Induction of phenoloxidases in the humoral fluids of amphioxus Branchiostoma belcheri by Vibrio alginolyticus and Escherichia coli

Hepatic cecum: a key integrator of immunity in amphioxus

The vertebrate liver is regarded as an organ essential to the regulation of immunity and inflammation as well as being central to the metabolism of nutrients. Here, we discuss the functions that the hepatic cecum of amphioxus plays in the regulation of immunity and inflammation, and the molecular basis of this. It is apparent that the hepatic cecum performs important roles in the immunity of amphioxus including immune surveillance, clearance of pathogens and acute phase response. Therefore, the hepatic cecum, like the vertebrate liver, is an organ functioning as a key integrator of immunity in amphioxus.

Induction of phenoloxidase and other immunological activities in the humoral fluids of amphioxus Branchiostoma belcheri challenged with Lipopolysaccharide (LPS)

The knowledge concerning the humoral immunity is scarce in amphioxus Branchiostoma belcheri. This study measured the humoral parameters including phenoloxidase (PO) activity, lysozyme activity, antimicrobial activity, microbial agglutinin, and hemagglutinin in amphioxus humoral fluids before and after lipopolysaccharide (LPS) challenge. Humoral fluids from unchallenged Branchiostoma belcheri (B. belcheri) had PO activity, lysozyme, antimicrobial, microbial agglutinating, and hemagglutinating activities, which may represent part of the baseline level of innate immunity in this organism. After challenge with LPS, many humoral parameters were all increased significantly including the PO activity, lysozyme activity, growth-inhibiting activities against Gram-negative bacteria Escherichia coli (E. coli) and Vibrio alginolyticus (V. alginolyticus), growth-inhibiting activities against Gram-positive bacteria Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtilis), microbial agglutinating activities against Micrococcus lysodeikticus (M. lysodeikticus), B. subtilis, and S. aureus, and hemagglutinating activities against rabbit and human A and O erythrocytes. In contrast, the agglutinating activities against V. harveyi and E. coli and the hemagglutinating activity against human B erythrocytes in the humoral fluids were reduced in response to LPS challenge. It appears that the humoral fluids of B. belcheri contain components that are able to differentiate different microbes and different human blood cell types.