What is Immunity? What are the types of Immunity? How does the Immune System function? What are Lymphoid Organs? Read further to know more.
The best defense mechanism in our bodies is the immune system. It works to protect us from harmful bacteria and maintains us healthy.
Cells, tissues, and organs that make up the immune system collaborate to defend our body. This system employs several strategies to protect the human body from intruding microorganisms. They operate using memory, some of which are innate and others of which are learned.
They, therefore, play a role in autoimmunity, allergies, and organ transplantation. White blood cells (or leukocytes), which are essential in eradicating disease-causing organisms or chemicals, are the most crucial immune system cells.
In addition to leukocytes, the immune system also includes antibodies as well as lymphoid organs, tissues, and proteinaceous molecules.
What is Immunity?
- Immunity is the body’s capacity to protect itself from pathogenic germs.
- Many microorganisms come into contact with our body daily, yet only a small number cause disease.
- The rationale is that our bodies can produce antibodies that fight against harmful viruses and defend the body from illnesses. Immunity is the name given to this defense strategy.
Types of Immunity
There are two major types of immunity:
Innate Immunity or Natural or Non-specific Immunity.
- Acquired Immunity or Adaptive Immunity.
- An organism has this form of immunity from birth. As soon as the pathogen hits, this is immediately activated.
- Barriers and defense systems that prevent foreign substances from entering the body are part of innate immunity.
- The body’s defense mechanism is referred to as innate immunity.
- The inherent defense mechanisms that this immunity provides, such as salivary enzymes, natural killer cells, undamaged skin, neutrophils, etc., help us fight off diseases at birth before being exposed to pathogens or antigens.
- Long-lasting immunity occurs when our body creates the necessary antibodies on its own. There aren’t many natural defenses in our bodies to keep germs out.
Cells Involved In Innate Immunity
- Phagocytes: They move around the body and scan for foreign objects. While the body is protecting itself against that pathogen, they engulf and kill it.
- Macrophages: They are capable of traversing the circulatory system’s cellular barriers. To enlist more cells at the location of infections, they emit specific signals like cytokines.
- Mast Cells: They are crucial for wound healing and infection defense.
- Neutrophils: They are made of poisonous granules that will destroy any pathogen that comes into contact with them.
- Eosinophils: They have highly poisonous proteins that are lethal to any bacteria or parasite that comes in touch with them.
- Basophils: They target multicellular parasites. They also release histamine, just like mast cells do.
- Natural Killer Cells: By eradicating the contaminated host cells, these prevent the spread of diseases.
- Dendritic Cells: They are found in the tissues that serve as the entry points for first infections. By presenting an antigen, these cells alert the rest of the immune system to the infection.
- The immunity that our bodies develop through time is known as acquired immunity or adaptive immunity. This is not innate immunity, which is present from birth.
- Acquired immunity refers to the immune system’s capacity to respond to illness and produce pathogen-specific immunity. It also goes by the name of adaptive immunity.
- The term “acquired immunity” refers to immunity that a person develops after birth.
- It is particular and is carried out by lymphocytes or antibodies that render the antigen harmless.
- Acquired immunity’s primary purpose is to both treat the infectious disease’s victim and shield others against it in the future.
- It primarily comprises an enhanced lymphatic defense system that recognizes and ignores its bodily cells to function.
- Our body’s immune system recognizes infections that it has already encountered. It is primarily brought on when a person is exposed to the virus or its antigen.
- To envelop the infection and eliminate its antigen, our body begins to produce antibodies.
- It is referred to as a primary response when it is encountered for the first time. Naturally acquired immunity is the ability of antibodies to target pathogens for the second time after the body becomes used to them.
- Our body’s acquired immunity has a few unique characteristics.
Cells Involved in Acquired Immunity
Acquired immunity involves two types of cells: B-cells and T-cells
- In the bone marrow, they grow.
- When these cells come into contact with external substances, they become active. These foreign-object signals are these particles.
- The B-cells instantly undergo plasma cell differentiation and create antibodies that are specific to that foreign substance, or so-called antigen.
- These antibodies adhere to the antigen’s or foreign agent’s surface.
- These antibodies find every antigen the body contains and eliminate it.
- Humoral immunity is the name for immunity that is B-cell dependent.
- They grow in the thymus after beginning in the bone marrow.
- Helper, cytotoxic, and regulatory T-cell subtypes can be produced. The bloodstream receives the discharged cells.
- Helper T-cells release cytokines that serve as messengers when these cells are activated by an antigen.
- These cytokines start the process of B-cells differentiating into plasma cells, which thereafter secrete antibodies against the antigens.
- The cancer cells are destroyed by the cytotoxic T lymphocytes.
- Immune responses are regulated by regulatory T cells.
Types of Acquired Immune Response- Humoral Immune Response:
- The blood cells carry and distribute the antibodies made by B-lymphocytes throughout the body. Because it includes an antibody made by lymphocytes, it is known as the humoral immune response.
- It depends on how antibodies moving throughout the body are acting. Humoral immunity is activated when an antibody on a
- B-cell interacts with an antigen. The helper T cell is exposed to the antigen after the B cell has internalized it. The B-cell is triggered by this.
- The B cells that have been stimulated develop into plasma cells.
- Antibodies are released into the bloodstream by these plasma cells. To stop any disease brought on by that pathogen shortly, the memory B cells store information about the pathogen.
Cell-mediated Immune Response:
- The T helper cells start cell-mediated immunity.
- By releasing toxins, the cytotoxic T cells destroy the infected cells from the body and encourage apoptosis, or programmed cell death.
