LYMPHATIC SYSTEM, RESISTANCE, AND IMMUNITY

What are the functions of the Lymphatic System?

• fluid return to the cardovascular system from interstitial fluid

  • 20L out, 17L taken back in by capillaries, remaining 3L back to lymphatic system

• lymphocyte maturation

• transport of fats + dietary substances absorbed in the small intestine

What are the components of the Lymphatic System?

• lymph: similar to plasma + WBC

• vessels: similar structure to veins, 3 layers, thin tunica media

• nodes: enlargements along vessels

• lymphoid organs: red bone marrow, spleen, thymus, tonsils

What is a Lymphatic Capillaries and what happens with Lymph?

• lymphatic vessels pick up interstitial fluid which becomes lymph and drains into cardiovascular system

• higher pressure in interstitial space than in lymphatic capillaries

• valves, skeletal muscle pump, respiratory pump

What is the relationship between the Cardiovascular System and the Lymphatic Drainage?

• right lymphatic duct drains into right subclavian vein

• vice versa

What does the Bone Marrow do as a Primary Lymphoid Organ?

• synthesis of all blood cells

• synthesis of lymphocytes

• B cell maturation

What does the Thymus do as a Primary Lymphoid Organ?

• T cell maturation

• larger in childhood

What do Lymph Nodes do as a Secondary Lymphoid Organ?

• filters lymph

• location of adaptive immune response

What does the Spleen do as a Secondary Lymphoid Organ?

• removes pathogens from blood

• immune response to blood-borne pathogens

What do the Tonsils do as a Secondary Lymphoid Organ?

• develop immunity to oral pathogens

• some reduced in adult

What is Resistance and Susceptibility?

• resistance is the ability to prevent disease

• susceptibility is the lack of resistance

What is a Pathogen and Disease?

• pathogens are living things that can cause disease (bacteria, viruses, parasites)

• a disease is when pathogens take over the cell’s machinery, causing cells to lose function

What are the Surface Defenses?

• first line of defense; innate

• mechanical barriers from invading pathogens

  • skin, mucous membranes, mucus, hairs, cilia, tears, saliva, urine, vaginal seretions, epiglottis

• chemical factors (secreted substances that destroy pathogens)

  • gastric juice, acidic ph of skin, components of sweat, lysozyme

• defacation and vomiting

What are the Soluble Mediators?

• innate immunity

• substamces secreted by damaged cells

• increase inflammatory and immune response

  • examples: cytokines

  • complement proteins that promote innate response

What is Phagocytosis?

• innate immunity

• monocytes become macrophages that can ingest + digest pathogens when they enter tissue spaces

• neutrophils (bacteria and fungus) are main phagocyte in the inflammatory response

• eosinophils (allergy, parasite) and basophils (general inflammation / histamine) are also phagocytic

What is Inflammation?

• localized; innate immunity

• a series of responses to injury or destroy invading pathogens, preventing spread of infection, and to begin repair

• characteristics like redness, heat, pain, swelling occur

• injury, vasodilation, incresaed capillary permeability, phagocyte recruitment

What is a Fever?

• systemic; innate immunity

• generalized elevated temperature inhibits growth of bacteria

• speeds up body reactions for faster healing

What is a Neutrophil?

• phagocytic, bacteria (also fungi and burns

What is a Monocyte?

• phagocytic

• act as antigen presenting cells (APC)

• called macrophages in ECF

• release chemicals to attract other WBC

What is an Eosinophil?

• phagocytic

• relaese antihistamines

• parasitic worms and autoimmune

What is a Basophil?

promotes inflammation (histamines), parasites and allergies

What are Antigens?

• adaptive immunity

• substances that can trigger an immune response (antibody generator)

• antigens on pathogens are usually different from ones located in humans

• antibodies can bind antigens only if they are specific for the antigen

How does the body recognize Antigens?

• free floating pathogens can display their own antigens which can be detected by the immune system

• macrophages / dendritic cells engulf + beak up pathogen to display pathogen’s antigens on its membrane (APC)

What is the Cell Mediated Immunity Pathway?

• mediated by T cells which mature in the thymus

• activated by infected cells flagging for help and antigen presenting cells

• responds by developing special cells that destroy pathogens

What is the Humoral Immunity Pathway?

• mediated by B cells which mature in the bone marrow

• activated by cells detecting free pathogens or soluble particles

• responds by releasing chemicals (antibodies) that destroy pathogens

What are the steps towards Lymphocyte Development and Maturation?

1. all lymphoid stem cells originate in red bone marrow

2. t cells precursors migrate to thymus and mature

3. B cells mature in the bone marrow

4. naive lymphocytes leave thymus and bone marrow to lymph organs and blood (tested before release)

5. lymphocyte can be activated when antigen receptors bind its antigen

6. activated lymphocytes proliferate and differentiate into effector cells and memory cells

What are the Functions of all T cells?

• t cells originate in bone marrow, mature in thymus, activate into cytotoxic, helper or memory t cells

• cytotoxic t cells kill infected or altered host cell

• helper t cells secrete substances (cytokines) that stimulate b cell and t cell activation

• memory t cells differentiate into cytotoxic t cell on second expposure to same antigen

What are the Functions of all B cells?

• b cells originate and mature in bone marrow and activate into memory B cells or plasma cells

• memory b cells differentaite into plasma on second exposure to same antigen

• plasma cells secrete antibodies

What is Immunization?

• induction of immunity

• based on memory cels produced in cellular and humoral immunity

• active (immune system is challenged) vs passive (antibodies provided)

How is Immunization accomplished?

vaccination

• inactivated vaccine: person injected with dead organisms (polio, typhoid, diptheria, hepatitis A)

• attenuated vaccine: person injected with live but attenuated (weakened organisms) (measles, mumps, rubella)

• modified toxin vaccine: person injected with modified toxins (tetanus, botulism)

• pre formed antibody vaccine: person inkected with pre fored antibody (snake bites)

What is Immunological Tolerance?

• immune cells do not react to and attack body’s own proteins and tissues

• generated during lymphocyte maturation

What is an Immunodeficiency?

• inherited or acquired

• inherited are genetically based and can cause early death without bone marrow transplant

• acquired are due to a virus like HIV or AIDS

What is Autoimmune Disease?

• result from loss of immunological tolerance, meaning immune system does not recognize self cells

• can be localized, such as rheumatoid arthritis, type 1 diabetes mellitis or inflammatory bowel disease

• can be general, such as lupus

What are Blood Types?

• erythrocytes each present a certain group of antigens which are recognized by certain antibodies

• many different types of classes of antigens

• two most important are ABO and Rh

What is the Rhesus Factor?

• those with a D antigen are Rh+ or +

• those without antigen are Rh- or -

What is Erythroblastosis Fetalis?

1. Rh+ fetal erythrocytes leak into maternal after embryonic chorion breakage, which normall yisolates the fetal and maternal blood

2. maternal B cells are activated by Rh antigen and produce large amounts of anti-Rh antibodies

3. Rh antibody titer in mother’s blood is elevated after first exposure

4. Rh antibodies are small enough to cross the embryonic chorion and attack the fetal erythrocytes