Chapter 1 Study Guide 1 PDF

Chapter 1 1 • What is the importance of the immune system? The importance of the immune system is multifaceted and central to maintaining overall health. Its primary physiological function revolves around the prevention and eradication of infections, acting as a robust defense mechanism against m...

Chapter 1 1 • What is the importance of the immune system? The importance of the immune system is multifaceted and central to maintaining overall health. Its primary physiological function revolves around the prevention and eradication of infections, acting as a robust defense mechanism against microbial threats. Additionally, the immune system plays a critical role in the defense against tumors, inhibiting their growth and offering a line of protection against certain cancers. Furthermore, it contributes significantly to the control of tissue regeneration and scarring, showcasing its involvement in the repair and maintenance of bodily tissues. However, it is essential to recognize the dual nature of the immune system, as it has the capacity to injure cells and induce pathologic inflammation under certain circumstances. Beyond these functions, the immune system exhibits a remarkable ability to recognize and respond to tissue grafts and newly introduced proteins, illustrating its adaptability in addressing a wide array of foreign substances. In summary, the immune system's importance lies in its multifaceted roles, including infection and tumor defense, tissue regeneration control, and the ability to navigate complex interactions with various external elements. • The adaptive immune system includes lymphocytes with diverse receptors, like antibodies, to combat foreign substances. These immune responses are vital for defending against diseasecausing infectious microbes. The adaptive immune system likely evolved to resist innate immunity, forming a crucial defense against pathogenic threats. • What is the nature of an antigen? The nature of an antigen is defined by its role as any molecule specifically recognized by lymphocytes or antibodies. In essence, an antigen is a substance that triggers an immune response, prompting the immune system to produce a targeted reaction through the activation of lymphocytes or the generation of antibodies. • Who are the members of the innate immune response? The members of the innate immune response encompass various mechanisms that collectively provide the initial defense against infections. These mechanisms include: Epithelial Barriers: These physical barriers, such as the skin and mucous membranes, form the first line of defense by preventing infections from entering the body. Phagocytes: Cells like macrophages and neutrophils are key members of the innate immune response that engulf and digest pathogens, contributing to the elimination of microbes. Natural Killer (NK) Cells: These cells are involved in the detection and elimination of infected or abnormal cells, providing a rapid response to potential threats. Innate Lymphoid Cells (ILCs): These cells are part of the innate immune system and play roles in tissue homeostasis, inflammation, and defense against pathogens. Complement System: A complex system of proteins that enhances the ability of antibodies and phagocytic cells to clear microbes from the body, contributing to the elimination of infectious agents. • What cells serve as sentinels in tissues? Tissue-resident dendritic cells, macrophages, and mast cells serve as sentinels to detect the presence of microbes in tissues and initiate immune responses. Chapter 1 2 • What is the time required from first exposure to effector cells or antibody production? The kinetics of the innate and adaptive immune responses are approximations and may vary in different infections. The innate immune response acts rapidly within hours to days upon the first exposure to a pathogen. In contrast, the adaptive immune response takes days to weeks for the initial response but establishes memory for a faster and more effective secondary response upon re-exposure. The adaptive immune response includes a crucial feature known as immunological memory. Following the first exposure to a pathogen, memory cells are generated. These memory cells "remember" the specific pathogen, allowing for a faster and more robust response upon subsequent exposures • What is similar between neutrophils and macrophages and what is different? Similarities: • Origin: Both neutrophils and macrophages originate from hematopoietic stem cells in the bone marrow. • Phagocytosis: Neutrophils and macrophages are phagocytic cells, meaning they can engulf and digest foreign particles, such as bacteria and debris. • Microbicidal Activity: Both cell types release antimicrobial substances to destroy engulfed pathogens. • Innate Immune Response: