The Immune System and Vaccines: A Primer

The immune system plays an important role in our overall well-being and survival. Without it, there is no way we can defend ourselves from the relentless attacks of various disease-causing microorganisms in our midst.

In the light of the 2020 health crisis, the immune system finds itself in the center stage once again. How does it work and how can a vaccine protect us from the unseen enemy? Here are some things you need to know.

How the Immune System Works

The immune system consists of a vast network of cells, tissues, and organs whose primary task is to detect and neutralize pathogenic agents like bacteria, viruses, and parasites.

Once a foreign pathogenic agent enters the body, the vast immune system network instantly recognizes that a breach has been made and launches an immediate yet non-specific response to destroy the invaders, typically within hours of initial infection. It also sends out distress signals to alert other pattern recognition receptors of the presence of potentially harmful microorganisms. If the innate immune response has been successful, the infection may not produce any symptoms.

However, there are times when the innate response fails. When this happens, the adaptive immune system, which has been previously activated by the innate immune response, is launched several days after the initial infection to eliminate the pathogens and control the situation.

Cells of the Immune System

The innate immune system is mainly made up of leukocytes or white blood cells, which include phagocytes, granulocytes, dendritic cells, innate lymphoid cells, and natural killer cells.

• Phagocytes are cells that travel throughout the body in search of invading pathogens and other foreign particles. Neutrophils (the most common phagocytes in the bloodstream that are responsible for attacking bacteria) and macrophages (cells that engulf pathogens and cellular debris, including dead and dying cells) are some good examples of phagocytes.
• Granulocytes are white blood cells (mast cells, basophils, and eosinophils) that are characterized by the presence of granules in their cytoplasm. Basophils and eosinophils secrete chemical mediators that provide protection against parasites, infections, and allergic reactions while mast cells (migrant cells of connective tissues) are primarily involved in immune tolerance, pathogen defense, and wound healing.
• Dendritic cells are phagocytes located in the skin, nose, lungs, stomach, and intestines. These cells are responsible for bridging the connection between the bodily tissues and the immune systems.
• Innate lymphoid cells (ILCs) are immune cells found predominantly at mucosal surfaces that secrete signaling molecules and regulate innate and adaptive immune cells.
• Natural killer cells are lymphocytes have the features of both innate and adaptive immunity and are responsible for destroying compromised host cells (e.g., virus-infected cells, tumor cells, etc.).

On the other hand, the adaptive immune system consists of lymphocytes, specifically B-lymphocytes and T-lymphocytes, which were derived from the stem cells in the bone marrow. These cells are capable of recognizing and warding off previous invaders when they attack.

• B-lymphocytes are involved in the humoral immune response and are responsible for producing antibodies (IgM, AgG, IgD, IgE, IgA) designed to neutralize specific microbes. They are also tasked with presenting antigens to T-cells.
• T-lymphocytes are involved in cell-mediated immune response and are tasked with neutralizing infected cells and activating other immune cells. T-cells have two major sub-types: killer T-cells which kill virus-infected, damaged, and dysfunctional cells and helper T-cells which regulate the innate and adaptive immune responses and determine the most appropriate immune response for a particular pathogen.

Vaccines and the Immune System: Working Together for Good

In a nutshell, vaccines work by stimulating the immune system to develop a response against a particular pathogen. Although the person may experience symptoms (e.g., fever) as the pathogenic antigen is introduced into the body, the immune system will start producing plasma B-cells and antibodies which will attach themselves to the target antigen and block them from entering the cells.

Once vaccinated, the body will recognize particular antigens as the enemy. And since the immune system has been previously exposed to that particular pathogen, it can launch a faster and more effective response should it encounter the real disease in the future.

The immune system plays an important role in our overall well-being and survival. Without it, there is no way we can defend ourselves from the relentless attacks of various disease-causing microorganisms in our midst.

In the light of the 2020 health crisis, the immune system finds itself in the center stage once again. How does it work and how can a vaccine protect us from the unseen enemy? Here are some things you need to know.

How the Immune System Works

The immune system consists of a vast network of cells, tissues, and organs whose primary task is to detect and neutralize pathogenic agents like bacteria, viruses, and parasites.

Once a foreign pathogenic agent enters the body, the vast immune system network instantly recognizes that a breach has been made and launches an immediate yet non-specific response to destroy the invaders, typically within hours of initial infection. It also sends out distress signals to alert other pattern recognition receptors of the presence of potentially harmful microorganisms. If the innate immune response has been successful, the infection may not produce any symptoms.

However, there are times when the innate response fails. When this happens, the adaptive immune system, which has been previously activated by the innate immune response, is launched several days after the initial infection to eliminate the pathogens and control the situation.

Cells of the Immune System

The innate immune system is mainly made up of leukocytes or white blood cells, which include phagocytes, granulocytes, dendritic cells, innate lymphoid cells, and natural killer cells.

• Phagocytes are cells that travel throughout the body in search of invading pathogens and other foreign particles. Neutrophils (the most common phagocytes in the bloodstream that are responsible for attacking bacteria) and macrophages (cells that engulf pathogens and cellular debris, including dead and dying cells) are some good examples of phagocytes.
• Granulocytes are white blood cells (mast cells, basophils, and eosinophils) that are characterized by the presence of granules in their cytoplasm. Basophils and eosinophils secrete chemical mediators that provide protection against parasites, infections, and allergic reactions while mast cells (migrant cells of connective tissues) are primarily involved in immune tolerance, pathogen defense, and wound healing.
• Dendritic cells are phagocytes located in the skin, nose, lungs, stomach, and intestines. These cells are responsible for bridging the connection between the bodily tissues and the immune systems.
• Innate lymphoid cells (ILCs) are immune cells found predominantly at mucosal surfaces that secrete signaling molecules and regulate innate and adaptive immune cells.
• Natural killer cells are lymphocytes have the features of both innate and adaptive immunity and are responsible for destroying compromised host cells (e.g., virus-infected cells, tumor cells, etc.).

On the other hand, the adaptive immune system consists of lymphocytes, specifically B-lymphocytes and T-lymphocytes, which were derived from the stem cells in the bone marrow. These cells are capable of recognizing and warding off previous invaders when they attack.

• B-lymphocytes are involved in the humoral immune response and are responsible for producing antibodies (IgM, AgG, IgD, IgE, IgA) designed to neutralize specific microbes. They are also tasked with presenting antigens to T-cells.
• T-lymphocytes are involved in cell-mediated immune response and are tasked with neutralizing infected cells and activating other immune cells. T-cells have two major sub-types: killer T-cells which kill virus-infected, damaged, and dysfunctional cells and helper T-cells which regulate the innate and adaptive immune responses and determine the most appropriate immune response for a particular pathogen.

Vaccines and the Immune System: Working Together for Good

In a nutshell, vaccines work by stimulating the immune system to develop a response against a particular pathogen. Although the person may experience symptoms (e.g., fever) as the pathogenic antigen is introduced into the body, the immune system will start producing plasma B-cells and antibodies which will attach themselves to the target antigen and block them from entering the cells.

Once vaccinated, the body will recognize particular antigens as the enemy. And since the immune system has been previously exposed to that particular pathogen, it can launch a faster and more effective response should it encounter the real disease in the future.