title: Production of colony-stimulating activity by normal and neoplastic human B lymphocytes.
abstract: 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.
mesh_terms: D000954:Antigens, Surface / Q000032:analysis; D001402:B-Lymphocytes / Q000378:metabolism*; D002478:Cells, Cultured; D003115:Colony-Stimulating Factors / Q000096:biosynthesis* / Q000302:isolation & purification; D006410:Hematopoiesis; D006801:Humans; D007249:Inflammation / Q000097:blood; D007945:Leukemia, Lymphoid / Q000097:blood; D008213:Lymphocyte Activation; D008970:Molecular Weight; D014411:Neoplastic Stem Cells / Q000378:metabolism*; D014066:Palatine Tonsil / Q000166:cytology
chemical_list: D000954:Antigens, Surface; D003115:Colony-Stimulating Factors