9.4 Comparative immunology in different animal groups
4 min read•august 7, 2024
Comparative immunology reveals a fascinating evolutionary journey of immune systems across animal groups. From invertebrates relying solely on innate defenses to vertebrates developing , each group has unique features tailored to their environment.
Vertebrates showcase a diverse array of immune strategies. Fish pioneered adaptive immunity, while amphibians and reptiles adapted to land. Birds and mammals further refined their defenses, developing specialized organs and antibody classes to combat pathogens effectively.
Invertebrate and Vertebrate Immunity
Innate Immunity in Invertebrates
Top images from around the web for Innate Immunity in Invertebrates
Cellular Defenses of the Host | Microbiology View original
Is this image relevant?
Frontiers | The Role of Semaphorins and Their Receptors in Innate Immune Responses and Clinical ... View original
Is this image relevant?
23.1. Innate Immune Response – Concepts of Biology – 1st Canadian Edition View original
Is this image relevant?
Cellular Defenses of the Host | Microbiology View original
Is this image relevant?
Frontiers | The Role of Semaphorins and Their Receptors in Innate Immune Responses and Clinical ... View original
Is this image relevant?
1 of 3
Top images from around the web for Innate Immunity in Invertebrates
Cellular Defenses of the Host | Microbiology View original
Is this image relevant?
Frontiers | The Role of Semaphorins and Their Receptors in Innate Immune Responses and Clinical ... View original
Is this image relevant?
23.1. Innate Immune Response – Concepts of Biology – 1st Canadian Edition View original
Is this image relevant?
Cellular Defenses of the Host | Microbiology View original
Is this image relevant?
Frontiers | The Role of Semaphorins and Their Receptors in Innate Immune Responses and Clinical ... View original
Is this image relevant?
1 of 3
- Invertebrates rely solely on which includes physical barriers, cellular responses, and humoral responses
- Physical barriers consist of the exoskeleton or shell, mucus secretions, and epithelial layers that prevent pathogen entry
- Cellular responses involve hemocytes (blood cells) that perform , encapsulation, and nodule formation to eliminate pathogens
- Humoral responses include antimicrobial peptides, lectins, and the prophenoloxidase system that neutralize or kill invading microbes
Adaptive Immunity Emergence in Vertebrates
- Vertebrates possess both innate and adaptive immunity, with the latter providing specific and long-lasting protection against pathogens
- Adaptive immunity evolved in jawed vertebrates and is characterized by the presence of lymphocytes, antibodies, and immunological memory
- Key components of adaptive immunity include that produce antibodies and that coordinate cellular immune responses
- The evolution of adaptive immunity in vertebrates allowed for more efficient and targeted defense against a wide range of pathogens
Innate Immunity in Vertebrates
- Vertebrates maintain a robust innate immune system that works in conjunction with adaptive immunity
- Innate immune components in vertebrates include physical barriers (skin, mucus), , , and phagocytic cells (, neutrophils)
- (PRRs) on innate immune cells detect conserved pathogen-associated molecular patterns (PAMPs) to initiate immune responses
- and secreted by innate immune cells help coordinate and amplify the overall immune response
Fish Immunity
Jawless Fish Immunity
- Jawless fish (hagfish and lampreys) lack adaptive immunity but possess a unique system called (VLRs)
- VLRs are generated through gene rearrangement and provide a form of antigen-specific recognition
- Jawless fish rely on innate immune components such as phagocytic cells, complement system, and antimicrobial peptides for defense against pathogens
Cartilaginous Fish Immunity
- Cartilaginous fish (sharks, rays, skates) were the first group to develop adaptive immunity with the presence of B cells, T cells, and antibodies
- Their antibodies are primarily of the IgM class and have a unique pentameric structure
- Cartilaginous fish also possess a well-developed innate immune system, including (TLRs) and the complement system
Bony Fish Immunity
- Bony fish (teleosts) have a fully functional adaptive immune system with B cells, T cells, and a diverse repertoire of antibodies (IgM, IgD, IgT)
- The (GALT) and (SALT) play crucial roles in mucosal immunity
- Bony fish have a unique organ called the head kidney that serves as a major lymphoid organ and site of hematopoiesis
