Immunity – Definition, Types and Vaccination

Immunity is a defense mechanism of the body that is provided by the immune system and helps in fighting disease-causing organisms. There are two immunity types: innate and acquired immunity. Immunity-enhancing foods help boost the body’s immune system

Vaccination also enhances immunity by exposing the immune system to harmless antigens, preparing it to give a quicker and stronger response upon encountering the disease-causing pathogen. In this article, we will study immunity and its type, vaccination, and immunization.

What is Immunity?

Immunity Definition – Immunity is the body’s defense system that protects against infections and diseases by recognizing and fighting against harmful pathogens.

Immunity allows the body to recognize and eliminate pathogens, preventing their harmful effects and promoting overall health. The two main types of immunity are innate, providing immediate but nonspecific protection, and adaptive, offering targeted and memory-based responses. Adaptive immunity involves T and B cells that recognize and remember specific pathogens.

Immunization, or vaccination, enhances adaptive immunity by exposing the immune system to harmless antigens, promoting a quicker and more effective response upon subsequent exposure to the actual pathogen. Autoimmunity occurs when the immune system mistakenly targets the body’s own tissues, leading to various autoimmune diseases.

Types of Immunity

Immunity means the body’s ability to defend against pathogens, and it is achieved through the immune system’s ability to recognise and eliminate harmful pathogens. Immunity is of two types:

• Innate immunity
• Acquired immunity

Innate Immunity

Innate immunity refers to the body’s natural defence system that provides immediate protection against pathogens. This type of immunity is present in an organism by birth. It is non-specific which means it is common for all pathogens. Innate immunity generates a rapid response. It includes physical barriers, physiological barriers, and cellular defences which recognize and eliminate pathogens. Also, the inflammatory response, fever and cytokines barriers are crucial aspects of innate immunity that eliminate infections. Two levels of defence come under Innate Immunity:

• First level of defence
• Second level of defence

First Level of Defence

The first level of defense is provided by the body’s physical and chemical barriers, such as the skin and mucous membranes. It act as a protective shield against pathogens, preventing their entry into the body. These barriers act as the initial line of defense, forming an important part of the innate immune system. The first level of defence includes two types of barriers-

• Physical Barriers: Skin act as a physical barrier for incoming pathogens. Mucus epithelium in the nose and gut in the small intestine trap pathogens and prevent their entry into the body.
• Chemical Barriers: HCl in the stomach creates a strong acidic environment that kills pathogens. Saliva in the mouth, and tears in the eyes have anti-biotic properties.

Second Level of Defence

The second level of defense involves the innate immune system’s cellular response, where white blood cells like macrophages and neutrophils recognize and engulf pathogens. This rapid, nonspecific defense helps neutralize and eliminate invaders that breach the initial physical barriers. The second level of defence includes:

• Cellular Barriers: Cellular barriers involve immune cells like macrophages and neutrophils, which actively protects tissues, engulfing and digesting pathogens to prevent infection. These include two types of cells: Phagocytic Cells and Non-Phagocytic cells
• Inflammation: Inflammation is the body’s natural and protective response to injury or infection, characterized by redness, swelling, heat, and pain at the affected site.
• Fever: A condition in which body temperature increases more than normal. Pathogens release toxins or pyrogens and WBCs release Intraleukins (type of cytokines) or pyrogens. These pyrogens stimulate the Hypothalamus which increases body temperature to decrease the growth of pathogens. Antipyretic drugs like paracetamol can be used to decrease body temperature.
• Cytokines Barriers: Virus-infected cells release interferons. Interferons are small proteins containing 270 amino acids that stimulate non-infected cells to release an antiviral protein known as T.I.P. (Translation Inhibition Protein) that inhibits the translation of viral protein in non-infected cells.

