Colocalization of tumor necrosis factor-alpha and nitric oxide-synthase immunoreactivity in mast cell granules of nasal mucosa.

We have demonstrated, with immunohistochemical techniques, the colocalization of tumour necrosis factor-alpha (TNF alpha) with a constitutive neuronal isoform of nitric oxide-synthase (NOS) in granules of the majority (52.77%) of the mast cells (MCs) of healthy human nasal mucosa. Very few cells were positive for NOS alone (2.54%). Some cells were positive for TNFa alone (16.73%) or negative for both antigens (18%). Since dim degranulation occurs in MCs of healthy nasal mucosa at any time, we propose that low concentrations of TNF alpha and NOS secreted by these cells are involved not only in the regulation of homeostasis of normal human nasal mucosa, but also in the survival and function of MCs themselves.