1. ¹Department of Dermatology, University of Wuerzburg, Josef-Schneider-Str. 2, 97080 Wuerzburg, Germany
2. ²Department of Ophthalmology, St Vincentius-Hospital gAG, Steinhaeuerstr. 18, 76135 Karlsruhe, Germany

Correspondence: Professor Dr JC Becker, E-mail: becker_jc@klinik.uni-wuerzburg.de

Received 14 November 2003; Revised 6 July 2004; Accepted 6 July 2004; Published online 21 September 2004.

Abstract

Uveal melanoma differs from cutaneous melanoma with respect to aetiology, metastatic behaviour and immune biology. The notion that loss of classical MHC class I molecules in uveal melanoma lesions is associated with an improved prognosis suggests that NK cells act as the predominant cells responsible for immune surveillance of this tumour. Consequently, immune escape mechanisms of uveal melanoma should impair the innate immunity. To this end, expression of the ligand for the NK receptor NKG2D, that is, MIC-A/B was expressed by 50% of primary tumours, but none of the metastatic lesions. MIC⁺ tumours were characterised by a NKG2D⁺ infiltrate, which was absent in MIC^- lesions subsequent to chemoimmune therapy. Strikingly, MIC-A/B expression in metastatic lesions was observed subsequent to chemotherapy with fotemustine in one case. In summary, MIC/NKG2D interactions seem to be involved in the immune surveillance of primary uveal melanomas, whereas for metastatic tumours this ligand/receptor system seems not to be relevant, thus, suggesting an immune selection of MIC negative tumour cells.