| Abstract
| - Three major molecules have been recognized as IgE-binding structures on hematopoletic cells: the heterotrimeric high-affinity receptor for IgE (FcεRI), the low-affinity receptor for IgE (FcεRII/CD23) and the Mac-2/IgE-bindlng protein (εBP). The latter has been shown to be expressed on polymorphonuclear neutrophils (PMN), where it regulates IgE-dependent activation. Experiments were undertaken to determine whether the IgE-binding capacity of PMN is mediated exclusively by this molecule. No detectable binding of human myeloma IgE to unstimulated PMN from normal volunteers could be evidenced. In contrast, PMN stimulated with granulocyte macrophage colony stimulating factor (GM-CSF) (500 U/ml) for 24 h displayed positive IgE binding. This binding was significantly inhibited in the presence of mAb directed against Mac-2/εBP and also in the presence of anti-CD23 mAb, but not of anti-FcεRI mAb or isotype-matched controls. By flow cytometry, CD23 expression was detected on GM-CSF-primed PMN by several anti-CD23 mAb, including EBVCS-5, BB10 or Mab135, which recognize different epitopes. CD23 was also evidenced by immuno cytochemistry in GM-CSF-primed PMN. By in situ hybridization, GM-CSF-treated PMN exhibited a hybridization signal for CD23 mRNA and the presence of the CD23b isoform-specific mRNA was detected by RT-PCR. These findings Indicate that PMN can synthesize CD23 molecules under GM-CSF induction. This strong CD23 expression might be of physiopathological relevance in IgE-dependent activation during allergic processes.
|
