Intravenous gammaglobulin treatment of chronic idiopathic thrombocytopenic purpura

High-dose intravenous gammaglobulin (IVIgG) was given to 12 children and adults with chronic idiopathic thrombocytopenic purpura (ITP) to avoid splenectomy or because they either failed to respond to or required maintenance with high doses of steroids and/or immunosuppressives. The average platelet count increase to initial therapy was 239,500/microliters (range 23,000-790,000). A concomitant IgG Fc receptor blockade, measured by IgG-sensitized 51Cr-labeled autologous erythrocytes, was seen in 11 of 11 patients tested, both splenectomized and not splenectomized, lasting 3-4 wk. Six or more months after treatment, 2 children are in remission, 2 children and 2 adults are stable requiring no therapy with platelet counts of approximately 50,000 and 30,000, respectively, 3 children require maintenance IVIgG therapy at 2-10-wk intervals, and 1 child and 2 adults have become refractory to further IVIgG. Splenectomy was not performed in 4 children. Two adults were able to discontinue daily prednisone. The 3 patients who became unresponsive to Swiss Red Cross gamma-globulin (IgSRK) therapy did so in conjunction with a markedly elevated platelet-associated IgG and IgM. Serum IgM increased an average of 103 mg/dl after the IVIgG infusions. No significant side effects were seen.     

The guanylate kinase domain of the beta-subunit of voltage-gated calcium channels suffices to modulate gating

Inactivation of voltage-gated calcium channels is crucial for the spatiotemporal coordination of calcium signals and prevention of toxic calcium buildup. Only one member of the highly conserved family of calcium channel β-subunits—Ca_Vβ—inhibits inactivation. This unique property has been attributed to short variable regions of the protein; however, here we report that this inhibition actually is conferred by a conserved guanylate kinase (GK) domain and, moreover, that this domain alone recapitulates Ca_Vβ-mediated modulation of channel activation. We expressed and refolded the GK domain of Ca_Vβ_2a, the unique variant that inhibits inactivation, and of Ca_Vβ_1b, an isoform that facilitates it. The refolded domains of both Ca_Vβ variants were found to inhibit inactivation of Ca_V2.3 channels expressed in Xenopus laevis oocytes. These findings suggest that the GK domain endows calcium channels with a brake restraining voltage-dependent inactivation, and thus facilitation of inactivation by full-length Ca_Vβ requires additional structural determinants to antagonize the GK effect. We found that Ca_Vβ can switch the inactivation phenotype conferred to Ca_V2.3 from slow to fast after posttranslational modifications during channel biogenesis. Our findings provide a framework within which to understand the modulation of inactivation and a new functional map of Ca_Vβ in which the GK domain regulates channel gating and the other conserved domain (Src homology 3) may couple calcium channels to other signaling pathways.     

T-cell death by apoptosis in vertically human immunodeficiency virus- infected children coincides with expansion of CD8+/interleukin-2 receptor-/HLA-DR+ T cells: sign of a possible role for herpes viruses as cofactors?

One mechanism proposed to play a role in T-cell depletion in human immunodeficiency virus (HIV) infection is apoptosis (activation-induced cell death). We assessed whether apoptosis is related to activation of T cells in vivo and its possible triggers. DNA was extracted from peripheral blood mononuclear cells (PBMC) taken from 16 vertically HIV- infected children and 9 HIV-negative children born to HIV-positive mothers (controls) and tested by agarose gel electrophoresis for the presence of DNA fragments specific for apoptosis. Signs of apoptosis were found on in vitro culture of PBMC from 12 of 16 HIV-infected children, but not in PBMC from the nine controls. Eleven of the 12 HIV- infected children with apoptosis showed an elevated (> 15%) proportion of CD3+/HLA-DR+ cells. This was due to an increased proportion of CD8+/HLA-DR+ cells, as shown in 7 of 7 further tested patients. In none of the probands an increased (> 5%) proportion of IL-2 receptor expressing CD3+ cells was found. T cells undergoing apoptosis were preferentially of the CD8+ phenotype. Expansion of circulating CD8+/interleukin-2 receptor (IL-2R)-/HLA-DR+ T cells is known to occur during active infection with herpes viruses. To investigate the possible role of herpes viral coinfections for apoptosis in HIV infection, we focused on Epstein-Barr virus (EBV) as an example for a herpes virus usually acquired during childhood. In 10 of 12 patients with apoptosis, we found increased levels of EBV genome in PBMC and/or tissues, indicating active EBV replication. By contrast, no increased burden of EBV was found in the four HIV-infected patients without apoptosis or in the controls. Our data indicate that in children the occurrence of apoptosis in HIV infection is closely related to activation of CD8+ T cells. Furthermore, primoinfection with or reactivation of herpes viruses, such as EBV, may substantially contribute to such T-cell activation and the ensuing apoptosis. Additional studies are warranted to evaluate the contribution of herpes virus-triggered apoptosis to the T-cell loss leading to the acquired immunodeficiency syndrome.     

