Immunity And Immune System: Definition, Difference, Examples

What is Immunity?

The immune system is the body’s defence, especially against pathogenic agents, which include bacteria, viruses, and other invaders. The immune system is a sophisticated process that embraces cells, tissues, and vital organs that protect the body. Immunity, meaning in a biological view, consists of both the natural immunity and the immunity one gains from a vaccine. The first level of defence is natural immunity, which, although it offers fast protection, is not very targeted. Passive immunity is immediate, while acquired immunity is slower and offers specific immunity against specific pathogens. To fairly grasp the concept of immunity and how it works for keeping the body healthy and preventing illness, it is necessary to know the types of immunity and their functions.

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This Story also Contains

1. What is Immunity?
2. Types of Immunity: Innate and Adaptive
3. Innate Immunity
4. Types of Barriers
5. Cells Involved In Innate Immunity
6. Acquired Immunity
7. Cells involved in acquired immunity
8. Characteristics of Acquired Immunity
9. Different immune response mechanisms.
10. Humoral Immune Response
11. Cell-Mediated Immune Response
12. Types of Acquired Immunity
13. Autoimmunity
14. Vaccines
15. Immune System
16. Diagram Representing Lymphoid Organs
17. Lymphoid Organs
18. How the Immune System Works
19. Disorders of the Immune System
20. Boosting the Immune System
21. Immunology Techniques and Applications
22. How vaccines work?
23. Immunotherapy
24. Diagnostic tests
25. Recommended Topic Video

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Types of Immunity: Innate and Adaptive

The classification of immunity includes two main types: specific immunity, followed by nonspecific immunity. Innate immunity is immediately available at the time of birth and provides primary protection, while acquired immunity is developed as the organism responds to various pathogens as it grows.

Innate Immunity

The immune response called innate immunity is immediately available to the body to combat pathogens and is perhaps programmed at birth. It offers instant but broad immunity and doesn’t involve prior infection with the said pathogen. It consists of diverse physical and chemical barriers and the cells that detect pathogens and destroy them with the help of inflammation, or phagocytosis.

Types of Barriers

There are primarily 5 types of barriers:-

Physical Barriers

Physical barriers are the easiest to understand as they actively prevent pathogens from entering body tissue through structural restraint. The skin also has components that give it a hard, tight barrier; mucous membranes also encapsulate the bacteria or virus and eliminate the organisms through such activities as coughing or sneezing. These barriers are important as a form of protection for the body against infections in the event of a breakdown.

Chemical Barriers

Chemical barriers are those products or materials that reduce or can kill pathogens. Indeed, stomach acidity was found to kill the majority of microorganisms before they got to the intestines. For example, lysozyme present in saliva, tears, and mucus digests the bacterial cell wall. Defensins, which are part of the antimicrobial peptides, affect microbial membranes. These are chemical weapons that immobilize pathogens at the site of entry.

Cellular barriers

Tissue barriers include white and red blood cells in the body that are responsible for identifying and annihilating Antibodies. Macrophages are phagocytes that engulf and destroy microbes and debris, as are neutrophils. Macrophages are located in tissues, while during infections neutrophils are obtained from the intravascular environment. Natural killer (NK) cells are cytotoxic in that they identify, attack, and cause the death of infected cells.

Biological Barriers

The biological barriers include the beneficial microorganisms comprising the normal flora of the body that reduce the chances of pathogenic microorganisms gaining soil, nutrients, and space. These friendly microbes secrete chemicals that slow down the multiplication of pathogens and, at the same time, sharpen the immune response system.

Cytokine barriers

Cytokine barriers consist of signalling proteins controlling immune reactions and inflammation. Interleukins are autoinducers synthesised by several different kinds of cells in response to infection and play an essential role in regulating the immune response by recruiting immune personnel to the scene of the crime. These molecules are critical for the immune response to the pathogens to occur.

Cells Involved In Innate Immunity

Various cells are involved in innate immunity:-

Phagocytes

Phagocytes are other types of cells that are involved in their destruction by engulfing all the pathogens and decomposing them. These are the macrophages that are long-lived and have the function of ingesting and killing pathogens, and Neutrophils are short-lived, but very active in the destruction of pathogens within a short time.

