Nerve growth factor (NGF) immunoreactivity modulation of mast cells in the thymus of subjects with myasthenia gravis

Abstract

Recent evidence indicates that some thymic cells produce NGF and express its receptors under both normal and pathological conditions, including autoimmune diseases. We have previously reported that the thymus of patients affected by myasthenia gravis is characterized by elevated level of NGF, an endogenous polypeptide important in the cell biology of the nervous and immune system. To evaluate the molecular mechanisms implicated in NGF action in human myasthenic thymus, it is necessary to identify the thymus structural organization and cellular expression of NGF and its receptors. Mast cells are actively involved in both physiological and pathological events in the thymus. We investigated the cellular distribution of NGF immunopositive and Annexin V reactive mast cells in the thymus of patients with myasthenia gravis at light microscopic level. Increased density of Tryptase immunopositive and NGF immunopositive mast cells, as well as double NGF/tryptase and annexin V/tryptase positive mast cells were detected in pathological thymus. Our data provide original structural and immunocytochemical evidence for NGF immunoreactivity modulation of mast cells and raise the question about the role of NGF in the local auto- and/or paracrine regulatory processes during myasthenic transformation.