Innate Immunity vs Adaptive Immunity- Definition and 29 Differences
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The immune system is the body`s defense mechanism against harmful agents such as bacteria, viruses, parasites, toxins and cancer cells. It consists of two main components: innate immunity and adaptive immunity. These two types of immunity work together to protect the body from infections and diseases.
Innate immunity, also known as natural or nonspecific immunity, is the first line of defense that is present from birth. It provides a rapid and general response to any foreign substance that enters the body, regardless of its identity. Innate immunity consists of physical barriers (such as skin and mucous membranes), chemical barriers (such as saliva and stomach acid), cellular components (such as phagocytes and natural killer cells) and molecular components (such as complement proteins and cytokines).
Adaptive immunity, also known as acquired or specific immunity, is the second line of defense that develops after exposure to a specific antigen. It provides a slower but more effective and specific response to a particular pathogen or foreign substance. Adaptive immunity consists of two types of lymphocytes: B cells and T cells. B cells produce antibodies that bind to antigens and neutralize them or mark them for destruction by other immune cells. T cells recognize and kill infected cells or activate other immune cells.
The main difference between innate and adaptive immunity is that innate immunity is nonspecific and does not change with repeated exposure to the same antigen, while adaptive immunity is specific and improves with repeated exposure to the same antigen. Another difference is that innate immunity does not have memory, while adaptive immunity does have memory and can remember previous encounters with an antigen.
In this article, we will explore the definition and 29 differences between innate and adaptive immunity in more detail. We will also compare their advantages and disadvantages in fighting infections and diseases.
Innate immunity is the first line of defense against pathogens and foreign substances. It is also known as natural or nonspecific immunity. It consists of physical barriers, such as the skin and mucous membranes, and cellular and molecular components, such as phagocytes, natural killer cells, complement proteins, cytokines and interferons. Innate immunity is present at birth and does not require prior exposure to antigens. It responds rapidly and uniformly to any type of infection, but it does not have the ability to recognize specific pathogens or to generate immunological memory. Innate immunity is essential for preventing the spread of microbes and for activating the adaptive immune system. Innate immunity can be divided into two types: external and internal innate immunity.
External innate immunity refers to the physical and chemical barriers that prevent the entry of pathogens into the body. These include the skin, which is composed of keratinized epithelial cells that form a waterproof layer; the mucous membranes, which line the respiratory, gastrointestinal and urogenital tracts and secrete mucus that traps and expels microbes; the cilia, which are hair-like structures that move mucus and debris out of the airways; the tears, saliva and sweat, which contain antimicrobial substances such as lysozyme, lactoferrin and defensins; and the acidic pH of the stomach and vagina, which inhibits the growth of many bacteria.
Internal innate immunity refers to the cellular and molecular mechanisms that recognize and eliminate pathogens that have breached the external barriers. These include:
- The phagocytes, which are white blood cells that engulf and destroy microbes by producing reactive oxygen species and lysosomal enzymes. The main types of phagocytes are neutrophils, monocytes, macrophages and dendritic cells.
- The natural killer cells, which are lymphocytes that kill virus-infected cells and tumor cells by releasing perforins and granzymes that induce apoptosis (programmed cell death).
- The complement system, which is a group of plasma proteins that can be activated by three pathways: classical, alternative and lectin. The complement system enhances phagocytosis by opsonizing (coating) pathogens with C3b molecules; lyses (breaks) pathogens by forming membrane attack complexes (MACs); recruits inflammatory cells by releasing anaphylatoxins (C3a and C5a); and activates the adaptive immune system by binding to antigen-antibody complexes.
- The cytokines, which are small proteins that act as messengers between cells. They regulate inflammation, cell proliferation, differentiation and apoptosis. Some examples of cytokines are interleukins (ILs), tumor necrosis factor (TNF), interferons (IFNs) and chemokines.
- The interferons, which are a type of cytokine that are produced by virus-infected cells. They inhibit viral replication by inducing antiviral genes in neighboring cells; activate natural killer cells and macrophages; and increase the expression of major histocompatibility complex (MHC) molecules, which present antigens to T cells.
In summary, innate immunity is the first line of defense against pathogens and foreign substances. It consists of physical barriers, such as the skin and mucous membranes, and cellular and molecular components, such as phagocytes, natural killer cells, complement proteins, cytokines and interferons. Innate immunity is present at birth and does not require prior exposure to antigens. It responds rapidly and uniformly to any type of infection, but it does not have the ability to recognize specific pathogens or to generate immunological memory.
Adaptive immunity, also known as specific or acquired immunity, is the type of immunity that is mediated by specialized cells called lymphocytes and their products, such as antibodies and cytokines. Adaptive immunity is characterized by its ability to recognize and respond to a wide range of antigens, which are molecules that can trigger an immune response. Adaptive immunity can also remember previous encounters with antigens and mount a faster and stronger response upon re-exposure, a phenomenon known as immunological memory.
