AI Resumen Notes: Basic Concepts in Immune Function PDF

Basic Concepts in Immune Function The immune system has many roles in maintaining health. It\'s like the body\'s security force, working to: - **Fight infections:** The immune system\'s primary job is to stop infections from taking hold. - **Destroy cancer cells:** It also keeps an eye ou...

Basic Concepts in Immune Function The immune system has many roles in maintaining health. It\'s like the body\'s security force, working to: - **Fight infections:** The immune system\'s primary job is to stop infections from taking hold. - **Destroy cancer cells:** It also keeps an eye out for abnormal cells and gets rid of them. - **Recognize and respond to tissue grafts:** The immune system can tell the difference between its own cells and those from other people, which is important for things like organ transplants. However, sometimes the immune system can overreact and cause problems. This is called an autoimmune response. For example, it can attack healthy tissues, leading to things like: - **Cell injury:** When the immune system attacks healthy cells, it can damage them. - **Pathologic inflammation:** This happens when the immune system causes inflammation in the wrong place or for too long. In summary, while the immune system is essential for health, it can also be a source of problems if it doesn\'t work properly. Top of Form The text compares the inflammatory and immune responses, which are our body\'s defenses against infection and injury.  **Inflammatory Response (Innate Immunity):** - **Rapid:** Acts quickly to fight infection or injury. - **Nonspecific:** Responds to a wide range of threats, not just specific pathogens. - **No Memory:** Doesn\'t learn or remember past infections.  - **Many Cells:** Involves various cells like neutrophils, macrophages, and platelets. **Immune Response (Adaptive Immunity):** - **Slower:** Takes time to develop, but provides a strong defense. - **Specific:** Targets specific pathogens, learning to recognize and attack them. - **Memory:** Remembers past infections and mounts a faster response if it encounters the same threat again. - **Lymphocytes and Antibodies:** Involves specialized white blood cells called lymphocytes and antibodies.  - **Vaccination:** Can be triggered by vaccination, which introduces a weakened or inactive form of a pathogen to stimulate the immune system. Bottom of Form An antigen is a molecule that the body\'s immune system recognizes as foreign. This recognition triggers an immune response, involving lymphocytes and antibodies. Here\'s a breakdown of the key points: - **Foreign antigens** are molecules not normally found in the body. These include: - Viruses - Bacteria - Pollens - Food or drugs - **Self-antigens** are molecules found on the surface of the body\'s own cells. The most important self-antigen is the **Human Leukocyte Antigen (HLA)**.  - - HLAs are present on all cell membranes except red blood cells (RBCs). - They help the immune system distinguish between self and non-self. - **Major Histocompatibility Complex (MHC)** is a region on chromosome 6 that contains genes responsible for producing HLA antigens. - **RBC antigens** are found on the surface of red blood cells. They are responsible for blood types (A, B, and Rh). Top of Form Bottom of Form The immune system is designed to recognize and destroy foreign invaders (antigens). This process has two main phases: generation of clonal diversity and clonal selection.  **Generation of Clonal Diversity**  involves the creation of a diverse population of lymphocytes, each capable of recognizing a specific antigen. This starts in the bone marrow with lymphoid stem cells that migrate to the primary lymphoid organs (thymus for T cells, bone marrow for B cells). Lymphocytes mature into immunocompetent T or B cells in these organs, each possessing a unique receptor specific for a single antigen. The result is a vast pool of lymphocytes, collectively able to recognize a wide range of foreign antigens.  These mature lymphocytes then leave the primary lymphoid organs and circulate to the secondary lymphoid tissues like lymph nodes, spleen, and mucosal tissues, where they \"take up residence\" and await their activation by specific antigens during the next phase, clonal selection.  