Lymphatic System and Immunity

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Introduction: Lymphatic System and Immunity

• Pathogens are microscopic organisms that cause disease, including viruses, bacteria, fungi, and parasites, each attacking in a specific way.
• The lymphatic system (lymphoid system) protects the body against disease.
• Lymphatic system cells respond to environmental pathogens, toxins, and abnormal body cells, like cancers.
• Lymphocytes are a part of the immune response that identify, attack, and develop immunity to specific pathogens.
• The immune system provides immunity, which is the ability to resist infection and disease.
• All body cells and tissues are involved in the production of immunity and not just the lymphatic system.

Components of the Lymphatic System

• Lymph is a fluid similar to plasma but without plasma proteins.
• Lymphatic vessels carry lymph from peripheral tissues to veins
• Lymphoid tissues and lymphoid organs are scattered throughout the body.
• Lymphoid cells include lymphocytes, phagocytes, and other cells.
• Lymphocytes are produced in primary lymphoid tissues and organs, such as red bone marrow and the thymus.
• Lymphocytes are activated in secondary lymphoid tissues and organs such as the tonsils, MALT, lymph nodes, and spleen.
• Functions of the lymphatic system: produce, maintain, and distribute of lymphocytes and other lymphoid cells, return excess fluid to the bloodstream, maintain normal blood volume, and to transport hormones, nutrients, and wastes.
• Lymphatic vessels (lymphatics) carry lymph, which is interstitial fluid that has entered the lymphatic vessels, from peripheral tissues to the venous system.

Lymphatic Capillaries

• Lymphatic capillaries differ from blood capillaries in several ways.
• They are closed at one end and do not form a tube.
• They have larger luminal diameters.
• They have thinner walls and a flat or irregular outline in cross-section.
• Endothelial cells are loosely bound together.
• The overlap of endothelial cells acts as a one-way valve, which allows fluids, solutes, viruses, and bacteria to enter but prevents them from returning to intercellular spaces.
• Lymph flows from lymphatic capillaries to larger lymphatic vessels containing one-way valves.
• Lacteals are special lymphatic capillaries in the small intestine that transport lipids from the digestive tract.

Lymphatic Vessels

• Superficial lymphatics, deep lymphatics, found in the skin, mucous membranes, and serous membranes that accompany arteries and veins lining body cavities.
• Lymphatic vessels join to form large lymphatic trunks that empty into two major collecting vessels: the thoracic duct and right lymphatic duct.
• The thoracic duct expands at its base to form the cisterna chyli, which receives lymph from the right and left lumbar trunks and the intestinal trunk.
• The thoracic duct's inferior segment collects lymph from the left bronchomediastinal trunk, left subclavian trunk, and left jugular trunk.
• The thoracic duct empties into the left subclavian vein.
• The right lymphatic duct collects lymph from the right jugular trunk, right subclavian trunk, and right bronchomediastinal trunk.
• The right lymphatic duct empties into the right subclavian vein.
• The thoracic duct carries lymph from tissues inferior to the diaphragm and from the left side of the upper body, while the right lymphatic duct carries lymph from the rest of the body.
• Lymphedema occurs when there is a blockage of lymph drainage from a limb, causing severe swelling and interfering with immune system function.
• Lymphoid cells are immune system cells and supportive cells in lymphoid tissues.
• Lymphocytes make up 20-40% of circulating leukocytes, with most being stored rather than circulating.
• The types of lymphocytes: T cells (thymus-dependent), B cells (bone marrow-derived), and NK cells (natural killer cells).
• Lymphoid tissues are connective tissues dominated by lymphocytes

Lymphoid Nodules

• Lymphoid nodules (lymphatic nodules) are composed of areolar tissue containing densely packed lymphocytes.
• Germinal centers contain dividing lymphocytes.
• Distributed in lymph nodes, spleen, the respiratory tract (tonsils), and along the digestive, urinary, and reproductive tracts.
• There are five tonsils in the wall of the pharynx, called the pharyngeal tonsil (adenoid), the left and right palatine tonsils, and two lingual tonsils.
• Tonsillitis involves inflammation of the tonsils, especially the palatine tonsils.
• Mucosa-associated lymphoid tissue (MALT) consists of lymphoid tissues associated with the digestive system.
• Aggregated lymphoid nodules are clustered deep to the intestinal epithelial lining.
• The appendix (vermiform appendix) contains a mass of fused lymphoid nodules.