- Innate immune components in bony fish include the complement system, natural killer-like cells, and phagocytic cells
Tetrapod Immunity
Amphibian Immunity
- Amphibians have a well-developed adaptive immune system with B cells, T cells, and antibodies (IgM, IgY, IgX)
- Their skin secretions contain a diverse array of antimicrobial peptides that provide a first line of defense against pathogens
- Amphibians also possess a robust innate immune system, including phagocytic cells, natural killer cells, and the complement system
Reptile Immunity
- Reptiles have a complex adaptive immune system with B cells, T cells, and a diverse antibody repertoire (IgM, IgY, IgD)
- The spleen and gut-associated lymphoid tissue (GALT) are important lymphoid organs in reptiles
- Reptiles have a well-developed innate immune system, including toll-like receptors (TLRs), antimicrobial peptides, and the complement system
- Temperature variations can influence the immune response in ectothermic reptiles
Avian Immunity
- Birds have a sophisticated adaptive immune system with B cells, T cells, and antibodies (IgM, IgY, IgA)
- The is a unique lymphoid organ in birds that is crucial for B cell development
- Avian innate immunity includes the complement system, natural killer cells, and phagocytic cells (heterophils)
- Maternally derived antibodies (IgY) provide passive immunity to hatchlings
Mammalian Immunity
- Mammals have a highly developed adaptive immune system with B cells, T cells, and a diverse antibody repertoire (IgM, IgG, IgA, IgE, IgD)
- Lymph nodes, spleen, and mucosal-associated lymphoid tissues (MALT) are key lymphoid organs in mammals
- Mammalian innate immunity includes the complement system, natural killer cells, dendritic cells, and phagocytic cells (macrophages, neutrophils)
- Passive immunity is provided to newborns through the transfer of maternal antibodies (IgG) via the placenta or colostrum
- The thymus is a critical organ for T cell development and selection in mammals
Key Terms to Review (29)
Adaptive immunity: Adaptive immunity is a specialized immune response that develops over time, allowing an organism to recognize and remember specific pathogens for more effective defense against future infections. This type of immunity involves the activation of lymphocytes, particularly B cells and T cells, which can produce antibodies and mount targeted attacks against invaders. The distinction between adaptive immunity and innate immunity is crucial, as adaptive responses are tailored to specific pathogens, while innate immunity provides immediate but non-specific defense.
Antibody production: Antibody production is the process by which B cells, a type of white blood cell, generate antibodies in response to antigens, which are foreign substances like pathogens. This process is crucial for the adaptive immune response and varies significantly across different animal groups, highlighting the evolutionary adaptations in immune strategies.
Antigens: Antigens are substances that the immune system recognizes as foreign, triggering an immune response. These can be proteins, polysaccharides, or other molecules found on the surfaces of pathogens like bacteria and viruses. Antigens play a crucial role in both cellular and humoral immunity, as they stimulate the production of specific antibodies and activate immune cells to attack the invaders.
Autoimmunity: Autoimmunity refers to a condition in which the immune system mistakenly targets and attacks the body’s own cells, tissues, or organs, viewing them as foreign. This misdirected immune response can lead to a variety of autoimmune diseases that can affect different systems in the body. Understanding autoimmunity involves recognizing its ties to both innate and adaptive immune responses, the distinct roles of cellular and humoral immunity, and its variations across different animal groups.
B cells: B cells are a type of white blood cell that play a crucial role in the immune system by producing antibodies to help fight infections. They are an essential component of the adaptive immune response, enabling the body to remember and respond more effectively to previously encountered pathogens.
Bursa of Fabricius: The bursa of Fabricius is a specialized organ found in birds that plays a critical role in the development and maturation of B lymphocytes, which are essential components of the immune system. Located near the cloaca, this organ is unique to avian species and is crucial for the adaptive immune response, allowing for the production of antibodies and the establishment of immunological memory.
