     

Platelet functions and clinical effects in acute myelogenous leukemia

Platelets interact with normal peripheral blood cells via adhesion as well as soluble mediators, and platelet released mediators can affect hematopoietic stem and progenitor cells. Interactions may also be involved between platelets and circulating malignant cells, which is suggested by the effects platelets seem to have on metastasis and the various platelet abnormalities observed in various malignant disorders, including acute myelogenous leukemia (AML) and other leukemias. It is only recently that the interactions between platelets and AML cells have been characterized in detail, and studies show that; i) platelets and AML blasts can affect functional characteristic of each other, ii) chemotherapeutic drugs frequently used in AML therapy can alter several platelet functions, iii) the systemic levels of various cytokines are enhanced during AML chemotherapy, including cytokines known to affect both leukemic blasts and platelet activation, and iv) platelet secretion of growth factors are clearly detected in peripheral blood stem cells autografts. In this review we describe platelet interactions with normal leukocytes, normal hematopoietic and leukemic cells and the possible clinical relevance of these interactions in AML.