We investigated the release of the 5-lipoxygenase derivatives of arachidonic acid (AA) in purified human basophils and compared them with similar results obtained in the human lung mast cell. We have shown that purified basophils (average purity = 51± 6%) challenged with 0.1 μg/ml anti-IgE released histamine (35 ± 9%), and LTC4 (32 ± 10 ng/106 cells) but failed to release measurable quantities of immunoreactive LTB4. In contrast, the non-specific stimulus, A23187, caused the release of histamine and both LTC4 (279 ± 95 ng/106 cells) and LTB4 (148 ± 41 ng/106 cells). Closer analysis of the data revealed an inverse relationship between the levels of LTB4 released and the purity of the basophils, strongly suggesting that the contaminating monocytes were responsible for LTB4 synthesis. Purified human lung mast cells have been shown to release 6 ng of immunoreactive LTB4 106 cells, indicating that basophils release significantly less LTB4 following an IgE-mediated challenge. In a series of experiments using highly purified basophils prelabeled with [3H]AA, we demonstrated that exposure to 0.1 μg/ml anti-IgE led to the release of [3H]LTC4, with no detectable [3H]LTB4, whereas exposure to 1.0 μg/ml A23187 caused the release of [3H]LTC4 and smaller quantities of [3H]LTB4, [3H]LTD4, and [3H]LTE4. We failed to detect any [3H]LTB4 in the cell pellet following challenge with either anti-IgE or A23187, indicating that LTB4 was not synthesized and retained within the cell pellet. Finally, we found that exogenously added [3H]LTB4 was not metabolized, either by basophils alone or by basophils stimulated with anti-IgE (O.1 μg/ml).
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