Cell-mediated immunity in reptiles: Cell-mediated immunity in reptiles is a crucial part of their immune response that primarily involves T cells, which help recognize and eliminate infected or abnormal cells. This form of immunity is significant in protecting reptiles from pathogens and plays a vital role in their overall immune system, especially as they have a unique physiological makeup compared to other animal groups. Understanding how reptiles utilize this immune mechanism provides insight into the evolutionary adaptations and comparative immunology among various species.
Chemokines: Chemokines are a family of small cytokines that play a crucial role in cell signaling, particularly in the immune system. They are responsible for the directed migration of immune cells to sites of inflammation, injury, or infection, effectively guiding the immune response. Their primary function is to attract leukocytes, helping to orchestrate both cellular and humoral immunity, while also exhibiting varying roles in different animal groups.
Complement system: The complement system is a complex series of proteins in the blood that enhances the ability of antibodies and phagocytic cells to clear pathogens from an organism. It plays a crucial role in both the innate and adaptive immune responses by promoting inflammation, opsonization, and direct lysis of pathogens. This interconnected network helps coordinate the immune response and can vary across different animal groups, highlighting its evolutionary significance.
Cytokines: Cytokines are small signaling proteins secreted by cells that play a crucial role in cell communication within the immune system. They help regulate immune responses by facilitating communication between immune cells, influencing cell growth, differentiation, and activity during both innate and adaptive responses. Cytokines can act in an autocrine, paracrine, or endocrine manner, impacting various aspects of inflammation and immunity.
Flow cytometry: Flow cytometry is a powerful analytical technique used to measure the physical and chemical characteristics of cells or particles as they flow in a fluid stream through a laser beam. This method allows for the rapid analysis of thousands of cells per second, providing important information about cell size, complexity, and specific protein markers. It is particularly valuable in comparative immunology for studying immune responses across different animal groups.
Gut-associated lymphoid tissue: Gut-associated lymphoid tissue (GALT) is a component of the immune system that plays a crucial role in protecting the gut from pathogens while maintaining tolerance to non-harmful antigens. It consists of various lymphoid structures, such as Peyer's patches and isolated lymphoid follicles, strategically located throughout the gastrointestinal tract. GALT serves as a critical site for immune responses and interactions between the gut microbiota and the host's immune system.
Humeral immunity in mammals: Humeral immunity in mammals refers to the aspect of the adaptive immune system that is mediated by antibodies produced by B cells. This form of immunity is crucial for defending against extracellular pathogens, such as bacteria and viruses, by neutralizing them and marking them for destruction by other immune cells. Humeral immunity also plays a significant role in the context of comparative immunology, as it highlights the evolutionary adaptations of different animal groups in their immune responses.
Immune evolution: Immune evolution refers to the process by which immune systems of organisms adapt and change over time through evolutionary pressures, such as pathogen interactions and environmental challenges. This concept highlights how different animal groups have developed varying immune strategies to survive and thrive in their unique ecological niches.
Immunohistochemistry: Immunohistochemistry is a technique used to detect specific proteins or antigens in tissues using antibodies that bind to those targets, allowing researchers to visualize their distribution and localization within the cells or tissues. This method is essential for understanding cellular functions, especially in the nervous system and in comparative immunological studies across different animal groups.
Immunopathology: Immunopathology is the study of diseases that are caused by dysfunctions in the immune system, including both excessive and insufficient immune responses. This field examines how these immune responses can lead to tissue damage and contribute to various conditions such as autoimmune diseases, allergies, and transplant rejection. Understanding immunopathology is crucial for developing targeted therapies and interventions to manage these immune-mediated diseases across different animal groups.
Innate immunity: Innate immunity is the first line of defense in an organism's immune system, providing a rapid and non-specific response to pathogens. This type of immunity is present at birth and includes physical barriers like skin, as well as various immune cells and proteins that act immediately to protect against infections. Innate immunity serves as a crucial complement to adaptive immunity, which takes longer to activate but provides a more targeted response to specific pathogens.
