Hematogones: a multiparameter analysis of bone marrow precursor cells

Morphologically distinct lymphoid cells with homogeneous, condensed chromatin and scant cytoplasm can be observed in large numbers in the bone marrow of children with a variety of hematologic and nonhematologic disorders. In some patients, these cells may account for greater than 50% of the bone marrow cells, creating a picture that can be confused with acute lymphoblastic leukemia (ALL) or metastatic tumor. Although originally called hematogones (HGs), a variety of other names have been proposed for these unique cells. The clinical significance of expanded HGs has not been resolved, and the biologic features of these cells are incompletely described. In this study, we correlate the clinical, morphologic, cytochemical, flow cytometric, molecular, and cytogenetic properties of bone marrow samples from 12 children with substantial numbers of HGs (range 8% to 55% of bone marrow cells). Diagnoses in these patients included anemia, four; neutropenia, one; anemia and neutropenia, one; idiopathic thrombocytopenic purpura, two; retinoblastoma, two; Ewing's sarcoma, one; and germ cell tumor, one. Flow cytometric analyses of bone marrow cells demonstrated a spectrum extending from early B-cell precursors (CD10+, CD19+, TdT+, HLA-Dr+) to mature surface immunoglobulin-bearing B cells in these patients, corroborating our morphologic impression of HGs, intermediate forms, and mature lymphocytes. DNA content was normal, and no clonal abnormality was identified by either cytogenetic or immunoglobulin and T-cell receptor (TCR) gene rearrangement studies. Follow-up ranged from 3 months to 3 years. None of the patients has developed acute leukemia or bone marrow involvement by solid tumor. The possible role of HGs in immune recovery and hematopoiesis is presented.     

Proteolytic inactivation of human factor VIII procoagulant protein by activated human protein C and its analogy with factor V

Purified human factor VIII procoagulant protein (VIII:C) was treated with purified human activated protein C (APC) and the loss of VIII:C activity correlated with proteolysis of the VIII:C polypeptides. APC proteolyzed all VIII:C polypeptides with mol wt = 92,000 or greater, but not the doublet at mol wt = 79-80,000. These results and our previous thrombin activation studies of purified VIII:C, are analogous with similar studies of factor V and form the basis for the following hypothesis: activated VIII:C consists of heavy and light chain polypeptides [mol wt = 92,000 and mol wt = 79-80,000 (or 71-72,000), respectively] which are similar in Mr to the heavy and light chains of activated factor V. Thrombin activates VIII:C and V by generating these polypeptide chains from larger precursors and APC inactivates both molecules by cleavage at a site located in the heavy chain region of activated VIII:C and V.     

Peripheral Plasma Cells Associated with Mortality Benefit in Severe COVID-19: A Marker of Disease Resolution

BackgroundCytokines seen in severe coronavirus disease 2019 (COVID-19) are associated with proliferation, differentiation, and survival of plasma cells. Plasma cells are not routinely found in peripheral blood, though may produce virus-neutralizing antibodies in COVID-19 later in the course of an infection.MethodsUsing the Johns Hopkins COVID-19 Precision Medicine Analytics Platform Registry, we identified hospitalized adult patients with confirmed severe acute respiratory coronavirus 2 (SARS-CoV-2) infection and stratified by presence of plasma cells and World Health Organization (WHO) disease severity. To identify plasma cells, we employed a sensitive flow cytometric screening method for highly fluorescent lymphocytes and confirmed these microscopically. Cox regression models were used to evaluate time to death and time to clinical improvement by the presence of plasma cells in patients with severe disease.ResultsOf 2301 hospitalized patients with confirmed infection, 371 had plasma cells identified. Patients with plasma cells were more likely to have severe disease, though 86.6% developed plasma cells after onset of severe disease. In patients with severe disease, after adjusting for age, sex, body mass index, race, and other covariates associated with disease severity, patients with plasma cells had a reduced hazard of death (adjusted hazard ratio: 0.57; 95% confidence interval: 0.38-0.87; P value: .008). There was no significant association with the presence of plasma cells and time to clinical improvement.ConclusionsPatients with severe disease who have detectable plasma cells in the peripheral blood have improved mortality despite adjusting for known covariates associated with disease severity in COVID-19. Further investigation is warranted to understand the role of plasma cells in the immune response to COVID-19.     

