Negative Regulation by Interleukin-3 (IL-3) of Mouse Early B-Cell Progenitors and Stem Cells in Culture: Transduction of the Negative Signals by bc and bIL-3 Proteins of IL-3 Receptor and Absence of Negative Regulation by Granulocyte-Macrophage Colony-Stimulating Factor

The receptors for interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-5 share a common signaling subunit bc. However, in the mouse, there is an additional IL-3 signaling protein, bIL-3, which is specific for IL-3. We have previously reported that IL-3 abrogates the lymphoid potentials of murine lymphohematopoietic progenitors and the reconstituting ability of hematopoietic stem cells. We used bone marrow cells from bcand bIL-3– knock-out mice to examine the relative contributions of the receptor proteins to the negative regulation by IL-3. First, we tested the effects of IL-3 on lymphohematopoietic progenitors by using lineage-negative (Lin2) marrow cells of 5-fluorouracil (5-FU)-treated mice in the two-step methylcellulose culture we reported previously. Addition of IL-3 to the combination of steel factor (SF, c-kit ligand) and IL-11 abrogated the B-lymphoid potential of the marrow cells of both types of knock-out mice as well as wild-type mice. Next, we investigated the effects of IL-3 on in vitro expansion of the hematopoietic stem cells. We cultured Lin2Sca-1–positive, c-kit–positive marrow cells from 5-FU–treated mice in suspension in the presence of SF and IL-11 with or without IL-3 for 7 days and tested the reconstituting ability of the cultured cells by transplanting the cells into lethally irradiated Ly-5 congenic mice together with ‘‘compromised’’ marrow cells. Presence of IL-3 in culture abrogated the reconstituting ability of the cells from both types of knock-out mice and the wild-type mice. In contrast, addition of GM-CSF to the suspension culture abrogated neither B-cell potential nor reconstituting abilities of the cultured cells of wild-type mice. These observations may have implications in the choice of cytokines for use in in vitro expansion of human hematopoietic stem cells and progenitors. r 1998 by The American Society of Hematology.