Cycle number versus relative fluorescence for stimulated peripheral blood mononuclear cells (PBMC) standard. Separate GAPDH amplification curves are shown for different numbers of activated PBMC. Each pair of colored lines represents replicate sample amplification plots. Circles represent amplification of a synovial biopsy to show that it is within the detection range of quantitative PCR. The dashed line indicates the threshold cycle, C(t), for this assay. The dark bar at C(t) indicates the range of C(t) of biopsies containing sufficient mRNA for evaluation. RA, rheumatoid arthritis; R(n), normalized reporter signal.