Annie Falkenrodt

Immunological classification of acute myeloblastic leukemias : Relevance to patient outcome

Immunophenotyping is a major tool to assign acute leukemia blast cells to the myeloid lineage. However, because of the large heterogeneity of myeloid-related lineages, no clinically relevant immunological classification of acute myeloblastic leukemia (AML) has been devised so far. To attempt at formulating such a classification, we analyzed the pattern of expression of selected antigens, on blast cells collected at AML diagnosis. Patients were eligible if they had a first diagnosis of de novo AML and a sufficient number of blast cells for proper immunophenotyping. The relative expression of CD7, CD13, CD14, CD15, CD33, CD34, CD35, CD36, CD65, CD117, and HLA-DR were analyzed by cytometry in a test series of 176 consecutive AML cases. Statistical tools of clusterization allowed to remove antigens with overlapping distribution, leading us to propose an AML classification that was validated in a second AML cohort of 733 patients. We identified five AML subsets (MA to ME) based on the expression of seven antigens within four groups (CD13/CD33/CD117, CD7, CD35/CD36, CD15).-MA and MB-AML have exclusively myeloid features with seldom extramedullary disease and rare expression of lymphoid antigens. No cases of acute promyelocytic leukemia (APL) were observed within MB AML. MC AML have either myeloid or erythroblastic features. MD AML have more frequently high WBC counts than other subsets, which were related to the expression of CD35/CD36 and CD14 and to monoblastic differentiation. ME AML lack CD13, CD33, and CD117 but display signs of terminal myeloid differentiation. Specific independent prognostic factors were related to poor overall survival in each immunological subset: CD34+ (P<3 × 10−4) in MA AML, CD7+ in MB AML, non-APL cases (P<0.03) in MC AML, CD34+ (P<0.002) and CD14+ (P<0.03) in MD AML, CD14+ in ME AML (P<0.01). The inclusion of seven key markers in the immunophenotyping of AML allows a stratification into clinically relevant subsets with individual prognostic factors, which should be considered to define high-risk AML populations.

High incidence of Hox11L2 expression in children with T-ALL.

The orphan homeobox gene HOX11L2 was previously found to be transcriptionally activated as a result of the t(5;14)(q35;q32) translocation in three T-ALL cases. We now tested by RT-PCR Hox11L2 expression in 23 consecutive cases of T-ALL (15 children aged 0.8–14 years, eight adults aged 17–55 years) and as control 13 B-ALL patients from a single institution. Hox11L2 expression was undetectable in all patients with B-ALL, nor in adults with T-ALL. Nine children (60% of the cases), all boys, expressed Hox11L2. Blast cells from most of the latter patients carried surface CD1a, CD10 and not CD34 antigens, in contrast to the other children. FISH, M-FISH and IPM-FISH analysis failed to detect a t(5;14)(q35;q32) in one of them, which suggests a possible distinct genetic mechanism in Hox11L2 expression induction. Hence, Hox11L2 expression seems to be the most frequent abnormality in childhood T-ALL to date, comparable to the t(12;21) in child B-ALL.

New human MHC class I antigens segregating with HLA-A antigens detected on some lymphocyte subpopulations

Recent genetic studies of the murine chromosome 17 have demonstrated that many genes encode class I antigens, most of which are still not detected serologically; most of these genes belong to the Tla region. Five human alloantisera were selected from 383 female sera and were further studied using a panel of peripheral blood lymphocytes (PBL), B lymphocytes (BL), and PHA activated lymphocytes (PHA-L) from the same blood donors. After intensive platelet absorption, the five sera still reacted positively by a complement-dependent cytotoxicity technique with PHA-L, but negatively with PBL and BL. The antigens detected by these antibodies segregated with an HLA-A allele and were assumed to belong to the class I antigen series as they could be blocked by a turkey anti-beta 2 microglobulin serum. They were found on some lymphocyte populations: PHA-L, common acute lymphoblastic leukemia (cALL) cells, and (preliminary results) a small subpopulation of PBL cells (mostly NK cells), but were not found on chronic lymphocytic leukemia (CLL) cells, T and early T acute lymphoblastic as well as myeloblastic leukemia cells. Kinetic studies showed that several hours of culture with PHA were necessary for the antigen to be expressed. These results show that the antigens described do not belong to the classic HLA antigen series but could be considered to belong to the human Qa-like antigens or to be the human counterpart to the second murine H-2K locus antigens.

A new DR14 allele (DRB1∗1411) containing a short DR11 sequence and its haplotypic association

In the present work, we describe a new DR14 allele. Sequencing of its second DRB1 exon showed it to be DRB1*1404 from codon numbers 9 to 56 and 61 to 86, and DRB1*11 from codons 57 to 60 inclusive.