Development of a sampling method for the isolation of head kidney macrophages from fish at the pond-side

Citation

Crumlish M, Dung TT, Somsiri T, Inglis V & Thompson K (2000) Development of a sampling method for the isolation of head kidney macrophages from fish at the pond-side. Journal of Fish Diseases, 23 (4), pp. 289-293. https://doi.org/10.1046/j.1365-2761.2000.00236.x

Abstract
First paragraph: During a recent study investigating the innate defence system of farmed tropical ranids, Rana rugulosa, in Thailand, bacteria were frequently observed by light microscopy in macrophages isolated from the spleen of these animals. However, the animals appeared clinically healthy, with no external or internal signs of disease. This finding was regarded as unusual, since high levels of bacteria are not usually present in the macrophages of clinically healthy animals. The only study found relating to the presence of bacteria in the spleen leucocytes, or splenocytes of frogs was that of Haynes, Harding, Keniski & Cohen (1992). The authors found bacteria present in the splenocytes of healthy laboratory frogs, Xenopus laevis, but no pathology was associated with the infection, apart from splenomegaly. Bacteria recovered from the X. laevis leucocytes were not identified other than as small coccobacilloid bacteria. As no reports were found in the literature of bacteria within the macrophages of farmed fish, a brief study was carried out to establish if bacteria were present in the macrophages of healthy hybrid catfish, Clarias sp. Catfish are cultured in freshwater systems in Thailand, similar to those used in frog culture. The fish were transported back to the laboratory where macrophages were isolated from the head kidney of the animals using Percoll density gradients, according to the method of Secombes (1990), based on a method previously described by Braun-Nesje, Bertheussen, Kaplan & Seljelid (1981). As seen with splenocytes from the farmed frogs, bacteria were found in the cytoplasm of head kidney macrophages sampled from the farmed fish.

Journal
Journal of Fish Diseases: Volume 23, Issue 4