Macrophages

Macrophages are the large cells that consume and destroy the pathogens and materials in the body. They are a part of both the acute and chronic response mechanisms and also present antigens to T-cells to start the process of adaptive immunity.

Neutrophils

Neutrophils are the most numerous type of leukocyte and are the first to react to the presence of infection. They readily eliminate pathogens through ingestion and also through the production of toxic substances.

Natural Killer (NK) Cells

NK cells are cytotoxic lymphocytes that are involved in the diagnosis and destruction of cells that are infected or have become malignant. They are vital in the regulation of viral diseases and tumour proliferation.

Mast Cells

The cells include mast, which plays a role in allergic reactions and the secretion of histamines. They have involvements in parasite and bacterial defence mechanisms.

Eosinophils

Eosinophils are useful in maintaining immunity against parasitic organisms and specific diseases. It is also involved in allergies.

Basophils

These are the least common white blood cells and play a role in inflammation and allergy.

Dendritic Cells

Dendritic cells are known as antigen-presenting cells that, seize antigens, and at the same time deliver the antigens to T cells, as a connection between innate and adaptive immunity.

Acquired Immunity

Acquired immunity, also known as adaptive immunity, is the second level of protection the body puts up against pathogens. It is defined as the enhanced ability of the immune system to recognise specific pathogens and respond to them faster at the second time of meeting the same pathogens. This form of immunity is attained progressively and functions with the help of certain specialised cells and processes

Definition and characteristics

Specificity, memory, and capacity to differentiate between self and non-self substances & organisms define Acquired immunity. Also unlike innate immunity, acquired immunity grows in effectiveness each time that an individual is exposed to a pathogen; it is quicker to respond when the same pathogen is encountered yet again.

Cells involved in acquired immunity

Primarily, 2 kinds of cells are involved in acquired immunity:

B Cells

B cells are other large mononuclear leukocytes that are involved in the acquired immunity besides actively participating in the humoral immunity. They produce substances that form a lock-key system with particular antigens that are present on the pathogen. On stimulation, the B cells differentiate through proliferation to plasma cells or memory B cells and start producing antibodies. B cells also differentiate into memory B cells to give the organism long-term immunity.

T Cells

T lymphocytes are significant leukocytes that are involved in acquired immunity, especially in cell-mediated immunity. Effector T cells, also known as cytotoxic T cells, CD8 T cells are involved in killing infected or cancerous cells by apoptosis. CD4+ T cells or helper T cells mobilize immune responses through the active identification of antigens and releasing substances known as cytokines which stimulate other immune cells. Memory T cells are alive after the first immune response and can give quick and stronger responses when encountering similar antigens again.

Characteristics of Acquired Immunity

There are various characteristics of acquired immunity:

Specificity

Specific immunity targets specific antigens that are involved in the pathogens, and this makes the immune response very fit.

Memory

The ability of the immune system to mobilise enhanced quick and aggressive response to the pathogen previously encountered is called immunological memory.

Diversity

Specific immunity can find several pathogens because of many types of antibodies and T cell receptors present in the immune system.

Distinction between the self and non-self.

One more capability of the immune system is the ability to tell the difference between the organism’s cells and cells that belong to pathogens, and thus refrain from attacking the organism’s tissues.

Different immune response mechanisms.

There are 2 kinds of immune response mechanisms:

Humoral Immune Response

The two main components of the circulating arm of the immune response include B cells, which are types of lymphocytes that target toxins and other pathogens or foreign molecules based on their antigens. After binding with antigen, B cells become sensitised and differentiate into plasma cells that release humorously large amounts of antibodies. They are protein substances that move in the bloodstream and through the lymphatic system, where they adhere to antigens in the pathogen’s body. This binding can either kill the pathogen, tag the pathogen for destruction by phagocytes, or activate the complement system to improve the killing of the pathogen.

Cell-Mediated Immune Response

Cell-mediated immunity entails the participation of T cells, another type of lymphocyte, in the body tissues. It is required for killing intracellular parasites like viruses and specific bacteria as well as for the identification of the transformed cell. Cytotoxic T cells, or CD8-positive cells, recognise and destroy infected or malignant cells through apoptosis. The helper T cells are important in controlling the immune response as they secrete cytokines which stimulate other immune cells, such as macrophages and cytotoxic T cells.

