Lymphatic Vessels
Carries lymph, that has leaked out of capillaries. from peripheral tissues to the venous system
Lymph
Fluid similar to plasma but does not have plasma proteins
Why doesn’t lymph contain plasma proteins?
They can’t leave the blood vessels
What does lymph contain?
Glucose
Hormones
Electrolytes
What does the lymphoid system produce, maintain, and distribute?
Lymphocytes
Where does the lymphoid system return fluid and solutes to?
The blood
Another function of the lymphoid system:
Distribut hormones, nutrients, and waste products from their tissues of origin to the general circulation
Which lymphatic vessels have valves?
Contractile vessels
Thoracic Duct
Left upper body
Lower body
Right Lymphatic Duct
Right upper body
3 Classes of Lymphocytes
T cells
B cells
NK cells
T Cells Derived In…
Thymus
B Cells Derived In…
Bone marrow (bursa)
General Types of T Cells (4)
Cytotoxic
Helper
Suppressor
Memory
Cytotoxic T Cells
Directly attack foreign infected cells
Cause lysis/destruction
Helper T Cells
Stimulate T and B cells to become active
Attract macrophages
Suppressor T Cells
Inhibit T and B cells
Secrete chemicals that moderate immune response once it is active
Memory T Cells
Respond to previously encountered antigens by cloning more T cells
Turn into cytotoxic or helper cells if they recognize certain bacteria
What percent of lymphocytes are T cells?
80%
What percent of lymphocytes are B cells?
10-15%
B Cells
Differentiate (change) into plasma cells
Plasma Cells
Produce and secrete antibodies that bind to and help destroy foreign cells and infected cells
What percent of lymphocytes are NK cells?
5-10%
Natural Killer Cells
Attack foreign cells, virus-infected cells, and cancer cells
Immunological Surveillance
Activity of NK cells
Where do lymphocytes constantly move around?
Blood
Lymph/Lymph nodes
Peripheral tissue
Lymphoid organs
Life Span of Lymphocytes
Years to decades
Where are blood cells produced?
Red bone marrow
Hemocytoblasts
Produce stem cells that can travel to the thymus (then become T cells)
Some stay in bone marrow to become B cells and NK cells
Lymphoid Tissue
Connective tissues containing large numbers of lymphocytes (macrophages)
Lymphoid Organs
Lymph nodes
Thymus gland
Spleen
Lymph Nodes
About 400 in body
Filters lymph from extremities before it reaches the trunk/torso
MALT
Mucosa-Associated Lymphoid Tissue
Collections of lymphoid tissue in digestive, respiratory, urinary tracts
Types of Tonsils
Pharyngeal
Lingual
Palentine
Tonsillectomy
Removal of tonsils
Slight risk of damage to internal carotid artery
Where do lymph nodes lie?
Along lymphatic vessels
What happens in a lymph node?
Lymph flows through several regions and is filtered
It then warns the immune system of any pathogens
What do macrophages in lymph nodes do?
Removes 99% of antigens in the lymph before it reaches the veins and then present the antigens to lymphocytes
Spleen
Largest lymphoid organ with good blood supply
What are the functions of the spleen? (3)
Macrophages phagocytize and recycle damaged/old RBCs
Stores iron
Exposes B and T cells to antigens/microorganisms in blood
What does the spleen contain?
Red Pulp
White Pulp
Red Pulp
Lots of red blood cells
White Pulp
Lymphoid tissue (lymphocytes)
What is the spleen hard to fix if ruptured?
Its soft tissue doesn’t like to hold stitches
2 Types of Immune Defenses
Innate Defenses
Adaptive Defenses
Innate Defenses
Nonspecific
Adaptive Defenses
Specific
7 Types of Nonspecific Defenses
Physical barriers Phagocytes Immunological surveillance Interferons Complement Inflammatory response Fever
Physical Barriers
Pathogens must cross skin or mucous membrane to enter body
How is the skin used as a physical barrier?
Multiple layers of cells, keratin, desmosomes
Oil and sweat gland secretions
How do desmosomes work as a physical barrier?
Their interlocking creates a barrier
How are mucous membranes used as a physical barrier?
