Identification of an IL-7-associated pre-pro-B cell growth-stimulating factor (PPBSF). I. Production of the non-IL-7 component by bone marrow stromal cells from IL-7 gene-deleted mice.
Mouse bone marrow (BM) stromal cell conditioned medium (CM) from our long-term lymphoid culture system selectively induces the in vitro proliferation and presumptive differentiation of pre-pro-B cells (B220+, HSA-, TdT- or TdT+, c[mu-]) from adult rat, mouse, and human BM. However, the responsible growth factor(s) has not yet been identified. Inasmuch as IL-7 is one of the cytokines most closely associated with early B-lineage development, we utilized BM adherent cells and stromal cell lines from IL-7 gene-deleted (-/-) mice in combination with rIL-7 and anti-IL-7 mAb to investigate its possible regulatory role in our culture system. The results show that, although rIL-7 and IL-7 (-/-) CM each can maintain the viability of freshly harvested pre-pro-B cells in vitro, neither induces them to proliferate and/or differentiate, even in the presence of recombinant stem cell factor (rSCF) and/or recombinant insulin-like growth factor (rIGF). The results also show that anti-IL-7 mAb fails to neutralize the pre-pro-B cell growth-stimulating activity in IL-7 (+/+) CM. Yet rIL-7 enables IL-7 (-/-) CM to induce proliferation of pre-pro-B cells, and to "prime" them to respond directly to monomeric IL-7. Furthermore, anti-IL-7 mAb adsorbs the pre-pro-B cell growth-stimulating activity from both IL-7 (+/+) CM and rIL-7-supplemented IL-7 (-/-) CM; but rIL-7 does not restore this activity. Lastly, both pre-pro-B cell growth-stimulatory activity and IL-7 are quantitatively recovered by ultrafiltration in the 50 to 100 kDa, rather than the 10 to 50 kDa, apparent molecular mass fraction. These results suggest that the pre-pro-B cell growth-stimulating activity in our culture system is the property of a self-associating complex of IL-7 and a second BM stromal cell-derived cofactor.
McKenna
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SD
Department of Pathology, School of Medicine, University of Connecticut Health Center, Farmington 06030, USA.
Chen
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Lai
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Goldschneider
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D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001402:B-Lymphocytes / Q000166:cytology*; D001854:Bone Marrow Cells / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D054377:Chemokine CXCL12; D018925:Chemokines / Q000096:biosynthesis* / Q000378:metabolism / Q000502:physiology; D019743:Chemokines, CXC; D017077:Culture Media, Conditioned / Q000378:metabolism; D017353:Gene Deletion; D006133:Growth Substances / Q000096:biosynthesis* / Q000378:metabolism / Q000502:physiology; D015851:Interleukin-7 / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D046911:Macromolecular Substances; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008970:Molecular Weight; D051381:Rats; D011917:Rats, Inbred Lew; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D013234:Stem Cells / Q000166:cytology*; D017154:Stromal Cells / Q000378:metabolism
D000911:Antibodies, Monoclonal; C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D018925:Chemokines; D019743:Chemokines, CXC; D017077:Culture Media, Conditioned; C515256:Cxcl12 protein, mouse; D006133:Growth Substances; D015851:Interleukin-7; D046911:Macromolecular Substances; D011994:Recombinant Proteins