Evaluation of atypical human immunodeficiency virus immunoblot reactivity in blood donors

Blood donors reactive by enzyme-linked immunosorbent assay for antibody to the human immunodeficiency virus (HIV) who showed atypical patterns of viral core protein reactivity on Western blot were monitored for several months. Characterization of their antibodies was performed by 1) use of recombinant HIV proteins; 2) determination of cross-reactivity to HTLV-I, HTLV-II, and HTLV-IV: 3) assessment of immune status; and 4) identification of potentially interfering autoantibodies. Nineteen of 20 donors maintained the same HIV antibody reactivity throughout the follow-up period; the other donor became fully antibody-positive. Eighteen of 20 donors' sera showed clear reactivity with HIV recombinant core proteins. Ten of 19 donor samples demonstrated cross-reactivity to HTLV-IV; 3 of these 10 also cross-reacted with HTLV-I. The immune status of all donors was normal, although the medical histories and HLA antibody screens suggested possible autoimmune reactivity in 9 of 18 donors. During follow-up interviews, three donors reported possible risk factors for HIV infection that had not been acknowledged at the time of blood donation. We conclude that exclusion of donors with these atypical serologic test results is warranted while further studies to determine significance are being conducted.     

Inhibition of a thrombin anion-binding exosite-2 mutant by the glycosaminoglycan-dependent serpins protein C inhibitor and heparin cofactor II

Antithrombin (ATIII), heparin cofactor II (HCII) and protein C inhibitor (PCI; also named plasminogen activator inhibitor-3) are serine protease inhibitors (serpins) whose thrombin inhibition activity is accelerated in the presence of glycosaminoglycans. We compared the inhibition properties of PCI and HCII to ATIII using R93A/R97A/R101A thrombin, an anion-binding exosite-2 (exosite-2) mutant that has greatly reduced heparin-binding properties. Heparin-enhanced PCI inhibition of R93A/R97A/R101A thrombin was only approximately 2-fold compared to 40-fold enhancement with wild-type recombinant thrombin. Thrombomodulin (TM) (with or without the chondroitin sulfate moiety) accelerated PCI inhibition of both wild-type and R93A/R97A/R101A thrombins. HCII achieved the same maximum activity in the presence of heparin with both wild-type and R93A/R97A/R101A thrombins; however, the optimum heparin concentration was 20 times greater than the reaction with wild-type thrombin, indicative of a decrease in heparin affinity. Dermatan sulfate (DSO4)-catalyzed HCII thrombin inhibition was unchanged in R93A/R97A/R101A thrombin compared to wild-type recombinant thrombin. These results suggest that PCI is similar to ATIII and depends upon ternary complex formation with heparin and these specific thrombin exosite-2 residues to accelerate thrombin inhibition. In contrast, HCII does not require Arg(93), Arg(97) and Arg(101) of thrombin exosite-2 and further supports the hypothesis that HCII uses an allosteric process following glycosaminoglycan binding to inhibit thrombin.     

Thymic cysts in mediastinal Hodgkin disease

Three cases of proved thymic cysts associated with mediastinal Hodgkin disease are presented. Two illustrate regression of lymphoma with chemotherapy but persistence of thymic cysts. The third case demonstrates a thymic cyst in untreated Hodgkin disease. These cases suggest that such cysts are probably neither coincidental with nor a consequence of therapy but are probably related to initial thymic involvement by Hodgkin disease.     

The impact of the inflammatory response on coagulation

Inflammation contributions to the thrombotic response involve both cellular and humoral modulation. Inflammation impacts the initiation, propagation and the inhibitory phases of blood coagulation. Inflammatory mediators like endotoxin and tumor necrosis factor alpha (TNF alpha) elicit the expression of tissue factor on blood cells. Under normal circumstance, negatively charged membrane surfaces are limiting so that, even if some activated coagulation factors are generated, propagation of the coagulant stimulus is minimal. Complement activation, however, or exposure of collagen in combination with thrombin, provides a potent stimulus eliciting the exposure of negatively charged phospholipid membrane surfaces. Natural anticoagulant mechanisms limit the thrombotic response, but these pathways are depressed by inflammatory mediators. The protein C pathway is one of the major targets. Thrombomodulin and the endothelial cell protein C receptor are both required for optimal protein C activation, but both are down regulated by inflammatory mediators. Furthermore, free protein S levels often decrease resulting in impaired anticoagulant function of the activated protein C that is generated. In addition, anti-phospholipid antibodies severely impair the protein C pathway further inhibiting this pathway in inflammatory states associated with auto-immunity. In addition to shifting the hemostatic system in favor of clot formation, inflammation elevates the levels of plasminogen activator inhibitor thereby decreasing fibrinolytic activity. The procoagulant impact of inflammation can also be seen at the cellular level. Inflammatory mediators like interleukin 6 can increase both platelet count and their responsiveness to agonists like thrombin. All of these events tend to shift the hemostatic balance in favor of clot formation.     