Top of Form Clonal selection is the process where the immune system focuses on specific threats. Here\'s how it works: - **Antigen Encounter:** The immune system is exposed to a specific antigen (a foreign substance). - **Antigen Presentation:** Antigen-presenting cells (APCs) process and present the antigen to immature lymphocytes (B and T cells). - **Selection:** The immune system selects B and T cells with receptors that specifically recognize the antigen. - **Clonal Expansion:** These selected cells are stimulated to mature and multiply, creating a clone of cells specific to the antigen. - **Differentiation:** - **B cells** differentiate into plasma cells, which produce antibodies that target the antigen. - **T cells** differentiate into cytotoxic T cells that directly kill infected cells, or other types of T cells that help coordinate the immune response. - **Immune Response:** The antigen-selected cells mount a defense against the antigen. - **Memory Cells:** Long-lasting memory B and T cells are produced. These cells remember the antigen and can quickly mount a response if the body is re-exposed to the same antigen in the future. Bottom of Form Induction of the Immune Response This excerpt describes the steps involved in antigen processing and presentation, a crucial process for initiating an immune response.  Here\'s a breakdown: - **Antigen Presentation:** Antigen presenting cells (APCs) like macrophages, dendritic cells, and B cells engulf foreign invaders (antigens) through phagocytosis. - **MHC Class II Expression:** The APC then processes the antigen and displays fragments of it on its surface, attached to MHC Class II molecules. - **IL-1 Production:** The APC releases interleukin-1 (IL-1), a signaling molecule that alerts other immune cells. - **T Cell Activation:** Helper T cells (Th or CD4 cells) recognize the antigen-MHC Class II complex on the APC using their T cell receptors (TCRs). - **Th Differentiation:** Activated Th cells release interleukin-2 (IL-2), which stimulates them to mature into functional Th1 and Th2 cells. These steps are essential for initiating the adaptive immune response, involving the formation of B cells, T cells, and antibodies.  Top of Form Bottom of Form This text describes the role of interleukin-2 (IL-2) in immune responses and how it stimulates the proliferation and differentiation of lymphocytes. - **IL-2** is a signaling molecule released by helper T cells (Th1 and Th2) that promotes the growth and maturation of various immune cells. - **B lymphocytes (B cells)**, activated by Th2 cells, proliferate and differentiate into plasma cells. - **Plasma cells** are responsible for producing antibodies, which are proteins that bind to and neutralize foreign invaders like bacteria and viruses. - **T lymphocytes (T cells)**, activated by Th1 cells, can differentiate into cytotoxic T (Tc or CD8 T cells) which destroy infected or cancerous cells directly. - **Memory Cells** are long-lived B and T cells that are formed after an initial immune response. They provide long-term immunity to the body by responding quickly and effectively to subsequent encounters with the same pathogen.' The B lymphocyte response also known as the humoral response, involves the following steps: - **Activation:** B cells become activated by T helper cells. - **Differentiation:** Activated B cells differentiate into plasma cells. - **Antibody Production:** Plasma cells produce immunoglobulins (antibodies). Here\'s a breakdown of the key terms: - **Immunoglobulins:** These are glycoproteins produced by plasma cells. - **Antibody:** A specific type of immunoglobulin that binds to a particular antigen. In essence, when a B cell encounters its specific antigen, it is activated by a helper T cell. This activation leads to the B cell differentiating into a plasma cell. The plasma cell then produces antibodies that bind to the specific antigen, helping to fight infection. Immunoglobulins, or antibodies, are Y-shaped proteins that help fight off infections. They consist of two main parts: - **Antigen-binding fragment (Fab):** This is the top part of the Y, and it\'s responsible for recognizing and binding to specific antigens (foreign molecules that trigger an immune response). - **Crystalline fragment (Fc):** This is the bottom part of the Y, and it interacts with other immune cells to activate them. Here\'s a breakdown: - **Fab:** - **Recognition Sites:** The Fab contains specific regions called recognition sites that bind to matching antigens. These sites are like locks that can only be opened by specific keys (antigens). - **Specificity:** The Fab\'s specific recognition sites are what give antibodies their specificity. Each antibody can only bind to one specific antigen. - **Fc:** - **Complement Activation:** The Fc region can bind to complement proteins, which are part of the immune system and help to destroy pathogens. - **Inflammation:** The Fc region also interacts with immune cells like macrophages and neutrophils, which are responsible for engulfing and destroying pathogens. This interaction triggers an inflammatory response, which helps to fight off infection. In short, the Fab part of an antibody recognizes and binds to a specific antigen, while the Fc part activates the immune system to fight the infection. Top of Form Antibodies are proteins that are part of the immune system. They are specifically designed to target and neutralize harmful substances like bacteria or viruses.  