Differences in Functional Consequences and Signal Transduction Induced by IL-3, IL-5, and Nerve Growth Factor in Human Basophils

Abstract

Previous studies have indicated a redundancy in the effects of the cytokines, IL-3, IL-5, and nerve growth factor (NGF) on acute priming of human basophils. In the current study, we have examined the effects of these three cytokines on 18-h priming for leukotriene C4 generation, their ability to induce FcεRIβ mRNA expression, or their ability to sustain basophil viability in culture. We also examine a variety of the signaling steps that accompany activation with these cytokines. In contrast with the ability of IL-3 to alter secretagogue-mediated cytosolic calcium responses following 18-h cultures, 18-h treatment with IL-5 or NGF did not affect C5a-induced leukotriene C4 generation or alter C5a-induced intracellular Ca2+ concentration elevations. IL-3 and IL-5, but not NGF, induced FcεRIβ mRNA expression and all three improved basophil viability in culture with a ranking of IL-3 > IL-5 ≥ NGF. All three cytokines acutely activated the extracellular signal-regulated kinase pathway and the signaling elements that preceded extracellular signal-regulated kinase and cytosolic phospholipase A2 phosphorylation, consistent with their redundant ability to acutely prime basophils. However, only IL-3 and IL-5 induced Janus kinase 2 and STAT5 phosphorylation. This pattern of signal element activation among the three cytokines most closely matched their ability to induce expression of FcεRIβ mRNA. Induction of the sustained calcium signaling that follows overnight priming with IL-3 appeared to be related to the strength of the early signals activated by these cytokines but the relevant pathway required was not identified. None of the signaling patterns matched the ability of the cytokines to promote basophil survival.

STAT5 in human basophils: IL‐3 is required for its FcεRI‐mediated phosphorylation

“…Stimulation of the basophils with IL-3 was confirmed to induce a rapid, dose-dependent and sustained phosphorylation of STAT5 that peaks after 10-20 min and remains on plateau for over 1 h (25). However, as expected, this was not associated with degranulation of the cells (as assessed by the upregulation of CD63) (29,30).…”

“…Traditionally, analysis of signaling in human basophils and mast cells has been performed using Western blot techniques (18,25). Recently, it has been demonstrated that flow cytometry can generate qualitative results concerning dose responses and kinetics of signaling molecules similar and complementary to the data obtained with blotting techniques (19,(26)(27)(28).…”

“…Since IL-3 has been demonstrated to increase synthesis and expression of the FceRIb (25,32), probably in a STAT5 dependent manner (25), it can be hypothesized that IL-3 induced STAT5 phosphorylation might affect basophil responsiveness as the bchain amplifies FceRI signaling (33). Interestingly, basophils regulate their own priming with IL-3 by releasing autocrine IL-3 after activation of the basophils with anti-IgE (34), which might affect basophil sensitivity even more.…”

Transendothelial Migration of Human Basophils

“…Results from our and other laboratories have established that IL-3 stimulates various aspects of basophil functions, such as mediator release (21,22) and in vitro survival (23,24). Furthermore, our earlier study using Boyden chamber systems demonstrated that IL-3 potently enhances in vitro locomotive responses by basophils (11).…”

“…We and others have demonstrated that IL-3 represents the most potent basophil-activating cytokine and stimulates various aspects of basophil functions, including mediator release (21,22), survival (23,24), motility (11), adhesiveness to the endothelium (14), and expression of activation markers (14). Our present finding that IL-3 potentiated basophil TEM broadens the current concept of the capacity of IL-3 to modulate allergic inflammatory responses by up-regulating basophil functions.…”