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The Immune System Understanding Interactions with Substances.pptx
- 1. The Immune System Understanding Interactions with Substances A Look at Immunotoxicology Muhammad Ahmed Rayan Mphil Pathology
- 2. Introduction to Immunotoxicology • Assessing unwanted interactions between substances and the immune system • Toxic responses from passive targeting or antigen-specific reactions • Increased susceptibility to infection, allergy, autoimmune disease, or neoplasia • Vulnerability during immune development and specific life stages • Importance of understanding histophysiology for interpreting effects
- 3. Immune Organs and Tissues • The immune system comprises a network of organs and cells distributed throughout the body. • Primary lymphoid organs (thymus, bone marrow) generate immune cells. • Secondary lymphoid organs (lymph nodes, spleen) provide sites for antigen presentation and immune cell activation. • Mucosa-associated lymphoid tissue (MALT) protects mucosal surfaces. • Tertiary lymphoid tissues can develop in response to chronic inflammation. • Immune cells, including lymphocytes (T cells, B cells), antigen-presenting cells (dendritic cells), and phagocytes (macrophages), collaborate to defend against pathogens and maintain tissue homeostasis.
- 5. Antigen Processing and Presentation • Antigen exposure triggers a cascade of events. • Antigen-presenting cells (APCs) ingest and process antigens. • MHC molecules present antigen fragments to T cells. • T cell activation leads to clonal expansion and differentiation. • Cytotoxic T cells directly attack infected cells. • Helper T cells activate B cells and macrophages. • B cells differentiate into plasma cells and produce antibodies. • Antibodies neutralize pathogens and promote phagocytosis. • Regulatory T cells suppress immune responses to prevent autoimmunity.
- 7. Immune Dysfunction: A Spectrum of Adverse Effects • Immunosuppression: Increased susceptibility to infections. • Hypersensitivity: Excessive immune response to allergens. • Autoimmunity: Immune system attacks self-tissues. • Immunotoxicity can disrupt critical pathways: • Antigen presentation and processing • T and B cell development and function • Cytokine production and signaling • Phagocytosis and complement activation • Immune regulation and tolerance
- 8. SUMMARY • Primary lymphoid organs (thymus, bone marrow) generate immune cells. • Secondary lymphoid organs (lymph nodes, spleen) provide sites for antigen presentation and immune cell activation. • Mucosa-associated lymphoid tissue (MALT) protects mucosal surfaces. • Tertiary lymphoid tissues can develop in response to chronic inflammation.
- 9. • Ubiquitous & multifaceted: The immune system operates throughout the body via diverse cell types and organs. • Homeostasis and challenges: It strives for balance, constantly adapting to external influences. • Beneficial and adverse effects: Immune changes can protect (vaccination) or harm (infections, allergies, autoimmune disease). • Toxicology focus: Understanding immunotoxicology requires analyzing structure, physiology, and external interactions. • Species & age matter: Species differences and age-related changes must be considered. • Histopathology & beyond: Histopathology is key, but additional assays and biomarkers are needed to understand mechanisms. • Translating findings: Animal and in vitro studies help predict human outcomes.
Editor's Notes
- In this lecture, we will explore the field of immunotoxicology, which focuses on the adverse effects of substances on the immune system. We will discuss how toxic responses can occur when the immune system is a passive target of chemical insults, leading to altered immune function and increased susceptibility to infection, allergy, autoimmune disease, or neoplasia. We will also examine how toxicity can arise when the immune system responds to the antigenic specificity of a substance, leading to substance-specific allergy or autoimmune disease. We will pay particular attention to the immune system's vulnerability during development, pregnancy, stress, and aging. Finally, we will delve into the histophysiology of the immune system and how it plays a crucial role in interpreting undesired alterations.
- The immune system is a complex network of organs and cells that work together to defend the body against pathogens and maintain tissue homeostasis. Primary lymphoid organs, such as the thymus and bone marrow, generate immune cells. Secondary lymphoid organs, such as lymph nodes and the spleen, provide sites for antigen presentation and immune cell activation. Mucosa-associated lymphoid tissue (MALT) protects mucosal surfaces, such as the lining of the digestive and respiratory tracts. Tertiary lymphoid tissues can develop in response to chronic inflammation in organs that are not normally considered part of the immune system. The key players in the immune system are immune cells, including lymphocytes (T cells and B cells), antigen-presenting cells (dendritic cells), and phagocytes (macrophages). These cells collaborate to identify and eliminate pathogens, while also maintaining a state of balance in the body.
- The immune response is a highly Balance process that unfolds in response to antigen exposure. When an antigen, such as a virus or bacteria, enters the body, antigen-presenting cells (APCs), such as dendritic cells, engulf and process it. APCs then display antigen fragments on their surface molecules called major histocompatibility complex (MHC) molecules. T cells, the quarterbacks of the immune system, scan MHC molecules and become activated upon recognizing specific antigen fragments. Activated T cells differentiate into different effector types, each with a specialized function. Cytotoxic T cells directly attack and kill infected cells. Helper T cells activate B cells and macrophages, which play crucial roles in antibody production and phagocytosis, respectively. B cells differentiate into plasma cells, which churn out antibodies that specifically target the invading pathogen. Antibodies neutralize pathogens and promote their engulfment by phagocytes. Regulatory T cells play a critical role in dampening down the immune response and preventing autoimmunity.
- Immune dysfunction can manifest in a variety of ways, ranging from immunosuppression to hypersensitivity and autoimmunity. Immunosuppression, which can be caused by medications, stress, or malnutrition, leaves individuals vulnerable to infections.