The rise of the phoenix: the expanding role of the eosinophil in health and disease.

We have entered a new phase in the evolution of our understanding of the role of the eosinophil with a greater appreciation of novel potential functions that may be ascribed to this enigmatic cell type. This review not only provides an update to our current understanding of the various immunobiological roles for the eosinophil, but also attracts attention to some novel observations predicting functions beyond its putative effector role. These observations include the intriguing possibility that the eosinophil may possess the capacity to regulate the immune and inflammatory responses in diseases such as asthma.