Lymphoid Organs

• Lymphoid organs include the lymph nodes, thymus, and spleen.
• They are separated from surrounding tissues by a fibrous connective tissue capsule.
• Lymph nodes have trabeculae, which bundles of collagen fibers that extend from the capsule into interior of node.
• The hilum in lymph nodes are shallow indentation where blood vessels and nerves reach lymph node.
• Afferent lymphatics carry lymph from peripheral tissues to lymph node, while efferent lymphatics leave lymph node at hilum and carry lymph to venous circulation.
• Lymph flows through nodes, first from the subcapsular space containing macrophages and dendritic cells, then through the outer cortex, containing B cells within germinal centers and the paracortex( dominated by T cells.
• This continues through the core(medulla) and is organized into medullary cords containing B cells and macrophages, passing finally, into efferent lymphatics at hilum.
• Lymph node function involves purifying lymph before returning it to venous circlation.
• The nodes remove 99% of antigens and antigens that are released due to infection and enter lymph which stimulates macrophages and lymphocytes to produce cytokines.
• Lymphoid tissues and lymph nodes monitor peripheral infections and respond before infections reach vital organs.
• Lymph nodes of the gut, trachea, lungs, and thoracic duct, protect against pathogens in digestive and respiratory systems.
• The largest lymph nodes are in the groin, axillae, and base of neck and tend to swell in response to infection.
• Lymphadenopathy involves chronic or excessive enlargement of lymph nodes. May indicate infections or cancer.
• The thymus shrinks in size, or atrophies, after puberty.
• A diminishing effectiveness of immune system occurs.
• The cells also decrease, but still plays vital role, making it important.
• Thymus is divided into two thymic lobes.
• Septa divide lobes into smaller lobules.
• Dense outer cortex and pale central medulla are features of thymic lobules, that divide in the cortex, migrate into the medulla and then mature T cells that leave thymus by medullary blood vessels.
• Epithelial reticular cells surround lymphocytes in cortex and form layered structures in medulla known as thymic (Hassall's) corpuscles.
• These maintain the blood thymus barrier in cortex in thymus.
• Absent in medulla.
• Thymic horomes involves thymosin-an which is an extract from thymus containing several hormones and promotes development and maturation of T cells.

Spleen Anatomy & Function

• Functions of the spleen are centered around the removal of abnormal blood cells and other blood components, as well as the storage of iron recycled from red blood cells by phagocytosis.
• The spleen initiates immune responses by B cells and T cells in response to antigens in circulating blood.
• The anatomy of the spleen involves its attachment to the stomach by the gastrosplenic ligament and its contact with the diaphragm and the left kidney.
• Splenic veins, arteries, and lymphatic vessels communicate with the spleen at its hilum.
• The cellular components within the capsule of the spleen make up the pulp.
• Red pulp contains many red blood cells, while white pulp resembles lymphoid nodules.
• Trabecular arteries branch and radiate toward the capsule, with finer branches surrounded by white pulp, and their capillaries discharge red blood cells in red pulp.
• The spleen contains elements of circulating blood, including both fixed and free macrophages.
• In splenic circulation, blood passes through a network of reticular fibers, which empty into trabecular veins.
• Spleen macrophages identifies and then attacks damaged and infected cells in circulating blood.
• Splenectomy is a removal of a severely ruptured spleen

Innate and Adaptive Immunity

• Immunity is the ability to resist and defend against infectious organisms and other damaging substances.
• Resistance is the ability of the body to maintain immunity.
• The immune response is the body's reaction to infectious agents and other abnormal substances.
• Two types of immunity: innate (nonspecific) immunity, which always works the same way against any type of invading agent and adaptive (specific) immunity.
• Adaptive (specific) immunity protects against specific pathogens that depends on activities of lymphocytes and develops after exposure to environmental hazards.
• Lymphocytes include B cells, T cells, and NK cells.

Lymphocyte Distribution

• Lymphocyte Tissues maintain different T cell and B cell populations, and the lymphocytes wander through tissues.
• Lymphocytes enter blood vessels or lymphatics for migration and can survive many years.
• Lymphocytopoiesis is the process of lymphocyte production, involves the bone marrow, thymus, along with peripheral lymphoid tissues, and hemocytoblasts in bone marrow.
• Division leads to two distinct lymphoid stem cell populations, including group 1 that produce stromal cells remain in the bone marrow and aided by stromal cells.
• B cells and NK cells differentiate when exposed to interleukin-7 and group 2 that develops an environment separated from blood migrate into thymus.
• T cells differentiate with the use of hormones.
• There are T cells annd B cells migrate throughout body to defend peripheral tissues and retain their abilty to divde which is essential to ensure that the immune system functions correctly.
• Innate (nonspecific) defenses block or attack any foreign substance or pathogen and cannot distinguish one another.

