Ch_22_Lecture_Objectives

Lymphatic System and Immunity: Key Questions and Answers

1. What are the parts of the immune system?

   • Lymph: A fluid circulating in the lymphatic system, containing water, proteins, and immune cells, responsible for transporting immune cells and removing waste.

   • Lymph Vessels: Transport lymph throughout the body, feature valves to prevent backflow, and are more permeable than blood vessels.

   • Lymphoid Tissues/Organs:

     • Primary: Thymus (for T cell maturation) and Bone Marrow (for B cell and innate immune cell production).

     • Secondary: Spleen (blood filtration and lymphocyte activation), Lymph Nodes (pathogen trapping and activation of lymphocytes), Tonsils (immune response to oral/nasal pathogens).

   • Lymphoid Cells: Include B cells, T cells, and natural killer cells involved in adaptive and innate immunity.

2. How do lymphatic capillaries differ from blood capillaries?

   • Lymphatic capillaries are more permeable and have flap-like valves that prevent backflow, allowing them to absorb larger particles.

3. Where do superficial and deep lymphatics collect lymph from?

   • Superficial Lymphatics: Collect lymph from the skin and subcutaneous tissues.

   • Deep Lymphatics: Collect lymph from deep muscles and organs.

   • Both converge into lymphatic trunks.

   • Right Lymphatic Duct: Collects lymph from the right side of the body superior to the diaphragm.

   • Thoracic Duct: Collects lymph from the left side superior to the diaphragm and areas below the diaphragm.

4. What structure receives lymph from the inferior parts of the abdomen, pelvis, and lower limbs?

   • Cisterna Chyli.

5. What is the germinal center of lymphoid tissues?

   • A site where naive B cells proliferate and differentiate in response to antigens.

6. What are the 5 tonsils and their locations?

   • Palatine Tonsils: On either side of the throat.

   • Lingual Tonsils: At the base of the tongue.

   • Pharyngeal Tonsils (Adenoids): On the posterior wall of the nasopharynx.

   • Tubal Tonsils: Near openings of the auditory tubes.

7. What is MALT and its location?

   • Mucosa-associated lymphoid tissue, found at mucosal surfaces such as the gastrointestinal tract (Peyer’s patches) and respiratory tract.

8. What are the differences and functions of the 3 lymphoid organs?

   • Lymph Nodes: Have afferent (into the node) and efferent (out of the node) lymphatics for filtering lymph and activating lymphocytes.

   • Thymus: Contains a blood-thymus barrier for T cell maturation and produces thymosin.

   • Spleen: Has red pulp (blood filtration) and white pulp (lymphocyte activation); may require splenectomy if ruptured.

9. What are the main differences between innate and adaptive immunity?

   • Innate Immunity: Non-specific, present at birth, involves immediate immune responses (e.g., physical barriers, phagocytes).

   • Adaptive Immunity: Specific, acquired through exposure, involves lymphocytes providing long-lasting immunity.

10. What stem cells initiate lymphocytopoiesis, and where are they located?

    • Hemopoietic Stem Cells in bone marrow; they divide into two groups: one group becomes B cells in the marrow, and the other travels to the thymus to become T cells.

11. What are the 7 types of innate immunity?

    • Physical Barriers: Skin and mucous membranes.

    • Phagocytes: Microphages (immediate response) and macrophages (fixed/free types, involving processes like emigration, chemotaxis, and adhesion).

    • Immune Surveillance: NK cells that patrol the body and attack abnormal cells.

    • Interferons: Proteins that inhibit viral replication.

    • Complement System: Proteins enhancing the function of antibodies and phagocytes.

    • Inflammation: Triggered by cytokines, which recruit neutrophils and create pus.

    • Fever: A temperature increase caused by pyrogens to enhance immune function.

12. What are the 3 types of T cells in adaptive immunity?

    • Cytotoxic T Cells: Kill infected or cancerous cells.

    • Helper T Cells: Activate other immune cells.

    • Regulatory T Cells: Suppress immune responses for homeostasis.

