Expression of Mhc class I mRNA in tissues from vaccinated and non-vaccinated Atlantic salmon (Salmo salarL.)

The expression of Mhc class I heavy chain mRNA in tissues from a group (n=5) of non-vaccinated and a group (n=5) of vaccinated Atlantic salmon (Salmo salarL.) smolts was investigated using a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) approach. An expected 455 nucleotide RT-PCR product was produced and sequence analysis demonstrated that the amplified product was in concordance with the expected segment of the Mhc class I heavy chain complementary deoxyribonucleic acid (cDNA). Computer-assisted morphometric analysis of agarose gels containing the RT-PCR products allowed a semi-quantitative estimate of the level of expression in the different tissues from the two groups. There was considerable individual variation within the groups. However, the general observation in the non-vaccinated fish was that high expression was present in the gills and intestine, moderate expression in the spleen and heart, and low to negligible expression in the head kidney, liver, brain and muscle. The level of expression of Mhc class I in some tissues differed in the vaccinated group. The level of expression was significantly increased in the liver and head kidney and significantly decreased in the foregut of the vaccinated group.