NGF overexpression and distribution in cortical thymic epithelial cells of mice with experimentally-induced leukemia.

BACKGROUND Thymic epithelial cells often form lymphoid-epithelial cell (LEC) complexes, thought to contribute both to normal T-cell differentiation and to leukemogenesis. The distribution of the nerve growth factor (NGF) and NGF immunoreactivity modulation of complex-forming thymus epithelial cells were studied in mice with experimental acute L1210 leukemia. MATERIALS AND METHODS Light and electron microscopic methods and cell separation techniques were applied. RESULTS Immunoperoxidase and immunogold labelling showed subcapsular and subseptal overexpression of NGF by epithelial cells in leukemic thymus. NGF immunopositive epithelial cells were closely associated with lymphoid cells. The increased immunoreactivity of epithelial cells correlated with LEC complex formation, including thymic nurse cell-like structures and rosettes in the external cortex. CONCLUSION These results provide new structural and immunocytochemical evidence for intimate contact between NGF-producing epithelial cells and lymphoid cells and suggest that NGF immunoreactive LEC complexes are involved in thymic microenvironmental reorganization during leukemogenesis.