The modern world has identified 1,400 known species of human pathogens (viruses, bacteria, fungi, protozoa, and helminths). Several pathogens surround humans daily. Humanity is facing a severe viral disease, COVID-19, that is highly contagious and might be fatal.
What is COVID-19?
COVID-19 is a respiratory tract viral infection. Coronaviruses are a cause of common cold, probably second only to rhinoviruses in frequency. There are three serotypes found in humans, and there is no vaccine for any of them. The virus enters through the eyes, mouth, or nose.
Read more on COVID-19: Coronavirus: History, myths, symptoms, prevention, and updates
Body Defense Mechanism
Nature has provided a natural defense mechanism in the body to fight against viruses and bacteria. Skin and mucosal lining of the nose and gastrointestinal tract are the first-line defense against microbial infections. They prevent the penetration of microbes into the body.
Ever since the outbreak of COVID-19, scientists have been working on identifying the mechanism of infection and the spread of the virus. According to the China Medical Treatment Expert Group for COVID-19, it is not necessary that the individuals exposed to the virus will get infected. Neither all the infected ones develop severity in their symptoms.
Immune System Activation
When the age of people increases their immune systems degrade because it becomes depleted, overwhelmed, and exhausted. Because of weak immunity, older people are more likely to develop a serious condition when they come in contact with a virus or bacteria. Usually, a healthy immune system provides a defense against the invading organisms and combats the pathogens.
Coronavirus contacts with mucosal cells of the respiratory tract through eyes or nose. Then it gains entry into the cells, takes over the machinery, and starts dividing and producing its progeny, which attacks further. It enters the cell by attaching to the ACE – 2 receptor that is protein present on the surface of cells.
When the virus damages cells, it activates the immune system of the body. There are two types of cells to fight against the infection cytotoxic T cells and B cells. Macrophages and helper T cells recognize the antigen in the initial response and present it to T cells and B cells.
Role of T-cells
T cells attack the infected cells and kill the virus to eliminate the threat. B-cells form the plasma cells to assist in the production of antibodies to fight the virus—the antigen-antibody complex forms with a combination of both, which is removed by T cells.
Role of B-cells
B cells produce antibodies to fight against the ongoing active infection, and they produce Immunoglobin G (IgG). Immunoglobin G remains in blood to eliminate the virus if it gains entry into the system again. The antibodies combine with IgG to fight the virus providing active immunity. These antibodies may last for a shorter period or may last for years and even for life long.
Natural Killer Cells
National Clinical Research Center for Infectious Diseases, Beijing studied the responses of the immune system to COVID-19. Natural killer cells (NK cells) are present in the immune system and they play a vital role in combating the virus. These cells have cytotoxic properties that have perforin and proteases which are proteins of the natural killer killers.
Perforin protein forms cell pores upon the release of COVID-19 virus in proximity to these cells destined to kill. The process induces apoptosis which further assists in the destruction of the virus, while the infected cell produces virions.
The natural killer cells work to keep the virus contained, avoiding the spread. Alongside this, the immune system responds in an adaptive manner to generate the cytotoxic T cells to eliminate the infection. People who have a deficiency in the NK cells are at risk for the development of severe and fatal infection.
A mutated form of micro-organism can also trigger immune response resulting in the production of antibodies. These antibodies fight against active infection by normal same organism .i.e. active immunity. The procedure to develop a vaccine for the virus is in process. The infection produces an inflammatory response. Following this, the bone marrow produces immune cells in the site of infection. It leads to the activation of the complement system.
The complement system is a cascade of activation of various proteins. These proteins combine with the antigen that invades the body to either kill them or assist the immune system to recognize and eliminate it. Several chemicals are released at the site of injury and in the blood, which increases the body temperature that makes the invaders less likely to survive.
Future Directions in Research
Researchers are working on the development of antiviral therapies and vaccines for the treatment of COVID-19. Immunotherapy utilizes the natural immunity systems to boost an active response against viral infections.
The approach assists and increases the functioning of natural killer cells, that are innately present in the immune system and they respond to kills the virus. Individuals lacking an innate and adequate immunity response have increased chances of survival and less-severe symptoms with the utilization of immunotherapy.
Researchers are trying to answer if the antibodies formed against COVID-19 provides life-long immunity. They are using the antibodies from patients getting recovered from COVID-19, giving them to diseased that helps to fight the infection, and patients are recovering following that treatment.
A robust immune system helps to fight against the infection. The increased production of proteins and chemicals in cells fights the invading organism. A healthy diet provides building blocks as precursors to boost the immune system:
- Reduce stress because it suppresses the functioning of the immune system
- Vitamins and minerals are a healthy source of increasing the immunity, consume fruits and vegetables that increase immunity