An immunohistochemical study on complement component C3 in juvenile Atlantic halibut (Hippoglossus hippoglossus L.)

The complement systems of fish are well developed and play an important role in the immune response. Complement C3 is the central protein of all three activation pathways, being the major opsonin of the complement system and essential for the generation of the membrane attack complex. Very little is known about the development of the complement system in fish. In this study, we detect the presence of C3 in halibut larvae from the age of 37 degrees d post hatching until 1050 degrees d (i.e. 5-99 d post hatching) using immunohistochemistry with specific antibodies produced against the beta-chain of halibut C3. At the different stages of larval maturation, C3 was detectable in yolksac, muscle, liver, brain, chondrocytes, spinal chord, eye, heart, stomach, intestines, oesophagus, pharynx and kidney. Our findings suggest a role of complement in the formation and generation of different organs, besides its important functions in the immune defence against invading pathogens.