13. What specific type of immunity do cytotoxic T cells provide, and what are the steps?

    • Recognizes infected cells through the steps of 1) Recognition, 2) Activation, 3) Release of perforins and granzymes.

14. What specific type of immunity do B cells provide, and what are the steps?

    • Involves antibody production through the steps of 1) Antigen recognition, 2) Clonal selection and expansion, 3) Antibody production with T cell assistance.

15. What is clonal selection?

    • A process in which B cells recognize antigens and proliferate and differentiate based on the recognition of that antigen.

16. How do the four types of immunity differ?

    • Naturally Acquired Active Immunity: From natural infections.

    • Artificially Acquired Active Immunity: From vaccinations.

    • Naturally Acquired Passive Immunity: From maternal antibodies.

    • Artificially Acquired Passive Immunity: Through injection of pre-formed antibodies.

17. What are the four properties of adaptive immunity?

    • Specificity: Targets specific pathogens.

    • Versatility: Adapts to a range of pathogens.

    • Memory: Provides rapid response to previously encountered pathogens.

    • Tolerance: Prevents attacking the body’s own cells.

18. What are the two pairs of polypeptide chains in antibodies, and what is the role of constant vs. variable segments?

    • Antibodies have two heavy and two light chains. The variable segments contain the antigen-binding site, while constant segments determine the antibody class.

19. What are the six actions of antibodies when forming an antigen-antibody complex?

    • Neutralization: Prevents pathogen entry.

    • Opsonization: Marks pathogens for destruction by phagocytes.

    • Complement Activation: Triggers pathogen cell lysis.

    • Agglutination: Clumps pathogens for removal.

    • Precipitation: Clumps soluble antigens for removal.

    • Antibody-dependent Cellular Cytotoxicity (ADCC): Recruits immune cells to destroy target cells.

1. What is the difference between primary and secondary immune response?

   • Primary Immune Response: Occurs upon the first exposure to a pathogen and takes time to develop as the body must produce specific antibodies. This process is typically slower and can take several days to weeks before effective antibodies are produced.

   • Secondary Immune Response: Takes place upon subsequent exposures to the same pathogen. It is faster and more robust due to the presence of memory B and T cells created during the primary response, allowing antibody production to occur within days.

2. What is antibody titer?

   • Antibody titer refers to the concentration of antibodies in the blood. It is measured to determine the strength of the immune response against a specific pathogen. A higher titer indicates a stronger immune response, correlating with how well the body can fight off the pathogen in subsequent exposures.

3. Overall, what is the order of cells that appear when the immune system is exposed to a pathogen?

   • Upon exposure to a pathogen, the first responders are typically macrophages and dendritic cells, which assist in antigen presentation. This activates T helper cells, which stimulate B cells to differentiate into plasma cells that produce antibodies. Additionally, cytotoxic T cells are activated to target and kill infected cells, resulting in a coordinated defense against the pathogen. Initially, innate immune cells respond, followed by adaptive immune cells, leading to a robust immune response.

4. Know these lymphatic conditions:

   • Lymphedema: Accumulation of lymph fluid in tissues due to blockages in lymphatic vessels, resulting in swelling.

   • Tonsillitis: Inflammation of the tonsils, often caused by infection, leading to sore throat and difficulty swallowing.

   • Lymphadenitis: Inflammation of lymph nodes, frequently due to infection, characterized by swelling and tenderness in the affected area.

   • Hypersensitivities (Anaphylaxis and Antihistamines): Anaphylaxis is a severe allergic reaction that can occur rapidly, causing symptoms like difficulty breathing and swelling. Antihistamines are medications that counteract the effects of histamine, alleviating allergic symptoms.

   • Autoimmune Disorders: Conditions in which the immune system mistakenly attacks the body’s own tissues, resulting in inflammation and damage (e.g., rheumatoid arthritis, lupus).

   • SCID (Severe Combined Immunodeficiency): A genetic disorder leading to severe impairment of both T and B lymphocyte systems, increasing vulnerability to infections.

   • AIDS (Acquired Immunodeficiency Syndrome): Caused by HIV, which primarily targets CD4+ T cells, leading to a weakened immune system and making individuals susceptible to opportunistic infections.