Fish Immunology (1+1)

Unit 4- Fish Leucocytes

4.3. Granulocytes
Fish granulocytes are involved in non-specific defence mechanisms and activate in the presence of foreign material in the body but do not stimulated by specific antigens. These cell are involved in phagocytosis, respiratory burst activity, and chemotaxis. Granulocytes are generated in the haemopoietic tissues of the kidney, have wide morphological variations in granulocyte subpopulations and immature (blast) cells are circulated throughout the fish.
In fish, we can find three types of granulocytes they are neutrophils and eosinophils are the most common while basophils are much rare in fish.
Neutrophil: This is the most abundant among leucocyte. Neutrophils has no affinity for acidic or basic dyes, but stainable with neutral dye. They can migrate into the tissues from blood to engulf bacteria.
Eosinophil: This is a polymorphonuclear leucocyte that can be stained with eosin which is an acidic dye. Eosinophils can neutralize internal parasites and also can modulate allergic inflammatory reactions.
Basophil: These basophils are present only in few fish species, even though they are present their numbers are normally very low in blood. Basophils shows an affinity for basic dyes. Basophils also participate in neutralizing microorganisms.