A New Method for Collecting Neutrophils Using Swim Bladder

Tilapia Oreochromis niloticus, weighing about 30 g, were used in this study. Fish were injected with 0.2 ml of HBSS containing a stimulant into the swim bladder. Proteose peptone solution, formalin-killed bacterial suspension (Escherichia coli; 5 mg/ml in HBSS), LPS, and liquid paraffin suspension were tested as stimulant. The phagocytes were collected from the swim bladder at 12, 24, and 48 h post-administration. The largest number of phagocytes was collected with bacteria suspension at 24 h. They were enumerated for the viability analyses, or smeared on slide glass to be identified. The high viability (96.9% plus or minus 2.1) was attained in this method. Most of the exudated phagosytes into swim bladder seem to be neutrophils.