Circulating Cd34+ cell count differentiates primary myelofibrosis from other Philadelphia-negative myeloproliferative neoplasms: a pragmatic study.

A high number of circulating CD34+ cells has been advocated to distinguish primary myelofibrosis from other Philadelphia-negative myeloproliferative neoplasms. We re-evaluated the diagnostic interest of measuring circulating CD34+ cells in 26 healthy volunteers and 256 consecutive patients at diagnosis for whom a myeloproliferative neoplasm was suspected. The ROC curve analysis showed that a number of CD34+ <10/µl excludes the diagnosis of primary myelofibrosis with a sensitivity of 97 % and a specificity of 90 % (area under the curve: 0.93 [0.89-0.98]; p < 0.001). Patients with PMF harboring a CALR mutation had more circulating CD34+ cells than patients with either a JAK 2 or MPL mutation (p = 0.02 and p < 0.01, respectively). These results suggest that this fast, simple, non-invasive, and standardized test is of particular interest to exclude the diagnosis of primary myelofibrosis.

CD5-induced apoptosis of B cells in some patients with chronic lymphocytic leukemia.

Although B chronic lymphocytic leukemia (B-CLL) is characterized by prolonged survival of CD5(+) B cells in vivo, these cells apoptose spontaneously in vitro. The effect of CD5 ligation on apoptosis was studied in 27 newly diagnosed patients with B-CLL, in relation to the expression of surface IgM (sIgM), CD79b, CD38, CD72 and CD19. B cells from 15 patients (group I) were resistant to anti-CD5-induced apoptosis, whereas apoptosis above spontaneous levels was seen in the remaining 12 studied (group II). Group II was then subdivided on the basis of differences in the time required to reach maximum apoptosis: whilst B cells from seven patients underwent apoptosis by 18 h, those from the remaining five needed 36 h to apoptose. The expression of sIgM, CD5, CD79b and CD38 was higher in group II than group I, suggesting that signaling for apoptosis might operate via CD79, and that CD38 expression was required. As shown by flow cytometry and confirmed by Western blotting, apoptosis was associated with a decrease in the ratios of Bcl-2/Bax and Bcl(XL)/Bax, due to an increase in the level of Bax, but no change in that of Bcl-2. This heterogeneous apoptotic response to CD5 ligation offers an explanation for the incomplete success of anti-CD5 monoclonal therapy, and might help identify patients who would respond to such treatment.

[Importance of flow cytometry in the detection of anti-erythrocyte autoantibodies]. / Intérêt de la cytométrie en flux dans la détection des auto-anticorps anti-érythrocytaires.

Coombs test and flow cytometry have been compared in terms of specificity and sensibility in a population of hospitalized patients, for whom a Coombs test had been required. The Coombs test seems more sensible than flow cytometry to detect red cell-bound IgG. For a given patient and over the time, flow cytometry seems better correlated with the severity of haemolysis if erythrocytes are strongly sensitized by IgG. The results of flow cytometric analysis, in percentage of sensitized erythrocytes, do not allow to define a sensibilization threshold for haemolysis prediction. Flow cytometric analysis would be more sensible than Coombs test in the detection of red cell-bound C3d, but these cases are not associated with autoimmune haemolytic anemia. Direct Coombs test should remain the diagnostic test of autoimmune haemolytic anemia.

In vitro study of translocation t(4;11) acute leukemia. Sequential range of phenotype.

The nature of translocation t(4;11) acute leukemia cells has been widely discussed over the past few years. Many authors report their phenotypic heterogeneity, ranging from apparently common acute lymphoblastic leukemia antigen-positive to monoblastic leukemia, through "promiscuous" phenotype. We studied in vitro phenotypic modulation of three typical cases after induction by 12-O-tetradecanoyl phorbol 13 acetate. The initial phenotype was different in each case, but all of them exhibited changes in morphologic shape, cytochemistry, and immunophenotype; common features appeared after induction by 12-O-tetradecanoyl phorbol 13 acetate, including esterase activity, expression of CD-9, CD-15, and CD-18 surface antigens, and monocyte/macrophage morphology. In all cases a B-associated surface antigen, CD-19, persisted. During clinical evolution, some previously reported cases have shown a karyotypic and phenotypic transformation. In one of our cases this phenomenon correlated with in vitro phenotypic modulation of initial blast population. Furthermore, clinical relapses and in vitro modulation always seem to evolve toward a more "mature" phenotype. Those results support the "promiscuous lineage" hypothesis, and point out the usefulness of in vitro studies to express the myeloid potential of this category of acute leukemia, which can be regarded as a model of early hematopoietic differentiation.

Morphologic and phenotypic heterogeneity of two cases of translocation t(4;11) acute leukemia.

The morphological, ultrastructural, and immunological characteristics of two cases of acute leukemia with t(4;11) (q21;q23) were studied. The blasts from both cases were initially classified as L1 lymphoblasts. Ultrastructural examination indicated a heterogenous blast population in both cases, with some regular lymphoblast-like cells, and others exhibiting nuclear irregularity, small bundles of microfilaments, or large inclusions. In one case at diagnosis, fresh cells expressed B-associated and a myeloid antigen (B4 and 1G10). At the second relapse, the cells from this patient expressed another myeloid-associated antigen, LFA1 molecule, recognized by the monoclonal antibody M232 (CD18). At the end of clinical evolution, a further myeloid antigen was expressed (OKM1), while 8% peroxidase were noted. The other case was studied at diagnosis only and did not express any myeloid marker but expressed the B-associated B4 antigen. Furthermore, the case that exhibited a phenotypic transformation, was noted to show a chromosomal clonal evolution not described so far in other reported cases of t(4;11) acute leukemia. A dual lymphoid-myeloid nature of t(4;11) acute leukemia has been widely discussed. One of the cases reported here supports this hypothesis while the other does not. We would like to underline the possibility of heterogeneity of a case at presentation and transformation to a myeloid phenotype through clonal evolution.