Wantke F, MacGlashan D W, Langdon J M, MacDonald S M
Johns Hopkins Asthma & Allergy Center, Baltimore, MD 21224, USA.
J Allergy Clin Immunol. 1999 Apr;103(4):642-8. doi: 10.1016/s0091-6749(99)70237-x.
We have previously shown that the human recombinant histamine releasing factor (HrHRF) caused histamine release from a subset of basophils from donors with allergy, and this release seemed to be dependent on the presence of a certain type of IgE, termed IgE+. IgE molecules that did not support HrHRF-induced histamine release were termed IgE-. However, subsequently we demonstrated that HrHRF primes anti-IgE-antibody-induced histamine release from all basophils, irrespective of the type of IgE on the cell surface.
Because these data suggested that HrHRF does not exert its biologic effects by binding to IgE, but rather that it interacted with a surface receptor on the basophil, we wanted to obtain functional evidence that HrHRF did or did not bind to the IgE molecule.
The rat basophilic leukemia cell line (RBL-SX38), which has been transfected to express a functional human FcepsilonRI (alpha-, beta-, and gamma-chains of the receptor) in addition to the normal rat FcepsilonRI, was used. The presence of the human FcepsilonRI receptor enables these cells to be sensitized with human IgE. Cells were passively sensitized with 1000 ng/mL human IgE+ or 1000 ng/mL human IgE- for 60 minutes at 37 degrees C. Unsensitized cells served as a control. After the cells were washed, 1 x l0(5) cells were stimulated in the presence of 1 mmol/L Ca2+ with 0.1 microg/mL anti-IgE, 40 microg/mL HrHRF, or 40 microg/mL mouse recombinant HRF (MrHRF), which has 96% homology to HrHRF.
Mean anti-IgE-induced histamine release was 33% +/- 15%, and there was no difference between IgE+ sensitization (32% +/- 12%) and IgE- sensitization (34% +/- 18%). However, in contrast to human basophil experiments, neither HrHRF (0% +/- 0%) nor MrHRF (3% +/- 5%) caused histamine release in RBL cells sensitized with IgE+. In addition, priming the transfected RBL-SX38 cells or the parental cell line, RBL-2H3 cells, with HrHRF or MrHRF did not increase anti-IgE-induced histamine release.
The results indicate that HrHRF does not bind to IgE, either IgE+ or IgE-. Therefore it appears likely that rHRF signals through its own specific receptor, which is not expressed or functional on RBL-SX38 or RBL-2H3 cells, but which seems to be expressed on basophils of atopic and nonatopic donors.
我们之前已经表明，人重组组胺释放因子（HrHRF）可使过敏供体的一部分嗜碱性粒细胞释放组胺，并且这种释放似乎依赖于某种类型的IgE（称为IgE +）的存在。不支持HrHRF诱导的组胺释放的IgE分子称为IgE -。然而，随后我们证明，HrHRF可引发抗IgE抗体诱导的所有嗜碱性粒细胞释放组胺，而与细胞表面IgE的类型无关。
因为这些数据表明HrHRF不是通过与IgE结合来发挥其生物学作用，而是与嗜碱性粒细胞表面的受体相互作用，所以我们想获得功能性证据，证明HrHRF是否与IgE分子结合。
使用大鼠嗜碱性白血病细胞系（RBL - SX38），该细胞系除了正常大鼠FcepsilonRI外，还被转染以表达功能性人FcepsilonRI（受体的α、β和γ链）。人FcepsilonRI受体的存在使这些细胞能够用人IgE致敏。细胞在37℃下用1000 ng/mL人IgE +或1000 ng/mL人IgE -被动致敏60分钟。未致敏的细胞用作对照。细胞洗涤后，在1 mmol/L Ca2 +存在下，用0.1 μg/mL抗IgE、40 μg/mL HrHRF或40 μg/mL与HrHRF有96%同源性的小鼠重组HRF（MrHRF）刺激1×10(5)个细胞。
抗IgE诱导的组胺平均释放率为33%±15%，IgE +致敏（32%±12%）和IgE -致敏（34%±18%）之间没有差异。然而，与人类嗜碱性粒细胞实验不同，在用IgE +致敏的RBL细胞中，HrHRF（0%±0%）和MrHRF（3%±5%）均未引起组胺释放。此外，用HrHRF或MrHRF预处理转染的RBL - SX38细胞或亲本细胞系RBL - 2H3细胞，并未增加抗IgE诱导的组胺释放。
结果表明，HrHRF不与IgE +或IgE -结合。因此，rHRF似乎可能通过其自身的特异性受体发出信号，该受体在RBL - SX38或RBL - 2H3细胞上不表达或无功能，但似乎在特应性和非特应性供体的嗜碱性粒细胞上表达。