Hospitalization of children with acute immune thrombocytopenic purpura – is it necessary?

OBJECTIVE:

To identify a target group of children with acute immune thrombocytopenic purpura (ITP) that may not require hospitalization for management.

METHODS:

A retrospective chart review was conducted of all children admitted over a two-year period to a tertiary care paediatric hospital with the diagnosis of acute ITP. Patients were classified according to typical and atypical presentations. Typical patients were defined as those aged between one and 10 years, with no hepatomegaly or significant splenomegaly and who had typical laboratory features for ITP. Patients who did not meet these criteria were categorized as atypical. Outcome measures included length of stay (LOS) in hospital; frequency of bone marrow aspiration (BMA); type of treatment; incidence of intracranial hemorrhage (ICH) or severe bleeding; and admission and discharge platelet counts.

RESULTS:

There were 74 patients hospitalized for a mean of 3.6 days. No patients suffered an ICH or bleeding requiring transfusion. Patients with typical presentations (42) were compared with patients with atypical presentations (32) and were not significantly different for clinically important outcomes such as admission and discharge platelet counts, serious complications or type of therapy. Typical patients had significantly fewer BMAs than did atypical patients – 22 of 42 (52%) versus 25 of 32 (78%) (P=0.02), and a shorter LOS – 3.1 (±0.9) days versus 4.2 (±1.8) days (P=0.01).

CONCLUSIONS:

Children presenting with ITP have a low incidence of bleeding complications and many of these patients can be managed as outpatients. A multicentre study is needed to properly delineate a low risk group suited for outpatient medical management.     

Bench-to-bedside review: functional relationships between coagulation and the innate immune response and their respective roles in the pathogenesis of sepsis

The innate immune response system is designed to alert the host rapidly to the presence of an invasive microbial pathogen that has breached the integument of multicellular eukaryotic organisms. Microbial invasion poses an immediate threat to survival, and a vigorous defense response ensues in an effort to clear the pathogen from the internal milieu of the host. The innate immune system is able to eradicate many microbial pathogens directly, or innate immunity may indirectly facilitate the removal of pathogens by activation of specific elements of the adaptive immune response (cell-mediated and humoral immunity by T cells and B cells). The coagulation system has traditionally been viewed as an entirely separate system that has arisen to prevent or limit loss of blood volume and blood components following mechanical injury to the circulatory system. It is becoming increasingly clear that coagulation and innate immunity have coevolved from a common ancestral substrate early in eukaryotic development, and that these systems continue to function as a highly integrated unit for survival defense following tissue injury. The mechanisms by which these highly complex and coregulated defense strategies are linked together are the focus of the present review.     

Calorie restriction in nonhuman primates: mechanisms of reduced morbidity and mortality

Long term chronic calorie restriction (CR) of adult nonhuman primates significantly reduces morbidity and increases median age of death. The present review is focused upon an ongoing study of sustained adult- onset calorie restriction, which has been underway for 15 years. Monkeys, initially calorie restricted at about 10 years of age, are now approximately 25 years old. The median life span of these restricted monkeys is increasing, now exceeding that of ad libitum (AL)-fed monkeys. In our laboratory, maximum life span for AL-fed monkeys appears to be about 40 years. Thus, whether CR can also increase maximal life span, as it does in rodents, cannot be determined for at least another 15 years. The earliest detectable positive benefit on morbidity in these monkeys was previously reported as the prevention of obesity. Current evidence, as reviewed here, suggests that much obesity- associated morbidity is also mitigated by sustained calorie restraint in nonhuman primates. Furthermore, probably because of the prevention of obesity, diabetes has also been prevented. Recent findings include the identification of extraordinary changes in the glycogen synthesis pathway, and on the phosphorylation of glycogen synthase in response to insulin. This calorie restriction-induced prevention of morbidity does not require excessive leanness, but is clearly present when body fat is within the normal range of 10 to 22%, and this is likely to be true in humans as well.      

Noncardiogenic pulmonary edema caused by decompression sickness: rapid resolution following hyperbaric therapy

Noncardiogenic pulmonary edema is a recognized but uncommon manifestation of type 2 decompression sickness. It typically occurs within 6 hours of a dive. Because the adult respiratory distress syndrome in this setting is believed to be due to microbubbles in the pulmonary vasculature, recompression in a hyperbaric chamber has been recommended as a form of therapy. A patient developed noncardiogenic pulmonary edema following a seawater dive to 75 feet. There was complete radiologic and clinical resolution within 5 hours of hyperbaric therapy.