Adaptive immunity can be divided into two branches: humoral immunity and cell-mediated immunity. Humoral immunity involves the production of antibodies by B lymphocytes, which can bind to antigens and neutralize them or mark them for destruction by other immune cells. Cell-mediated immunity involves the activation of T lymphocytes, which can directly kill infected or abnormal cells or help other immune cells to do so.
Adaptive immunity is usually triggered by the presentation of antigens to lymphocytes by specialized cells called antigen-presenting cells (APCs), such as dendritic cells, macrophages, and B cells. APCs process and display antigens on their surface in association with molecules called major histocompatibility complex (MHC), which are recognized by T cell receptors on T lymphocytes. Depending on the type of antigen and the type of MHC molecule, different subsets of T lymphocytes are activated, such as helper T cells, cytotoxic T cells, or regulatory T cells. Helper T cells secrete cytokines that stimulate B cells to produce antibodies or activate other immune cells. Cytotoxic T cells directly kill infected or abnormal cells by releasing perforins and granzymes that induce apoptosis. Regulatory T cells suppress excessive or unwanted immune responses and maintain immune tolerance.
Adaptive immunity is essential for the protection against pathogens that can evade or overcome innate immunity, such as viruses, bacteria, fungi, and parasites. However, adaptive immunity can also cause problems when it is misdirected against self-antigens (autoimmunity), harmless foreign antigens (allergy), or transplanted tissues (rejection). Therefore, adaptive immunity needs to be tightly regulated by various mechanisms to ensure its specificity, diversity, memory, and tolerance.
Innate and adaptive immunity are two types of immune responses that work together to protect the body from infections. Innate immunity is the first line of defense that is present from birth and responds quickly and nonspecifically to any foreign substance or pathogen. Adaptive immunity is the second line of defense that is acquired after exposure to specific antigens and responds slowly and specifically to eliminate them.
The main components of innate immunity are physical barriers (such as skin and mucous membranes), chemical barriers (such as lysozyme and complement), cellular barriers (such as phagocytes and natural killer cells), and inflammatory responses (such as cytokines and fever). The main components of adaptive immunity are lymphocytes (such as B cells and T cells), antibodies (such as immunoglobulins), and antigen-presenting cells (such as dendritic cells and macrophages).
The main characteristics of innate immunity are:
- It is present in all multicellular organisms
- It does not require prior exposure to antigens
- It does not have memory or specificity
- It responds within minutes to hours
- It recognizes conserved molecular patterns on pathogens
- It activates the complement system and the adaptive immune system
The main characteristics of adaptive immunity are:
- It is present only in vertebrates
- It requires prior exposure to antigens
- It has memory and specificity
- It responds within days to weeks
- It recognizes unique molecular structures on antigens
- It produces antibodies and memory cells
The following table summarizes some of the differences between innate and adaptive immunity:
| Innate Immunity | Adaptive Immunity |
|---|---|
| Present from birth | Acquired after exposure |
| Nonspecific | Specific |
| No memory | Memory |
| Fast response | Slow response |
| Conserved recognition | Unique recognition |
| Complement activation | Antibody production |
Innate and adaptive immunity are not mutually exclusive, but rather cooperate and complement each other to provide optimal protection against infections. Innate immunity provides immediate and broad defense, while adaptive immunity provides delayed and specific defense. Innate immunity also helps to activate and regulate adaptive immunity through antigen presentation and cytokine production. Adaptive immunity also enhances innate immunity by producing antibodies that opsonize pathogens, activate complement, and neutralize toxins. Therefore, both types of immunity are essential for the survival and health of the host.👍
The innate and adaptive immunity differ in various aspects, such as their origin, components, specificity, diversity, memory, response time, and functions. Here are 29 differences between them:
| S.N. | Innate Immunity | Adaptive Immunity |
|---|---|---|
| 1 | It is present from birth and inherited from parents. | It is acquired after exposure to antigens or vaccination. |
| 2 | It consists of physical barriers (skin, mucous membranes), cellular components (neutrophils, macrophages, dendritic cells, natural killer cells, mast cells, eosinophils, basophils), and soluble factors (complement system, cytokines, acute phase proteins, defensins). | It consists of lymphocytes (B cells and T cells) and their products (antibodies and cytokines). |
| 3 | It recognizes conserved molecular patterns shared by many pathogens or damaged cells, such as lipopolysaccharides, peptidoglycans, flagellin, nucleic acids, etc. | It recognizes specific antigens displayed by pathogens or infected cells, such as proteins, polysaccharides, lipids, etc. |
| 4 | It has a limited diversity of receptors that can bind to a broad range of antigens. | It has a high diversity of receptors that can bind to a virtually unlimited number of antigens. |