Innate Defenses

• Physical barriers, phagocytes, immune surveillance, interferons, complement, inflammation, and fever.
• Physical barriers include the outer layer of skin, hair, and epithelial layers of internal passageways.
• Secretions that flush away materials including sweat, mucus, and urine, as well as those that kill or inhibit microorganisms containing enzymes, antibodies, or stomach acid.
• Pahgocytes attack remove dangerous microorganisms, including microphages (neutrophils and eosinophils that enter tissues to fight infections).
• Macrophages are large phagocytic cells derived from monocytes distributed throughout the body and make up the monocyte-macrophage system (reticuloendothelial system).
• Activated macrophages respond to pathogens by engulfing and destroying it with lysosomal enzymes, binding to a pathogen so other cells can destroy it or destroying pathogen by releasing toxic chemicals into interstitial fluid
• Types of macrophages: fixed macrophages (histrocytes) which stay in specific tissues and microglia.
• Free macrophages (wandering macrophages) travel throughout the body, and alveolar macrophages (phagocytic dust cells).
• Macrophages and microphages move through capillary walls (emigration) and are attracted or repelled by chemicals in surrounding fluids (chemotaxis).
• Phagocytosis begins when phagocyte attaches to the target through (adhesion) and covers the site with a vesicle

Immune Surveillance

• Immune surveillance is carried out by natural killer (NK) cells and can be activated;
  1. Identify and stick to abnormal cells.
  2. Golgi apparatus will then start to produce vesicles containing perforins.
  3. Vesicles release perforins by exocytosis.
  4. Perforins make holes in the plasma cells.
• Tumor-specific antigens are on plasma membranes of cancer cells which are identified as abnormal by NK cells.
• Some cancer cells avoid detection (immunological escape).Cells infected with viruses present abnormal proteins on their plasma membranes. (NK Cells ID and destroy them).
• Interferons( IFNS) which are small proteins released by acivated lymphocytes and macrophages triggering production fo anitviral proteins.
• Antiviral proteins do not kill viruses directly, which inhibits viral replicatation in the cell.
• IFNS are one type of cytokine, which are chemical messengers that are important for immune response secreted by cells.
• Interferons are either interferon Alpha (Infected Cells) or interferon beta (fibroblast cell) or gamma.
• Complement system where a system consisting of more than 30 proteins in plasma working together in cascades as a method that antibody use.
• These cascade come in three distinct pathways, include:
• Classical Pathway.
• Lectin Pathway.
• Alternative Pathway.
• All 3 of those pathways cause conversation to 3rd compliment which activates protein.
• Killing a pathogen with cell lysis can be done in to way, which proteins can form a membrane or increase.
• Inflammation is a type of localized response which tends to prevent limited spread of further injury with cardinal signs.
  1. Redness
  2. Swelling
  3. Pain
  4. Heat
• Some of product of inflammation can lead to a. Necrosis, Pus or Abcess.
• Fever is raised temperate around 37.2°C in response to pyrogens increasing metabolism.
• Fever, or elevated body temperature, greater than 99°F (37.2°C), which is made by pyrogens ( fever inducing agent) such as, fungi, viruses, bacteria eht produce cytokine.

Adaptive Defenses

• In the world of Adaptive (specific) Immunity, coordination the actions of T cells and B cells results in better protection.
  1. T cells - Attack Physically and chemically.
  2. Helper T - stimulate body parts.
  3. Regulatory T - Moderate
  4. Memory T - Antigen Recognition.
• There are different kind of T cells that can have different regulatory actions such as;
  1. Inflammatory T cells.
  2. Suppressor/inucer cells.
• There are B cells who contribute 10 to 15 present of the population, and Differentiate into plasma cells and produce antibodies.
• NK cells help contribute at least with 5 to 10 percent circulating lymphocytes.
• Cell-mediated immunity (also known as cellular immunity) which is used to remove any abnormal cells or pathogens. (T cells only).
• Antibody-mediated immunity with the help of cells ( B Cells) help remove pathogens through bodily fluids.

Immune Response

• Adaptive Immunoty or (Antigens) are chemical that induce stimulation that activate the immune cells.
• A activated lymphocyte clone will trigger divison.
• This leads to clone selection as the new antigen.
• Some types of immunity, may result from birth while some occurs after birth

Forms of Immunity

• There various types of immunity when it comes to body.
  1. We got Innate which the body has with the genetic inheritance
  2. We got Adaptive which the body has the ability to gain with specific interactions (not genetic)
  3. We got Active Immune where immune cells are forced to adapt thanks to antigens.
  4. Passive is that antibodies transfer the memory over from any sort of source.
• But how is Active Immunity acquired is the main question?
• Active Immunity comes through, Naturally acquired in the enviroement or Actifically aquired are both forms of Active Immunity.
• A body would need Naturally aquired Passive Immunity are obtained through the mothers milk. -While Actifically Aquired Passive Immuntiy comes from the injection of some sort or injection of Anti-Bodies.
• Four protreties when to comes to Adapative Immunity.
  1. Specificity
  2. Versatilly
  3. Memory
  4. Tolerance

