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Title: APOPTOSIS IN ICHTHYOPHTHIRIUS MULTIFILIIS IS ASSOCIATED WITH EXPRESSION OF FAS RECEPTOR OF THERONTS

Author
item Xu, Dehai
item Klesius, Phillip
item Shoemaker, Craig

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2006
Publication Date: 3/15/2006
Citation: Xu, D., Klesius, P.H., Shoemaker, C.A. 2006. Apoptosis in Ichthyophthirius multifiliis is associated with expression of Fas receptor of theronts. Journal of Fish Diseases 29: 225-232.

Interpretive Summary: This study examined the expression of membrane Fas receptors (type I-membrane protein) on the surface of theronts of Ichthyophthirius multifiliis (Ich) and the possible association between Fas expression and theront apoptosis (programmed cell death) induced by the immune antibody. The objective was to understand the effect of antibody from immune fish on Ich theronts. Fas receptors were detected on the theronts surface and Fas-positive theronts were significantly increased with time post harvest or with increasing theront concentration. A high correlation was noted between theront Fas expression and immune cutaneous antibody induced theront apoptosis. These results are critically important for understanding immune protection of antibody from fish immune to Ich and will aid in developing methods to prevent or control Ich. Ichthyophthirius, a severe fish parasite, infects most species of fresh water fish world wide and leads to high mortality. Preventing or controlling this parasite will greatly reduce the economic loss in aquaculture.

Technical Abstract: Previously, we demonstrated that apoptosis of Ichthyophthirius multifiliis theronts was induced by cutaneous antibody from channel catfish immune to Ich. In this study, we examined the expression of type I-membrane Fas receptors on the surface of Ich theronts and the possible association between Fas expression and theront apoptosis induced by the immune antibody. Fas receptors were detected on the theronts surface using fluorescein isothiocyanate-conjugated mouse monoclonal-antibody against the Fas. Fas-positive theronts were demonstrated to significantly increase with time in vitro incubation and with increasing theront concentration. Furthermore, the immune cutaneous antibody induced theront apoptosis, however Fas ligand did not. A highly significant correlation was noted between theront Fas expression and immune cutaneous antibody induced theront apoptosis (correlation coefficient = 0.95, P < 0.01). Numbers of apoptotic theronts was observed to increase with the increase in the number of Fas positive theronts. The data indicated that theront apoptosis induced by immune cutaneous antibody appears to be positively correlated with the expression of Fas on the surface of Ich theronts.