Introduction
What stands between the viral infections from entering your body? There must be some sort of defense system activated to prevent that from happening in the first place! And that goes to your immune system. The immune system is where a complex network of your organs, proteins, and cells protects your body’s own cells by fighting against possible infections from the outside. It’s said that the more infections your body takes in, the more equipped your body is because it allows for your immune system to remember patterns of the same invader.
Now, your body doesn’t just “fight off” viruses. There are three important lines of defense that the immune system activates when the body senses foreign invaders.
First Line of Defense
The first defense that the virus must penetrate are the physical and chemical barriers of your body. Physical barriers include skin, mucous membranes, and endothelia. Normal flora is a kind of bacteria that just lives on our skin and helps make it hard for other bacteria to enter. Chemical ones are acidic fluids like urine and lysozyme in saliva or sweat. Most often, the invader could overcome this first defense – especially when we let it in through a hole in our body either by cut or contraction from others.
Second Line of Defense
The nonspecific innate response seeks to destroy invaders without targeting specific individuals such as starting a fever, releasing chemical signals, causing inflammation, and more within the body. Two types of phagocytes are found in tissues and blood: neutrophils and macrophages. Neutrophils are one of the first immune cells to respond to infections by consuming a pathogen and then bursting in response. While macrophages could repeat this process countlessly, would use their cytoplasmic extensions to reach, engulf, digest, and later spit the rest of the pathogen they’ve consumed out. These two types of white blood cells would continuously contribute which would lead to an inflammatory response.
Third Line of Defense
Specific adaptive response would occur throughout the whole body instead of only focusing on the site of infection. Mainly involving two types of white blood cells to accomplish the work: B lymphocytes and T lymphocytes. B lymphocytes are made in the bone marrow and are responsible for a humoral response, which means there will be viruses free in the fluids of the body that B cells must produce antibodies to fight against. Antibodies are Y-shaped proteins produced by our body infinitely and depending on the shape for what’s infecting, the antibody docks to the antigen to mark antigens where macrophages can easily find. Meanwhile, T lymphocytes are made in the thymus gland and create killer T cells, which finds any of the infected-with-virus cells inside our body and kill our own cells if needed. This is called the cell-mediated response.
References
Dutta, D. S. (n.d.). What are the Three Lines of Defense? Retrieved from News Medical Life Sciences: https://www.news-medical.net/health/What-are-the-Three-Lines-of-Defense.aspx#:~:text=Reviewed%20by%20Emily%20Henderson%2C%20B,responses%2C%20and%20specific%20adaptive%20responses.
In brief: The innate and adaptive immune systems. (2023). Retrieved from National Library of Medicine: https://www.ncbi.nlm.nih.gov/books/NBK279396/ Assessed and Endorsed by the MedReport Medical Review Board