Recombinant Interleukin-7 Supports the Growth of Normal B Lymphocyte Precursors

Abstract

Hemopoiesis occurs under the influence of regulatory elements in bone marrow. Long term culture of bone marrow (LTBMC) cells under conditions described by Dexter and associates (Dexter et al. 1977) demonstrated that association with adherent stromal cells is critical in the maintenance of hemopoietic stem cells and myelopoiesis (reviewed in Allen and Dexter 1984). Similarly, lymphopoiesis in Whitlock-Witte type LTBMC (Whitlock and Witte 1982) is dependent upon adherent cells (Whitlock et al. 1985). Detection of macrophage, granulocyte or granulocyte/macrophage colony stimulating activity m culture supernatants of stromal cell lines from Dexter cultures (Shadduck et al. 1983; Song et al. 1985; Rennick et al. 1987) suggests that stroma derived soluble factors may account in part for myelopoiesis in these cultures. Furthermore, stromal cell lines able to support lymphopoiesis have also been isolated trom LTBMC (Hunt et al. 1987; Whitlock et al. 1987; Collins and Dorshkind 1987; Namen et al. 1988; Pietrangeli et al. 1988) and some of these have been shown to secrete factors that independently maintain the growth of B cell precursors from LTBMC (Hunt et al. 1987; Whitlock et al. 1987; Namen et al. 1988). A 25.000 da protein, designated interleukm-7 (IL;7), with this activity has recently been purified from a bone marrow derived stromal cell line (Namen et al. 1988) and the cDNA for it cloned (Namen et al. submitted). We have now examined the activity of recombinant IL-7 on subpopulations of normal B lineage cells.