Mucous secretions
Stomach acid
Types of Phagocytes
Neutrophils
Eosinophils (microphages)
Macrophages
Reticuloendothelial System
Removing bacteria
Also called monocyte-macrophage system
Fixed Macrophages
Stay in certain part of body and wait for antigen to approach it
Free Macrophages
Travel through body
Functions of Phagocytes (3)
Bind to pathogen and phagocytize
Bind to pathogen and wait for other cells to assist
Release chemicals to destroy pathogen
Immunological Surveillance
NK cells recognize abnormal antigens in cells and then attack those cells, whether they are self or bacterial
NK Cell Activation Process (3)
Recognition of antigen and adhesion to cell
Realignment of golgi apparatus toward target cells
Secretion of perforin via exocytosis
What does perforin do when secreted?
Perforates plasma membrane of a foreign cell making it unable to maintain homeostasis
Interferons
Proteins released form activated lymphocytes, macrophages, and viral-infected cells
Warn other cells of a virus in the body
Where do interferons bind to?
Membrane receptors in normal cell and use a second messenger to cause production of antiviral proteins which interfere with viral replication
What do interferons act like when released?
Hormones
What is the complement system made up of?
11 plasma proteins
How do complement reactions occur?
If a complement is activated by contact with antibody-coated cells (fastest) or contact with bacterial capsules
What do complement reactions result in?
MAC
MAC
Membrane Attack Complex (pore in bacteria)
Forms multiple holes in bacterium plasma membrane
What does MAC enhance?
Phagocytosis (opsonization) by making cells easier targets for macrophages and microphages
What does MAC trigger?
Histamine release by basophils and mast cells which increases local inflammation and blood flow
Inflammation
Tissue response to injury or infection
Release of chemicals from damaged cells
Release of histamine and heparin from mast cells
Result of Inflammation (5)
Redness Heat Swelling Pain Loss of function
Inflammation Protective Result
Capillaries allow clotting proteins and complement to enter wound site
Phagocytes are attracted
How does clotting help inflammation?
It walls off the area, slowing the spread of bacteria
What regulates body temp?
Hypothalamus
What do pyrogens do?
They are circulating proteins that can trigger hypothalamus to increase body temp
How are pyrogens secreted?
By macrophages
What does a fever indicate?
It is a signal that an infection is being fought
Functions of a Fever (2)
Increased metabolic activity
Inhibition of bacterial and viral activity
What results in an increase of metabolic activity?
Increased activity of immune cells
Increased speed of chemical reactions
Specific Defenses
Activity of T cells and B cells
What type of immunity are T cells?
Cell-mediated
What type of immunity are B cells?
Antibody-mediated
Active Immunity
Your body develops immunity
Naturally Acquired Active Immunity
Through environment exposure to pathogens
Induced Active Immunity
Through vaccines containing heat killed/treated/neutralized pathogens
Passive Immunity
Antibodies come from other source
Naturally Acquired Passive Immunity
Antibodies acquired from the mother through placenta and breast feeding
Induced Passive Immunity
By an injection of antibodies (meds create antibodies)
4 Properties of Immunity
Specificity
Versatility
Memory
Tolerance
Specificity of Immunity
T and B cells respond to one specific antigen
Versatility of Immunity
T and B cells can respond to millions of different antigens
Memory of Immunity
In an immune response some cells are produced to fight and some to act as memory cells for future exposure
Tolerance of Immunity
Immune cells do not respond to self antigens unless an autoimmune disease is acquired
What must happen before T cells can be activated?
They must encounter an antigen that is presented to them by an infected cell or a phagocyte
MHC Proteins
Major histocompatibility complex
Continuously synthesized and added to plasma membrane
What is required to activate T cells?
T cell sensitization exposure
Chemicals released by macrophages
What do B cells have sticking off of them?
Antigens
How are B cells sensitized?
Encounter with foreign antigen
How are B cells activated?
Encounter with helper T cells
What do activated T cells allow B cells to do?
Attack
What happens when B cells are activated?
They divide, producing populations of plasma cells and memory B cells
Plasma Cells
Produce antibodies specific to the antigen being attacked
Antibodies
Y shaped
2 pairs of polypeptide chains (heavy & light)
Constant and variable regions
Antigen-Binding Site
Variable region
Tips of chains
Region that will stick to antigen to form antigen-antibody complex that can cause agglutination
Action of Antibody (7)
If bonded to antigen.. Neutralization Precipitation/Agglutination Activation of complement Attraction of phagocytes Opsonization Stimulates inflammation Prevention of bacterial or viral adhesion to external surfaces
What does neutralization do?
Prevent viruses from entering cells
Agglutination is…
Clumping
Opsonization
Makes phagocytes easier