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 (ALL). Both the lymphoblasts of the patient and the cells of the cell Line SEM showed the t(4:11) chromosomal rearrangement. The analysis of the immunophenotype of the SEM cell Line revealed the B-cell differentiation antigens CD19, CD22 and CDw75 in the absence of CD20, CD24 and immunoglobulin expression. Besides Blineage antigens, SEM cells were positive for the myeloid antigens CD13, CD15, CD33 and CDw65. Immunogenotypic analysis of SEM cells showed a monoclonal rearrangement of immunoglobulin heavy-chain (IgH), T-cell receptor (TCK)gamma and delta genes. 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 regulatory activities for biphenotypic leukaemic ALL cells.