| Research Abstract |
In mammals, an activation fragment(C3d) of the third complement component(C3) plays a crucial role in supporting nomal humoral immune responces, by stimulating B cells thrugh a specific receptor termed CR2. In the present study, we have examined if the adaptive immunity-regulatory effect is conserved in bony fish. First, we have analyzed physiolocial brakedown of carp C3 in serum activated by zymosan, and found that carp C3 generates a fragment equivalent to human C3d. It was also demonstrated that both C3-H1 and C3-S isoforms of carp C3 are fragmented into C3d. Next we have constructed expression vectors for fusion proteins of glutathione-S-transferase(GST) and C3d, and succeeded to prepare the recombinant proteins. Using the GST-C3d protein as a probe, we have attemted to detect receptors that recognize carp C3d fragment on carp peripheral lymphocytes. As a result, we observed significant and specific binding of GST-C3d to the lymphocytes. Anti-carp C3 rabbit IgG, but not EDTA, inhibited the binding, suggesting that carp lymphocytes carry receptors specific for C3d. The divalent-independent nature agrees well with that of mammalian CR2.
|