Marrow transplantation with or without donor buffy coat cells for 65 transfused aplastic anemia patients

Sixty-five multiply transfused patients with severe aplastic anemia were given cyclophosphamide followed by grafts anemia were given cyclophosphamide followed by grafts from HLA-identical siblings. The effect of the administration of viable donor buffy coat cells following the marrow inoculum was evaluated with regard to graft rejection and survival. Results in 43 patients so treated are presented along with those in 22 concurrent patients given marrow alone. Most patients given buffy coat had positive in vitro tests of sensitization indicating a high risk for graft rejection, while all but one of the patients given marrow alone had negative tests. Thirty of the 43 (70%) patients given marrow and buffy coat are alive between 10 and 61 mo (median 36) after grafting; 4 died after graft rejection and 6 with acute or chronic graft-versus-host disease (GVHD). Eleven of the 22 (50%) patients given marrow alone are alive between 29 and 65 mo (median 52); 7 died after graft rejection and 3 with GVHD. The addition of buffy coat cell infusions to the marrow inoculum reduced the risk of rejection and increased survival in the currently reported transfused patients when compared to patients grafted before 1976. However, there was an increased risk of chronic GVHD. Recipients of marrow from female donors survived slightly better (73%) than recipients of male marrow (58%).     

Chemokine stromal cell-derived factor-1alpha modulates VLA-4 integrin-dependent adhesion to fibronectin and VCAM-1 on bone marrow hematopoietic progenitor cells

Stromal cell-derived factor-1alpha (SDF-1alpha) is a potent chemoattractant for hematopoietic progenitor cells (HPC), suggesting that it could play an important role during their migration within or to the bone marrow (BM). The integrin VLA-4 mediates HPC adhesion to BM stroma by interacting with CS-1/fibronectin and VCAM-1. It is required during hematopoiesis and homing of HPC to the BM. As HPC migration in response to SDF-1alpha might require dynamic regulation of integrin function, we investigated if SDF-1alpha could modulate VLA-4 function on BM CD34(hi) cells.CD34(hi) BM cells and hematopoietic cell lines were tested for the effect of SDF-1alpha on VLA-4-dependent adhesion to CS-1/fibronectin and VCAM-1, as well as to BM stroma. CD34(hi) BM cells that adhered to VLA-4 ligands after SDF-1alpha treatment were characterized in colony-forming and long-term culture-initiating cell (LTC-IC) assays.SDF-1alpha rapidly (1 minute) and transiently upregulated the adhesion of CD34(hi) BM cells and hematopoietic cell lines to both CS-1/fibronectin and VCAM-1, and to BM stromal cells. The upregulation of VLA-4-dependent cell adhesion by SDF-1alpha targeted primitive LTC-IC as well as committed CD34(hi) cells. SDF-1alpha-triggered enhancement in VLA-4 function was inhibited by pertussis toxin (PTx) and cytochalasin D, indicating the involvement of G(i) protein downstream signaling and an intact cytoskeleton. Instead, activation of p44/42 MAP kinases by SDF-1alpha did not functionally correlate with enhancement of VLA-4-dependent cell adhesion.Modulation of VLA-4-mediated CD34(hi) BM cell adhesion by SDF-1alpha could play a key role in their migration within and to the BM and therefore influence their proliferation and differentiation.     

