Estrogens Modulate IL-6 Production by Cultured Normal and Pathological Human Thymic Epithelial Cells

Abstract

Interleukin-6 (IL-6) is a multifunctional cytokine, which regulates the immune response by polyclonal B cell activation and differentiation; it enhances peripheral T lymphocyte responses, thymocyte growth and induction of cytotoxic T cell differentiation [1]. Many clinical and experimental observations suggest that IL-6 could be involved in pathogenetic processes; in fact, elevated levels of IL-6 have been detected during autoimmune diseases, infections, and tissue injury. It has been shown that cultured human thymic epithelial cells (TECs) are able to secrete IL-6 both constitutively and after stimulation with interleukin-1ß (IL-1ß) and/or LPS [2]. Some authors have suggested that TEC IL-6 production may be related to the thymic abnormalities found with a high frequency in Myasthenia Gravis (MG) [3]. Thymoma is found in about 10% of the MG patients, while hyperplastic thymus is often observed in MG female patients with young-age at onset. The thymus has estrogen receptors [4]; these steroids modulate IL-6 production in different tissues, such as bone marrow-derived stromal cells, osteoblasts and blood mononuclear cells in vitro [5, 6, 7] and are able to increase secretion of thymic hormones by TECs in vitro [8].