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Immune System/Virus
| Question | Answer |
|---|---|
| The Immune System has two main branches: | Innate immunity (phagocytes are primary effector cells) and Adaptive Immunity (lymphocytes are primary effector cells). |
| Innate Immunity (Non-specific defense): | First line of defense against pathogens. Present from birth; does not require prior exposure. Responds quickly (within hours). No immune memory after exposure. General response to a broad range of pathogens. |
| Adaptive Immunity (Specific defense): | Develops after exposure to specific antigens, takes days to weeks to form, is highly specific, creates immunological memory, and involves B cells (antibodies) and T cells (cell-mediated immunity). |
| How are dendritic cells, neutrophils, and macrophages involved with innate immunity? | Dendritic cells, neutrophils, and macrophages are key components of the innate immune system, acting as the body’s first line of defense against pathogens. |
| Dendritic Cells (Innate Immunity): | sentinels that capture antigens and then present them to T cells, serving as the crucial bridge between innate and adaptive immunity. |
| Neutrophils (Innate Immunity): | first responders that rapidly migrate to infection sites, where they engulf and destroy microbes using enzymes and reactive oxygen species. |
| Macrophages (Innate Immunity): | arrive later, performing phagocytosis and releasing cytokines to trigger inflammation and recruit other immune cells. They also help clean up dead cells and debris. |
| How are T and L lymphocytes involved with adaptive immunity? | B cells make antibodies that target specific pathogens, while T cells either activate other immune cells or kill infected cells directly. |
| Blood: | Fluid connective tissue composed of plasma (55%) and formed elements including cells. Transports oxygen, nutrients, waste, hormones, and immune cells throughout the body. |
| Plasma: | Liquid component of blood (90% water, 10% dissolved substances). Contains proteins like antibodies, clotting factors, electrolytes, nutrients, and waste products. |
| Thymus: | An organ located in the upper chest where T cells mature. It’s essential for developing adaptive immunity early in life. |
| Mucosa-associated lymphoid tissue (MALT): | Lymphoid tissue found in mucous membranes like the gut and respiratory tract. It defends against pathogens entering through mucosal surfaces. |
| Spleen: | An organ that filters blood, removing old red blood cells and pathogens. It also helps activate lymphocytes to mount immune responses. |
| Lymph nodes: | Small bean-shaped structures distributed throughout the body that filter lymph fluid. They are sites where immune cells encounter and respond to antigens. |
| Bone marrow: | A soft tissue inside bones where all blood cells, including immune cells, are produced. It’s also where B cells mature before entering circulation. |
| Left subclavian vein: | A large vein that collects lymph from the thoracic duct and returns it to the bloodstream. It ensures that immune cells and proteins circulate throughout the body. |
| Thoracic duct: | The largest lymphatic vessel in the body that drains lymph from most of the body into the bloodstream. It connects to the left subclavian vein. |
| Red bone marrow: | The site of hematopoiesis, producing all blood and immune cells from stem cells. It supports both innate and adaptive immunity. |
| Hematopoietic stem cell: | A multipotent stem cell that gives rise to all blood cells. It differentiates into myeloid or lymphoid precursors. |
| Myeloid precursor: | A progenitor cell that develops into innate immune cells like macrophages, neutrophils, and dendritic cells. It supports rapid, nonspecific defense mechanisms. |
| Lymphoid precursor: | A progenitor that gives rise to adaptive immune cells (T and B cells) and some innate cells (natural killer cells). It’s crucial for specific, memory-based immune responses. |
| Red blood cells (erythrocytes): | oxygen transport, not part of immune defense. |
| White blood cells (leukocytes): | immune defense — include all the immune cells shown in the diagram (neutrophils, macrophages, lymphocytes, etc.). They are divided into two main categories: Innate and Adaptive immune cells. |
| Adaptive (Specific) White Blood Cells: | B cells (produce antibodies; part of antibody-mediated (humoral) immunity, Plasma cells (activated B cells that secrete antibodies in large amounts), T cells (coordinate cell-mediated immunity). |
| Monocyte: | A type of white blood cell that circulates in the blood and differentiates into macrophages or dendritic cells in tissues. It helps with phagocytosis and antigen presentation. |
