Molecular characterization and expression analysis of major histocompatibility complex class IIA and IIB genes of Odontobutis potamophila

Abstract

The major histocompatibility complex (MHC) has a critical role in the adaptive immune system by presenting a foreign peptide to the T cell receptor. The full length of MHC class IIA and IIB cDNA was cloned from Odontobutis potamophila by expressed sequence tag and rapid amplification of cDNA ends polymerase chain reaction (RACE-PCR). Tissue distribution and expression of MHC IIA and IIB were examined to study the functions of the MHC II gene in fish. The domain structure and antigen-binding motifs of other teleosts and mammals MHC II are conserved in O. potamophila as MHC IIA and IIB genes. The alignments of the deduced amino acid sequences from MHC IIA and MHC IIB in O. potamophila with those from other vertebrates demonstrated a 25–52 % similarity between other fish and mammalians. Real-time quantitative PCR demonstrated that MHC IIA and IIB genes were ubiquitously expressed in all tested tissues. The challenge of O. potamophila with Aeromonas hydrophila resulted in a significant change in the expression of MHC IIA and IIB mRNA in the liver, spleen and kidney. All these results suggest that both genes play crucial roles in immune responses of O. potamophila.