The Four Pillars of the Immune System- Cell Walls
Last week we introduced the 4 pillars that together form the immune system of fish: Cell Walls, Power, Blood and Eicosanoids. This edition covers cell walls, or more specifically the cell plasma membrane. We will also describe the mechanisms that pathogens use to penetrate the cell plasma membrane with a focus on salmonoids and viruses.
Viruses are not alive. They can only replicate by using the power and nutrients found inside healthy cells. To enter the interior requires the virus to first penetrate through the animal's outer defenses, enter the blood stream then penetrate cell plasma membrane and infect healthy cells. Once it destroys the healthy cell, it repeats until it is destroyed by the immune system or kills its host.
To enter the blood stream a virus has to penetrate the animal's outer defenses, namely skin and the gill lining. (for this series we are ignoring the food born pathogens entering through the digestive tract)
- Skin Cells:
Sea lice are a parasite causing circa 19% mortality rates. The penetration of the skin opens up a direct pathway for pathogens to enter into the bloodstream. Any wound that penetrates the skin during transfer or handling also opens up a direct pathway into the bloodstream.
- Gill Walls
Cells that line the gils are an entry point for waterborne pathogens. The cells lining the gills are particularly vulnerable as they are required to defend the bloodstream from pathogens yet allow for the exchange of oxygen, carbon dioxide and ammonia with the seawater. Cells also have signaling chemistry called eicosanoids to "talk" with other cells throughout the body. These chemical pathways that enable these exchanges are weak points that are exploited by pathogens to enter the bloodstream.
Once a virus penetrates into the blood stream, it has to penetrate the cell plasma membrane of healthy cells to replicate. Each virus has its own strategy for infecting healthy cells. For example, the Infectious Pancreatic Necrosis(IPN) virus has antigens or "keys' that bind with surface proteins that form part of the pancreatic cell plasma membrane. The keys are used by the virus to "unlock" the cell and penetrate into and infect the cell.
Once a virus enters the bloodstream, the immune system's white blood cells are the primary weapon against the virus.
But there is another compound that if present in the cell plasma membrane plays a role in protecting cells from viral infections, the 3S, 3'S form of the micronutrient astaxanthin.
Viruses have surface proteins that act as antigens or keys to unlock cells. Viruses are held together by a "sack" made up of glycoproteins (a protein with a sugar attached). This sack is a weak point for viruses. The COVID19 virus for example can be destroyed using bleach, soap or alcohol. If you destroy the sack the the RNA/DNA inside spills out and is rendered harmless.
In our upcoming article on Power, we will cover the antioxidant side of astaxanthin in more detail. Astaxanthin also has antimicrobial properties. Astaxanthin has a dangling ester group on either end of its backbone. One tail is exposed to the bloodstream and one tail hangs in the cytoplasm inside the cell.
If a virus gets close enough, the tail will steal an oxygen from the glycoprotein breaking open the sack and rendering the virus harmless.
This mechanism is just one of the layers of defense that fish have against viral and microbial infections. Next up- Power
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Amplifeed Topcoat contains our lipid-rich nano emulsified 3S, 3'S form of natural astaxanthin to protect the animal from mitocondrial dysfunction, boosting power production for faster growth and protecting micronutrients from oxidation, Omega 3/DHA to help support the anti-inflammatory eicosanoid system, and heme iron which helps blood move oxygen from gills into cells.