High sensitivity and linear detection of anti-Th/To antibodies in the IP-qPCR assay demonstrated by titration analyses. One prototype anti-Th/To sample and NHS were analyzed, and Ct values plotted against serial dilution of cell lysate used as substrate for IP (A), RNA extracted from IP (B), or the derived cDNA (D). Dilutions start with lysate from 107 K562 cells per sample. C. The sensitivity of our new IP-qPCR method is compared with RNA dilution detected by silver staining, which allows the identification of the two RNA bands (8-2 RNA, 7-2 RNA) only up to 1:16 dilution. Ct, cycle threshold; IP-qPCR, immunoprecipitation-quantitative polymerase chain reaction; NHS, normal human serum.