| Dendritic cell: | An antigen-presenting cell that captures pathogens and presents their antigens to T cells. It bridges innate and adaptive immunity. |
| Macrophage: | A large phagocytic cell that engulfs and digests pathogens and dead cells. It also releases signaling molecules to recruit other immune cells. |
| Neutrophil: | The most abundant white blood cell, specializing in rapid response to infection. It engulfs and destroys pathogens using enzymes and reactive oxygen species. |
| Eosinophil: | A white blood cell that fights parasitic infections and contributes to allergic responses. It releases toxic granules and inflammatory mediators. |
| Basophil: | A rare granulocyte that releases histamine and other chemicals during allergic reactions. It promotes inflammation and recruits other immune cells. |
| Mast cell: | A cell found in connective tissues that releases histamine upon activation. It plays a key role in allergic responses and defense against parasites. |
| Natural killer (NK) cell: | An innate immune cell that kills virus-infected or cancerous cells without prior sensitization. It recognizes abnormal cells lacking normal “self” markers. |
| T cell: | White blood cells that mature in the thymus and are key players in cell-mediated immunity. They identify and destroy infected or abnormal cells and help regulate other immune cells. |
| B cell: | White blood cells that mature in the bone marrow and are central to humoral immunity. They produce antibodies that bind to specific antigens to neutralize pathogens. |
| Plasma cell: | A fully differentiated B cell that secretes large amounts of antibodies. These antibodies target specific antigens for destruction or neutralization. |
| Physical + Chemical Barriers: | mucous, skin, mucous membranes, tears, lysozyme, ear wax, saliva, hair |
| Bubo: | sign of infection |
| Acronym for White Blood Cells (Never Let Monkeys Eat Bananas): | neutrophils, lymphocytes, monocytes, eosinophils, basophils |
| Epidermis: | The outermost layer of skin providing the first physical barrier against pathogen entry. Composed of multiple layers of keratinized cells that prevent microbial invasion. |
| Dermis: | The middle layer of skin containing blood vessels, nerves, hair follicles, and immune cells. Site where the innate immune response begins once bacteria breach the epidermis. |
| Subcutaneous Tissue: | The deepest layer of skin composed of fat and loose connective tissue. Provides cushioning and insulation while serving as another barrier to deeper infection. |
| Sebaceous Gland: | Glands in the dermis that secrete sebum (oil) onto the skin surface. Sebum contains antimicrobial fatty acids that inhibit bacterial growth. |
| Hair Follicle: | Structure extending through skin layers from which hair grows. Can serve as a potential entry point for pathogens if damaged or infected. |
| Blood Vessel: | Tubes (capillaries, arteries, veins) that carry blood through the dermis. Essential for delivering immune cells from circulation to the infection site. |
| Capillary Endothelial Cell: | Cells lining the inner wall of capillaries that form a barrier between blood and tissue. Become activated during inflammation to allow immune cell exit and increase permeability. |
| Diapedesis (of Neutrophil): | The process where neutrophils squeeze between endothelial cells to exit the bloodstream and enter infected tissue. Also called extravasation or transmigration; critical for immune cells to reach infection sites. |
| Phagocytosis: | The cellular process of engulfing and destroying pathogens by surrounding them with cell membranes. Involves chemotaxis, adherence, ingestion, digestion in phagolysosomes, and waste elimination. |
| Inflammation: | nonspecific reaction to noxious stimuli (such as physical injury, toxins, and pathogens). Redness, swelling, pain, and heat localized at site of infection. |
| Cytokine and Chemokine Gradient: | Concentration gradient of chemical signaling molecules released by damaged cells and resident immune cells. Directs neutrophils and other leukocytes from blood vessels toward the site of infection. |
| Vascular Permeability (shown by leaky capillaries): | The ability of fluid, proteins, and cells to move across capillary walls into tissues. Increases during inflammation, allowing immune cells and antibodies to reach the infection site but causing swelling. |
| Vasodilation (shown by enlarged blood vessels): | Widening of blood vessels that increases blood flow to infected or damaged tissue. Causes redness and heat while delivering more immune cells and nutrients to the area. |
| Fever: | certain cytokines will cause the host’s body temperature to rise, causing a fever. |