Neutrophils and macrophages are key components of the innate immune system, providing a rapid and non-specific response to infections. • Repair of Damaged Tissues: Macrophages also play a role in repairing damaged tissues in addition to their function as sentinels and destroyers of microbes. • • • • • • Differences: Lifespan: Neutrophils have a relatively short lifespan (a few hours to days), while macrophages have a longer lifespan and can persist for weeks to months. Abundance: Neutrophils are more abundant than macrophages and are often the first responders to infection. Tissue Distribution: Neutrophils are primarily found in the bloodstream and are quickly recruited to sites of infection. Macrophages are found in tissues throughout the body, where they act as resident immune cells. Function in Adaptive Immunity: Macrophages play a role in linking the innate and adaptive immune responses by presenting antigens to T cells. Neutrophils are not as involved in adaptive immunity. Granules: Neutrophils contain specific granules that contribute to their microbicidal activity, while macrophages have lysosomes that aid in phagocytosis. Chapter 1 Feature 3 Neutrophils Derived from hematopoietic stem cells Origin (HSCs) in bone marrow Life Span in Short-lived, around 1–2 Tissues days Responses to Rapid, short-lived, with Activating Stimuli enzymatic activity Phagocytosis Reactive Oxygen Species Nitric Oxide Degranulation Cytokine Production Extracellular Traps Secretion of Lysosomal Enzymes Rapid ingestion of microbes Rapidly induced by the assembly of phagocyte oxidase Low levels or none Major response induced by cytoskeletal rearrangement Low levels per cell, rapidly induced Induced by extrusion of nuclear contents Prominent Macrophages Derived from HSCs in bone marrow (inflammatory reactions). Tissue-resident macrophages originate from fetal liver yolk sac. Early development. Inflammatory macrophages: Days to weeks. Tissue-resident macrophages: Years. More prolonged, slower, often dependent on new gene transcription Prolonged ability to ingest microbes, apoptotic cells, tissue debris, and foreign material Less prominent Induced following transcriptional activation of iNOS Not prominent Major functional activity with large amounts per cell, requiring transcriptional activation of cytokine genes Little to none Less prominent • What types of microbes require clearance by cell-mediated immunity (CMI)? Phagocytosed microbes in macrophage • What role do Helper T cells and Cytotoxic T cells play in cell-mediated immunity? Helper T Cells: Elimination of phagocytosed microbes Cytotoxic T cells: Kill infected cells and eliminate reservoirs of infection. Chapter 1 4 • How do secreted antibodies differ from CMI? Humoral Immunity: Secreted antibodies enter the circulation, extracellular tissue fluids, and the lumens of mucosal organs such as the gastrointestinal and respiratory tracts. The antibodies defend against microbes. present in these locations by preventing them from invading tissue cells and by neutralizing toxins made by the microbes. Block infections and eliminate extracellular microbe. CMI (Cell Mediated Immunity): Defense against microbes that have already entered host cells is called cell-mediated immunity. Cell-mediated immunity is especially import- ant to defend against intracellular organisms that can survive and replicate inside cells. • What is the difference between Memory and Diversity? Diversity: Enables the immune system to respond to a large variety of antigens. Memory: Leads to enhanced responses to repeated exposures to the same antigens. • What is the difference between passive immunity and active immunity? Active Immunity: Induced in an individual by infection or vaccination. Passive Immunity: Conferred on an individual by transfer of antibodies or lymphocytes from an actively immunized individual. • What is the clonal selection hypothesis? Clonal Selection Hypothesis: Formulated in the 1950s, the clonal selection hypothesis correctly predicted that clones of lymphocytes specific for different antigens develop before an encounter with these antigens. Each antigen elicits an immune response by selecting and activating the lymphocytes of a specific clone. • What is the importance of the lymphocyte repertoire? the lymphocyte repertoire's importance lies in its ability to confer specificity, versatility, adaptability, and memory to the adaptive immune system, enabling it to effectively recognize, respond to, and remember a wide array of antigens to protect the body against infections and other threats. The adaptive immune system is capable of distinguishing millions of different antigens or portions of antigens, a feature that is referred to as specificity. It implies that the total collection of lymphocyte specificities, sometimes called the