17.3 Adaptive Immunity
3 min read•june 18, 2024
is our body's specialized defense system. It uses , , and to fight off specific threats like viruses and bacteria. This targeted approach allows for more effective and long-lasting protection against pathogens.
The adaptive immune system has two main branches: cell-mediated and . These work together to combat different types of invaders, with directly attacking infected cells and producing antibodies to neutralize pathogens.
Components and Mechanisms of Adaptive Immunity
Components of adaptive immunity
Top images from around the web for Components of adaptive immunity
The Adaptive Immune Response: T lymphocytes and Their Functional Types | Anatomy and Physiology View original
Is this image relevant?
The Adaptive Immune Response: B-lymphocytes and Antibodies | Anatomy and Physiology II View original
Is this image relevant?
The Adaptive Immune Response: B-lymphocytes and Antibodies | Anatomy and Physiology II View original
Is this image relevant?
The Adaptive Immune Response: T lymphocytes and Their Functional Types | Anatomy and Physiology View original
Is this image relevant?
The Adaptive Immune Response: B-lymphocytes and Antibodies | Anatomy and Physiology II View original
Is this image relevant?
1 of 3
Top images from around the web for Components of adaptive immunity
The Adaptive Immune Response: T lymphocytes and Their Functional Types | Anatomy and Physiology View original
Is this image relevant?
The Adaptive Immune Response: B-lymphocytes and Antibodies | Anatomy and Physiology II View original
Is this image relevant?
The Adaptive Immune Response: B-lymphocytes and Antibodies | Anatomy and Physiology II View original
Is this image relevant?
The Adaptive Immune Response: T lymphocytes and Their Functional Types | Anatomy and Physiology View original
Is this image relevant?
The Adaptive Immune Response: B-lymphocytes and Antibodies | Anatomy and Physiology II View original
Is this image relevant?
1 of 3
- Lymphocytes are white blood cells that play a central role in
- (B cells) produce antibodies and are involved in humoral immunity (-mediated responses)
- (T cells) are involved in (direct killing of infected cells)
- () activate and coordinate immune responses by stimulating B cells to produce antibodies and activating and
- Cytotoxic T cells () directly kill infected or abnormal cells (cancer cells)
- ###-presenting_cells_0### (APCs) such as , macrophages, and B cells present to T cells to initiate adaptive immune responses
- APCs display antigens on their surface using molecules for T cell recognition
- Antibodies are Y-shaped proteins produced by B cells that bind to specific antigens (bacteria, viruses) and neutralize pathogens and mark them for destruction
- Memory cells are long-lived B and T cells that quickly respond to subsequent exposures to the same antigen (flu virus) and provide long-lasting immunity (measles)
- Memory cells are a key component of , allowing for faster and more effective immune responses upon re-exposure to pathogens
Cell-mediated vs humoral immune responses
- Cell-mediated immunity is mediated by T cells and targets intracellular pathogens (viruses, some bacteria like tuberculosis)
- Key cells: Cytotoxic T cells directly kill infected cells and helper T cells secrete (signaling molecules) to activate other immune cells
- Humoral immunity is mediated by B cells and antibodies and targets extracellular pathogens (bacteria, fungi)
- Key cells: B cells produce antibodies that neutralize pathogens (tetanus toxin) and mark them for destruction and helper T cells stimulate B cells to produce antibodies
- Interaction between cell-mediated and humoral immunity: Helper T cells are involved in both responses by activating cytotoxic T cells in cell-mediated immunity and stimulating B cells to produce antibodies in humoral immunity
Lymphoid organs and immune cell development
- ( and ) are sites where lymphocytes develop and mature
- ( nodes, spleen, and mucosa-associated lymphoid tissues) are where adaptive immune responses are initiated
- occurs in secondary lymphoid organs, where lymphocytes with receptors specific to an antigen are activated and proliferate
Immune Tolerance and Autoimmunity
Immune tolerance and autoimmune prevention
- is the ability of the immune system to distinguish between self and non-self and prevents the immune system from attacking the body's own tissues
- occurs during lymphocyte development in the thymus (T cells) and bone marrow (B cells) where lymphocytes that strongly react to self-antigens are eliminated or inactivated
- occurs in peripheral tissues after lymphocytes mature through mechanisms including:
- (unresponsiveness)
- Suppression by
- Deletion of self-reactive cells
- Breakdown of immune tolerance can lead to where the immune system mistakenly attacks the body's own tissues (Type 1 diabetes, rheumatoid arthritis, multiple sclerosis)
- Maintaining immune tolerance is crucial for preventing autoimmune disorders through proper development and regulation of lymphocytes and balance between immune activation and suppression
Key Terms to Review (48)
Active immunity: Active immunity is the protection against disease through the production of antibodies by the immune system in response to exposure to a pathogen. It can be acquired naturally through infection or artificially through vaccination.
