Lack of Involvement of T-Lymphocytes in the Leukaemic Population During: Prolonged Chronic Phase of Philadelphia Chromosome Positive Chronic Myeloid Leukaemia

Abstract

Nine patients with prolonged (> 2 years) chronic phase chronic myeloid leukaemia (CML) were investigated for the presence of T-cell involvement in the leukemic clone. Pure populations of peripheral blood T-cell populations were obtained by culturing separated mononuclear cells in the presence of pokeweed mitogen and IL2, until cultures showed > 99% pure T-cells. Purified T-cells and bone marrow and peripheral blood hematopoietic precursors were analysed for the presence of bcr-abl mRNA transcripts following RNA extraction and message amplification using polymerase chain reaction. In none of the 9 patients was bcr-abl mRNA found in T-lymphocytes while in all cases such transcripts were found in bone marrow and peripheral blood hematopoietic cells. Failure to detect T-cell involvement in patients with prolonged chronic phase CML using techniques designed to enhance even low level involvement of these cell populations supports the view that acquisition of the Ph chromosome abnormality does not occur in the totipotent stem cells but in more committed precursor cell/s with multilineage capacity but which only rarely retain the capacity for T-cell differentiation.

FISH analysis for CML monitoring ?

“…Generally dc-FISH showed a lower rate of BCR-ABLc cells compared with metaphase analysis. The discrepancy we observed, might be attributed to three factors: (a) FISH does not discriminate between myeloid and nonmyeloid cells, whose involvement in the Phc clone is still a matter of debate [21,22]. In most cases, however, the percentage of lymphoid elements was modest and did not affect the overall result.…”

Variable expression of CD3‐zeta and associated protein tyrosine kinases in lymphocytes from patients with myeloid malignancies

“…These disorders arise in a common tissue, are disseminated, are in intimate contact with cells of the immune system, and are present when there is already a large bulk of malignant cells. Although MDS and CML are stem cell disorders, clonality studies demonstrate that the T cells are not usually part of the malignant clone ( Ariad et al , 1993 ; MacKinney et al , 1993 ; Garicochea et al , 1994 ; Kibbelaar et al , 1992 ). If the alterations in signalling proteins are due solely to the presence of a large number of malignant cells in direct contact with lymphocytes, then these abnormalities would occur in all leukaemias.…”

Fluorescence in situ hybridization (FISH) on peripheral blood smears for monitoring Philadelphia chromosome-positive chronic myeloid leukemia (CML) during interferon treatment: A new strategy for remission assessment

“…This problem can be overcome at least in part when FISH is performed on PB smears, because the percentage of lymphocytes is routinely evaluated by peripheral differential counting. These cells can be excluded from the evaluation, as described in Materials and Methods, because T lymphocytes are generally Ph negative and B-lymphocytes carry the BCR/ABL translocation only to a minimal extent in the chronic phase of CML (Nitta et al, 1985;Ariad et al, 1993). Approaches have been used to distinguish between cell subsets (van Lom et al, 1993;Torlakovic et al, 1994), but these are expensive and probably not suitable for routine diagnostic investigations.…”