ICAR AIEEA PG 2024 - Fisheries Science

In teleost fish immunology, T-lymphocytes (thymus-derived lymphocytes expressing T-cell receptors and CD4/CD8 coreceptors) mediate cellular immunity, including cytotoxic elimination of virus-infected cells and cytokine activation of phagocytes. B-lymphocytes mediate humoral antibody immunity.

Neutrophils (heterophils in some teleosts) are the primary, most motile granulocytic white blood cells that act as first responders in acute inflammation, rapidly migrating via chemotaxis to the site of infection within minutes to hours to phagocytose pathogens and release reactive oxygen species (ROS).

Columnaris disease (caused by the gliding bacterium Flavobacterium columnare) produces a pathognomonic pale band of skin necrosis and depigmentation encircling the base of the dorsal fin, widely recognized clinically as the classic 'saddleback lesion'.