Types of Acquired Immunity

Two types of acquired immunity exist:

Active Immunity

Active immunity occurs when the immune system of the body produces antibodies that are specific to the antigen or activate the T cells. However, it can be initiated naturally due to an infection or artificially through the administration of vaccines. The common memory cells that are developed during active immunity include memory B cells and memory T cells that provide longer protection on subsequent exposures to the same antigen. Active immunity is pathogen-specific and offers highly effective, long-lasting protection.

Passive Immunity

All forms of passive immunity are obtained when antibodies that have been directly provided and already exist in the body are administered to another body. This transfer can happen transplacentally, for example, through the passing of maternal antibodies to the foetus or taro milk. It can also be artificially induced through the administration of antibodies, such as through immunoglobulin therapy. In the case of passive immunity, the antibodies transferred to the recipient’s body offer immediate protection, with this protection being temporary since the antibodies will be metabolised and expelled for elimination in the body. It is highly valuable in cases where prompt coverage is required or where an organism is incapable of producing an adequate immune response, for example, in newborns and HIV-positive clients.

Autoimmunity

Autoimmunity is characterised by the immune system attacking body tissues, and this conditions the individual for rheumatoid arthritis, and type 1 diabetes, among others.

Vaccines

Vaccines can be described as processed substances that are used to enhance the body’s immunity to particular diseases. They rely on copying symptoms of diseases and causing the body’s defence mechanisms to be activated without the development of conditions.

Immune System

The immune system is a protection system in the body that prevents pathogen invasion by bacteria, viruses, and fungi, among others. It includes two main components: innate immunity, which gives a quick and generalised reaction, and adaptive immunity, which offers a precise response to the invaders through a specific reaction.

Immunology, as defined by the above meanings, is the branch of medicine that is concerned with the identification of the body and the immune system's response to foreign particles. It focuses on the aspects of the immunological structure that are inherent and acquired and the conventional and abnormal roles they play when they are not well. Immunologists also strive to establish effective vaccines and immunotherapies for strengthening or modulating immune responses.

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Some examples of parts of the immune system are white blood cells, such as macrophages, neutrophils, B lymphocytes, T lymphocytes, and natural killer cells; and organs such as the thymus, bones, spleen, and lymph nodes. Proteins like antibodies, cytokines, and complement proteins act as mediators and pathogens’ inhibitors. These elements function to track and expel illness-causing agents within the body and thus prevent infections.

Immunology is an essential component of the study of the nature of health and illness. It helps in the production of vaccines, formulation of treatments for illnesses such as cancer and auto-immune diseases, and in the identification of disorders with the immune system. Immunology is important in enhancing medical science and the welfare of patients, thus being a crucial field of study both in academic institutions and in practice.

Diagram Representing Lymphoid Organs

Lymphoid Organs

Lymphoid tissues are those tissues that contribute to the formation, differentiation, and activation of immune cells.

Primary Lymphoid Organs

Bone Marrow: More specifically, bone marrow is the part of the human body that is responsible for producing all types of blood cells, the red ones and the white ones included.

Thymus: It is in the thymus that T cells develop to be able to respond to a given antigen.

Secondary Lymphoid Organs

Spleen: The spleen is involved with blood filtering as well as leading the immune response by presenting the antigens to the cells involved in the immune response.

Lymph Nodes: Lymph nodes act as a filter for the lymph as well as a place where it's containing immune cells harmonise as well as plan on how best to deal with the invading pathogen.

Tertiary lymphoid organs

Tertiary lymphoid organs are observed in the zones of chronic inflammation and are involved in local immune processes.

How the Immune System Works

The working mechanism of immunue system is explained below:

Recognition of Pathogens

Organisms of disease-causing agents are identified by the immune cells through specific antigens, which are located on the outer membrane of the pathogens.

Response to Pathogens

When it senses a pathogen, the immune system initiates an attack to get rid of it. This also involves stimulation of the immune cells and resources, the release of antibodies, as well as inflammation.

