Subpopulatipns of CD10‐positive cells in bone marrow of children with acute lymphoblastic leukemia off therapy

Abstract

CD 10-positive lymphoid cells are of interest because they are the most immature recognizable B cells and because they are usually present in acute lymphocytic leukemia (ALL) [l]. Although the presence of CD10-positive lymphoid cells has been considered an early marker of relapse in off-therapy ALL children [2], studies dealing with CDlO antigen intensity in such patients are virtually absent. In fact, fluorescence intensity of CDlO-positive cells is heterogeneous. It has previously been shown that normal CD 10-positive cells display a lower mean CDlO antigen density than do cells from most cases of CDIO-positive ALL [3]. This separation, however, is far from absolute.Ten off-therapy ALL children in continued remission formed the basis of this study aimed at investigating the presence of bone marrow (BM) CDlO-positive cells. There were 4 males and 6 females. Median age at the diagnosis of ALL was 7 years (range: 5-12 years). As far as antileukemic therapy is concerned, all patients were treated according to the Associazione Italiana Ematologia Oncologia Pediatrica (AIEOP) protocols. At the time of the BM study, all had remained disease-free for 1-12 months (median: 7 months) from the discontinuation of therapy. In each patient, BM aspirates were analyzed by flow cytometry with fluorescein-labeled monoclonal antibodies.The results of BM cell phenotyping were as follows [mean % (range)]: CD3 = 28.9 (16.9-56); CD4 = 12.6 (8.4-11.6); CD8 = 16 (6.8-30); CD2 = 26.3 (5.9-66.6); HLA-DR = 62.9 (44-74.3); CD19 = 49.2 (1 1.4-72.7); CD20 = 43.2 (11-67.6); CDlO (weakly) = 40 (32.1-58.5); CDlO (strongly) = 2.1 (1.5-3.2); CD34 = 9.7 (4.5-16. I).The FACS profile from a representative patient stained for CDlO is shown in Figure 1. The histogram suggests the presence of cell subpopulations with weak and strong fluorescence. The inflection point between the peaks occurred approximately at the value of 100 in a scale of 250 channels of fluorescence intensity. By setting a cutoff at this value we defined two subpopulations of CD1O-positive cells that differ with respect to their fluorescence intensity, with mean specific fluorescence 0 1991 Wiley-Liss, Inc. 119.7 2 12.6 and 86.5 -t 10.9 for cells displaying strong and weak CDlO antigen density, respectively.Our results demonstrate that strongly CD10-positive BM subpopulation, similar to that shown by CD10-positive ALL, can be found in off-therapy ALL children without clinical or hematological evidence of relapse. This feature suggests the immaturity of the strongly CD1O-positive lymphoid cells. Further studies should address the proper role of this observation with regard to the outcome of disease.

Age-related changes of lymphocyte subsets in normal bone marrow biopsies

“…Most of the B cells expressed the immature phenotype CD19 ϩ CD10 ϩ , in agreement with the findings reported in previous studies (8,18,10,31,(36)(37)(38). Longacre et al (28) and Davis et al (11) described increased percentages of hematogones expressing CD10 in the BM from children and adults with different hematological and nonhematological disorders.…”

“…Previously reported analyses of lymphoid marker distribution in BM from children have been performed only on aspirates (8,10,28,31,37). Moreover, because in most studies children of different ages were analyzed indistinctly, the results may have been influenced by the relative number of children of preschool age in each group analyzed.…”

“…Except for the study by Clark et al (9), all the previous studies were performed on aspirates (4,8,10,11,18,27,28,31,36,37). Because it has been demonstrated that PB contamination leads to an increase in the number of T cells of one-third to one-half, to an increase of the CD4/CD8 ratio, and to a slight reduction in the relative numbers of CD10 ϩ cells in BM (9), caution must be taken when comparing the results obtained with specimens of different sources.…”