ANALYSIS OF T-CELL RECEPTOR AV AND BV CHAIN GENE-EXPRESSION BY INFILTRATING LYMPHOCYTES IN SPITZ NEVI AND IN HALO NEVI

Spitz naevi and halo naevi are benign melanocytic lesions that share m any histological features with malignant melanoma. All lesions are cha racterized by a brisk infiltration of lymphocytes, mainly of the T cel l subtype, and halo naevi are known to undergo spontaneous regression. Since the benign nature of Spitz naevi and halo naevi might therefore be caused by specific T cell responses against tumour-associated anti gens, it was found of interest to characterize this T cell response in detail. A reverse transcriptase-polymerase chain reaction (RT-PCR)-ba sed method adapted for analysis of paraffin-embedded material combined with Southern blot analysis has been used to analyse the T cell recep tor (TCR) AV and BV repertoires of infiltrating lymphocytes in 14 diff erent melanocytic lesions. The results have shown that only a few part icular TCRAV and TCRBV regions are expressed in each lesion. To evalua te the T cell response, it is of interest to know the HLA-type of the analysed lesions, since most melanoma-specific effector lymphocytes ar e CD8+ cytotoxic T cells and therefore HLA class I-restricted, As bloo d samples were not available from any of these patients, an RT-PCR met hod using HLA-AS-specific primers was used to analyse for the presence of this allele. The preferentially expressed TCRAV genes were sequenc ed, and this analysis showed that the high expression of these TCRAV g enes was due to a clonal or oligoclonal expansion of T cells. In summa ry, the expression of relatively few TCR variable regions indicates a clonal expansion of T cells.