lymphocyte repertoire, is extremely diverse. • What type of immune response occurs with immunologic memory compared to the initial adaptive immune response? The adaptive immune system mounts faster, larger, and more effective responses to repeated exposure to the same antigen. This feature of adaptive immune responses implies that the immune system remembers every encounter with antigen, and this property of adaptive immunity is therefore called immunologic memory. • What is the significance of the primary and secondary immune response with serum antibody titers? The primary immune response is initiated by lymphocytes called naive lymphocytes that are encountering the antigen for the first time. The term "naive" refers to these cells being immunologically inexperienced, having not previously responded to antigens. Subsequent encounters with the same antigen lead to responses called secondary immune responses, which are usually more rapid, larger, and better able to eliminate the antigen than primary responses. Secondary responses result from the activation of memory lymphocytes, which are long-lived cells induced during the primary immune response. Immunologic memory optimizes the ability Chapter 1 5 of the immune system to combat persistent and recurrent infections, as each exposure to a microbe generates more memory cells and activates previously generated memory cells. Immunologic memory is a mechanism by which vaccines confer long-lasting protection against infections. • What cells are lymphocytes? B lymphocytes; T lymphocytes • What are the principal functions of the lymphocytes? Specific recognition of antigens and generation of adaptive immune responses: B lymphocytes: mediators of humoral immunity T lymphocytes: mediators of cell-mediated immunity • What cells are Antigen-presenting cells? dendritic cells; macrophages; B cells; follicular dendritic cells • What is the difference between a dendritic cell and a follicular dendritic cell? Dendritic cells: initiation of T cell responses Follicular dendritic cells: display of antigens to B lymphocytes in humoral immune responses • What is the difference in the effector function of macrophages and T cells? T Lymphocytes: activation of phagocytes, killing infected cells Macrophages: phagocytosis and killing of microbes • How do antibodies cooperate with elements of the adaptive immune response? Although all lymphocytes share a morphologically similar and rather unremarkable appearance, they exhibit heterogeneity in lineage, function, and phenotype, engaging in complex biological responses and activities. Distinguishing these cells is often achieved through the expression of surface proteins identified using panels of monoclonal antibodies. Within the adaptive immune system, various classes of lymphocytes recognize distinct types of antigens and undergo differentiation into effector cells aimed at eliminating the antigens. Chapter 1 6 • How do helper T cells affect neutrophils? Helper T Cells and Neutrophils Interaction: Activation of Neutrophils: Helper T cells release cytokines upon recognizing antigens presented by antigen-presenting cells (APCs). Notably, Interleukin-17 (IL-17) plays a crucial role in activating neutrophils. Activated neutrophils become more responsive to signals guiding them to the infection site. Chemotaxis: Helper T cells release chemotactic factors that attract neutrophils to infection or inflammation sites. This is vital for recruiting neutrophils to specific locations where their antimicrobial activities are needed. Enhanced Phagocytosis: Cytokines from helper T cells can enhance the phagocytic activity of neutrophils, making them more effective at engulfing and digesting pathogens, contributing to the elimination of infectious agents. Extended Lifespan: Helper T cells release cytokines that prolong the lifespan of neutrophils. This is crucial for maintaining a sustained and effective immune response at the infection site. Overall Immune Response Coordination: Helper T cells play a central role in orchestrating the immune response. By activating and regulating neutrophils, they ensure that the innate immune system functions harmoniously with the adaptive immune response to eliminate pathogens. • CD8 T cells and tumor cells: Killing of cells infected with intracellular microbes, tumor cells CD8 T Cells and Immune Defense: Recognition: CD8 T cells play a crucial role in immune defense against intracellular microbes and tumor cells by recognizing specific antigen-MHC class I complexes on infected or tumor cells. Cytotoxic Action: Upon recognition, CD8 T cells release cytotoxic substances (such as perforin and granzymes), inducing apoptosis and eliminating the threat. Tumor Surveillance: In the context of tumors, CD8 T cells actively contribute to immune surveillance, targeting