The text you provided describes the different classes of antibodies, which are distinguished by their structure, function, and where they are found in the body. Here is a breakdown: - **IgM:** The first antibody produced during an immune response. It is also found in blood and lymph fluid. - **IgG:** The most common antibody in the body. It is produced after IgM and is responsible for long-term immunity. - **IgA:** The main antibody found in bodily secretions like sweat, saliva, tears, and breast milk. It protects against infections in these areas. - **IgE:** Primarily involved in allergic reactions. It binds to mast cells and basophils, which release histamine and other substances, triggering allergic symptoms. Bottom of Form Antibodies are proteins produced by the immune system that help fight off infections. They work by binding to antigens, which are molecules on the surface of pathogens like bacteria and viruses.  Here\'s a breakdown of how they work: - **Antigen Binding:** Antibodies bind to specific antigens, forming antigen-antibody complexes. - **Neutralization:** Antibodies can block pathogens from entering cells or binding to their target sites, effectively neutralizing them. - **Opsonization:** Antibodies can coat pathogens, making them more attractive to phagocytes, which are cells that engulf and destroy pathogens. - **Complement Activation:** Antibodies can trigger the complement cascade, a series of reactions that results in the destruction of pathogens. The text describes the primary and secondary immune responses, which are part of the adaptive immune system. Here\'s a breakdown: - **Primary Immune Response:** This is the first time your immune system encounters a specific antigen. It\'s like your immune system is meeting a new person and learning their face. - **Antigenic Challenge:** Contact with the antigen (like a virus or bacteria). - **Production of Immunoglobins (Antibodies):** Your immune system produces antibodies (proteins that target the specific antigen) primarily of the IgM type.  - **Latent Period:** A delay of about 5 days before a measurable amount of antibodies is produced. - **Secondary Immune Response:** This is the second (or subsequent) time your immune system encounters the same antigen. Since it already knows the \"face\" of the antigen, it can respond faster and more effectively. - **More Rapid and Larger Production of Immunoglobins:** The immune system produces more antibodies in a shorter time. These antibodies are mainly of the IgG type, which are better at fighting off infections than IgM. **In essence, the secondary immune response is much stronger and quicker than the primary response, making you less susceptible to the same pathogen in the future.** This is the basis of how vaccines work.  T lymphocytes Response The lymphocyte response, also known as the cellular response, involves two main types of T cells: - **Cytotoxic T cells (Tc):** These cells directly attack and kill cells that display foreign antigens on their surface. They recognize and destroy infected cells or cells that have become cancerous. This is a critical part of fighting off infections and preventing the spread of disease. - **Memory T cells (Tm):** These cells \"remember\" past encounters with specific antigens. They persist in the body long after an infection has been cleared. If the same antigen is encountered again, these memory T cells can rapidly activate and mount a stronger, faster immune response. This is why we generally only get sick from a particular pathogen once. **Top of Form** **Bottom of Form** **The text describes two types of T lymphocytes: Td cells and Treg cells.** - **Td cells (Lymphokine-producing T cells):** They are likely Th1 cells, which are a type of helper T cell. They are responsible for **delayed hypersensitivity reactions**, which are immune responses that take time to develop. - **Treg cells (Regulatory T cells):** They are developed in the thymus or other parts of the body. They suppress the activation of B cells and T cells, helping to regulate the immune system and prevent overreactions. Natural Killer Cells Natural killer (NK) cells are a type of white blood cell that are part of the immune system. They develop from lymphoid stem cells in the bone marrow. NK cells account for about 10% of lymphocytes in the blood. NK cells play an important role in fighting infections and cancer. They can recognize and kill cells that are infected with viruses or that are cancerous.  