- Other immune cells are stimulated by the T helper cells. In the case of transplant recipients, cell-mediated immunity is made obvious.
- It is possible to transplant one of our sense organs to replace another when one stops working. With the immunological response, though, things are more complicated.
- It indicates that T-lymphocytes can distinguish between tissue or organs that are from our body and those that are from foreign bodies.
- Because our bodies could reject a transplanted organ, we cannot transplant or implant organs into our bodies, even if we discover a donor with the same blood group. The T-cells instantly identify the tissue or organ as alien and prevent it from assimilating into the body.
- Because of this, immunosuppressant medicine is required for the rest of the recipient’s life. The T-lymphocytes are in charge of regulating this reaction.
Immune System in the Body
- The lymphoid organs, tissues, cells, and soluble molecules like antibodies make up the human immune system. As you’ve read, the immune system is distinct in that it can identify foreign antigens, react to them, and retain those responses. Moreover, organ transplants, autoimmune illnesses, and allergy reactions all depend heavily on the immune system.
- Organs of Lymph: These are the locations of lymphocyte genesis, maturation, and/or proliferation.
The thymus and bone marrow are the main lymphoid organs, where immature lymphocytes develop into antigen-sensitive lymphocytes.
- The lymphocytes move to secondary lymphoid organs like the appendix, spleen, lymph nodes, tonsils, and Peyer patches of the small intestine after maturation.
- The places where lymphocytes engage with antigens and multiply to become effector cells are provided by the secondary lymphoid organs.
- The primary lymphoid organ, the bone marrow, is where all blood cells, including lymphocytes, are made.
- The thymus is a lobed organ that sits beneath the breastbone and closes to the heart. The thymus is relatively large at birth, but as people age, it gets smaller and smaller until it is very small by the time they reach adolescence.
- T-lymphocyte formation and maturation take place in the microenvironments provided by the thymus and bone marrow, respectively.
- The spleen is a sizable organ with a bean shape. Mostly lymphocytes and phagocytes are present. It filters the blood by capturing microorganisms that are carried in the blood. Spleen also has a large reservoir of erythrocytes.
- Little, solid structures known as lymph nodes are scattered throughout the lymphatic system. Microorganisms or other antigens that accidentally enter the lymph and tissue fluid are captured by lymph nodes.
- The immunological response is brought on by antigens that become lodged in the lymph nodes and activate the lymphocytes there.
- Mucosal-associated lymphoid tissue is another type of lymphoid tissue that can be found in the lining of the three main tracts (respiratory, digestive, and urogenital) (MALT). About 50% of the lymphoid tissue in the human body is made up of it.
- The antigens of the pathogen that causes the disease are used to create vaccines. For instance, the smallpox vaccination contains the pathogen’s antigens that cause the sickness.
- Antibody-producing cells that make smallpox antibodies are stimulated when a person receives the smallpox vaccination. The body is thus shielded from the sickness developing in the future.
- Artificially acquired immunity is the result of purposely introducing pathogenic bacteria into our bodies; it creates a comparable reaction.
- Immunization is a method that gives people resistance to infectious diseases and dangerous bacteria by administering a vaccine into their bodies. By vaccination, the body’s immune system is stimulated to defend against upcoming infections or diseases.
- Lymphoid organs are those parts of the immune system that protect the body from invaders that could potentially infect it or spread tumors. Bone marrow, blood vessels, lymphatic vessels, thymus, spleen, and several other collections of lymphoid tissue are all included in it.
- The origin, maturation, and proliferation of lymphocytes occur in lymphoid organs. Depending on where they are in their growth and development, they might be classified as primary, secondary, or tertiary.
- These organs are made up of fluid connective tissues and several leukocytes or white blood cells kinds. Leukocytes, or white blood cells, contain the highest concentration of lymphocytes.
Primary lymphoid organs
- Lymphocytes are produced and allowed to mature by the principal lymphoid organs. Developing lymphocytes from immature progenitor cells also serves a purpose.
- As a result, it is known as the core lymphoid organs.
- Primary lymphoid organs include the thymus and bone marrow, for instance.
Secondary lymphoid organs
- Because they are engaged in encouraging the locations where lymphocytes interact with the antigen to become effector cells, the secondary lymphoid organs are also known as the peripheral lymphoid organs.
- They start the immune system’s adaptive response.
- The extracellular lymphoid tissues Spleen, tonsils, lymph nodes, the appendix, and other organs are instances of secondary lymphoid organs.
Tertiary lymphoid organs
- There are typically very few lymphocytes in the tertiary lymphoid organs.
- It is significant in the process of inflammation.
- Innate and acquired immunity, B cells, T cells, cellular and humoral immunological responses, and the immune system are all discussed in this context.
- Health is more than just being free from illness. It is a condition of whole bodily, mental, social, and psychological health.
- Humans are frequently distressed by illnesses like typhoid, cholera, pneumonia, fungal skin infections, malaria, and many more.
- If left untreated, vector-borne illnesses like malaria, particularly the Plasmodium falciparum variety, can be lethal.
When we are exposed to chemicals that cause disease, our immune system is crucial in preventing certain illnesses.
- Our body’s natural defenses, including our skin, mucous membranes, saliva, tears, and phagocytic cells, assist in preventing the entry of infections into our bodies.
- Certain antibodies (humoral immune response) and cells (cell-mediated immune response) serve to kill infections if they manage to enter our body.
- The immune system remembers. The immune response is quicker and more severe after a subsequent encounter with the same virus. This serves as the cornerstone of the defense provided by vaccination and immunization.
Article written by Aseem Muhammed