Membrane-associated sickle hemoglobin: a major determinant of sickle erythrocyte rigidity

Micropipette aspiration tests on single erythrocytes have previously shown that the static rigidity (membrane shear modulus) of oxygenated sickle cells increased with increasing hemoglobin concentration, whereas the rigidity of normal cells was independent of hemoglobin concentration. Moreover, it was observed that after mechanical extension, sickle cells exhibited persistent deformation more frequently and to a greater extent than normal cells. To ascertain if differences in association of normal and sickle hemoglobin with the membrane could account for these observations, we measured rheologic properties of normal membranes reconstituted with sickle hemoglobin and sickle membranes reconstituted with normal hemoglobin. The static rigidity of normal ghosts reloaded with sickle hemoglobin was higher than those of either normal ghosts reloaded with normal hemoglobin or native normal cells. On the other hand, the increased rigidity of native sickle cells decreased to near-normal values following reconstitution with normal hemoglobin. Furthermore, we observed that normal ghosts reconstituted with sickle hemoglobin exhibited persistent bumps after mechanical extension, but no bumps formed on normal ghosts reconstituted with normal hemoglobin. Moreover residual bumps were not produced on sickle cells reloaded with normal hemoglobin. Since mechanical characteristics peculiar to sickle cells could be induced in normal cells by incorporation of sickle hemoglobin, and since normal characteristics could be restored to sickle cells by incorporation of normal hemoglobin, we suggest that the interaction of sickle hemoglobin with the cell membrane is responsible for augmented static rigidity of oxygenated sickle erythrocytes.     

Expression of CD27 and its ligand, CD70, on chronic lymphocytic leukemia B cells

Crosslinking the CD27 antigen on T cells provides a costimulatory signal that, in concert with T-cell receptor crosslinking, can induce T- cell proliferation and cellular immune activation. We find that chronic lymphocytic leukemia (CLL) B cells from most patients coexpress both membrane-bound and soluble CD27, along with its newly identified ligand, CD70. The expression of soluble CD27 may preclude leukemic B cells from stimulating T cells via CD70, thereby potentially impairing their ability to function as effective antigen-presenting cells. We find that leukemic B-cell expression of soluble and membrane-bound CD27 can be downmodulated through a CD40-dependent signal. This signal also induces enhanced expression of CD70 on both normal and leukemic B cells. We find that tumor necrosis factor (TNF)-alpha, or the Th1 cytokine interferon (IFN)-gamma, also can induce downmodulation of CD27, whereas Th2-associated cytokines interleukin-4 (IL-4) or IL-10 can enhance leukemic B-cell expression of this accessory molecule. The modulation of CD27 induced by these conditions is accompanied by reciprocal changes in the expression levels of CD70, suggesting that these accessory molecules may be engaged in reciprocal receptor-ligand downmodulation. Consistent with this, we observe that co-culture of CLL B cells with transfected murine plasmacytoma cells that express human CD70 affects downmodulation of CD27 and enhanced expression of CD70 on leukemic B cells, but does not affect expression of CD27 mRNA. However, we find that CD40-crosslinking, in addition to reducing the level of CD27 protein, also reduces leukemic B-cell expression of CD27 mRNA. This argues that the changes in the expression levels of CD27 following CD40-signaling are not simply due to induced increases in the expression levels of CD70. Finally, we demonstrate that reciprocal changes in expression of CD27 and CD70 may contribute to the enhanced antigen-presenting capacity of CLL B cells after CD40-dependent leukemic B-cell activation. These findings expand the understanding of the regulation of costimulatory molecules important in antigen presentation and also have implications for the immunobiology of and therapy for CLL.     

Increased serum levels of YKL-40 in patients with inflammatory bowel disease

BACKGROUND AND AIMS: Initiation of a fibrotic process has been suggested as part of the intestinal response to chronic inflammation in inflammatory bowel disease. YKL-40 has been proposed as a new serum marker of fibrosis. We studied compared the serum levels of YKL-40 in patients with ulcerative colitis or Crohn's disease with inflammatory and healthy controls. PATIENTS AND METHODS: YKL-40 serum levels were measured in 179 patients with inflammatory bowel disease (94 ulcerative colitis, 85 Crohn's disease), in 23 with intestinal inflammation of other causes, and 70 matched healthy controls using a commercially available enzyme-linked immunosorbent assay. YKL-40 levels were assessed in terms of disease activity, type and localization. RESULTS: Mean serum YKL-40 levels were 102.6+/-82.7 ng/ml in ulcerative colitis patients and 112.2+/-83.7 ng/ml in Crohn's disease patients, significantly higher than in healthy controls (64.1+/-21.4 ng/ml) but not significantly different from inflammatory controls (77.8+/-23.1 ng/ml). Disease activity and C-reactive protein levels were significantly correlated with YKL-40 levels in both ulcerative colitis and Crohn's disease. Crohn's disease patients with ileum localization had significantly higher YKL-40 levels than those with ileocolonic or colonic disease. Patients with stenotic disease had mean YKL-40 levels not significantly different than those with nonstenotic disease. CONCLUSION: Serum levels of YKL-40 are increased in patients with inflammatory bowel disease, and this is associated with the inflammatory process rather than with the degree of fibrosis.     

