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In Vitro Growth and Maturation of Human B-Cell Precursors

Purified B cell precursors (BCP) (CD10+ CD19+ surface-membrane (s)Ig-cells) isolated from human fetal bone marrow (BM) were cultured with various cytokines, in the presence or absence of a fibroblastic stromal cell layer derived from adult human BM. We demonstrated that IL-7, IL-3, and stem-cell factor (SCF) participate in inducing low magnitude BCP proliferation in the absence of stroma. Addition of either IL-4, IFN (alpha and gamma), or TGF beta, resulted in significant inhibition of proliferation. Strikingly, BCP proliferated at remarkably higher levels when cultured on BM stromal cells, and this effect was further enhanced by exogenously supplied IL-7. Proliferating cells were mostly CD20+, and included both c mu- and c mu+ cells. Furthermore, BCP proliferated in response to anti CD40 antibody presented by Fc gamma RII-transfected murine fibroblastic Ltk- cells (CD40 system) (Banchereau et al. 1991), demonstrating a functional role for CD40 in B cell ontogeny. However, this effect was shown to require a second signal, which could be specifically provided by IL-3 among a panel of cytokines examined. Finally, although suggestive of BCP maturation, the culture systems examined did not permit the transition to mature B cells (sIgM+ sIgD+).

Heterogeneity of the inhibitory effects of IL-4 in two novel B lineage acute lymphoblastic leukemia cell lines

The present study describes two novel cell lines, DUNATIS and SILVANUS, established from B lineage acute lymphoblastic leukemia patients. Respectively, DUNATIS and SILVANUS display an early pre-B cell and a pre-B cell phenotype. Spontaneous DNA replication of both cell lines was strongly inhibited by IL-4. This effect was directly mediated by IL-4 and exerted through the CD124 IL-4 receptor chain. Notably, IL-4 was associated with rapid cell death and reduction of cellularity in DUNATIS, whereas these parameters were considerably less pronounced and only observed after longer-term exposure of the SILVANUS cells to IL-4. In addition to these differences, although both cell lines expressed FES oncoprotein, a 100 kDa protein associated with FES was strikingly found to be tyrosine-phosphorylated in response to IL-4 exclusively in DUNATIS cells. These data demonstrate that IL-4 displays heterogenous effects on leukemic B cell precursors responsive to inhibition of DNA synthesis via IL-4 mediated engagement of the CD124 receptor chain. The present findings may be of use for appreciation of the effects of IL-4 in B lineage ALL, and the novel cell lines could represent a model for further identification of target molecules in IL-4 signalling.