and eliminating cells with abnormal growth. Memory Response: CD8 T cells form memory cells, providing long-term immunity and ensuring a faster response upon reencountering the same pathogen or tumor cells. Chapter 1 7 • What cells are CD3+ and CD4+? CD4+ helper T lymphocytes and Regulatory T cells • Difference between generative lymphoid organs and the peripheral (secondary) lymphoid organs. Lymphoid Organs Locations Function Process Outcome Lymphocytes Mature Produce mature mature in bone lymphocytes leave Generative Bone marrow lymphocytes from marrow (B cells) and enter (Primary) and thymus precursors and thymus (T cells) circulation Lymph nodes (B), spleen, Major sites of Circulating mature Activation of mucosal, and immune responses lymphocytes lymphocytes Peripheral cutaneous where lymphocytes respond to foreign contributes to (Secondary) tissues are activated antigens immune responses • What is the difference between a naïve lymphocyte and an effector lymphocyte? Difference between Naïve and Effector Lymphocytes: When naive lymphocytes recognize microbial antigens and receive additional signals induced by microbes, they undergo proliferation and differentiation into effector cells and memory cells. Naive lymphocytes express receptors for antigens but do not perform the functions required to eliminate antigens. On the other hand, effector lymphocytes are the differentiated progeny of naive cells and possess the ability to produce molecules that function to eliminate antigens. Specifically, in the B lymphocyte lineage, effector cells are represented by antibody-secreting cells known as plasma cells. The key distinction lies in the functional capabilities, where naive lymphocytes are primarily receptors for antigens, and effector lymphocytes actively produce molecules, such as antibodies, contributing to the elimination of antigens. Characteristic Migration: Frequency of Cells Responsive to Particular Antigen: Effector Functions: Membrane Immunoglobulin (Ig) Isotype: Affinity of Ig Produced: • Activated Lymphocytes Naive Lymphocytes (Effector) Peripheral lymphoid inflamed tissues upon organs encountering antigens. Low frequency Limited or none. IgM, IgD Low High frequency Antibody Secretion Low Level of Plasma Cells (e.g., IgG, IgA, IgE) Increase during immune response What cells produce memory cells? Memory cells, also generated from the progeny of antigenstimulated lymphocytes, or B Lymphocytes. Chapter 1 • 8 Where are naïve T cells localized and where are they in the effector stage? A Naïve T cells are initially localized or generated in the thymus. After their development in the thymus, naïve T cells enter lymph nodes through high endothelial venules (HEV) and exit through efferent lymphatics. During the effector stage, T cells differentiate into short-lived activated cells known as effector T cells. Effector T cells play a crucial role in defending the body during an immune response. Effector T cells, also referred to as T helper (TH) cells or cytotoxic T lymphocytes (CTLs) for CD4+ and CD8+ T cells, respectively, migrate to peripheral sites of infection. These peripheral sites include mucosal and cutaneous lymphoid tissues. Effector T cells are responsible for eliminating infectious microbes and contributing to the immune response against pathogens. • Trends in T cells, memory, and thymic output. As individuals age, the gradual accumulation of memory cells compensates for the reduced output of new, naïve T cells from the thymus, which involutes after puberty. This adaptation allows the immune system to maintain a level of responsiveness even as thymic output decreases. • What top 4 tissues have the greatest number of lymphocytes? Lymph Nodes, Spleen, Bone Marrow, Intestines • What best describes Peyer’s patches? Peyer's patches are specialized mucosal lymphoid tissues in the small intestine, playing a key role in immune defense (Innate and adaptive). They contain dendritic cells, T lymphocytes, and macrophages, providing protection against invading microbes. • What type of antibody is abundantly produced in mucosal tissues? Immunoglobulin A (IgA) is a type of antibody abundantly produced in mucosal tissues that is transported into the lumen, where it binds and neutralizes microbes • What cells make up the follicles in the lymph nodes? Lymph node follicles are indeed composed of B-lymphocytes (B-cells), along with other cells such as T-cells, follicular dendritic cells, and macrophages. • How do naïve B and T cells enter the lymph node? high endothelial venule (HEV) • How do dendritic cells enter the lymph node? afferent lymphatic vessels • What happens to activated T cells in the lymph node? Activated T cells exit the nodes, enter the bloodstream, and migrate preferentially to peripheral tissues at sites of infection and inflammation.