| 5 | It does not have memory and responds in the same way to repeated exposures to the same antigen. | It has memory and responds faster and stronger to repeated exposures to the same antigen. |
| 6 | It responds immediately or within hours of antigen encounter. | It responds after a lag period of days or weeks of antigen encounter. |
| 7 | It provides the first line of defense against infections and inflammation. | It provides the second line of defense and enhances the innate immunity. |
| 8 | It is non-specific and does not distinguish between self and non-self antigens. | It is specific and can distinguish between self and non-self antigens. |
| 9 | It does not require antigen presentation by major histocompatibility complex (MHC) molecules. | It requires antigen presentation by MHC molecules on antigen-presenting cells (APCs). |
| 10 | It does not involve clonal selection or expansion of lymphocytes. | It involves clonal selection or expansion of lymphocytes that recognize a specific antigen. |
| 11 | It does not undergo somatic recombination or hypermutation of receptor genes. | It undergoes somatic recombination or hypermutation of receptor genes to generate diversity and affinity maturation. |
| 12 | It does not have a primary or secondary response. | It has a primary response that is slow and weak and a secondary response that is fast and strong. |
| 13 | It does not confer long-term protection or immunity against pathogens. | It confers long-term protection or immunity against pathogens through memory cells. |
| 14 | It is mediated by both cellular and humoral components. | It is mediated by either cellular (T cell) or humoral (B cell) components. |
| 15 | It does not have subclasses or types based on the nature of antigens or responses. | It has subclasses or types based on the nature of antigens or responses, such as humoral vs cellular, active vs passive, natural vs artificial, etc. |
| 16 | It is regulated by various receptors and signaling pathways that modulate the activation, differentiation, migration, and function of innate immune cells. | It is regulated by various co-stimulatory molecules and cytokines that modulate the activation, differentiation, proliferation, and function of adaptive immune cells. |
| 17 | It can recognize both extracellular and intracellular antigens through pattern recognition receptors (PRRs) such as toll-like receptors (TLRs), NOD-like receptors (NLRs), RIG-I-like receptors (RLRs), C-type lectin receptors (CLRs), etc. | It can recognize either extracellular antigens through antibodies produced by B cells or intracellular antigens through T cell receptors (TCRs) expressed by T cells. |
| 18 | It can eliminate pathogens or infected cells through various mechanisms such as phagocytosis, degranulation, cytotoxicity, opsonization, complement activation, inflammation, etc. | It can eliminate pathogens or infected cells through various mechanisms such as neutralization, opsonization, complement activation, antibody-dependent cellular cytotoxicity (ADCC), cytotoxic T lymphocyte (CTL) activity, helper T cell (Th) activity, etc. |
| 19 | It is not affected by immunodeficiency diseases or immunosuppressive drugs. | It is affected by immunodeficiency diseases or immunosuppressive drugs that impair the function of lymphocytes or their products. |
| 20 | It does not cause hypersensitivity or allergic reactions. | It can cause hypersensitivity or allergic reactions due to the production of IgE antibodies or the activation of Th2 cells. |
| 21 | It does not cause autoimmune diseases. | It can cause autoimmune diseases due to the loss of tolerance to self antigens or the activation of autoreactive lymphocytes. |
| 22 | It does not have a role in transplant rejection. | It has a role in transplant rejection due to the recognition of foreign MHC molecules or antigens on the donor tissue or organ. |
| 23 | It does not have a role in tumor immunity. | It has a role in tumor immunity due to the recognition of tumor-associated antigens or neoantigens on the cancer cells. |
| 24 | It does not have a role in immunotherapy. | It has a role in immunotherapy due to the manipulation of lymphocytes or their products to enhance the immune response against pathogens or cancer cells. |
| 25 | It is conserved and similar among different species of animals. | It is diversified and different among different species of animals. |
| 26 | It is influenced by various factors such as age, nutrition, stress, infection, etc. | It is influenced by various factors such as age, nutrition, stress, infection, vaccination, etc. |
| 27 | It is not affected by antigenic variation or mutation of pathogens. | It is affected by antigenic variation or mutation of pathogens that can escape the recognition by antibodies or TCRs. |
| 28 | It does not require the cooperation or interaction of different types of cells. | It requires the cooperation or interaction of different types of cells, such as APCs, B cells, T cells, etc. |
| 29 | It is not influenced by the previous exposure or history of infection. | It is influenced by the previous exposure or history of infection that can induce memory cells and confer immunity. |
Innate and adaptive immunity are two complementary aspects of the immune system that work together to protect the body from infections and diseases. Innate immunity is the first line of defense that provides immediate and nonspecific responses to foreign invaders. Adaptive immunity is the second line of defense that provides delayed and specific responses to antigens that have been recognized by the innate system. Adaptive immunity also generates immunological memory that allows for faster and stronger responses upon re-exposure to the same antigen.
