IgH DJ rearrangements within T-ALL correlate with cCD79a expression, an immature/TCRγδ phenotype and absence of IL7Rα/CD127 expression

Abstract

cCD79a and IgH VDJ/DJ rearrangements are considered to be relatively specific for B lymphoid precursors. We looked for both in cCD3 þ , CD7 þ , CD19-T-ALLs classified by TCR status into ab or cd/immature (IM) lineages, with individualization of HOX11L2 þ T-ALLs since they represent an intermediate ab/cd category. cCD79a was expressed at low levels in 47% of T-ALL and was most frequent in IMc T-ALLs. IgH rearrangements were common in cd/IM (45%) and HOX11L2 þ (35%) T-ALLs compared to HOX11L2-negative cases (3%; Po0.001). CD127 (IL7Ra) expression was also more common in the cd/IM lineage but its expression was virtually mutually exclusive of IgH rearrangement. Low-level cCD79a expression alone should therefore not be interpreted as evidence of B lineage affiliation in immature leukemias. cd/IM lineage T-ALLs potentially include two distinct categories: predominantly IgH þ , cCD79a þ , CD127-cases which retain cd and B lymphoid potential and IgHÀ, cCD79aÀ, CD127 þ cases with restricted T lineage potential.

Childhood near‐tetraploid acute lymphoblastic leukemia: an EGIL study on 36 cases

“…Co‐expression in blasts of immunophenotypic markers associated with other differentiation lineages was found in this study like CD2 in 2 of seven tested cases of BCP‐ALL, cyCD79a in four of five tested cases of T‐ALL and CD117 in two cases of T‐ALL and two cases of BCP‐ALL. These results confirm that these markers can be regarded as lineage‐associated but not specific (35–39) and that the usefulness of a lineage non‐specific marker for allocation of blasts to a single lineage is limited (39). Large panels should be used to properly appreciate blast immunophenotypic features (40).…”

First proposed panels on acute leukemia for four-color immunophenotyping by flow cytometry from the Brazilian group of flow cytometry-GBCFLUX

“…The main objective of the AL screening panel (ALST) is to provide information about the lineage of the leukemic blasts (Table ). In addition, ALST allows identification of expression of some lineage infidelity markers, such as the expression of cytoplasmic (Cy) CD79a and CD19 by t(8;21) positive acute myeloid leukemia (AML) patients , Cy CD79 positivity in some T‐ALL , and CD7 in some AML cases .…”

EuroFlow antibody panels for standardized n-dimensional flow cytometric immunophenotyping of normal, reactive and malignant leukocytes

“…Consequently, CyCD79a was added to improve B-lineage assignment, even though it is also expressed in t(8;21) + AML cases 50, 51, 54, 55 and at low levels in a significant number of T-ALL cases, particularly the immature and T-cell receptor (TCR)γδ + T-ALL subgroups. 62, 63, 64 Of note, CyCD79a was preferred to CyCD22 because CD22 is not lineage specific as it is also expressed at high levels in normal basophils, mast cells and some dendritic cells. 65, 66, 67 Finally, CD7 was selected because it is positive in virtually all cases of T-ALL and in a subset of, usually CyMPO-negative, AML.…”

“…The choice of fluorochromes resulted from the strategic decision to use less common fluorochromes for gating markers so that the more common fluorochromes could be used for characterization markers in a more flexible way. Importantly, three T-ALL backbone markers were also included in the ALOT to benefit from the ALOT information on CyMPO, 36 CyCD79a 62, 63, 64 and CD34 49 expression using the merge function of the Infinicyt software. 16 …”