4. Cellular Immune ComponentsThe immune cell populations present in fish are not very different from those found in mammals. Immune cells in teleosts include natural killer cells, non-specific cytotoxic cells, macrophages, granular leucocytes, thrombocytes, monocytes, dendritic cells, lymphocytes, mast cells, and eosinophilic granule cells. In addition, fish also possess rodlet cells and melanom..