Expression profile of the ubiquitously expressed CT genes IL13RA/CT19, TSP50/CT20, OY-TES-1/CT23, and PLU-1/CT31. A standardized, quantitative end-point RT-PCR assay was used to evaluate the mRNA expression profile of IL13RA/CT19, TSP50/CT20, OY-TES-1/CT23, and PLU-1/CT31 in a series of 16 normal tissues (MTC panels I and II, BD Biosciences, Palo Alto CA). The level of PLU-1/CT31 expression was low in all tissues with the exception of testis. TSP50/CT20 transcripts were detected at high levels in testis, kidney, liver, and pancreas; at a moderate level in thymus and at low levels in all other normal tissues. Transcripts encoding IL13RA/CT19, SPA17/CT22, and OY-TES-1/CT23 were detected at high levels in 11/13 non-gametogenic tissues.