Transcription of major histocompatibility complex class I (Kb) and transporter associated with antigen processing 1 and 2 genes is up‐regulated with age

Summary The transporter associated with antigen processing 1 and 2 (TAP1 and TAP2) genes belong to the ATP‐binding cassette family of transporter genes. They provide peptides necessary for the assembly of major histocompatibility complex (MHC) class I molecules by transporting these peptides into the endoplasmic reticulum. As MHC class I protein expression increases with age, we have explored the effect of age on the transcription of MHC class I genes (Kb) and TAP1 and TAP2 genes in C57BL/6 mice. Blood and spleen lymphocytes were isolated from mice aged from 3 months to over 24 months. RNA was extracted and mRNA for Kb, TAP1, TAP2 was quantified using slot‐blot hybridization followed by densitometry. There was a parallel age‐related increase (1·5‐fold) in blood lymphocyte mRNA of these genes from 3 months to 21 months. In mice over 24 months old there was a decrease in Kb and TAP1 mRNA, but an increase in TAP2 mRNA. In spleen lymphocytes an age‐related increase in all three mRNA species occurred throughout life. While MHC class I and Tap genes underwent very similar age‐related changes, MHC class I mRNA was about 50 times more abundant than either TAP1 or TAP2 mRNA.