| Pyrogens: | fever-causing cytokines are called pyrogens because they generate (gen) heat (pyro). |
| Reasons why a Fever is Beneficial: | it increases circulation rate, which allows leukocytes to get to the site of infection. It is also beneficial because some pathogens cannot withstand the increased temperature (not killed). Fever is also associated with an increase in transferrins. |
| Transferrins: | iron-binding blood plasma proteins that transport iron throughout the body. They sequester iron, keeping it away from pathogens and limiting their growth. |
| Interfons: | small cytokine proteins produced by virally infected cells that act as warning signals, preventing viral replication by stimulating antiviral protein production in nearby uninfected cells. |
| Can you boost your immune system? | It cannot be boosted beyond normal function, but you can support it by getting enough sleep, eating nutritious foods, and managing stress. These habits help keep the immune system balanced and strong. |
| Immune System: | The body’s defense network of cells, tissues, and organs that protect against infections and foreign substances (like bacteria, viruses, and toxins). |
| Stress: | Prolonged or chronic stress weakens immune function, making the body less effective at fighting infections and slower to heal. |
| What does it mean that the immune system is immunocompromised? | Means the immune system is weakened or not functioning properly, so the body is more vulnerable to infections. |
| Adaptive Immunity Vs. Innate Immunity: | while innate immunity is characterized by broadly targeted responses triggered by common structural features on microorganisms, adaptive immunity is directed toward specific molecular components of the microbes (their antigens). |
| Specificity: | Adaptive immunity targets a specific antigen unique to each pathogen. Each B or T cell recognizes only one particular molecular structure. |
| Memory: | After first exposure, memory cells form to remember the antigen. They enable a faster and stronger response upon re-exposure. |
| Selection: | Only lymphocytes with useful, non-self-reactive receptors are allowed to survive. When exposed to an antigen, only matching cells are activated to multiply. |
| Tolerance: | The immune system learns to ignore the body’s own cells and molecules. This prevents self-reactive lymphocytes from causing autoimmune attacks. |
| Does Antibodies Interact With an Entire Antigen? | No. Antibodies bind only to specific epitopes (antigenic determinants), not the entire antigen. These may be sugars, short peptides (4–6 amino acids), or other small molecular components. |
| Antigenic Determinant: | The specific part of an antigen that is recognized and bound by an antibody or a receptor on a B or T cell. |
| Epitope: | Another name for an antigenic determinant — it’s the precise molecular region on the antigen’s surface where the antibody or immune cell actually attaches. |
| Classes of Adaptive Immunity: | Active & Passive. The immune response may be active, which is generated from exposure to an antigen or passive, which is the transfer of antibodies or immune cells. |
| Active Immunity Characteristics: | Exposure to antigen through infection or vaccination. The body makes its own immune response. Activated by antigen; has immune memory. Maintained by memory cells (boosters help). Develops slowly (weeks). |
| Passive Immunity Characteristics: | No antigen exposure; antibodies or T cells are given. Immune response made by donor. No immune activation or memory. Temporary; fades quickly. Acts immediately. |
| You recover from chicken pox as a child → | active natural |
| You have measles → | active natural |
| A pregnant woman is getting the tetanus vaccine → | active artificial |
| A mother is breastfeeding her child → | passive natural |
| You are getting an antibody infusion to treat Covid → | passive artificial |
| Antibody: | or immunoglobulin (Ig) is a soluble protein made by a B lymphocyte or a plasma cell in response to antigen exposure. Each antibody binds to a specific antigen. |
| What Do Antigens Do? | Recognize and bind antigens from pathogens and their products, and facilitate the removal of these foreign substances from the body by a variety of mechanisms. |
| Fab Region (Fragment antigen-binding): | This region includes the variable domains (VH and VL) plus the first constant domains (CH1 and CL). Each antibody molecule has two identical Fab arms that bind to antigens. |
| Fc Region (Fragment crystallizable): | region comprises the CH2 and CH3 domains and forms the stem of the Y-shaped structure. It binds to cell surface receptors and complement proteins to trigger immune responses after antigen binding occurs. |