This is how NK cells work: - They recognize virally infected or stressed cells by detecting changes in their surface proteins. - Once activated, they release interferon-gamma, which helps macrophages kill the infected cell. - NK cells can also directly kill infected and cancerous cells. Vaccines Vaccination is the process of introducing a weakened or inactive form of a microbe into the body to trigger an immune response. This response primes the body to fight off the actual infection when exposed later.  There are different types of vaccines: - **Inactivated Vaccines:** These use killed microbes that still retain the ability to trigger an immune response. You usually need multiple doses and booster shots. These vaccines contain viruses or bacteria that have been killed or weakened, but can still trigger an immune response. - **Live Attenuated Vaccines:** These use weakened versions of the microbe that are less likely to cause disease. They often provide longer-lasting immunity but may not be safe for people with weakened immune systems. These vaccines use weakened versions of the virus or bacteria that can replicate in the body, but not cause disease. This allows for a stronger immune response. - **Toxoid Vaccines:** These use inactivated toxins from bacteria (like tetanus). These vaccines contain a weakened version of a toxin produced by a bacteria. This helps the body develop immunity to the toxin. - **Subunit Vaccines:** These contain only specific parts of the microbe, like proteins or polysaccharides, to stimulate the immune system. These vaccines only contain specific parts or antigens of a virus or bacteria. - **Conjugate Vaccines:** These combine a weak part of the microbe (like a polysaccharide) with a strong part (like a protein) to make the vaccine more effective. These combine a weak antigen with a stronger antigen to improve the immune response.  - **Synthetic Vaccines:** These use laboratory-made versions of antigens to trigger an immune response. These vaccines are made using synthetic versions of antigens. - **DNA Vaccines:** These vaccines contain genetic material from a virus or bacteria, which instructs the body to produce the antigen. Summary of Vaccine Types and Protection **Type of Vaccine** **Examples** **Form of Protection** -------------------------------- ------------------------------------------------------------- --------------------------------------- Inactivated or killed virus Polio, hepatitis A Antibody response Inactivated or killed bacteria Cholera, bubonic plague, pertussis Antibody response Live attenuated virus Measles, mumps, rubella, varicella, flu, oral polio, rabies Antibody response and T cell response Live attenuated bacteria BCG vaccine for TB Antibody response and T cell response Toxoid Tetanus toxoid, diphtheria toxoid, rattlesnake venom Antibody response Subunit (antigen) vaccines HPV Antibody response Conjugate vaccines H. influenza type B Th response Synthetic vaccines Hepatitis B, H1N1 Antibody response Viral vectors Clinical trials of HIV antigen in canary pox vector Antibody response and T cell response DNA vaccines Clinical trials ongoing for several infections Antibody response and T cell response Top of Form Bottom of Form Vaccines work by introducing a weakened or inactive form of a pathogen (like a virus or bacteria) into your body. This \"training\" process helps your immune system learn how to fight off the real pathogen when you encounter it later: **Recognition:** Your immune system cells recognize the antigen associated with the vaccine (the part of the pathogen that triggers an immune response). - **Destruction:** The immune system destroys the weakened vaccine. - **Memory:** It then develops a \"memory\" of the antigen. This means it can quickly recognize and respond to the real pathogen if you encounter it in the future. - **Secondary Immune Response:** When you are exposed to the actual microorganism, your immune system mounts a rapid and potent secondary immune response. It produces high levels of antibodies (mainly IgG) and activates T cells (Tc cells) to fight off the infection. This secondary response is much faster and stronger than the initial response to the vaccine because your immune system has already learned to recognize the specific antigen and attack it. Top of Form Bottom of Form