Expression profile of cod teleost-specific tlr s in adult tissues and during early development. A. Tissue specific expression of Atlantic cod tlr21, tlr22 and tlr23 genes. Tlrs are mainly expressed in immune-related tissues such as head-kidney, kidney, spleen, liver and gills. Transcripts of most paralogues were also found in high levels in blood and testis. Eef1a was used as an internal reference for RT-PCR. Minus reverse transcriptase (−RT) and no template (NTC) controls were included to ascertain the specificity of PCR primers. Amplicon sizes in bp are indicated on the right hand side of the figure. B. Expression analysis of tlrs during embryonic development. Low expression of tlr21 was detected at later stages from hatching until first feeding, while tlr23a and tlr23b were not detected at any of the examined developmental stages. Tlr22c, tlr22, tlr22j and tlr22k transcripts were found in unfertilised eggs (UFE), while tlr22k was expressed at most developmental stages examined. Luciferase was used as an external reference for RT-PCR.