Innate and adaptive immunity differ in many aspects, such as their origin, components, mechanisms, duration, and regulation. Some of the differences are summarized in the table below:
| S.N. | Innate Immunity | Adaptive Immunity |
|---|---|---|
| 1. | Present from birth | Acquired during lifetime |
| 2. | Consists of physical barriers (skin, mucous membranes), cellular components (phagocytes, natural killer cells, mast cells, etc.), and soluble factors (complement system, cytokines, etc.) | Consists of lymphocytes (B cells and T cells) and their products (antibodies and cytokines) |
| 3. | Recognizes conserved molecular patterns on pathogens or damaged cells | Recognizes specific antigens on pathogens or infected cells |
| 4. | Responds within minutes to hours | Responds within days to weeks |
| 5. | Has limited diversity and specificity | Has high diversity and specificity |
| 6. | Does not improve with repeated exposure to the same antigen | Improves with repeated exposure to the same antigen |
| 7. | Does not generate immunological memory | Generates immunological memory |
| 8. | Regulated by pattern recognition receptors (PRRs) and toll-like receptors (TLRs) | Regulated by major histocompatibility complex (MHC) molecules and co-stimulatory molecules |
Understanding the differences between innate and adaptive immunity can help us appreciate the complexity and efficiency of the immune system in fighting infections and diseases. It can also help us design better strategies for vaccination, immunotherapy, and immunomodulation.
Summary and Key Points
- Innate immunity and adaptive immunity are two types of immune responses that work together to protect the body from infections.
- Innate immunity is the first line of defense that is present from birth and responds quickly and nonspecifically to any foreign substance or pathogen.
- Adaptive immunity is the second line of defense that is acquired after exposure to an antigen and responds slowly and specifically to a particular pathogen or its products.
- Innate immunity involves physical and chemical barriers, phagocytic cells, natural killer cells, complement system, inflammation and cytokines.
- Adaptive immunity involves lymphocytes, antibodies, antigen presentation, clonal selection, immunological memory and immunological tolerance.
- Some of the differences between innate and adaptive immunity are based on their origin, specificity, diversity, memory, response time, recognition mechanism, effector mechanism and regulation.
- Both innate and adaptive immunity are essential for maintaining health and preventing diseases. They also interact and cooperate with each other in various ways to enhance the immune response.
- Examples of Innate and Adaptive Immunity in Action
To illustrate the differences between innate and adaptive immunity, let us consider some examples of how they work in different scenarios.
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Innate immunity against viral infections: When a virus enters the body, it is recognized by innate immune cells such as macrophages and dendritic cells, which produce cytokines to alert other immune cells and induce inflammation. The virus is also detected by natural killer (NK) cells, which can directly kill virus-infected cells by releasing cytotoxic molecules. Additionally, the virus may trigger the complement system, which can coat the virus with proteins that make it easier for phagocytes to engulf and destroy it. The innate immune system can also activate interferons, which are antiviral proteins that inhibit viral replication and enhance the adaptive immune response.
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Adaptive immunity against viral infections: The adaptive immune system is activated when the virus is presented to T cells and B cells by antigen-presenting cells (APCs) such as dendritic cells and macrophages. The T cells can differentiate into helper T cells, which secrete cytokines to stimulate B cells and cytotoxic T cells, or into cytotoxic T cells, which can directly kill virus-infected cells by recognizing their viral antigens. The B cells can differentiate into plasma cells, which produce antibodies that can neutralize the virus or mark it for destruction by phagocytes or complement. The adaptive immune system also generates memory T cells and memory B cells, which can quickly respond to future encounters with the same virus.
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Innate immunity against bacterial infections: When a bacterium enters the body, it is recognized by innate immune cells such as macrophages and neutrophils, which phagocytose and destroy it. The bacterium may also activate the complement system, which can opsonize the bacterium with proteins that facilitate its phagocytosis or form pores in its membrane that cause its lysis. The bacterium may also trigger toll-like receptors (TLRs) on innate immune cells, which induce the production of cytokines and chemokines that recruit more immune cells and initiate inflammation. The innate immune system can also activate antimicrobial peptides, which can directly kill bacteria by disrupting their membranes or interfering with their metabolism.
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Adaptive immunity against bacterial infections: The adaptive immune system is activated when the bacterium is presented to T cells and B cells by APCs such as dendritic cells and macrophages. The T cells can differentiate into helper T cells, which secrete cytokines to stimulate B cells and macrophages, or into regulatory T cells, which suppress excessive inflammation and prevent tissue damage. The B cells can differentiate into plasma cells, which produce antibodies that can neutralize the bacterium or mark it for destruction by phagocytes or complement. The adaptive immune system also generates memory T cells and memory B cells, which can quickly respond to future encounters with the same bacterium.
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