Flow cytometry as a tool for measuring the kinetics of IgM-positive cells in the gill and spleen of sea bream juveniles after bath immunization against Photobacterium damselae subsp. piscicida ( Phdp ).

Flow cytometry (FC) is a straightforward, highly specific and sensitive procedure, which provides objective and quantitative recording of fluorescent signals from individual cells. FC has been used widely in the area of aquaculture research due mainly to the development of monoclonal antibodies (mabs). Phagocyte activity of head–kidney macrophages of several fish species, antibody production against specific antigens or detection of viruses inside immune cells are some of the several possible analysis approached by this assay. The aim of this work is to analyse and to compare kinetics of IgM-positive cells in the gill and spleen of sea bream juveniles after bath immunization against Photobacterium damselae subsp. piscicida (Phdp) using a direct staining method. Fish were immunized with three different inactivated vaccines prepared with 94/99 antigen and a commercial vaccine was used as a positive control. The effect on IgM-positive cells post-vaccination was compared among groups. Results show that the direct staining method with mabs is an effective and repeatable method for staining sea bream IgM-positive cells. [ABSTRACT FROM AUTHOR]