Detection of TNF alpha and Fas ligand mRNA within synovial mononuclear cells by fluorescence in-cell labeling PCR (FICL-PCR)

T cells that infiltrate the synovial lesions of rheumatoid arthritis may pl ay a key role in its pathogenesis. To learn more about their functional nat ure, we determined the frequency of synovial T cells that harbored the TNF alpha and Fas ligand transcript by a technique, called Fluorescence In-Cell Labeling Polymerase Chain Reaction (FICL-PCR). The mRNA of interest was de tected in fixed cells by the incorporation during PCR of a fluorescein-12-d UTP label following an initial reverse transcription PCR step. Using this t echnique the CD3 transcript was detected in the T leukemic cell line, MOLT- 4, with calculated sensitivity and specificity values of 91% and 100%, resp ectively. The percentage mean (+/- S.D.) of TNF alpha mRNA positive cells a nd Fas ligand mRNA positive cells in peripheral blood mononuclear cells fro m 12 rheumatoid arthritis patients were 5.1 +/- 2.3% and 4.8 +/- 3.1%, resp ectively. The percentage mean (+/- S.D.) of TNF alpha mRNA positive cells a nd Fas ligand mRNA positive cells among synovial mononuclear cells from six rheumatoid arthritis patients was 16.8 +/- 8.3% and 10.8 +/- 1.8%, respect ively. This result indicates that the cytotoxic T cells expressing TNF alph a accumulate in rheumatoid arthritic lesions where they may play a pathogen ic role.