G-CSF enhances the immunoglobulin generation rather than the proliferation of human B lymphocytes.

The effect of granulocyte-colony stimulating factor (G-CSF) on human B-cell function was studied in in vitro cultures. G-CSF alone had no effect on the proliferative response of resting B cells, but it slightly enhanced the proliferative response of these cells in the presence of polyclonal B-cell mitogen, Staphylococcus aureus Cowan strain I (SAC) at concentrations of 0.2 to 25 micrograms/ml (1.5-fold increase in the DNA synthesis). In contrast, immunoglobulin (Ig) secretion of activated B cells was increased approximately three-fold to four-fold by adding G-CSF to the cultures. The neutralization of G-CSF bioactivity with anti-G-CSF antibody abrogated this effect. Though cytoplasmic Ig-positive cells or plasma cell marker-positive cells did not change, the expression of IgM mRNA in antibody-producing B cells increased in the presence of G-CSF in the cultures. Interestingly, human B lymphocytes are shown to express the binding to biotin-conjugated G-CSF preparation, but not to biotin-conjugated GM-CSF preparation when examined by flow cytometry. These data suggest that G-CSF may influence B-cell function in special circumstances.