Adaptive immunity: Adaptive immunity is a part of the immune system that learns to recognize and specifically target pathogens after initial exposure. It involves the activation of lymphocytes and the formation of immunological memory.
Adaptive immunity: Adaptive immunity is a specialized and dynamic immune response that develops over time and provides long-lasting protection against specific pathogens. This type of immunity is characterized by the ability to recognize and remember specific antigens, leading to a more efficient and potent response upon subsequent exposures. Adaptive immunity involves the activation of lymphocytes, specifically B cells and T cells, which play crucial roles in targeting and eliminating pathogens.
Anergy: Anergy is a state of unresponsiveness in immune cells, particularly T lymphocytes, that occurs when they encounter an antigen without the necessary co-stimulatory signals. This process is crucial in preventing autoimmune responses, as it ensures that immune cells do not activate against self-antigens. By inducing anergy, the immune system can maintain tolerance to self while remaining capable of responding to foreign antigens.
Antibodies: Antibodies are specialized proteins produced by the immune system that identify and neutralize foreign objects like bacteria and viruses. They are crucial players in the adaptive immune response, helping to provide targeted defense against specific pathogens while also connecting with the circulatory system to travel throughout the body and ensure an effective immune response.
Antibody: An antibody is a protein produced by the immune system that recognizes and binds to specific antigens, such as pathogens or foreign substances. They play a crucial role in identifying and neutralizing harmful agents in the body.
Antigen: An antigen is any substance that triggers an immune response by being recognized as foreign by the immune system. Antigens can be proteins, polysaccharides, lipids, or nucleic acids.
Antigen-presenting cell (APC): An antigen-presenting cell (APC) is a type of immune cell that captures and processes antigens, presenting them on its surface to T-cells. This process activates adaptive immune responses.
Antigen-presenting cells: Antigen-presenting cells (APCs) are a specialized group of immune cells that play a crucial role in the adaptive immune response by capturing, processing, and presenting antigens to T cells. These cells, including dendritic cells, macrophages, and B cells, help initiate and shape the immune response by activating T lymphocytes, which are essential for recognizing and combating pathogens. APCs bridge the innate and adaptive immune systems, ensuring a coordinated and effective response to foreign invaders.
Antigens: Antigens are molecules or molecular structures that are recognized by the immune system as foreign and can trigger an immune response. They can be found on the surface of pathogens like bacteria and viruses, or even on infected cells. Understanding antigens is crucial for grasping how adaptive immunity functions, as they play a key role in the activation of lymphocytes and the production of antibodies.
Autoimmune disorders: Autoimmune disorders are conditions in which the immune system mistakenly attacks the body's own healthy cells, tissues, or organs. This malfunction occurs when the immune system fails to distinguish between foreign invaders and the body's own components, leading to inflammation and damage. These disorders can affect various parts of the body and result in a range of symptoms, highlighting the delicate balance required for effective immune responses.
B cells: B cells are a type of white blood cell that plays a critical role in the adaptive immune system by producing antibodies. These cells are responsible for recognizing specific antigens, such as pathogens, and generating an immune response that leads to the neutralization or destruction of these foreign invaders. By differentiating into plasma cells, B cells can produce large quantities of antibodies that help to protect the body from infections and provide long-term immunity.
B lymphocytes: B lymphocytes, or B cells, are a type of white blood cell that plays a crucial role in the adaptive immune system by producing antibodies. They are responsible for humoral immunity, which involves the secretion of antibodies that neutralize pathogens and mark them for destruction. These cells also have the ability to remember previous infections, allowing for a faster response upon re-exposure to the same pathogen.
Bone marrow: Bone marrow is a soft, spongy tissue found in the center of bones, primarily responsible for producing blood cells, including red blood cells, white blood cells, and platelets. It plays a vital role in the immune system by generating lymphocytes, which are crucial for adaptive immunity, helping the body recognize and remember pathogens.
CD4+ T cells: CD4+ T cells are a type of immune cell that play a critical role in the adaptive immune response by helping other cells in the immune system respond to infections. These cells are characterized by the presence of the CD4 glycoprotein on their surface, which acts as a co-receptor for the T cell receptor (TCR). They are essential for orchestrating the immune response, including activating B cells to produce antibodies and stimulating CD8+ T cells to kill infected cells.
CD8+ T cells: CD8+ T cells, also known as cytotoxic T lymphocytes, are a subset of T cells that play a critical role in the adaptive immune response by directly killing infected or cancerous cells. These cells express the CD8 glycoprotein on their surface, which helps distinguish them from other T cell types. When activated, CD8+ T cells recognize antigens presented by major histocompatibility complex (MHC) class I molecules and initiate a targeted immune response.
Cell-mediated immune response: Cell-mediated immune response is a type of adaptive immunity where T cells directly attack infected or abnormal cells. It is crucial for fighting intracellular pathogens like viruses and certain bacteria.