T-Cells and Immunity

• T Cells which exposure to one antigen are activcated and presented with (Antigen Presentation ) as a sort of introduction.
• To better understand the T-Cell are introduced in the world these cells relys on MHC so called "Membrane Glycoproteins that allows to the antigen to code in chromosome 6.
• There are different kinds of MHC proteins classses.
  • MHC proteins are a type of class, this allows the immune cells normal cells to fight off any virus.
  • Class I MHC proteins that are found in nuclaecells and cells who are infected, and the main duty is to carry cell the surface for T-Cells to examine.
• To help with cells with infected is (Class II MHC) whish presents an antigen to the protein (APCs).
• Then antigen with T cell is then detected to determine the best course of action.
• The CD markers cluster to show signs.
• Then to help with differentatiation or recognizing the signals, there are CD3 Receptors to send signals to the membrane.
• The body then has to perform CD4 and CD8 when the receptors are binded for CD3 complex.
• For CD4-T cell to be activated as a secondary signal or costimulation must occure to confimed signal.
• With all that process of binding all CD8 now will get exposure to the antigen on class so it can produce, but some T cells do produce cytotix.
• For the purpose of desotryiong the cell when it is in the active stae where (Realease perforins), is secrete cytokine and then secretes the lymphotoxin.
• Memory B cells are created and used to check with cytotix and regulation of T'cells .
• While in the world of the CD4 or acticated t cells (Helper T Cells) are there the help and release the cytokine (stimulate).
• Cytokines comes packed with the following components that form immune cells response.
  • Interleukins
  • Interferons
  • Tumor necrosis factors (TNFs)
  • Colony-stimulating factors (CSFs)
• Lymphokines help produce more cytotix T cells, while promoting the "B Cells"
• A body can suffer from (Tumor Necrosis Factors) where growth is then limited from producing leukocate preventing fever. With that all being released from T Cells the production for cells is ready to be done.

B Cells and Immunity

• The reason B cells are important is since they are responsible for antibody mediated to release antigens.
• To prepare to the cell to be attack by the antigen then B cell gets read and ( B CELL SENSEIZATION.
  1. The B cell senses the antigen to the extracellular fluid to send signals to release B (memory cell).
  2. The B cell will make contact with help T cell, this will have antigen on it with the use of MHC CLASS that will bind with cytokine).
• Now comes the world with the" B cells will be active and divison is now coming" the clone that make plasma will then release a antibody.
• Antibodies that come from the B CELL are made of two chains where has light chains and constant segments.
• In heavy chains the cells can recognize the body thanks to imnunlogbins (igs).
• Different Class with Immunlogbins.
  1. Igg = Resistance with 80 % high diversity allows a maternal resistance with disease.
  2. IGE- Exposed and releases basephils to help accelerate. ( allergies)
  3. IGD - An individuals where it binds as surface to help make them active.
  4. IGM - A "first repsonse" to something new while production makes this happen. (Responsible for blood transufsions).
  5. IGA- Found with Glandler actions protect from the insde

Immune System and Stress

• Stress in terms or the immune may be in the format of (Gluco-Coratic), long term stress that reduce body reistance. - Depression reduction - reduction to "Abundance" -Reduction to "interculated secrition" - The body can be affected by the imnune from allergies to overacting. - Anaphylaxis can be a sever reaction that affects perambalty caused by exposure.

Effects of Aging and Immune Response

• The Immune system can be damaged with age.
  • Thymic hormone for helping produce is limited.
  • -Cell reduce because of "B cells".

Learning Outcomes

• Identifying the major components of the lymphatic system, describing the structure and functions of each, and discussing the importance of B cells
• Distinguishing between innate (nonspecific) and adaptive (specific) immunity along with learning the repsonse with of lymphocytes.
• Learn the body's inneate defenses and how to functions.
• Identify different types of adaptive/speific and the various of immunity for cell-mediated and antibody-mediated immunity.
• Understand various types of T cell that adapt.

More on T-Cell Functions

• B cell activation is one of the key events in the humoral immune response
• Competence is the body function. The effects of stress on immunity, disorders
• Explain the relationship between the lymphatic system and the organ system to explain the nerous and endocrine system.

An overview of the lymphatic system and immunity. The lymphatic system protects the body against disease by responding to pathogens, toxins and abnormal cells. Lymphocytes identify, attack, and develop immunity to specific pathogens.