Acute lymphoblastic leukaemia (ALL) associated antigen—I. Expression in different haematopoietic malignancies

Abstract The cellular specificity of antisera to non-T, non-B ALL has been assessed in a series of 545 patients (adults and children) either presenting with untreated acute or chronic leukaemia or in relapse. The ‘ALL associated antigen’ was detected and evaluated by indirect immunofluorescence using standard microscopy and with the Fluorescence Activated Cell Sorter. Anti-ALL serum reacts with cells from a variable proportion of patients in the following groups: non-T, non-B ALL; Ph 1 positive acute leukaemia or CML in blast crisis; AUL; and a few lymphomas. A weak but definite expression of the ALL antigen was also detected in 10% of ALLs with a thymic phenotype (Thy-ALL). Cross-absorbtion studies indicate that a single antigen or antigenic complex is shared by these various cell types. These observations are interpreted to suggest that several clinically and karyotypically distinct leukaemias involve a similar lymphoid or pre-lymphoid cell type and that the ALL associated antigen is most likely a normal gene product of that cell type or lineage involved in the disease.