Two murine monoclonal antibodies to peripheral blood monocyte differentiation antigens discriminate within M5 acute non-lymphoid leukemia (ANLL) cells

Production and characterization of two immunotoxins specific for M5b ANLL leukaemia

We describe the production and functional characterization of 2 monocytic-cell-lineage-specific immunotoxins constructed with saporin emitoxin (SAP) from Saponaria officinalis. Interest in the production of these immunotoxins, of possible clinical relevance, has been raised by the availability of 2 MAbs of high specificity for circulating monocytes and M5b ANLL, thus envisaging their potential use in bone-marrow purging. SAP emitoxin was selected on the basis of the low cytotoxicity in unconjugated form, as opposed to highly specific cytotoxicity and favourable pharmacokinetical properties in the conjugated form. SPDP conjugation produced immunotoxins which retained serological specificity and protein-synthesis-inhibitory activity. The 2 immunotoxins did not interfere with bone-marrow progenitor-cell growth in a CFU-GM colony assay. On the contrary, they were capable of killing monocytic cells selectively, as demonstrated in phenotypical and functional assays. Thus these 2 novel immunotoxins appear to be promising reagents in purging autologous bone marrow prior to transplantation in patients suffering from monocytic leukaemia.

Immunological definition of acute promyelocytic leukemia (FAB M3): a study of 39 cases

Acute promyelocytic leukemia (FAB-M3) is a distinct entity among acute non-lymphoid leukemias (ANLL) with peculiar morphological, biological, clinical and prognostic features. An atypical form of M3 (M3v) could be confused with other FAB ANLL and therefore the diagnosis of this variant requires ultrastructural analysis and/or cytogenetic study and/or selective gene rearrangement studies. The immunological phenotype of blast cells in 39 APL patients was studied at diagnosis. The diagnosis of M3 FAB type was ascertained in 32 and the diagnosis of M3v in 7 cases. Using a large series of monoclonal antibodies (mAb), the APL blast cells were B and T cell antigens-negative, HLA-DR constantly negative, CD13- and/or CD33-positive, CD9-positive. Among ANLL this phenotype seems to be closely related to APL both in M3 type and M3v subtype. Because the diagnosis of APL (M3 or M3v) is important in order to establish the specific therapeutic approach, the discriminant capacity of the immunological typing to identify M3 and mainly M3v (hypogranular) could be determinant for a "quick" diagnosis.

Immunophenotyping of acute myeloid leukaemia: relevance of analysing different lineage-associated markers

The immunophenotype of 135 previously untreated patients with FAB defined acute myeloid leukaemia (AML) was studied at diagnosis. The panel of reagents included monoclonal antibodies (MoAb) recognising myeloid-associated determinants (CD11, CD13, CD14, CD33 and others) as well as MoAb directed towards lymphoid antigens (CD7, CD10, CD19) and TdT. The results indicate that CD13 and/or CD33 are consistently expressed in AML and only rarely in ALL blasts (131/135 + ve cases, versus 4/130 in ALL). Lymphoid antigen expression was rarely detected when CD10 and CD19 were investigated in AML (0.9% and 2% + ve cases, respectively), whereas significant positivities were found for TdT and CD7 (20% and 10% respectively). Concerning FAB subtypes, two new MoAb (LAM3 and LAM7) proved very useful in the specific recognition of AML with monocytic features. The phenotype CD13+ and/or CD33+, CD9+, HLA-DR- was found to be almost exclusive for M3 AML. The response to induction chemotherapy was analysed in CD7+ and in TdT+ patients. In the latter group a statistically significant lower response rate was found with respect to TdT-ve-AML patients.