Differences on the biological function of three Ig isotypes in zebrafish: a gene expression profile.

LPS challenge experiment was conducted to compare the different biological function of three Ig isotypes by checking the expression of Ig heavy chain in zebrafish adult and larvae. Overall, IgM and IgZ expression exceeded IgD in both the larvae and adult, and IgM expression exceeded IgZ in the larvae at later development stages and adult. Moreover, LPS challenge induced significant up-regulation of all the three Ig isotypes in adult zebrafish, and the increase range of IgM and IgZ significantly exceeded that of IgD, indicating that the former two Ig isotypes played more important immunological role in response to antigen invasion. In additon, LPS challenge induced marked responses of all the Ig isotypes in the larvae since 21 dpf onwards. The response pattern of three Ig isotypes after LPS challenge was very similar in the larvae on 21 dpf, but the response range of IgZ exceeded IgM and IgD, and IgZ responded to LPS challenge a bit faster than the other Ig isotypes in the larvae on 28 dpf, which might be related to its important role in the mucosal immunity that was firstly induced by LPS immersion.