EXPRESSION OF NGF RECEPTORS IN NORMAL AND PATHOLOGICAL HUMAN THYMUS

The expression of NGF receptors was investigated in normal human thymu s and in thymic hyperplasias, thymomas and thymic carcinomas. By RT-PC R, we detected TrkAI transcripts encoding for the high-affinity NGF re ceptor. Western blot analysis showed the presence of both TrkA and p75 (NGFR) proteins. In normal thymuses, epithelial subcapsular and medull ar cells were TrkA immunoreactive. Interdigitated medullar cells were stained for both TrkA and p75(NGFR). While epithelial cells of normal thymuses or benign thymomas exhibited a TrkA positive-p75(NGFR) negati ve phenotype, a switch to a TrkA negative-p75(NGFR) positive phenotype was observed in malignant epithelial cell tumours and was associated with cell proliferation-associated MIB1 expression. Our results argue for a local role of NGF and its receptors on thymic stromal cells both in normal and neoplastic conditions. (C) 1998 Elsevier Science B.V. A ll rights reserved.