| Variable Regions (Antigen-Binding Sites): | variable domains of the heavy chain and light chain, shown in red and tan at the top of the structure. The amino acid sequences in these regions vary greatly between different antibodies, allowing each antibody to recognize a specific antigen. |
| Constant Regions: | Constant regions on an antigen are portions of the molecule that remain structurally unchanged among different variants, helping maintain its overall shape and function. |
| Make sure you can draw and recognize the structure of an antigen! | -- |
| J chain (joining chain): | a small polypeptide that links antibody monomers—specifically IgA and IgM—together to form their multimeric (dimeric or pentameric) structures. |
| The secretory component: | a protein derived from the epithelial cell’s poly-Ig receptor that binds to the J chain–containing antibodies (mainly IgA) during secretion, protecting them from degradation as they cross mucosal surfaces. |
| IgG: | the most abundant serum antibody (~80%), can cross the placenta to provide passive fetal immunity, and functions in neutralization, agglutination, complement activation, opsonization, and ADCC. |
| IgM: | the first antibody produced in an immune response and forms a pentamer held together by a J chain, with 10 antigen-binding sites. It is effective in agglutination and complement activation, and its monomer serves as the B-cell receptor. |
| Secretory IgA: | a dimer linked by a J chain and protected by a secretory component that allows it to survive in mucosal areas. It neutralizes and traps pathogens in mucus, providing immune defense at mucosal surfaces. |
| IgD: | found in very low concentrations in the blood and primarily functions as a B-cell receptor. It helps initiate B-cell activation upon antigen binding. |
| IgE: | involved in allergic reactions and defense against parasites. It binds to mast cells and basophils, triggering histamine release and inflammation upon antigen exposure. |
| Anamnestic immunity: | another name for the secondary immune response, occurring after repeated exposure to the same antigen. It is driven by memory B and T cells and produces a faster, stronger response dominated by high-affinity IgG. |
| Primary Antibody Response (Initial Antigen Exposure): | The first exposure to an antigen triggers a slow, weak response dominated by short-lived plasma cells producing mainly IgM. Antibody levels rise after several days, stay low, and decline quickly without continued antigen presence. |
| Secondary Antibody Response (Subsequent Exposures): | Upon re-exposure, memory B cells rapidly produce mostly high-affinity IgG, generating 10–100× more antibodies. The response is faster, stronger, and longer-lasting, with elevated antibody levels that decline slowly over time. |
| Make sure you’re able to understand and recognize the diagram of slide 15! | -- |
| Vaccination (immunization): | deliberate exposure to an antigen which triggers an adaptive immune response intended to protect an individual against future infection by a pathogen. The immunogen used to induce this artificial active immunity is called a vaccine. |
| Meningitis (Neisseria meningitidis) | Purified polysaccharide vaccine |
| Pertussis (whooping cough) | Killed bacteria or acellular proteins |
| Pneumonia (bacterial, Streptococcus pneumoniae) | Purified polysaccharide or polysaccharide-toxoid conjugate |
| Tetanus | Toxoid vaccine |
| Tuberculosis | Attenuated strain (BCG vaccine, though not routinely used in US) |
| Typhoid fever | Killed bacteria vaccine |
| Hepatitis A | Recombinant DNA vaccine |
| Hepatitis B | Recombinant DNA vaccine or inactivated virus |
| Influenza (seasonal or H1N1) | Inactivated or attenuated virus |
| Mumps | Attenuated virus (MMR vaccine) |
| Polio | Attenuated virus (Sabin) or inactivated virus (Salk) |
| Rotavirus | Attenuated virus |
| Rubella (German measles) | Attenuated virus (MMR vaccine) |
| Varicella (chickenpox/shingles) | Attenuated virus |
| Smallpox | Cross-reacting virus (vaccinia) - historically eradicated, stockpiled for bioterrorism preparedness |
| Whole Cell – Attenuated (Types of Vaccines): | Uses live but weakened pathogens that replicate without causing disease, creating strong, long-lasting immunity. |
| Mechanism of Attenuated Vaccines: | Weakened virus is administered. Produces virus-like particles. Triggers strong immune response. |
| Characteristics of Attenuated Vaccines: | Provokes strongest immune response. Some attenuated vaccines may not be suitable for people with compromised immune systems. Antigen presented to immune cells on Antigen Presenting Cells. Results in immune response and memory. |