Janeway's Work on Innate Immunity: Janeway's work on innate immunity has fundamentally shaped our understanding of the immune system's first line of defense against pathogens. He emphasized that innate immunity is not only the body's immediate response but also an essential component that helps shape the adaptive immune response. His research has highlighted how various cellular components, including pattern recognition receptors (PRRs), play critical roles in detecting pathogens and initiating immune responses across different animal groups.
Macrophages: Macrophages are large, specialized immune cells that play a critical role in the body's defense against pathogens and in the maintenance of homeostasis. They are derived from monocytes and are essential in both innate and adaptive immune responses, functioning as phagocytes that engulf and digest cellular debris, foreign substances, and pathogens. Macrophages also secrete cytokines that help regulate inflammation and coordinate the immune response.
Natural killer cells: Natural killer cells are a type of lymphocyte in the immune system that play a crucial role in the body's innate defense against tumors and viral infections. They are known for their ability to recognize and destroy infected or cancerous cells without prior sensitization, making them a key component of the immune response that operates rapidly and non-specifically.
Pathogen recognition receptors: Pathogen recognition receptors (PRRs) are a crucial component of the immune system that detects pathogens, such as bacteria and viruses, by recognizing specific molecular patterns associated with these invaders. These receptors play a key role in initiating an immune response, allowing the body to respond effectively to infections and maintain homeostasis. PRRs are essential for both innate and adaptive immunity across different animal groups, highlighting their evolutionary importance in immune defense.
Pattern Recognition Receptors: Pattern recognition receptors (PRRs) are proteins found on the surfaces of immune cells that play a crucial role in the innate immune response by detecting conserved molecular patterns associated with pathogens, known as pathogen-associated molecular patterns (PAMPs), and danger-associated molecular patterns (DAMPs). They are key components in the early detection of infections and help initiate an immune response, making them vital for understanding the comparative immunology across different animal groups.
Phagocytosis: Phagocytosis is a cellular process in which certain cells, known as phagocytes, engulf and digest foreign particles, such as bacteria or dead cells. This mechanism is crucial for the immune system, serving both innate and adaptive responses to eliminate pathogens and maintain tissue homeostasis.
Phylogenetic relationships in immunity: Phylogenetic relationships in immunity refer to the evolutionary connections and distinctions in immune system development and function among different animal species. Understanding these relationships helps researchers uncover how immune systems have evolved over time, providing insights into the diverse strategies animals use to combat pathogens, which vary widely across the animal kingdom.
Skin-associated lymphoid tissue: Skin-associated lymphoid tissue (SALT) refers to the specialized immune cells and structures located in the skin that play a crucial role in the immune response. This tissue serves as a frontline defense against pathogens and helps in the initiation of immune reactions, making it an essential component of the immune system in various animal groups.
T cells: T cells are a type of white blood cell that play a crucial role in the adaptive immune system by recognizing and responding to specific pathogens. They are essential for cell-mediated immunity, distinguishing between self and non-self cells, and orchestrating the immune response through various subtypes. T cells can directly kill infected cells, help other immune cells, and remember past infections for quicker responses in the future.
Toll-like receptors: Toll-like receptors (TLRs) are a class of proteins that play a crucial role in the immune system by recognizing pathogens and activating immune responses. They are essential for detecting a variety of microbial components, such as lipopolysaccharides and peptidoglycans, which helps the body mount a defense against infections. TLRs are present in many different animal groups, highlighting their importance in comparative immunology as they provide insight into how various species respond to pathogens.
Variable Lymphocyte Receptors: Variable lymphocyte receptors (VLRs) are a type of immune receptor found in certain vertebrates, particularly in jawless fish like lampreys and hagfish. They function similarly to antibodies in that they help recognize and bind to a wide array of pathogens, thus playing a crucial role in the adaptive immune response. VLRs exhibit a remarkable diversity, enabling these organisms to effectively adapt their immune defenses against various infectious agents.
Zinkernagel's research on T cells: Zinkernagel's research on T cells focuses on understanding how these immune cells recognize and respond to infected or abnormal cells, emphasizing the role of major histocompatibility complex (MHC) molecules. His work highlighted the importance of T cell specificity and the interactions between T cells and other immune components, which are crucial for mounting effective immune responses against pathogens.