Leka, a New Platelet Antigen Absent in Glanzmann''s Thrombasthenia

The serum of a patient who developed a posttransfusion purpura contained antibodies directed against a previously undescribed platelet antigen Lek a. The antiplatelet activity was present in the IgG fraction and was detected by immunofluorescence, 51Cr lysis and 14C-serotonin release. The frequency of the Lek a phenotype in the French population is 98.18%. Lek a does not appear to be sex-linked and seems to be closely related to the Bak a antigen. The Lek a antigen is not expressed on thrombasthenic platelets but is found on platelets from patients with the Bernard-Soulier syndrome which suggests that this antigen is carried by platelet glycoproteins IIb and/or IIIa.     

Major thrombopenia induced by heparin. Practical approach to cardiac surgery under extracorporeal circulation

Major heparin-induced thrombocytopaenia (HIT) is a condition which is feared more for its thrombotic complications than for the risk of haemorrhage. The platelet count is part of routine surveillance of patients receiving this treatment which must be withdrawn if HIT occurs. The use of heparin remains essential for cardio-pulmonary bypass surgery. There are two possible scenarios: The thrombocytopaenia occurs in the postoperative period: the standard heparin may be relayed by oral anti-vitamin K anticoagulants, platelet antiaggregant drugs or by low molecular weight heparin (LMWH). The diagnosis of HIT is made before surgery: three therapeutic attitudes are discussed with respect to the urgency of surgery: surgery is deferred for 6 to 8 weeks to allow the platelet count to return to normal and the responsible circulating antibody to disappear; the use of LMWH providing the tests of platelet aggregation are negative with this product; in addition, there are other problems specific to their use in cardiopulmonary bypass to be considered; blood exchange at the beginning of cardiopulmonary bypass to eliminate the circulating factor responsible and so allow the use of standard heparin during and after the operation: this is the only possible solution in cases with in vitro aggregant activity of LMWH.     

Purtscher retinopathy in acute alcoholic pancreatitis. A case report

Purtscher retinopathy is a retinal vasculopathy most commonly caused by head or chest trauma. The most frequent signs include white ischemic infarcts (cotton-wool spots) and retinal hemorrhages (intraretinal, preretinal, or flame). The signs of ischemic vasculopathy predominate in the interpapillomacular zone. We report a case of a 31-year-old woman with sudden bilateral loss of vision caused by Purtscher retinopathy in acute alcoholic pancreatitis.     

Prolonged remission in Raynaud's phenomenon after prostacyclin infusion

We infused prostacyclin (PGI2) (7.5 ng/kg/min) during 5 h, three times at weekly intervals in 8 patients with Raynaud's phenomenon (RP). In 4 patients, improvement was long-term, more than 90 days after the last infusion (good responders); in 3 patients, improvement was mild, less than 15 days, and in one patient no improvement was observed (poor responders). Clinical response was always accompanied by improvement, although less prolonged, of capillary appearance and/or function, as judged by microscopy and/or hemodynamic tests (pulse volume index; radial artery blood flow). Lastly, increased catabolism of PGI2 seemed to be excluded in poor responders, since no statistical difference in PGI2 metabolism could be observed between the two groups.     

Amniotic fluid peptides predict postnatal kidney survival in developmental kidney disease

1. Download : Download high-res image (387KB)
2. Download : Download full-size image

     

A serologic study of red cells and sera from 18 Rh:32,-46 (RN/RN) persons

The red cells (RBCs) and sera from 18 RN/RN persons were studied. The study confirmed the Rh type D+C+E-c-e+Cw-, which is characterized by an increased expression of the D antigen; a markedly decreased expression of the C and e antigens; the presence of a low-incidence antigen, Rh32; and the absence of a high-incidence antigen, Rh46, which is associated with an epitope recognized by a murine monoclonal antibody (MR432). Other Rh antigens of low and high incidence were investigated, and the presence of Rh17 and Rh44 on the RBCs was confirmed. Three persons exposed to Rh:46 cells by pregnancy or transfusion (or both) had anti-Rh46. This antibody gave positive reactions with all RBCs of common and rare Rh phenotype except Rhnull, and those of D--, D.., DCw-, and RN homozygotes. This antibody is considered to be of clinical significance in case of transfusion or pregnancy.     

Hemorrhagic rectocolitis associated with idiopathic thrombopenic purpura

This case report documents severe autoimmune thrombocytopenia in a 20 yrs. old patient with ulcerative colitis. Diagnosis of idiopathic thrombocytopenic purpura was made on the presence of bound antiplatelet antibodies and on the absence of any other disorder capable of provoking a platelet fall. Colonic lesions were moderate but were resistant to steroids and total parenteral nutrition. Thrombocytopenia resisted to steroids and vincristine and a major fall in the platelet count (less than 10,000/mm3) occurred in two instances. However, platelets rose transiently after high-dose intravenous gamma-globulins. The patient underwent splenectomy, colectomy and ileostomy because of life-threatening colonic hemorrhage. The platelet count rose to normal levels within one week after surgery. Ileorectal anastomosis was subsequently performed. One year later the patient was in good health and his platelet count had returned to normal.     

Etiologic causes of ptosis about a serie of 484 cases. To a new classification?

We have analyzed the etiological causes of ptosis in a retrospective study of 484 cases undergoing operation. This study has confirmed how difficult it is to classify ptosis despite the different existing classifications. Some authors divide ptosis into two groups: congenital and acquired. These classifications seem to have been abandoned now for classifications based on the mechanism that instigates ptosis rather than the moment when the deficit developed. We chose to classify ptosis into five subgroups: myogenic (42% of the cases studied), aponeurotic (35.3%), neurogenic (6.8%), mixed (15.9%), and pseudoptosis (enophthalmos, eyelid tumor, hypotropia, etc.), the latter of which were removed from this series. This classification is based on clinical and surgical criteria. It has the advantages of unity, simplicity, and practicality in terms of establishing a treatment plan for a given ptosis patient. Indeed, each subgroup requires a particular clinical examination and a more stereotyped surgical treatment.     

Immunochemical characterization of the platelet-specific alloantigen Leka: a comparative study with the PlA1 alloantigen

We report the immunochemical characterization of a new platelet- specific alloantigen detected using an IgG antibody isolated from the serum of a patient with posttransfusion purpura (PTP). In indirect immunoprecipitation experiments, the antibody, termed anti-Leka, predominantly precipitated glycoprotein (GP) IIb from Triton X-100 lysates of normal human platelets. In an immunoblot procedure, which involved the transfer of platelet polypeptides separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to nitrocellulose membrane, anti-Leka bound exclusively to GP IIb. Under identical conditions, four anti-PlA1 antibodies each reacted with GP IIIa. No binding of anti-Leka IgG occurred to Leka (-) platelets or to their separated polypeptides although GP IIb was normally detected by Coomassie blue staining. After electrophoresis of reduced platelet proteins, the Leka determinant was localized to the IIb alpha chain. Thus, unlike the PlA1 antigen, the Leka determinant was not destroyed by disulfide reduction. Analysis of platelets from a patient with Glanzmann's thrombasthenia revealed little or no binding in the GP IIb position. Anti-Leka permitted the identification of 76,000 and 60,000 dalton fragments of GP IIb retained by the platelet following chymotrypsin treatment. Our results further highlight the immunogenicity of the GP IIb-IIIa complex. They also suggest that antibodies against GP IIb can cause the thrombocytopenia observed in PTP and that anti-PlA1 antibodies do not account exclusively for the pathophysiology of this immune disorder.