Therapeutic cytokine stimulation of thrombocytopoiesis

IVIg increases interleukin-11 levels, which in turn contribute to increased platelets, VWF and FVIII in mice and humans

The mechanisms of action of intravenous immunoglobulins (IVIg) in autoimmune diseases are not fully understood. The fixed duration of efficacy and noncumulative effects of IVIg in immune thrombocytopenia (ITP) and acquired von Willebrand disease (AVWD) suggest other mechanisms besides immunological ones. Additionally to the peripheral destruction of platelets in ITP, their medullary hypoproduction emerged as a new paradigm with rescue of thrombopoietin receptor agonists (TPO-RA). In an ITP mouse model, interleukin (IL)-11 blood levels increase following IVIg. IL-11 stimulates the production of platelets and other haemostasis factors; recombinant IL-11 (rIL-11) is thus used as a growth factor in post-chemotherapy thrombocytopenia. We therefore hypothesized that IVIg induces IL-11 over-production, which increases platelets, VWF and factor VIII (FVIII) levels in humans and mice. First, in an ITP mouse model, we show that IVIg or rIL-11 induces a rapid increase (72 h) in platelets, FVIII and VWF levels, whereas anti-IL-11 antibody greatly decreased this effect. Secondly, we quantify for the first time in patients with ITP, AVWD, inflammatory myopathies or Guillain-Barré syndrome the dramatic IL-11 increase following IVIg, regardless of the disease. As observed in mice, platelets, VWF and FVIII levels increased following IVIg. The late evolution (4 weeks) of post-IVIg IL-11 levels overlapped with those of VWF and platelets. These data may explain thrombotic events following IVIg and open perspectives to monitor post-IVIg IL-11/thrombopoietin ratios, and to assess rIL-11 use with or without TPO-RA as megakaryopoiesis co-stimulating factors to overcome the relative hypoproduction of platelets or VWF in corresponding autoimmune diseases, besides immunosuppressant.

Platelet function in term and preterm neonates

Platelet dysfunction likely contributes to the pathophysiology of catastrophic hemorrhages in preterm neonates. In vitro studies have demonstrated that platelets of both term and preterm neonates are hyporesponsive to a variety of agonists. In contrast,template bleeding times of term neonates are shorter than those from adults. Very little is known about this and other tests of primary hemostasis in premature and sick neonates in the neonatal intensive care unit (NICU). This article covers the current knowledge of platelet function in preterm and term neonates and review show new agents (such as recombinant thrombopoietin and recombinant factor VIIa) may enhance neonatal platelet function.

Serum cytokine profiles in patients with Plasmodium vivax malaria: a comparison between those who presented with and without thrombocytopenia

One of the peculiar features of Plasmodium vivax malaria in South Korea is the surprisingly high frequency of thrombocytopenia. The mechanism by which this malaria-related thrombocytopenia develops and its role in the pathology and progress of human infection with P. vivax have not yet been completely understood. In the present study, the serum cytokine profiles of cases of P. vivax malaria who presented with thrombocytopenia were compared with those of similar cases who did not have thrombocytopenia at presentation. The subjects were the 94 consecutive cases of P. vivax malaria who presented at five hospitals in South Korea (all near the Demilitarized Zone) between May 2000 and October 2002, 47 of whom had thrombocytopenia at presentation. When mean values and (S.E.) were compared, the thrombocytopenic patients were found not only to be generally older than the non-thrombocytopenic [25.3 (1.1) v. 21.3 (0.18) years; P < 0.001] but also to have presented with higher serum concentrations of aspartate aminotransferase [77.6 (16.6) v. 32.3 (7.4) U/litre; P < 0.0001], alanine aminotransferase [96.7 (19.0) v. 44.7 (12.0) U/litre; P = 0.0001], interleukin-1 [49.9 (7.4) v. 23.7 (5.1) pg/ml; P < 0.001], interleukin-6 [174.9 (26.4) v. 57.3 (14.6) pg/ml; P = 0.001], interleukin-10 [308.2 (39.6) v. 137.9 (23.1) pg/ml; P < 0.002] and transforming growth factor-beta [1134.3 (387.5) v. 416.6 (183.8) pg/ml; P < 0.0001], and higher levels of parasitaemia [4345.7 (966.6) v. 1443.8 (222.7) parasites/microl; P = 0.03). The non-thrombocytopenic patients, however, had relatively high total leucocyte counts [5.8 (0.24) v. 5.4 (0.66) leucocytes/nl; P = 0.03]. The thrombocytopenia associated with P. vivax malaria in South Korea therefore appears to be associated with elevated serum concentrations of both pro- and anti-inflammatory cytokines. To define the role of each cytokine in the development of thrombocytopenia during the course of acute P. vivax malaria, further prospective studies are needed.

Role of IL-10 for induction of anemia during inflammation

Anemia is frequently observed in patients suffering from chronic inflammatory disorders. Recent in vitro data suggest that Th2 cytokines, such as IL-10, could be involved in its pathogenesis. We analyzed 1) changes in hemoglobin values in 329 patients with chronic active Crohn's disease receiving the anti-inflammatory cytokine IL-10 as part of a randomized, double-blind, placebo-controlled study, 2) serum iron parameters in a subgroup of these patients (n = 54), and 3) the in vitro effects of IL-10 on ferritin transcription and translation in human monocytic cells (THP-1) by means of Northern blot and immunoprecipitation after metabolic labeling. Patients receiving higher doses of IL-10 developed anemia and presented with a dose-dependent increase of ferritin and soluble transferrin receptor levels, an indicator of iron restriction to erythroid progenitor cells. According to our in vitro data, hyperferritinemia may result from direct stimulation of ferritin translation by IL-10 in activated monocytic cells, most likely by cytokine-mediated reduction of the binding affinity of translational repressors, iron-regulatory proteins, to the 5'-untranslated region of ferritin mRNA. In patients, all observed changes were most pronounced at the end of therapy (day +29), and thereafter hemoglobin levels and serum iron parameters returned to baseline levels within 4 wk of follow-up. Our data demonstrate that IL-10 causes anemia in patients with inflammatory bowel disease which may be referred to the induction of imbalances in iron homeostasis by the cytokine, leading to hyperferritinemia and limited iron availability to erythroid progenitor cells, a condition typically seen in the anemia of chronic inflammation.