The contribution of the haematocrit to thrombocytopenic bleeding in experimental animals

Clinical studies in anaemic uraemic patients have shown that increasing the haematocrit with either red blood cell (RBC) transfusions or erythropoietin corrects the prolonged bleeding time (BT) often seen in such individuals. In this present study we evaluated experimentally the effect of the haematocrit on the BT using a microvascular BT technique in New Zealand White rabbits. The correlation between haematocrit and BT was studied in both normal and thrombocytopenic rabbits. In non-thrombocytopenic animals the microvascular BT varied inversely with the haematocrit (r = -0.799); animals with haematocrit levels above 35% having significantly shorter BTs than animals with haematocrit values lower than 35% (P < 0.001). To assess the role of the haematocrit on the BT in thrombocytopenic animals, thrombocytopenia was induced by a combination of gamma-irradiation and heterologous platelet antiserum. Such experiments showed that anaemic rabbits had significantly longer BTs than non-anaemic animals with a similar degree of thrombocytopenia (P = 0.0001). These data thus provide evidence that anaemia contributes significantly to the prolonged BT in both thrombocytopenic and non-thrombocytopenic rabbits, and that RBC transfusions are capable of shortening the BT in thrombocytopenic anaemic animals. While results obtained from animal models cannot necessarily be extrapolated to the clinical situation, the fact that haematocrit influences the BT must be taken into account in the assessment of anaemic patients, particularly those who may have an associated haemostatic disorder.

Selectivity of human T lymphotropic virus type-1 (HTLV-1) and HTLV-2 infection among different populations in Brazil

A seroprevalence study for human T lymphotropic virus type-1 (HTLV-1) and HTLV-2 was conducted in Sao Paulo, Brazil among 2,312 individuals that included following groups: 1,148 volunteer blood donors, 37 patients with tropical spastic paraparesis (TSP), 53 with lymphoproliferative disorders, 171 with a history of multiple blood transfusions, 268 human immunodeficiency virus type-1 (HIV-1) seropositive subjects, and 635 Amazonian Indians. Antibodies to HTLV-1/2 were screened by enzyme-linked immunosorbent assay (ELISA) and confirmed by Western blot and/or radioimmunoprecipitation. The differentiation of HTLV-1 and HTLV-2 was achieved using a synthetic recombinant peptide (rgp46) ELISA. We confirmed the presence of HTLV-1 infection in Brazil, both in blood donors (0.4%) and in patients exposed to blood transfusions (2.9%), as well as the occurrence of HTLV-1-associated TSP (11 patients, or 30% of all TSP cases) and adult T cell leukemia/lymphoma (two cases, or 3.5% of all hematologic malignancies). The HIV-1 infected individuals were shown to be coinfected (8.9%) with either HTLV-1 or HTLV-2. All HIV-1 and HTLV-2 coinfected individuals were intravenous drug abusers. In addition, we also demonstrated the presence of HTLV-2 (4.7%), and HTLV-1/2 (0.8%) in tribes of Amazonian Indians who lived in the eastern Amazon basin (southeastern State of Para). The selectivity of these retroviral infections in particular groups is emphasized, as well as the need for HTLV-1/2 screening of all blood donors in Brazil as a public health measure.

Experimental animal model of refractoriness to donor platelets: the effect of plasma removal and the extent of white cell reduction on allogeneic alloimmunization

Platelet transfusion effectiveness may be limited in multiply transfused patients by the development of the refractory state. White cell (WBC)-reduction filters with variable efficiency (1-3 log10 reduction) are available and have been shown to be effective in reducing the incidence of platelet alloimmunization. However, the threshold number of WBCs below which alloimmunization would no longer occur is yet to be determined. A previously established animal model was used to examine the relative efficiency of second- and third-generation filters in reducing the frequency of refractoriness to allogeneic platelets. In this model, California Black rabbits are used as blood donors and New Zealand White rabbits as transfusion recipients. Eight weekly transfusions of either second-generation or third-generation WBC-reduced blood resulted in no difference between the two groups in mean platelet survival and rate of refractoriness to allogeneic platelets. To evaluate the possible incremental benefit of removing supernatant plasma to prevent platelet refractoriness, experiments were performed in which groups of animals were given transfusion(s) with red cell suspensions that had been WBC-reduced or both plasma-depleted and WBC-reduced. A significantly lower rate of allogeneic platelet refractoriness was seen in the rabbits that received WBC-reduced and plasma-depleted red cells than in those that received red cells that had been WBC-reduced only. These data provide evidence that the combined use of plasma depletion and WBC reduction can decrease still further the frequency of refractoriness produced by allogeneic blood transfusions.

Quantitation of red cell-bound IgG by an enzyme-linked antiglobulin test in human immunodeficiency virus-infected persons

Anemia, thrombocytopenia, and neutropenia have been observed in patients with acquired immune deficiency syndrome (AIDS) and AIDS-related complex. To investigate whether red cells (RBCs) of patients with human immunodeficiency virus infection were coated with IgG and/or complement (C3), blood samples of 239 patients were tested. The prevalence of a positive direct antiglobulin test on RBCs was 16.7 percent. By use of an enzyme-linked antiglobulin test (ELAT) to measure more accurately the number of IgG molecules per RBC in a group of 67 patients, 30 of the 67 individuals were observed to have increased numbers (mean, 155) compared to normal controls and to patients with hypergammaglobulinemia due to multiple myeloma or chronic liver disease. Hemoglobin level was correlated with the number of IgG molecules per RBC (p = 0.008), but no correlation could be demonstrated between those numbers and serum immunoglobulin (p = 0.10) or circulating immune complexes (p = 0.38). Our results with ELAT suggest that some AIDS patients may have specific binding of IgG on the surface of their RBCs, rather than nonspecific uptake; further clinical correlations are necessary to confirm these findings.

[ABO incompatibility in organ transplant. Report of case and review of the literature]

One case of a multiple organs donor that resulted in kidney and heart transplants with inadvertent ABO incompatibility is described. The renal recipients showed the presence of high anti A antibodies titers. The reviewed publications have revealed that the preparation of the receptor with plasmapheresis and splenectomy, before the transplantation may prevent the hyperacute rejection on ABO incompatible organs allografts. In emergency situations, liver transplantation is accepted with ABO incompatible donor without previous treatment.