GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR INDUCES FC-EPSILON-RII CD23 EXPRESSION ON NORMAL HUMAN POLYMORPHONUCLEAR NEUTROPHILS/

Three major molecules have been recognized as IgE-binding structures o n hematopoietic cells: the heterotrimeric high-affinity receptor for I gE (Fc epsilon RI), the low-affinity receptor for IgE (Fc epsilon RII/ CD23) and the Mac-2/IgE-binding protein (epsilon BP). The latter has b een shown to be expressed on polymorphonuclear neutrophils (PMN), wher e it regulates IgE-dependent activation, Experiments were undertaken t o determine whether the IgE-binding capacity of PMN is mediated exclus ively by this molecule, No detectable binding of human myeloma IgE to unstimulated PMN from normal volunteers could be evidenced, In contras t, PMN stimulated with granulocyte macrophage colony stimulating facto r (GM-CSF) (500 U/ml) for 24 h displayed positive IgE binding, This bi nding was significantly inhibited in the presence of mAb directed agai nst Mac-2/epsilon BP and also in the presence of anti-CD23 mAb, but no t of anti-Fc epsilon RI mAb or isotype-matched controls, By flow cytom etry, CD23 expression was detected on GM-CSF-primed PMN by several ant i-CD23 mAb, including EBVCS-5, BB10 or Mab135, which recognize differe nt epitopes, CD23 was also evidenced by immunocytochemistry in GM-CSF- primed PMN, By in situ hybridization, GM-CSF-treated PMN exhibited a h ybridization signal for CD23 mRNA and the presence of the CD23b isofor m-specific mRNA was detected by RT-PCR. These findings indicate that P MN can synthesize CD23 molecules under GM-CSF induction. This strong C D23 expression might be of physiopathological relevance in IgE-depende nt activation during allergic processes.