Peripheral arterial disease in HIV patients older than 50 years of age

Our objective was to analyze the prevalence of peripheral arterial disease (PAD) in HIV patients at risk and to compare them with the general population. All HIV patients older than 50 years who attended our unit from October 2005-July 2006 and all persons attending for an annual medical checkup at an employees' insurance association during the same period were invited to participate in the study. Of the latter (n = 407), a person of the same sex and age (+/-5 years) was included for each HIV patient. PAD was assessed by the ankle-brachial index (ABI) in all subjects, and all completed the Edinburgh questionnaire. Ninety-nine HIV patients and 99 persons from the general population of the same age and sex were included in the study. The HIV patients had a greater prevalence of dyslipidemia, diabetes, and PAD, which was symptomatic in five of them and in one subject from the general population. Patients with HIV infection older than 50 had a high prevalence of PAD, and as it was asymptomatic in half the cases, an ABI may be performed in this population to actively look for PAD. Control of cardiovascular risk factors and the use of such drugs as platelet antiaggregation agents should therefore be optimized in this population.     

Stress testing in patients one year after orthotopic cardiac transplantation

To evaluate the circulatory response of the denervated heart to exercise, the authors studied 15 patients with an orthotopic transplanted heart (TH). Mean age was 48 +/- 10 (range twenty-five to sixty-two) years. All patients underwent a symptom-limited bicycle stress testing following a continuous protocol increasing the work load by 30 watts every three minutes. Exercise test was performed 16 +/- 9 months after operation. Fifteen healthy subjects matched for age were used as the control group. There were significant differences (p less than 0.01) in heart rate, at rest, peak exercise, and at five minutes of the recovery period, in maximal oxygen consumption (VO2 max) and in duration of exercise between TH patients and controls. Synchronization between recipient and donor sinoatrial nodes was observed in 10 of 15 patients. A case of silent myocardial ischemia was also observed in a patient with vasculitis and acute rejection. In conclusion, the lack of neural control in TH patients allows them to maintain a normal resting cardiac output but precludes attaining a normal maximum oxygen uptake, despite a normal contractile state. The high resting heart rate due to parasympathetic denervation constitutes an important limiting factor for an adequate chronotropic reserve. Functional capacity of transplanted patients is slightly impaired, but it does not preclude a good quality of life.     

Denaturing interaction between sickle hemoglobin and phosphatidylserine liposomes

It is hypothesized that abnormal interaction between sickle hemoglobin (HbS) and erythrocyte membrane lipid might promote deposition of denatured hemoglobin (hemichrome) on the membrane. We compared the interaction of HbS and normal HbA with large unilamellar phosphatidylserine (PS) liposomes under low salt/pH conditions. Admixture of oxyHb and dioleoyl-PS resulted in loss of absorbance at 412 nm, the apparent first order rate constant for which was .25 +/- 0.02 hour-1 for HbA and .85 +/- 0.18 hour-1 for HbS. This was ascribable largely to formation of metHb and hemichromes and was accompanied by some actual transfer of heme from hemoglobin to lipid phase. By comparison, admixture of oxyHb with liposomes made from bovine brain PS having unsaturated acyl chains promoted even faster absorbance loss if the starting liposomal material contained detectable peroxidation by-product. In such cases, actual heme destruction developed with accompanying liberation of free iron and promotion of lipidperoxidation. Fluorescence quenching experiments indicate that hemoglobin/lipid interaction is characterized by very rapid initial electrostatic interaction, followed by development of irreversible changes. Similar changes still occur under conditions of physiologic salt/pH, but they develop much more slowly. The 3.4-fold faster oxidation of HbS versus HbA on lipid observed here represents an additional augmentation of the disparity in oxidation rates for hemoglobins in solution (1.7-fold faster for HbS than for HbA) observed previously. The accelerated promotion of Hb denaturation resulting from lipid contact may help explain deposits of hemichrome on sickle red blood cell membranes, particularly because these cells are in double jeopardy by virtue of having both the mutant HbS and abnormal amounts of peroxidized membrane lipid.