Primary Immune response

This is the first time the immune system comes across the pathogen, causing activation and multiplication of immune cells.

Secondary Immune response

The secondary immune response is usually faster and more efficient due to the point that it contains memory cells that are acquainted with the pathogen.

Role of Memory Cells in Adaptive Immunity

Some cells in the body keep information about the pathogens that have been encountered before to ensure a quick and efficient response.

Disorders of the Immune System

Autoimmune diseases

Autoimmune diseases are conditions where the immune system turns against the body and starts attacking the body’s tissues.

Examples include:

Rheumatoid Arthritis: The immune system targets the joints of the body causing inflammation.

Type 1 Diabetes: The immune system of the body malfunctions and goes after the insulin-producing cells in the pancreas.

Immunodeficiency disorders

Immunodeficiency disorders are those in which the body’s immune system is compromised in some manner.

Examples-

HIV/AIDS: HIV infects those cells and destroys the body’s defence system, which is the immune system, resulting in AIDS.

SCID (Severe Combined Immunodeficiency): An inherited disease in which the body’s ability to fight infections is significantly impaired.

Allergies and Hypersensitivities

Allergy is a condition where the immune system of the body behaves in an abnormal manner, resulting in response to substances that do not pose any threat to the body, including pollen and certain foods, and this results in some symptoms such as sneezing, itching and swelling of certain parts of the body.

Boosting the Immune System

Importance of a Healthy Diet

Vitamin intake, Minerals, and antioxidants; The overall functioning and strength of the immune system can be attributed to a vitamins, minerals, and antioxidant-rich diet. It is estimated that the foods that must be taken include fruits, vegetables, nuts, lean meats, beans, and dairy products.

Role of exercise

Physical activity increases circulation, meaning immune cells are transported throughout the body more effectively, and immune capabilities increase.

Vaccination

Vaccines are substances that help the body organise the production of antibodies without causing sickness, thus offering the body defence against diseases.

Adequate sleep and stress management

Stress and sleep management form critical components of the immune system since the body cannot fight diseases when it is stressed or has had inadequate rest. Both of them have a deep influence on the immune system and health status of the individual.

Immunology Techniques and Applications

Vaccines: Different types of vaccines are listed below:

1. Live-attenuated vaccines: Live-attenuated vaccines are made from forms of the pathogen that can infect the body but do not make the person sick but rather develop immunity.

2. Inactivated vaccines: Inactivated vaccines involve the use of organisms that have been killed, and therefore, there is no possibility of the disease developing; however, an immune response is triggered.

3. Subunit, recombinant, and conjugate vaccines: These vaccines, referred to as subunit vaccines, use only portions of the pathogen to stimulate an immune response but not the whole organism.

4. mRNA vaccines: As a vaccine, the messenger RNA tells cells to manufacture a protein that encourages an immune reaction and helps to guard against the disease.

How vaccines work?

Vaccines, in essence, act exactly the way pathogens do – they introduce antigens to the body, which trigger the immune response and the generation of memories without leading to the disease. This conditions the body to fight the actual pathogen if confronted with it in the future

Immunotherapy

Cancer treatment

Some of the immunotherapies are checkpoint inhibitors and CAR T-cell therapy, which strengthens the body's immune system to identify and destroy cancer cells.

Allergy treatments

Allergic immunotherapy slowly exposes the body’s immune system to allergens, thereby, introducing changes that promise to reduce allergic reactions.

Diagnostic tests

ELISA (Enzyme-Linked Immunosorbent Assay): Cross matches reagin antibodies or antigens in specimen fluid; Applies in diagnosing infection and autoimmune disease.

PCR (Polymerase Chain Reaction): Enhances DNA strands for amplifying genetic contents without the ability to detect organisms’ DNA.

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Thus, immunity is a concept that refers to the protection of the body against health-harming factors or agents and has two principal branches of defence – innate immunity as well as adaptive immunity. The role of the immune system includes the prevention of immunodeficiency disease, managing allergies, and immunity using diet, exercise, vaccines, and stress. Immunology presents appreciable skills and uses, including vaccines, immunotherapy, and diagnostics, emphasising the significance of optimal immune function for the control of diseases.

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