Response of mucosal and systemic sIgM-positive cells in turbot (Scophthalmus maximus L.) immunization with Edwardsiella tarda

Indirect fluorescence analyze technology (IFAT) and fluorescence-activated cell sorter (FACS) analysis were used to detect surface IgM positive cells (sIgM+ cells) in lymphoid tissues of unvaccinated turbots and vaccinated ones with inactivated Edwardsiella tarda. The results were as follows: (1) The percentage of sIgM+ cells respectively was 0 ± 0.00% of skin, 1.58 ± 0.40% of gills, 17.05 ± 0.39% of peripheral blood (PBL), 21.06 ± 1.79% of kidney in unvaccinated healthy turbots (average length: 7.12 ± 0.5 cm; average height: 3.8 ± 0.2 cm). (2) After direct immersion (d.i.), the response of sIgM+ cells was produced at first in the gills and thereafter in the kidney and PBL, and a significant increase of the number of sIgM+ cells was found in gills. (3) After immunization via intraperitoneal injection (i.p.), the response of sIgM+ cells was produced simultaneously in the gills, kidney and PBL after i.p., and a significant increase of the number of sIgM+ cells was found in PBL and kidney instead of in gills. These results strongly supported the different immunological role of gills, PBL and kidney upon the different administration routes, and the presence of two compartmental models for immune response in turbot.