Cell-mediated immunity: Cell-mediated immunity is a crucial aspect of the adaptive immune response that involves the activation of T lymphocytes, which play a key role in defending the body against intracellular pathogens, such as viruses and some bacteria. This type of immunity does not rely on antibodies but instead involves direct cell-to-cell interactions and the release of cytokines to eliminate infected cells and coordinate the immune response. It is essential for recognizing and responding to cells that have been altered by infection or cancer.
Central tolerance: Central tolerance is a crucial mechanism in the immune system that helps prevent the body from attacking its own tissues by eliminating self-reactive immune cells during their development in the thymus and bone marrow. This process ensures that T cells and B cells that recognize self-antigens are either destroyed or rendered inactive, maintaining immune system balance and preventing autoimmune diseases. Understanding central tolerance is essential for grasping how adaptive immunity protects the body while also guarding against harmful autoimmunity.
Clonal Selection: Clonal selection is a process that describes how specific immune cells, particularly B and T lymphocytes, are activated and proliferate in response to an antigen. When an antigen enters the body, only those immune cells that recognize the antigen bind to it, leading to their activation and clonal expansion, which generates a large population of identical cells that can effectively target the pathogen. This process is crucial for the adaptive immune response, as it ensures that the body can produce a targeted and efficient defense against specific infections.
Cytokines: Cytokines are small proteins that play crucial roles in cell signaling within the immune system. They are produced by various cells and act on other cells to regulate immunity, inflammation, and hematopoiesis. Cytokines help coordinate the innate and adaptive immune responses, influencing both the activation and differentiation of immune cells, which is essential for effective defense against pathogens.
Cytokinesis: Cytokinesis is the final stage of cell division where the cytoplasm divides to form two separate daughter cells. It typically follows mitosis or meiosis, ensuring each daughter cell has its own set of organelles and sufficient cytoplasmic material.
Cytotoxic T Cells: Cytotoxic T cells, also known as CD8+ T cells, are a type of white blood cell that play a crucial role in the adaptive immune response by directly killing infected or cancerous cells. These cells recognize specific antigens presented by major histocompatibility complex (MHC) class I molecules on the surface of target cells, leading to their activation and subsequent destruction of abnormal cells. This process is vital for controlling infections and eliminating tumor cells, showcasing their importance in the body's defense mechanisms.
Dendritic cell: Dendritic cells are antigen-presenting cells that play a critical role in the initiation and regulation of the adaptive immune response. They capture, process, and present antigens to T-cells, activating them to respond to pathogens.
Dendritic Cells: Dendritic cells are specialized antigen-presenting cells that play a crucial role in the adaptive immune response by capturing, processing, and presenting antigens to T cells. They act as a bridge between the innate and adaptive immune systems, helping to initiate and shape the immune response against pathogens. By doing this, dendritic cells are essential for activating T cells and ensuring that the immune system can respond effectively to infections.
Effector cells: Effector cells are activated immune cells that directly engage and destroy pathogens. They include various types such as cytotoxic T cells and plasma cells.
Helper T cells: Helper T cells are a type of white blood cell that play a crucial role in the immune response by assisting other immune cells in recognizing and responding to pathogens. They are primarily responsible for activating B cells to produce antibodies and stimulating cytotoxic T cells to kill infected cells. These cells are essential for orchestrating the adaptive immune response, ensuring that the body can effectively combat infections and maintain immunological memory.
Humoral immune response: Humoral immune response is an aspect of adaptive immunity that involves B cells producing antibodies to neutralize pathogens. It targets extracellular microbes and their toxins.
Humoral immunity: Humoral immunity is a critical component of the adaptive immune system that involves the production of antibodies by B cells in response to antigens. This type of immunity primarily targets pathogens and toxins present in body fluids, enabling the immune system to neutralize and eliminate these harmful agents. By producing specific antibodies, humoral immunity plays a vital role in providing long-lasting protection against infections and ensuring immune memory.
Immune tolerance: Immune tolerance is the state in which the immune system does not mount an attack against certain antigens, including self-antigens, thus preventing autoimmune reactions. This phenomenon is crucial for maintaining homeostasis and ensuring that the immune system can distinguish between harmful invaders and the body's own tissues. Understanding immune tolerance is vital for comprehending how the adaptive immune response operates and how disruptions in this balance can lead to various immune-related disorders.
Immunological Memory: Immunological memory is the ability of the immune system to remember past infections and respond more effectively to subsequent encounters with the same pathogen. This memory is primarily established through the activation of specific lymphocytes, such as B cells and T cells, which can persist in the body for long periods. The quick and robust response upon re-exposure to the pathogen is crucial for providing long-lasting immunity and is a key feature of adaptive immunity.
