Cells & Tissues of the Immune System PDF

Cells & Tissues of the Immune System  latrobe.edu.au How does the immune response begin? The immune system is triggered by antigens antigen /ˈantɪdʒ(ə)n/ — A toxin or other foreign substance which induces an...

Cells & Tissues of the Immune System  latrobe.edu.au How does the immune response begin? The immune system is triggered by antigens antigen /ˈantɪdʒ(ə)n/ — A toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies — Antigen – Ag – is an Antibody generator — Usually proteins, peptides (amino acid chains) and polysaccharides (chains of monosaccharides/simple sugars) — May originate from within the body ("self-antigen") or from the external environment ("non-self") — Vaccines are antigens that are administered to a recipient to induce the memory function of adaptive immune system to produce or artificially increase immunity to a particular disease  Immune response has 2 main branches: latrobe.edu.au innate and adaptive Innate Adaptive Dranoff (2004) Nature Reviews Cancer, 4, 11-22  latrobe.edu.au Innate and adaptive immunity timelines differ Innate Adaptive Rapid Slow Granulocytes are a critical group of white blood cells (WBCs) in the immune system that play a vital role in defending the body against infections, inflammation, and tissue damage. They are characterized by the presence of granules in their cytoplasm, which contain enzymes and other substances that help combat pathogens. Granulocytes are part of the innate immune system, meaning they provide a rapid, non-specific response to infections and tissue injury. Dranoff (2004) Nature Reviews Cancer, 4, 11-22  latrobe.edu.au Distinguishing features of innate and adaptive immunity Innate immune response – early Adaptive immune response – later — First line defence against an — Learned/adaptive response antigenic insult (eg infection) – Provides specificity and diversity of an individual’s immune response — Generic – Immunological memory Components include: — Humoral immunity: – Physical anatomical barriers – skin, mucus membrane – Antibody production for killing – Biochemical – complement, lysozyme, extracellular organisms interferons — Cell mediated immunity: – Cellular – macrophages, neutrophils – Cytotoxic / killer T cells > cell-mediated — Interacts with adaptive killing of virus and tumour cells immune response to prime it – Cytokine activation of phagocytes to kill ingested microbes  latrobe.edu.au The immune system responds with many types of cells — Antigen presenting cells (APCs) – Include dendritic cells, macrophages, B cells – Function: Capture antigens to display to lymphocytes — Lymphocytes Dendritic cell Macrophage – B lymphocytes (B cells) and T lymphocytes (T cells) – Function: recognise antigens — B lymphocytes mediate humoral immunity — T lymphocytes mediate cell-mediated immunity B lymphocyte T lymphocyte — Effector cells can be innate or adaptive – Include T lymphocytes (T cells), macrophages, granulocytes (neutrophils, basophils and eosinophils) – Function: Eliminate antigens  latrobe.edu.au The immune system responds with many types of cells — Antigen presenting cells (APCs) – Include dendritic cells, macrophages, B cells – Function: Capture antigens to display to lymphocytes — Lymphocytes Dendritic cell Macrophage – B lymphocytes (B cells) and T lymphocytes (T cells) – Function: recognise antigens — B lymphocytes mediate humoral immunity — T lymphocytes mediate cell-mediated immunity B lymphocyte T lymphocyte — Effector cells can be innate or adaptive – Include T lymphocytes (T cells), macrophages, granulocytes (neutrophils, basophils and eosinophils) – Function: Eliminate antigens Antigen-Presenting Cells (APCs): APCs are specialized immune cells that process and present antigens (foreign substances) to T-cells, playing a critical role in activating the adaptive immune system. Key Features of APCs Function: Capture antigens from pathogens or damaged cells. Process antigens into smaller fragments. Present these fragments on their surface via MHC molecules to T-cells. Activate naïve T-cells to start a specific immune response. Types of APCs: 1) Dendritic Cells: Most efficient APCs. Found in tissues that are in contact with the external environment (e.g., skin, mucosa). Key in initiating primary immune responses. 2) Macrophages: Engulf and digest pathogens (phagocytosis) and present antigens to T-cells. Found in tissues and can act as both APCs and effector cells. 3) B-Cells: Present antigens to helper T-cells to get activated and produce specific antibodies. Critical in humoral immunity. Mechanism: Antigen uptake: Via phagocytosis or receptor-mediated endocytosis. Antigen processing: Broken into peptides in endosomes or lysosomes. Antigen presentation: Peptides are loaded onto MHC Class I (for CD8+ T-cells) or MHC Class II (for CD4+ T-cells) molecules and displayed on the cell surface. Examples of APC-Dependent Responses: Dendritic cells presenting antigens to naïve T-cells to fight viruses like SARS-CoV-2. Macrophages activating helper T-cells in bacterial infections like tuberculosis. B-cells presenting antigens to helper T-cells to stimulate antibody production in flu infections  latrobe.edu.au Different blood lineages have different functions Table 23-1 Molecular Biology of the Cell (© Garland Science 2008) Figure 23-37e Molecular Biology of the Cell (© Garland Science 2008)  latrobe.edu.au Tissues of the immune system Ch 1 Basic Immunology Abbas et al, 7th Edition  latrobe.edu.au Summary — An immune response is triggered by an antigen — Innate immunity provides rapid natural or generic defences against infection: first response, happens within hours — Adaptive immunity creates a diverse and specific range of responses: later; ”learned” responses are remembered (immunological memory) — Immune cells fall into 3 major groups: antigen presenting cells, lymphocytes, and effector cells — They mostly function as first responders in the innate immune system or as highly specialised cells in the adaptive immune response — Innate and adaptive arms of the immune response operate on different timelines, and are distinguished in several ways — Generative and peripheral lymphoid organs are pivotal in generating, educating and maintaining cells of the immune system  Thank you latrobe.edu.au La Trobe University CRICOS Provider Code Number 00115M © Copyright La Trobe University 2024