Localization and content of nerve growth factor in peripheral blood eosinophils of atopic dermatitis patients

Atopic dermatitis (AD) is a chronic and relapsing eczematous skin disorder characterized by eosinophilia. Nerve growth factor (NGF) modulates the allergic response through interactions with immune-inflammatory cells. Eosinophils have been reported to store NGF as a preformed mediator.

To gain further insight into the significance of eosinophils in association with NGF in the pathogenesis of AD, the localization of NGF within eosinophils and the difference of the eosinophil-derived NGF content in the peripheral blood of normal volunteers vs. AD patients were investigated.

We examined the localization of NGF within human eosinophils using the post-embedding immunoelectron microscopy and compared NGF content in freshly isolated eosinophil sonicates from the peripheral blood of 31 normal volunteers vs. 42 AD patients by immunoenzymatic assay. A possible correlation between the levels of NGF and major basic protein was also examined.

Immunoelectron microscopic studies revealed that NGF was localized in the central core of normal eosinophil granules, where major basic protein is also present as a preformed mediator, in homogeneous granules and in intergranular ductal or vesicular structures adjacent to specific granules of eosinophils. NGF content in eosinophils was significantly increased in AD patients. Furthermore, there was a significant correlation between levels of NGF and major basic protein in eosinophils of AD patients.

Increased levels of NGF contained in eosinophils of the peripheral blood from AD patients, when released with other mediators such as basic proteins, could promote inflammation and local tissue damage.