Lymph: Lymph is a clear fluid that circulates through the lymphatic system, carrying cells that help fight infections and other diseases. It consists of white blood cells, especially lymphocytes, which are crucial for adaptive immunity.
Lymphocytes: Lymphocytes are a type of white blood cell that plays a crucial role in the adaptive immune response. They are responsible for identifying and targeting specific pathogens, such as viruses and bacteria, and are essential for developing immunological memory, which helps the body recognize and respond more effectively to previously encountered antigens. Lymphocytes can be divided into two main types: B cells, which produce antibodies, and T cells, which can directly kill infected cells or help coordinate the immune response.
Macrophages: Macrophages are a type of white blood cell that play a crucial role in the immune system by engulfing and digesting cellular debris, pathogens, and foreign substances. They act as key players in both innate and adaptive immunity, coordinating the body’s defense against infections and facilitating the healing process.
Major histocompatibility complex (MHC): The major histocompatibility complex (MHC) is a set of cell surface proteins essential for the adaptive immune system to recognize foreign molecules. MHC molecules present peptide fragments derived from pathogens to T cells, playing a crucial role in the activation of the immune response. This system allows the body to distinguish between self and non-self, which is vital for effective immune surveillance and defense.
Memory cell: A memory cell is a type of lymphocyte that remains in the body long after an infection has been eliminated. It 'remembers' specific pathogens and enables a quicker and more effective immune response upon re-exposure.
Memory Cells: Memory cells are a specialized type of immune cell that retain information about past infections and play a crucial role in the adaptive immune response. These cells enable the immune system to respond more rapidly and effectively to pathogens that the body has previously encountered, providing long-lasting immunity. By remembering specific antigens, memory cells ensure that the body can mount a faster and stronger defense upon re-exposure to the same pathogen.
MHC class II molecule: MHC class II molecules are proteins found on the surface of certain immune cells, including macrophages, dendritic cells, and B cells. They present processed antigens to helper T cells, initiating an immune response.
Passive immune: Passive immunity is the transfer of active humoral immunity in the form of ready-made antibodies from one individual to another. It provides immediate but temporary protection against pathogens.
Peripheral Tolerance: Peripheral tolerance is a critical mechanism in the immune system that helps prevent autoimmune reactions by inactivating or eliminating self-reactive lymphocytes that have escaped central tolerance. This process occurs outside the primary lymphoid organs, primarily within peripheral tissues, and is essential for maintaining self-tolerance and preventing the immune system from attacking the body’s own cells. It involves various cells and signaling pathways to ensure that immune responses are appropriately regulated.
Primary immune response: Primary immune response is the body's initial reaction to a foreign antigen. It involves the activation of naïve B and T cells and typically takes several days to develop fully.
Primary lymphoid organs: Primary lymphoid organs are specialized tissues where lymphocytes, a type of white blood cell, mature and differentiate. These organs are essential for the development of the adaptive immune system, as they create the environment necessary for lymphocyte maturation, including T cells in the thymus and B cells in the bone marrow. Their proper functioning is critical for establishing a robust immune response.
Regulatory T cells: Regulatory T cells, often referred to as Tregs, are a specialized subset of T cells that play a crucial role in maintaining immune tolerance and preventing autoimmune responses. They help to modulate the immune system by suppressing excessive immune reactions, ensuring that the body's defenses do not attack its own tissues while still allowing for effective responses against pathogens.
Secondary immune response: The secondary immune response is the body's enhanced and more rapid reaction to an antigen that it has previously encountered. This response is facilitated by memory cells that were generated during the primary immune response.
Secondary lymphoid organs: Secondary lymphoid organs are specialized tissues where immune responses are initiated and regulated, playing a critical role in adaptive immunity. These organs, including lymph nodes, spleen, and mucosa-associated lymphoid tissues (MALT), provide environments for the activation and proliferation of lymphocytes in response to antigens. They facilitate communication between immune cells and help filter pathogens from the lymphatic and blood circulation.
T cells: T cells are a type of white blood cell that play a critical role in the adaptive immune system. They are essential for recognizing and responding to pathogens, as well as regulating the immune response. T cells originate in the bone marrow and mature in the thymus, where they undergo a selection process to ensure they can effectively distinguish between self and non-self antigens.
T lymphocytes: T lymphocytes, or T cells, are a type of white blood cell that play a crucial role in the adaptive immune response. They originate from hematopoietic stem cells in the bone marrow but mature in the thymus, which is where they gain their name. T cells are essential for identifying and eliminating infected or cancerous cells and coordinating the immune response by interacting with other immune cells.
Thymus: The thymus is a small organ located in the upper chest, responsible for the development and maturation of T lymphocytes, or T cells, which are crucial components of the adaptive immune system. This organ plays a vital role in establishing immune tolerance and ensuring that T cells can effectively respond to pathogens while avoiding attacks on the body’s own tissues.