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V Pistoia, R Ghio, S Roncella, F Cozzolino, S Zupo and M Ferrarini
Normal human B cells were purified from peripheral blood or tonsils and
tested for their ability to release colony-stimulating activity (CSA) in
short-term cultures. The target cells used in the CSA assays were from
peripheral blood or bone marrow. Unstimulated B cells produced CSA in
amounts similar to those present in the GCT-conditioned medium used as a
positive control. The B cell-derived CSA predominantly promoted the growth
of colonies that contained macrophages alone or macrophages and
granulocytes. CSA eluted in a single peak from a G-75 Sephadex column with
an approximate molecular weight (mw) of 65 to 70 kilodaltons (kd).
Fractionation of tonsil B lymphocytes on Percoll density gradients showed
that large B cells, probably already activated in vivo, were the main
source of CSA. By contrast, small, resting B cells recovered from a
different fraction of the Percoll gradient released minimum amounts or no
CSA. However, these B cells became CSA producers following stimulation with
Staphylococcus aureus Cowan (SAC) in vitro. B cells purified from the
peripheral blood of nine out of 12 patients with B-cell chronic lymphocytic
leukemia (B-CLL) also released CSA in vitro in the absence of stimuli.
These findings suggest that by releasing CSA, B cells may have a role in
the regulation of hematopoiesis and in the control of the inflammatory
process.
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| Copyright © 1987 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
