Defenses of The Immune System

Humans are constantly exposed to diseases, toxins, and other inherent threats to their health. To protect against these threats, humans rely on an intricate defense system known as the immune system. This system comprises a complex network of cells and organs that identify, neutralize, and even remember any foreign substance entering the body. 

By recognizing and destroying potential threats, the immune system works to avidly protect the body from harmful substances and keep individuals healthy.

 

What is the Immune System?

The immune system is a complex network of cells and organs that work together to protect the body against potential threats. The immune system defends itself by a system of recognition, identification, and deactivation of foreign substances entering the body. It is responsible for keeping humans healthy and safe from illness, infection, and disease-causing organisms.

The components of the immune system are divided into two main categories: innate immunity and adaptive immunity. Innate immunity includes physical barriers such as the skin and mucous membranes as well as white blood cells which are able to search for and identify foreign substances. Adaptive immunity is a more complex form of defense that includes T and B cells which are trained to recognize and neutralize foreign substances. In order to effectively protect the body from any threats, these two components of the immune system work together to ensure proper defenses.

 

Types of Immune System Defenses

Although the two components of the immune system: innate and adaptive immunity, work together to protect the body, each provides distinct protection. In order to fully understand the defenses of the immune system, it is important to understand the different types of protections that are available.

 

Physical Barriers

Physical barriers are the body’s first line of defense and are made up of the skin, mucous membranes, lysozymes, and other structures which work to prevent potential pathogens from entering the body. The outer layer of the skin is a powerful barrier that is composed of dead skin cells and sebum which serve to attract and trap water-soluble substances. Additionally, sweat glands within the body create an acidic layer on the skin’s surface which works to repel certain pathogens.

Mucous membranes are also important as they offer an additional layer of protection by trapping pathogens and other foreign substances, keeping them from entering the body. The saliva, tears, and other secretory fluids which flow from these membranes contain lysozymes, which are enzymes that serve to destroy any pathogens that may have gotten past the initial physical barriers.

 

White Blood Cells

White blood cells often referred to as leukocytes or WBCs, are cells that are present in the circulating blood as well as lymphatic fluid. WBCs, which are produced by the bone marrow, are able to search, identify, and destroy foreign substances within the body. They are also responsible for releasing chemical signals that alert other cells to potential threats and toxins.

The five main types of white blood cells: neutrophils, basophils, eosinophils, monocytes, and lymphocytes all carry out different yet critical roles in the immune system. Neutrophils are the most abundant WBCs and are responsible for ingesting and destroying pathogens. Basophils and eosinophils release inflammatory chemicals which fight against parasites and other bacteria. Monocytes are large cells that act as scavengers of dead and damaged cells and foreign particles, while lymphocytes serve to produce antibodies that fight off any invading microorganisms.

 

Antibodies

Antibodies are proteins that are created by B cells to fight against any foreign antigens entering the body. Antibodies bind to antigens in order to destroy them and keep them from entering cells and spreading in the body. There are five main types of antibodies that are named after their structure: IgG, IgM, IgA, IgE, and IgD. Each of these antibodies is specialized and works differently to protect the body.

IgG antibodies are the most abundant and have multiple functions. They are able to bind to bacteria and viruses, preventing them from entering cells and causing infection. Additionally, they can also mark pathogens for destruction. IgM antibodies are produced shortly after an infection is identified and often serve as the first line of defense against foreign substances. These antibodies are specifically able to bind to the antigen causing the infection and facilitate its destruction.

IgA antibodies are present in secretory fluids, such as tears, saliva, and mucous, and primarily protect against infections in these areas. IgE antibodies are typically involved in allergies and other reactions and respond quickly to allergens. These antibodies, when exposed to allergens, trigger a cascade of reactions that can cause symptoms such as sneezing, coughing, and watery eyes.

Finally, IgD antibodies are present in the lymph nodes and are believed to play a role in producing other antibodies when needed. By producing and releasing these five different types of antibodies to interact with antigens, the body can effectively neutralize and remove any potential threats.

 

Inflammation

Inflammation is the body's response to injury or infection and is often a key component of the immune system’s defenses. White blood cells, such as neutrophils, release proteins known as cytokines which cause the blood vessels to become inflamed. This inflammation increases blood flow to the affected area, allowing for an increased immune response when needed. Additionally, neutrophils and other white blood cells can release chemicals that will activate other cells to join the fight against infection. Inflammation also occurs with the release of other inflammatory compounds such as histamine, prostaglandins, and leukotrienes. These compounds cause the characteristic redness and swelling of the affected area and attract other WBCs and other immune cells to the area.

 

Phagocytosis

Phagocytosis is a process in which a cell engulfs and destroys a foreign object or pathogen. Macrophages, which are white blood cells specialized in phagocytosis, are responsible for this process. Macrophages recognize and engulf foreign particles, small organisms, or damaged cells, and digest them using enzymes. This process helps to eliminate any potentially harmful particles from the body, keeping individuals healthy and safe from infection.

 

The Immune System’s Ability to Remember

The immune system has the ability to “remember” any foreign substance it’s been exposed to in the past. This memory response allows the body to quickly recognize and respond to any antigens or toxins that it may encounter in the future. This ability is most notable when it comes to vaccinations, or shots that expose the body to a weakened version of a virus, allowing it to build a defense against it. By activating individual B and T cells on a molecular level, the body is able to form a better defense against any potential future exposures. As an example, if the body has been exposed to measles in the past, these cells will recognize and respond to any encounter with the virus more quickly.

 

Conclusion

The immune system is a complex network of organs and cells that are responsible for protecting the body from harmful foreign substances. By recognizing, identifying, and neutralizing any potential threats, the immune system works diligently and continuously to ensure individuals maintain their health. The defense of the immune system is divided into two categories: innate and adaptive immunity, each of which works together to rid the body of any unwanted materials. Physical barriers, white blood cells, antibodies, inflammation, and phagocytosis are all components of the immune system which work together to protect the body. The immune system’s ability to remember any encounter with antigens allows it to quickly and efficiently respond to potential future exposures. Without an effective immune system in place, humans would be left vulnerable to a variety of deadly threats.