Showing papers by "Francesca Ricci published in 2003"

Autoimmune thrombocytopenia in malaria.

Abstract: In a recent study, about 30% of patients with malaria were found to have platelet counts of < 50 × 10 9 /l [1]. Some had variable numbers of pseudoaggregates, but many were actually affected by thrombocytopenia. Low platelet counts may be caused by peripheral destruction, but little is known about the basic mechanisms. Some data indicate autoimmune destruction of platelets in malaria [2,3], but nothing has been reported regarding the reactivity and specificity of any autoantibodies involved. We present the case of a 61-year-old Italian man, who had recently returned from Senegal, who presented at the Infectious Diseases Institute of S. Orsola-Malpighi Hospital, Bologna, Italy, with a diagnosis of malaria caused by infection with Plasmodium falciparum . Having cerebral malaria, he was urgently referred to our service for erythrocyte exchanges to reduce the level of parasitaemia. A very low platelet count was found (9 × 10 9 /l) before erythrocyte exchange was carried out. Any extraneous cause of thrombocytopenia, such as the presence of pseudoaggregates, was excluded. The patient had no previous history of haemorrhagic and/or thrombocytopenic disorders. Moreover, routine blood counts, carried out about 6 months before the malaria episode, had shown a normal platelet count (246 × 10 9 /l). To investigate a possible immune origin of the thrombocytopenia, we performed direct and indirect flow cytometry on the patient’s platelets and serum. This revealed plateletassociated immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies. Furthermore, the patient’s serum, in the monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay [4], reacted with glycoprotein (gp) IIb–IIIa (CD41) and gp Ia–IIa (CD49b). With a modified MAIPA assay for autoantibodies, autologous platelets were positive for antibodies against gp IIb–IIIa and gp Ia–IIa. When matched with the patient’s serum, platelets from human platelet antigen (HPA-1a/a (IIIa), HPA-1b/b (IIIa), HPA-5a/a (gp Ia–IIa) and HPA-5b/b (gp Ia–IIa)) donors were all found to be positive, both by immunofluorescence and MAIPA assays, thus excluding alloimmunization. The donors of our panel were all positive for HPA-3a (IIb) and HPA-4a (IIIa). Within 1 week after two erythrocyte exchanges and high-dose chloroquine therapy, the patient had recovered neurologically, and the platelet count reached 257 × 10 9 /l. As the rescue of platelets took place during chloroquine-based treatment, and the patient’s serum, after recovery, was negative when tested against autologous and donor platelets in the presence of chloroquine, we excluded a chloroquinemediated immune thrombocytopenia. Our hypothesis is that autoantibodies against platelet glycoproteins IIb–IIIa and Ia–IIa might be present during malaria and could lead to severe thrombocytopenia. Further studies are needed to confirm our results and to evaluate the true impact of autoimmune thrombocytopenia in patients with malaria. In our opinion, all malaria patients with severe thrombocytopenia (< 50 × 10 9 /l platelets) should be investigated for platelet autoantibodies. The results might be important in monitoring the disease course.

Flow cytometry characterization of white cell-reduced blood: apoptosis markers and morphology of postfiltration elements.

Abstract: Background and Objectives Apoptosis affects white blood cells (WBCs) contained in packed red blood cell (RBC) units. This phenomenon was recently described also in residual WBCs after filtration. The aim of this study was to better characterize the residual WBCs postfiltration by using apoptosis markers and morphology. Materials and Methods Immunofluorescence, flow cytometry and cell-sorting techniques were utilized. Results Residual leucocytes of leucodepleted packed RBC units showed increasing values of apoptotic elements in a time-course experiment. We also demonstrated that these elements are positive for APO 2·7 monoclonal antibody (mAb), poly ADP-ribose polymerase (PARP) cleavage and fluorescein isothiocyanate (FITC)-conjugated N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK), all of which indicate that programmed death is a feature of this population of cells. Phenotypic analysis with CD45 side-scatter gating demonstrated also that CD15 and CD16 granulocyte-associated antigens are present on a subset of postfiltration leucocytes. Moreover, the expression of human leucocyte antigen (HLA) class I antigens is maintained. Sorting of CD45-positive cells and morphological analysis of these samples confirmed that leucocytes in postfiltration units have morphological characteristics of dying cells. Conclusions Our study extends previous observations regarding the morphology and function of apoptotic cells in leucodepleted blood units, which suggested the presence of apoptotic cells in postfiltration leucocytes. Cleaved PARP, APO 2·7 mAb and positivity for the FITC-conjugated Z-VAD-analogous reagent strongly suggest the activation of programmed death pathways. In addition, the maintained granulocyte-associated and HLA class I antigens might recall an immune response in multitransfused patients.