The Thai Journal of Veterinary Medicine


Complement system is a powerful host defense mechanism that contributes to both innate and acquired immunities. C3 is the central component of all activation pathways and plays a crucial role in the early immune response. The aim of this present study was to look into ontogeny and expression of C3 in walking catfish Clarias macrocephalus by using molecular techniques. A 4140 bp part of the cDNA encoding the walking catfish C. macrocephalus complement component C3 was obtained by RACR-PCR amplification. The deduced amino acid sequence showed that this partial sequence of C. macrocephalus C3 exhibited 52-64% and 41-45% identity with fish and mammal orthologs, respectively. The C. macrocephalus C3 sequence contained many functionally important sites such as thioester site, cleavage sites for C3 convertase and factor I as well as properdin binding site, which are present in mammalian C3. Ontogeny study of C. macrocephalus showed that C3 transcripts were not present in unfertilized egg but present immediately after hatching and gradually increased with development. Tissue distribution analysis revealed that C3 transcript was mainly expressed in liver. In addition, the expression level of C3 mRNA was examined in catfish fingerlings fed on β-glucan for 1, 3, 7 and 14 days. Semi-quantitative PCR analysis showed that C3 expression in liver of walking catfish was significantly induced by β-glucan. The highest expression of C3 mRNA was observed in fish fed on β-glucan for 7 days. These results particularly represented that C3 played an essential role in innate immune responses and the expression profile of C3 could be used as a reference marker for assessment of fish health.

First Page


Last Page