By Jonny Lupsha, Wondrium Staff Writer
The human body has both innate and adaptive immune systems against disease. The overall immune system is comprised of the thymus, bone marrow, the spleen, and the lymphatic system. Immune system protection against COVID-19 is a mixed bag.
The Centers for Disease Control and Prevention (CDC) released a study of coronavirus patients in New York and California, comparing which medical histories protected the best against the global disease. Unsurprisingly, vaccinations remain the safest means of protection from COVID-19. Meanwhile, people who had survived a previous bout of COVID-19 and gotten vaccinated were the most protected.
Unvaccinated people with a past infection also exhibited some immunity, though this proved to be a riskier method of gaining immunity than vaccination.
This is a function of the adaptive immune system. In his video series An Introduction to Infectious Diseases, Dr. Barry Fox, Clinical Professor of Infectious Disease at the University of Wisconsin School of Medicine and Public Health, says the adaptive immune system targets specific pathogens, unlike the innate system.
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“The adaptive immune system is composed of highly specialized cells that adapt to and learn from prior invaders,” Dr. Fox said. “This is a system that remembers, for example, that you had measles as a child, and will protect you for life against measles. The adaptive system has two major branches: the cell mediated system and the antibody mediated humoral system.
“Note that humor is an old word that describes bodily fluid, like lymph and blood.”
Lymphocytes are a type of white blood cell that carry out immune responses in both systems. There are two kinds of lymphocytes. Stem cells that mature in bone marrow are called B-cells, while those that mature in the thymus are called T-cells. Each is specific for only one antigen, or foreign substance.
“B-cells work in the humoral immune system to mount a very specific antigen response,” Dr. Fox said. “B-cells can also inactivate viruses by neutralizing them before they can enter host cells. Some B-cells become memory cells, allowing a quicker, more specific immune response the next time the body encounters the same infection.”
T-cells work in the cell-mediated immune response. Some T-cells work to destroy viruses, while others become memory cells like B-cells in order to recognize foreign invaders more quickly with subsequent infections.
Vaccines and the Adaptive Immune System
Antibodies play a major role in the adaptive immune system: antibodies IgM is part of the first line of defense against invaders and IgG are formed in response to specific invaders, and usually stay with you for life.
“Let’s say as a child, you get the live measles vaccine; what happens after vaccination?” Dr. Fox asked. “The vaccine with measles antigens stimulates B-cells to mature into either an antibody-excreting plasma cell—which, within a couple weeks, produces IgM and IgG antibodies—or memory B-cells.”
According to Dr. Fox, this is known as the primary immune response. The antibody’s levels will gradually decline once the threat of measles has passed, but the memory B-cells remain dormant in the lymphatic system. If you’re then exposed to measles as an adult, the memory B-cells remember the virus remember the measles virus. Like a bouncer who’s learned a customer’s face from a “Do Not Serve” sign, they don’t take any guff from troublemakers.
“Similar to waking a bear out of hibernation, the cells will rapidly—within hours—start producing large amounts of measles-specific IgG antibodies,” Dr. Fox said. “Antibodies will attach themselves to the virus before [the virus] can attack healthy body cells. The memory immune lymphocytes would also recognize a pathogenic germ and assist in its destruction.”
Teamwork and communication between the innate and adaptive immune systems, he said, are vital to effectively fight off infection.