Mustafa F B, Ng F S P, Nguyen T H, Lim L H K
Inflammation and Cancer Laboratory, Department of Physiology and NUS Immunology Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
Clin Exp Immunol. 2008 Jan;151(1):94-100. doi: 10.1111/j.1365-2249.2007.03542.x. Epub 2007 Nov 14.
The role of basophils in an anaphylactic response is well recognized but is usually masked by mast cells, which contain similar mediators for the induction of generalized vasodilatation and laryngeal constriction. The rapid onset of systemic anaphylactic symptoms, particularly in insect stings and ingested food, suggest that basophils, a circulating pool of cells containing histamine and other potent mediators such as leukotrienes, may be more involved in systemic anaphylaxis than originally thought. We wished to examine if secretory phospholipase A2, a systemic allergen found in honey bee venom (HBV-sPLA2) may activate basophils directly leading to rapid systemic mediator release. Basophils were isolated from human blood and stimulated with increasing concentrations of HBV-sPLA2. We found that physiological concentrations of HBV-sPLA2 induce rapid leukotriene C4 production from purified human basophils within 5 min, while interleukin (IL)-4 expression and production was induced at later time-points. Histamine release was not induced, signifying that HBV-sPLA2 did not induce generalized degranulation. Surface expression of CD63, CD69 and CD11b were up-regulated following HBV-sPLA2 treatment. Stimulation of basophils with anti-immunoglobulin E (IgE) following treatment with HBV-sPLA2 did not induce more leukotriene release. To investigate the mechanism of leukotriene production, 9-12 octadecadiynioc acid, a cyclooxygenase-1 (COX-1) and 15-lipoxygenase inhibitor, was used and this abrogated leukotriene production. These results indicate that HBV-sPLA2 can directly activate human basophils in vitro to induce leukotriene production.
嗜碱性粒细胞在过敏反应中的作用已得到充分认识，但通常被肥大细胞掩盖，肥大细胞含有类似的介质，可诱导全身性血管舒张和喉部收缩。全身性过敏症状的迅速出现，尤其是在昆虫叮咬和摄入食物时，表明嗜碱性粒细胞作为含有组胺和其他强效介质（如白三烯）的循环细胞池，可能比最初认为的更参与全身性过敏反应。我们希望研究分泌型磷脂酶A2（一种在蜜蜂毒液中发现的全身性过敏原，HBV-sPLA2）是否可直接激活嗜碱性粒细胞，导致快速的全身性介质释放。从人血液中分离出嗜碱性粒细胞，并用浓度递增的HBV-sPLA2进行刺激。我们发现，生理浓度的HBV-sPLA2可在5分钟内诱导纯化的人嗜碱性粒细胞快速产生白三烯C4，而白细胞介素（IL）-4的表达和产生则在较晚时间点诱导。未诱导组胺释放，这表明HBV-sPLA2未诱导全身性脱颗粒。HBV-sPLA2处理后，CD63、CD69和CD11b的表面表达上调。用HBV-sPLA2处理后，用抗免疫球蛋白E（IgE）刺激嗜碱性粒细胞不会诱导更多白三烯释放。为了研究白三烯产生的机制，使用了一种环氧合酶-1（COX-1）和15-脂氧合酶抑制剂9-12十八碳二炔酸，这消除了白三烯的产生。这些结果表明，HBV-sPLA2可在体外直接激活人嗜碱性粒细胞以诱导白三烯产生。
