Cytokine gene expression of 18 T cell lines (TCL) derived from orbital tissue of six patients with thyroid-associated ophthalmopathy (TAO) using reverse transcription-polymerase chain reaction (RT-PCR). Following cDNA synthesis, all TCL (lanes 1–18) and as positive control cDNA prepared from stimulated peripheral blood mononuclear cells (PBMC) of a normal donor (X), were amplified by PCR simultaneously for each cytokine-specific oligonucleotide primer pair. Orbital TCL were generated from six patients with TAO (patient 1, lanes 1–4; patient 2, lanes 5–8; patient 3, lanes 9–12; patient 4, lanes 13–15; patient 5, lanes 16 and 17; patient 6, lane 18). Lanes right and left sideways represent the DNA molecular weight markers. Only the expected range of base pairs (bp) size with visualized transcripts after electrophoretic separation are shown (a). Additionally, positive signals are demonstrated by + and negative by − (b).