THE ACUTE LYMPHOBLASTIC-LEUKEMIA CELL-LINE SEM WITH T(411) CHROMOSOMAL REARRANGEMENT IS BIPHENOTYPIC AND RESPONSIVE TO INTERLEUKIN-7

A cell line, designated SEM, was established from the peripheral blood of a 5-year-old girl in relapse with acute lymphoblastic leukaemia (A LL). Both the lymphoblasts of the patient and the cells of the cell Li ne SEM showed the t(4:11) chromosomal rearrangement. The analysis of t he immunophenotype of the SEM cell Line revealed the B-cell differenti ation antigens CD19, CD22 and CDw75 in the absence of CD20, CD24 and i mmunoglobulin expression. Besides Blineage antigens, SEM cells were po sitive for the myeloid antigens CD13, CD15, CD33 and CDw65. Immunogeno typic analysis of SEM cells showed a monoclonal rearrangement of immun oglobulin heavy-chain (IgH), T-cell receptor (TCK)gamma and delta gene s. Addition of interleukin (IL)-7 promoted the growth of the patient's lymphoblasts in culture and enhanced the proliferation of SEM cells. The SEM cells also express messenger RNA (mRNA) for the IL-7 receptor (IL-7R), but no evidence for autocrine production of lL-7 by the cell line was found. Addition of IL-4, tumour necrosis factor (TNF)-alpha, interferon (IFN)-alpha, or lFN-gamma resulted in a profound inhibition of SEM growth. Thus, these cytokines may have important growth regula tory activities for biphenotypic leukaemic ALL cells.