High-dose etoposide and cyclophosphamide without bone marrow transplantation for resistant hematologic malignancy

Seventy-five patients with resistant acute leukemia or lymphoma received high-dose cyclophosphamide and etoposide to explore the activity of this combination in resistant hematologic malignancies, and to determine the maximum doses of these drugs that can be combined without bone marrow transplantation. Etoposide was administered over 29 to 69 hours by continuous infusion corresponding to total doses of 1.8 g/m2 to 4.8 g/m2. Cyclophosphamide, 50 mg/kg/d, was administered on 3 or 4 consecutive days total 150 to 200 mg/kg ideal body weight). At all dose levels myelosuppression was severe but reversible. Mucosal toxicity was dose-limiting with the maximum tolerated dose level combining etoposide 4.2 g/m2 with cyclophosphamide 200 mg/kg. Continuous etoposide infusion produced stable plasma levels that were lower than would be achieved after administration by short intravenous infusion, and this could explain our ability to escalate etoposide above the previously reported maximum tolerated dose. There were 28 complete (35%) and 12 partial (16%) responses. Median duration of complete response (CR) was 3.5 months (range 1.1 to 20+). Seventeen of 40 patients (42%) with acute myelogenous leukemia (AML) achieved CR, including 6 of 20 (30%) with high-dose cytosine arabinoside resistance. We conclude that bone marrow transplantation is not required after maximum tolerated doses of etoposide and cyclophosphamide. This regimen is active in resistant hematologic neoplasms, and the occurrence of CR in patients with high-dose cytosine arabinoside-resistant AML indicates a lack of complete cross-resistance between these regimens.     

Anti-cardiolipin and Anti-β2-glycoprotein I Antibodies in Patients with Inflammatory Bowel Disease

Patients with inflammatory bowel disease (IBD)frequently suffer from thromboembolic events.Anti-cardiolipin (aCL) antibodies have been shown to beassociated with thrombosis. Recently, the antibodies against the anti-cardiolipin cofactor₂-glycoprotein I(a₂GPI) have been found with higherspecificity for thrombosis. The presence of theseantibodies was assessed in 128 patients with IBD [83 with ulcerative colitis (UC) and 45 withCrohn's disease (CD)] and 100 healthy controls (blooddonors). Patients with UC and CD had a significantlyhigher prevalence of aCL (18.1% and 15.6%, respectively) than healthy controls (HC) (3%). Eleven IBDpatients (8.6%) but no HC had a₂GPI.None of the IBD patients with a history of thrombosishad aCL and only one of them (a UC patient with deepvein thrombosis of the right leg) had a high titer of IgGa₂GPI. In conclusion, these data showthat both aCL and a₂GPI aresignificantly associated with IBD but further studiesare needed to determine the significance of our findings.     

Mechanisms of Action and Resistance of Somatostatin Analogues for the Treatment of Hepatocellular Carcinoma: A Message Not Well Taken

Somatostatin (SST) acts as an inhibitory peptide of various secretory and proliferative processes. Apart from neuroendocrine tumors, where SST analogues have an established role, they have been tested in other tumors such as hepatocellular carcinoma (HCC) in the view of the fact that chemotherapy is not working. Several positive reports have been published. Approximately 40% of patients respond with improved survival and an impressive quality of life. A usual misunderstanding in trial designs is that, although SST is not a rescue drug, selection of patients is inappropriate, with mostly moribund patients being recruited. SST analogues do not seem to work in 60% of HCCs and this has been linked to the presence of SST receptors (SSTR) in the tumor, while several resistance mechanisms might be involved. Future management should engage more specific SST analogues targeted to a tumor with a known SSTR map. The use of somatostatin analogues as an adjunct therapy in combination with other treatment modalities should also be investigated.     

Deferred consent in a minimal-risk study involving critically ill subarachnoid hemorrhage patients

INTRODUCTION:

Alterations from first-party and surrogate decision-maker consent can enhance the feasibility of research involving critically ill patients.

OBJECTIVE:

To describe the use of a deferred-consent model to enable participation of critically ill patients in a minimal-risk biomarker study.

METHODS:

A prospective observational study was conducted in which serum biomarker samples were collected three times daily over the first 14 days following aneurysmal subarachnoid hemorrhage. Sample collection was initiated on intensive care unit admission and consent was obtained when research personnel could approach the patient or the patient’s surrogate decision maker.

RESULTS:

Twenty-seven patients were eligible for the study, of whom only five were capable of providing informed consent. Full consent was obtained for 21 (78%) patients through self- (n=4) and surrogate (n=17) consent. Partial consent or refusal (only permitting the collection of blood samples as a part of routine care or use of data) occurred in three patients. Among the 22 consents sought from surrogates, three (11%) refused participation. The refusals included the sickest patients in the cohort. Once consent was provided, no patient or surrogate withdrew consent before study completion.

DISCUSSION:

Use of a deferred consent model enabled participation of critically ill patients in a minimal-risk biomarker study with no withdrawals.

CONCLUSIONS:

Further research and enhanced awareness of the potential utility of hybrid models, including deferred consent in addition to patient or surrogate consent, in the conduct of low-risk and minimally interventional time-sensitive studies of critically ill patients are required.