Vaccination induces major histocompatibility complex class II expression in the Atlantic salmon eye

Area of Science:

• Immunology
• Ophthalmology
• Aquatic Animal Health

Background:

• Major histocompatibility complex (MHC) class II+ cells play a crucial role in immune responses within ocular tissues.
• Understanding their distribution and density is vital for assessing immune surveillance in fish eyes.

Purpose of the Study:

• To investigate the presence, distribution, and density of MHC class II+ cells in Atlantic salmon ocular tissues.
• To evaluate changes in these cells before and after vaccination.

Main Methods:

• Eyes from Atlantic salmon were collected at various time points before and after vaccination.
• Quantitative histological analysis was performed on retinal sections to count immunopositive cells.

Main Results:

• MHC class II+ cells were found in the limbus, uvea, choroid rete, and ventral ciliary cleft.
• A significant increase in MHC class II+ cells was observed in the outer plexiform layer and inner nuclear layer of the retina 4 days post-vaccination.
• These cells were present in all retinal layers except the photoreceptor layer.

Conclusions:

• Vaccination induces a notable immune cell response in the Atlantic salmon retina.
• MHC class II+ cells are dynamic components of the salmon ocular immune system, responding to vaccination.