Further characterization of platelet-type von Willebrand's disease in Japan

We studied four patients who showed aggregation of platelets in platelet-rich plasma at lower concentrations of ristocetin than those required for normal platelet-rich plasma and who demonstrated an increased capacity of the platelets to bind normal von Willebrand factor. The four patients were from two Japanese families. Platelets from one family aggregated spontaneously in vitro, and platelets from both families aggregated upon the addition of normal plasma and cryoprecipitate, in the absence of ristocetin or other agonists. Analysis of the multimeric composition of von Willebrand factor by sodium dodecyl sulfate-agarose gel electrophoresis revealed a decrease in large multimers or a decrease in both large and intermediate multimers in plasma, but normal multimers in platelets. 1-Deamino-[8-D- arginine]-vasopressin caused by an immediate appearance of larger multimers in plasma, followed by the rapid disappearance of these multimers from circulating plasma. Analysis of platelet membrane glycoproteins from the patients showed that there were two distinct bands in the glycoprotein I region; one migrated in a slower region and the other in a faster region than normal glycoprotein Ib. We suggest that the platelet receptor abnormality in these patients is related to this abnormality of glycoprotein Ib.     

Elevated Platelet-Associated IgG in PIA1-Negative Mothers following Sensitization to the PIA1 Antigen during Pregnancy

Between 1984 and 1990, we studied 25 infants with neonatal alloimmune thrombocytopenia caused by alloimmunization to the PlA1 alloantigen. We investigated whether mothers of these infants developed elevated platelet-associated immunoglobulin (PAIgG) in addition to anti-PlA1. Eight of the women were found to have PAIgG which persistent at least 7-10 days postdelivery. Eluates prepared from six of the women's platelets reacted with PlA1-positive and PlA1-negative donor platelets, and platelets from donors with Glanzmann's thrombasthenia. None of the women with elevated PAIgG had thrombocytopenia, eclampsia, or infections. Two women were found to have autoreactive antibodies present in plasma. These results indicate that elevated PAIgG may be found in women immunized to the PlA1 antigen. Some women may also have autoreactive antiplatelet antibodies in their plasma. These findings may lead to confusing serologic findings in evaluating the cause of neonatal alloimmune thrombocytopenia.     

A radiolabeled antiglobulin test for crossmatching platelet transfusions

Despite the use of HLA-matched platelets for alloimmunized recipients, transfusion failures occur. In order to reduce these failures, we investigated the use of a radiolabeled antiglobulin technique for platelet crossmatching. The principle of the test is that of an indirect Coombs test using 125I labeled goat anti-human IgG. Incompatibility is determined by calculating a radioactivity antiglobulin test (RAGT) index. Using this technique, we performed 89 crossmatches on 19 leukemic or aplastic patients who were refractory to random donor platelets and receiving varying degrees of HLA-matched platelets. Effectiveness of the transfusion was assessed from the posttransfusion corrected platelet count increment (CCI) determined at 1 and 20 hr. When the RAGT index was 1.9 or less, the mean CCI at 1 lhr was 17,570 +/- 7003/cu mm, n = 55. When the RAGT index was 2.0 or greater, the mean CCI was 4237 +/- 4100/cu mm, n = 34. At 20 hr when the RAGT index was 1.9 or less, the mean CCI was 8722 +/- 3143/cu mm, n = 33, and when the index was 2.0 or greater, the mean CCI was 571 +/- 1286/cu mm, n = 23. Using this technique, one false negative resulted. Nine positive crossmatches with good increments at 1 hr were found; at 20 hr, however, the survival of these units was zero. These data suggest that this method is a useful adjunct in the selection of platelets in the refractory patient.     

Tissue factor activity in patients with systemic lupus erythematosus: association with disease activity

OBJECTIVE: Tissue factor (TF) is the major intrinsic initiator of clotting. TF expression on monocytes has been associated with high titers of anticardiolipin antibodies (aCL) in patients with antiphospholipid syndrome (APS) with thrombosis. We investigated the influence of clinical factors on TF activity in blood from patients with systemic lupus erythematosus (SLE) and examined the relationship between aCL and TF. METHODS: In this cross sectional study, consecutive patients with SLE from one rheumatology clinic gave blood samples for measurement of TF activity, aCL, and Russell viper venom time. We assessed disease activity by measuring sedimentation rate, anti-dsDNA, and complement components C3 and C4, and measured clinical indices. Associations were investigated with the Wilcoxon rank-sum test and linear regression. RESULTS: Sixty-nine patients contributed blood samples. The median age was 38 years, and 10 of the SLE patients had a history of thrombosis. Patients with active arthritis had TF activity 1.3 times that in patients without arthritis (p = 0.028). Users of nonsteroidal antiinflammatory drugs (NSAID) had TF activity significantly lower than nonusers (p = 0.010). Patients with previous thrombosis had TF activity significantly lower than patients without thrombosis (p < 0.001). Overall, aCL and TF activity were not associated when we adjusted for these clinical factors. CONCLUSION: Arthritis, previous thrombosis, and use of NSAID significantly modified TF activity in patients with SLE. Unlike previous reports, we found no association between aCL titer and TF activity, which may be due to our adjusting for other important clinical factors.