Fibroblast-secreted macrophage colony-stimulating factor is responsible for generation of biphenotypic B/macrophage cells from a subset of mouse B lymphocytes.
Normal and malignant CD5+ B lymphocytes can develop macrophage-like characteristics. One stimulus of this phenotypic shift is culture of normal mouse splenic B lymphocytes with splenic fibroblasts or their conditioned media. These biphenotypic B/macrophage (B/M phi) cells simultaneously display macrophage characteristics, such as phagocytosis and F4/80 expression, while retaining B cell features, including expression of surface Ig, CD5, B220, and rearranged Ig genes. The present study investigated the fibroblast-secreted factor that promotes this phenotypic change from B cell to B/M phi cell. RT-PCR analysis demonstrated that mRNA for M-CSF is produced by splenic fibroblasts. Recombinant M-CSF (CSF-1) could replace fibroblast-conditioned medium to elicit the development and survival of B/M phi cells from splenic B lymphocytes. In addition, neutralization of fibroblast-secreted M-CSF with specific mAbs abrogated the ability of conditioned supernatants to promote outgrowth of B/M phi cells. The transition from B lymphocyte to B/M phi cell was marked by the kinetic appearance of mRNA for the M-CSF receptor, c-fms, at day 3 following culture initiation. These results demonstrate that M-CSF is important in the development and physiology of mouse B/M phi cells and potentially in the growth of human biphenotypic hematological malignancies. Interestingly, the presence of IFN-gamma in splenic B lymphocyte cultures abrogated the effect of fibroblast-conditioned medium or M-CSF on outgrowth of B/M phi cells. Furthermore, these findings suggest that a Th1 microenvironment favored by typical macrophages is detrimental to the outgrowth of B/M phi cells.
Borrello
M A
MA
Cancer Center, Department of Microbiology, University of Rochester School of Medicine, NY 14642, USA.
Phipps
R P
RP
D000818:Animals; D016175:B-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D002454:Cell Differentiation / Q000276:immunology; D002455:Cell Division / Q000276:immunology; D002460:Cell Line; D002474:Cell-Free System / Q000276:immunology; D017077:Culture Media, Conditioned / Q000737:chemistry; D005347:Fibroblasts / Q000276:immunology / Q000378:metabolism*; D006131:Growth Inhibitors / Q000276:immunology; D016130:Immunophenotyping; D016173:Macrophage Colony-Stimulating Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008264:Macrophages / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D012333:RNA, Messenger / Q000096:biosynthesis; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000096:biosynthesis / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D013234:Stem Cells / Q000378:metabolism
D017077:Culture Media, Conditioned; D006131:Growth Inhibitors; D012333:RNA, Messenger; D011994:Recombinant Proteins; D016173:Macrophage Colony-Stimulating Factor; D016186:Receptor, Macrophage Colony-Stimulating Factor