The Lymphatic and Immune System Jeffrey Zhao, Cindy Lee & Simona Dossi

The Lymphatic System Lymph vessels Organs Large vessels & Lymph capillaries (scattered throughout body) Skeletal muscle contracts  moves lymph fluid through valves One-way system: capillary  large vessel Lymph: clear watery fluid  formed from interstitial fluid Organs Bone marrow Lymph Nodes Spleen Thymus Associated with Circulatory System

The Lymphatic System

The Lymphatic System Bone Marrow: Lymph Nodes: Spleen: Thymus: Tissue produces lymphocytes B-Lymphocytes  bone marrow T-lymphocytes  thymus gland Blood cells: monocytes & leukocytes Lymph Nodes: Area of concentrated Lymphocyctes & macrophages Along lymphatic veins A mass of tissue Spleen: A larger Lymph Node filled with blood Reserves blood  Filters/Purifies blood & lymph fluid Thymus: Secretes hormone Thymosin  causes pre-T-cells to mature

The Lymphatic System Functions: Lymphocytes: Absorption of excess fluid Collects, Filters & Returns fluid to blood stream Absorption of fat Immunity: Fights infections with lymphocytes Lymphocytes: Invades pathogens (bacteria & virus) Respond to mutated cells (ex: cancer) and foreign proteins (ex: toxins) Multiply quickly when they meet an antigen

The Innate Immune Defenses Innate immunity mechanisms are fully functional without previous exposure to specific invaders No recognition of indtruders Innate defenses activate immediately after infection

Innate Defense: Physical & Chemical Barriers The skin Outside layer of dead skin and skin cells prevent entry Oil glands secret oil to trap invaders The Mucus Mucus lines respiratory track and digestive track Ensnares microbes Bacteria Certain bacteria in the intestine block binding sites that are potentially exploited by pathogens Saliva, tears, milk, and mucus all contain lysozyme Enzyme that kills bacteria Gastric juice Kills many bacteria and pathogens in stomach

THIS IS THE SLIDE BETWEEN THE FIRST LINE OF DEFENSE AND THE SECOND LINE OF DEFENSE. THE ONES THAT COME UNDER THESE ARE SECOND LINE OF DEFENSE. I THINK WE SHOULD CLARIFY THAT BUT IDK HOW

Innate Defense: Inflammatory Response Capillary changes→ Redness, heat, swelling, pain Histamine released by damaged cells→ capillaries dilate and become more permeable White blood cells migrate from bloodstream to damaged cells Monocytes turn into macrophages and dendritic cells Phagocytizes pathogens and release cytokines Chronic inflammation can be harmful Inflammatory chemicals in blood may cause fever Some bacteria or viruses may not survive the temp Blood clotting

Innate Defense: Phagocytes and Natural Killer Cells Phagocytes engulf and digest viruses and bacteria Neutrophils leave capillary and phagocytize Pus – white blood cells, dead cells, dead bacteria Macrophage and dendritic cells Engulf and stimulate T cells (adaptive immunity) Natural Killer Cells – Kills virus-infected cells and cancer ells by contact Also produces cytokines→ Promote adaptive immunity

Innate Defense: Protective Proteins These proteins in plasma are created by the liver Enhances inflammatory response Increased phagocytosis May bind to surface of pathogens and help white blood cells recognize it Membrane Attack Complexes Produces holes on bacteria

Adaptive Immune Defenses Third Line of Defense T Lymphocytes – T Cells B Lymphocytes Regulator T Cells and Self-Tolerance Major Histocompatibility Complex (MHC) Molecules APCs: Antigen-Presenting Cells Clonal Selection Antibodies

arise from stem cells in bone marrow THIRD LINE OF DEFENSE The adaptive third line of defense relies on: B lymphocytes T lymphocytes Once mature, both cell types circulate in the blood, lymph, and lymphatic tissue. Both cell types recognize different antigens and epitopes. arise from stem cells in bone marrow

Antigens – substance that stimulate an immune response from B cells or T cells. Epitopes – accessible piece of an antigen that provokes an immune response from a B or T cell

THREE PHASES RECOGNITION: ACTIVATION PHASE antigen receptors on B and T lymphocytes recognize specific antigens or epitopes by binding to them. ACTIVATION PHASE the binding of an antigen receptor activates B and T cells, which triggers rapid cell division and soon form populations of effector cells and memory cells EFFECTOR PHASE after activation, B cells produce antibodies and T cells engage in a cell-mediated response.

T LYMPHOCYTES – T CELLS Form in the bone marrow and mature in the thymus gland (where they got their name) Fight pathogens in the cell-mediated immune response Activation process begins when T cell antigen receptors bind with on the surface of antigen-presenting cells (APCs) by a molecule called major histocompatibility complex (MHC) Examples of APCs: Macrophages, dendritic cells, and sometimes B cells Once activated, T cells replicate to form effector cells and memory cells. Memory cells are responsible for immunological memory.

TWO MAIN TYPES OF T CELLS     Activated by interaction with APC “announce” the intrusion to the immune system Activate other cells by releasing cytokines, interleukin-1 (Il-1), and interleukin-2(Il-2) CD4 accessory protein on the surface Activated by helper cells Kill infected cells by releasing perforin and granzymes CD8 accessory protein on the surface

B LYMPHOCYTES B cells mature in bone marrow (^their name) Typical B lymphocytes  100,000 identical antigen receptors on surface Antigen receptors

B LYMPHOCYTES Provide adaptive immunity through humoral immune response (means they produce antibodies, or immunoglobins) Activated when an APC presents an antigen/epitope using a class II MHC molecule which then activates a helper T cell that recognized this epitope-MHC molecule complex Once activated, B cells produce thousands of clones. Some clones become effector cells, some plasma cells, and some memory cells.

MAJOR HISTOCOMPATIBILITY COMPLEX (MHC) MOLECULES Also known as HLA (human leukocyte anitgens) Collection of cell surface markers that identify the cells as self TWO MAIN CLASSES CLASS I MHC MOLECULES CLASS II MHC MOLECULES Surfaces of every nucleated body cell Specialized cells, including macrophages, B cells, dendritic cells, and activated T cells.

ANTIGEN-PRESENTING CELLS APCs ANTIGEN-PRESENTING CELLS Job: Taking in antigens and literally presenting them to our immune system. Examples: macrophage, dendritic cell, or B cell

ANTIBODIES (immunoglobins) Y-shaped molecule  four polypeptide chains: two identical heavy chains, two identical light chains Four constant regions (C) and four variable regions (V)

TYPES OF IMMUNITY TYPES OF IMMUNITY Passive Immunity Active Immunity Temporary Antibodies are transferred to an individual from someone else. Examples: maternal antibodies that pass through the placenta to the developing fetus or through breast milk to the baby Permanent The individual makes his or her own antibodies after being ill and recovering or after being given an immunization or vaccine.