Cells Involved In Innate Immunity

The cells involved in innate immunity are:

1. Macrophages: Engulf and digest pathogens; act as antigen-presenting cells to activate other immune cells.
2. Neutrophils: Phagocytic cells that rapidly respond to infections, eliminating pathogens through engulfment and destruction.
3. Natural Killer (NK) Cells: Target and destroy virus-infected cells and cancer cells; part of the early immune response.
4. Dendritic Cells: Capture and present antigens to T cells, initiating adaptive immune responses.
5. Mast Cells: Release histamines and other inflammatory mediators in response to injury or infection, contributing to the inflammatory response.
6. Basophils and Eosinophils: Involved in the immune response against parasites and play a role in allergic reactions.
7. Complement System: Consists of proteins that enhance the immune response by promoting phagocytosis, inflammation, and cell lysis.
8. Epithelial Cells: Form physical barriers and secrete antimicrobial substances, contributing to the defense against pathogens.

Acquired Immunity

Acquired immunity refers to the immune response that develops after exposure to specific pathogens. It is a learned and adaptive defence mechanism that targets and eliminates specific pathogens. This type of immunity is acquired after birth. This type of immunity provides long-term protection and the ability to generate a stronger and faster response upon re-exposure to the same pathogen. Acquired immunity involves the production of specialized cells, such as B cells and T cells, and the generation of targeted antibodies.

Cells Involved in Acquired Immunity

Acquired immunity is broadly classified into two types of cells:

B Lymphocytes mediated immunity or Antibody-mediated immunity or Humoral immunity: The antibodies produced by B-lymphocytes are present in blood and are transported all over the body. It has the following features:

• Stem cells in the bone marrow produce immature B lymphocytes that on maturation in the bone marrow itself, form mature B lymphocytes.
• B cells recognize specific antigens through their B cell receptor.
• The activated B cells produce plasma cells and memory cells.
• The plasma cells release antibodies in the blood.
• The memory B cells remember the information about the pathogen to prevent any disease caused by that pathogen in the future.

T lymphocytes mediated immunity or cell-mediated immunity: It has the following features:

• It involves Helper T cells, Killer T cells, Suppressor T cells and Memory T cells.
• T helper cells initiate Cell-mediated immunity.
• The active T killer cells eliminate the infected cells from the body by releasing perforin protein against cancerous cells and virus-infected cells and thereby promoting apoptosis or programmed cell death.
• The T helper cells also activate other immune cells.
• T lymphocytes are also involved in tissue grafting or organ transplantation.

Types of Immune Response

There are two types of immunity response:

• First Immune Response: First immune response is generated when a pathogen encounters the body for the first time. Antigen interacts with antibody present on B lymphocytes and stimulates cell division of B lymphocytes into plasma cells and memory cells.
• Second Immune Response: When the same pathogen enters the body next time, the antigens interact this time with antibodies on memory cells. Antibodies IgG are formed in high intensity after antigen-antibody interaction.

Types of Acquired Immunity

Active Immunity: It produces long-lasting responses and memory cells are also involved in preventing future infestations. Active Immunity is of two types:

• Natural immunity: It involves all-natural infections. Natural Infections induce the formation of antibodies from plasma cells. Memory cells help in the defence against future infestations.
• Artificial immunity: It involves all vaccinations. Vaccines help in the formation of memory cells and antibodies artificially

Passive Immunity: In this type of immunity prepared antibodies are provided to the host for the treatment of diseases. It is short-lived immunity and memory cells are not formed. Passive Immunity is also of two types:

• Natural immunity: Passive immunity through natural modes.
  • IgG antibodies through the placenta to the foetus.
  • IgA antibodies through Colostrum (First milk) to infants.
• Artificial immunity: Passive immunity through artificial modes.
  • Anti Tetanus Serum [A.T.S.]
  • Antivenom

Difference between Acquired Immunity and Innate Immunity

The difference between acquired and innate immunity are as follows:

Type of Acquired Immunity	Natural	Artificial
Active	Natural infections induce the formation of antibodies from plasma cells. Memory cells help in the defence against future infestations.	Vaccines help in the formation of memory cells and antibodies artificially.
Passive	Passive immunity through natural modes: IgG antibodies through the placenta to the fetus. IgA antibodies through Colostrum (First milk) to infants.	Passive immunity through artificial modes: Anti Tetanus Serum [A.T.S.], Antivenom.

