Hematopoetic precursors respond to a unique B lymphocyte-derived factor in vivo

Abstract

In this study we detected a factor that stimulates the proliferation of bone marrow-derived hematopoietic precursors in diffusion chambers implanted in mice. This factor, called diffusible colony-stimulating factor (D-CSF), was found in medium conditioned in the presence of spleen and peripheral blood cells from mice with B cell leukemia (BCL1). After the administration of D-CSF, the number of colonies formed in the plasma clot inside the chamber (CFU-DG) was increased, as were the number of hematopoietic precursors (CFU-MIX, CFU-S, CFU-C, and BFU-E) as judged by a subculture of diffusion chamber contents. Depletion of macrophages and T cells from the spleen cell suspension did not decrease the production of D-CSF, thereby indicating that it was derived from B cells. Neoplastic BCL1 cells appear to be the source because D-CSF could not be detected in medium conditioned with normal B cells. BCL1-conditioned medium (CM) did not enhance CFU-MIX, BFU-E, and CFU-C colony formation in vitro, which suggested that D-CSF is different from multi-CSF, EPA, or CSF. The addition of BCL1 CM to multi- CSF-, erythroid potentiating activity (EPA), and CSF (EL-4CM)- containing cultures had no effect on CFU-MIX, BFU-E, and CFU-C colony formation, thus indicating the absence of a synergistic or inhibitory activity. On the other hand, EL-4 CM, which stimulates CFU-MIX, BFU-E, and CFU-C in vitro, had no effect on CFU-DG in vivo. Biochemical characterization of BCL1 CM revealed that D-CSF is relatively heat stable and loses its bioactivity with protease treatments. It binds to lentil-lectin, according to gel-filtration chromatography has a relative molecular weight of approximately 43,000, and on reverse-phase high-performance liquid chromatography elutes with acetonitrile. These data also indicate that transformed B cells may serve as a source for hematopoietic regulators that act on hematopoietic precursors in vivo.

Lithium stimulation of diffusion chamber colony growth is mediated by factors other than colony‐stimulating factor

“…The inability of anti-CSF to totally inhibit DC colony growth, the equivalent levels of GM-CSF and CSF-1 in the control and lithium-treated groups and the indirect nature of the lithium stimulation implies the presence of another factor or factors responsible for DC colony growth and regulation. Further characterization of a recently described lymphocyte-derived factor which stimulated DC colony growth, termed diffusible colony-stimulating factor (D-CSF), may add to the understanding of the regulation of DC colony growth and, perhaps, the regulation of primitive progenitors [14]. It is interesting to note that exogenous D-CSF stimulates CFUdg growth to a similar magnitude seen with lithium, yet has no intrinsic effect on in vitro colony growth of CFU-gm, erythroid or multipotential hematopoietic progenitors.…”

“…Subculturing of DC was conducted as described previously [14]. In these experiments, normal saline or lithium pretreatment was performed and followed by a rest period.…”

Diffusion chamber colony‐forming unit (cfu‐d): A primitive stem cell

“…Erythropoietin, the physiological regulator of in vivo erythropoiesis, also enhances erythroid cell production in DCs [13, 30,36,871. Assessment of conditioned media from neoplastic cell line cultures has revealed that cells with T [24,50] and B cell [49] characteristics elaborate activities which stimulate CFUd. Glucan, a polysaccharide isolated from zymosan, probably induces macrophages to elaborate a factor stimulating cell growth in DCs in mice [99].…”

“…Initially, based on morphological evaluation, they were considered identical (or closely related) to cells giving rise to CFU-gm in vitro [38]. However, in other studies these two precursors have been distinguished by velocity sedimentation [39, 401, density [41], cell cycle status [26,[42][43][44], resistance to osmotic lysis [45], sensitivity to thermal challenges [46,47], growth kinetics [23,48] and by the difference in response to growth factors [24,49,501. The relationship between CFU-d and other colony-forming progenitors is less clear because they often have similar characteristics.…”