| Whole Cell – Inactivated (Types of Vaccines): | Contains pathogens that have been killed, so they cannot replicate but still trigger an immune response. |
| Inactivated Vaccine Mechanism: | Dead/killed virus is administered, Virus particles contain proteins and peptides, Heat or chemicals used to inactivate. |
| Inactivated Vaccine Characteristics: | Virus is already dead (safer than live vaccines), Inactivated vaccines require booster doses as immunity conferred may be weaker than live vaccines. Antigen presented to immune cells on Antigen Presenting Cells. Results in immune response and memory. |
| Subunit (Types of Vaccines): | Includes only specific antigens (like proteins or polysaccharides) from the pathogen to safely stimulate immunity. |
| Subunit Vaccine Mechanism: | SARS-CoV-2 antigen and adjuvants combined. Self-replication in the production system. Antigen assembled with adjuvants. Administered via injection |
| Subunit Vaccine Characteristics: | Contains contain only specific pathogen antigens, often need adjuvants, are very safe, may require multiple doses, and stimulate immune response and memory via antigen-presenting cells. |
| Conjugate (Types of Vaccines): | Combines a weak antigen (usually a polysaccharide) with a strong protein carrier to enhance immune response, especially in children. |
| Toxoid (Types of Vaccines): | Contains inactivated bacterial toxins that train the immune system to recognize and neutralize the toxin rather than the pathogen itself. |
| Replicating Viral Vector Vaccine (Types of Vaccines): | Uses low-pathogenic viruses as living carriers, altered to insert viral vectors that produce some of the same proteins as the disease-causing virus. |
| Replicating Viral Vector Vaccine Mechanism: | Disease-causing virus + low-pathogenic virus combined, Viral vector encoding target antigen created, Gene for SARS-CoV-2 antigen inserted into vector |
| Replicating Viral Vector Vaccine Characteristics: | Creates strong immune response but may not work for people who are already immune to the low-pathogenic virus. The virus replicates inside the body. Antigen presented to immune cells on Antigen Presenting Cells. Results in immune response and memory. |
| Non-Replicating Viral Vector Vaccine (Types of Vaccines): | Similar to replicating viral vector vaccines, but they cannot replicate inside the body |
| Non-Replicating Viral Vector Vaccine Mechanism: | Disease-causing virus + low-pathogenic virus combined, Key viral replication machinery deleted from low-pathogenic vector virus, Viral vector encoding target antigen created |
| Non-Replicating Viral Vector Vaccine Characteristics: | Improved efficacy and safety but requires high doses to confer immunity, Cannot replicate inside the body, Antigen presented to immune cells on Antigen Presenting Cells, Results in immune response and memory. |
| DNA Vaccine (Types of Vaccines): | Uses DNA plasmids containing a gene for SARS-CoV-2 along with additional genetic elements that will produce some of the same antigenic proteins as the disease-causing virus |
| DNA Vaccine Mechanism: | A DNA plasmid carrying the gene for a pathogen antigen (e.g., SARS-CoV-2 spike protein) is introduced into host cells. The cell’s machinery transcribes the DNA into mRNA, which is then translated into the antigenic protein. |
| DNA Vaccine Characteristics | Easy and quick to develop and manufacture, No risk of infection Quick and easy to produce, no risk of infection, may sometimes elicit a weak immune response, antigens presented on antigen-presenting cells, leading to immunity and memory. |
| RNA Vaccine (Types of Vaccines): | Uses a piece of messenger RNA (mRNA) that will produce some of the same antigenic proteins as the disease-causing virus |
| RNA Vaccine Mechanism: | mRNA delivered in lipid delivery vehicle. Self-replication occurs inside the cell. Antigen (protein) produced |
| RNA Vaccine Characteristics: | Risk of being degraded by the host immune system before producing the RNA molecules may trigger an unintended immune response in the body. Antigen presented to immune cells on Antigen Presenting Cells. Results in immune response and memory |
| Herd Immunity | defined as the resistance of a group to infection due to immunity of a high proportion of the group. If a high proportion of individuals are immune to infection, then the whole population will be infected. |
| How Can You Protect People Via Herd Immunity? | Immunized people protect nonimmunized people because the pathogen cannot be passed on, and the cycle of inefectivity is broken. Diseases such as influenza tend to occur in cycles. |
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