Autoimmunity

Autoimmunity evolved in higher vertebrates. It is based on the ability to differentiate non-self cells from self-cells. In autoimmunity, the body attacks self-cells. This results in damage to the body. These diseases in which the body attacks self-cells are called autoimmune diseases.

Myasthenia Gravis and Rheumatoid Arthritis are examples of autoimmune diseases. Both genetic tendency and environmental triggers, such as infections or certain medications, can contribute to the development of autoimmune disorders. Autoimmunity leads to inflammation and tissue damage, impacting the proper functioning of affected organs or systems.

Vaccination and Immunization

Vaccination involves the administration of weakened or inactivated forms of pathogens or their components, known as antigens, into the body. The vaccine was discovered by Edward Jenner and the first vaccine was prepared by Louis Pasteur. This stimulates the immune system to recognize and remember the specific antigens, preparing it for a rapid and robust response upon encountering the actual pathogen.

The interaction of antigen and antibody stimulates the division of B lymphocytes into memory cells and plasma cells. Plasma cells prepare antibodies that are responsible for minimal symptoms of the disease after vaccination and Memory cells will prepare antibodies in future infestations.

Immunization, achieved through vaccination, aims to prevent or mitigate the severity of infectious diseases by enhancing the body’s ability to fight off pathogens. Wide-scale immunization contributes to herd immunity, protecting even those who cannot be vaccinated, such as individuals with certain medical conditions.

Conclusion – Immunity

In conclusion, immunity is the body’s defense system against infections, achieved through innate and acquired immunity. Immunity-boosting foods and vaccination play vital roles in boosting the immune system and preparing it to fight against disease-causing organisms. Understanding the types of immunity and the mechanisms involved in immunization is crucial for promoting overall health and preventing the spread of infectious diseases.

FAQs on Immunity

What is Immunity in Biology?

Immunity is the body’s ability to defend against harmful pathogens like bacteria and virus. It prevents or limits the impact of infections and is classified into two types: Innate Immunity and Acquired Immunity.

What are the 4 Types of Immunity?

The four types of immunity are innate immunity, the body’s immediate and nonspecific defense against pathogens; adaptive immunity, a memory-based response involving T and B cells; passive immunity, it is acquired through the transfer of antibodies; and artificial immunity, it is achieved through vaccination.

What are T Cells?

T cells, or T lymphocytes, are a type of white blood cell that recognize and destroy infected or abnormal cells. It plays a central role in the adaptive immune system and help regulate immune response.

How to Increase Immunity?

To increase immunity, eat immunity-boosting foods and get vaccinated to boost the body’s defenses against infections. Regular exercise and sufficient sleep also contribute to a strong immune system

What is the Diffference Between Innate Immunity and Acquired Immunity?

Innate immunity is present at birth, provides nonspecific and immediate defenses against pathogens. Acquired immunity develops after exposure to pathogens or vaccination. It offers a specific and long-lasting protection against infection.

What is Immunity and its Function?

Immunity is the body’s defense system against infections, fighting harmful pathogens to maintain health. Its function is to recognize and eliminate pathogens, preventing diseases and promoting well-being.

What is Antibodies?

Antibodies, also known as immunoglobulins, are proteins produced by the immune system to neutralize and destroy harmful pathogens. They recognize specific antigens on pathogens, marking them for destruction by other immune cells.

What are some Immunity Disorder Symptoms?

Immunity disorder symptoms may include frequent infections, fatigue, and inflammation, indicating a compromised immune system.