Download Lymphatic and Immune System

Lymphatics and the Immune
System
Lymphatic System
 The lymphatic system actually consists of
two semi-independent systems
 Lymphatic Capillaries and Vessels
 Lymphoid Tissues and Organs
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Lymphatic System
 One way system: to
the heart
 Return of collected
excess tissue fluid
 Return of leaked
protein
 “Lymph” is this fluid
 Edema results if
system blocked or
surgically removed
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 Lymph capillaries
 Have one way minivalves allowing
excess fluid to enter but not leave
 Picks up bacteria and viruses as well
as proteins, electrolytes and fluid
(lymph nodes destroy most
pathogens)
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 Lymph flows from the lymphatic capillaries
through successively larger and thicker vessels.
 Capillaries – Collecting Vessels – trunks – lymph
ducts.
 With in this net work of tubing are Lymph Nodes.
 Lymph is transported by the same mechanism that
moves blood back to the heart.
- squeezing of skeletal muscles
- pressure changes in the bodies cavities
- capillary action and valves to prevent back flow
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Lymph Nodes
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Superficial groups
-Cervical
-Axillary
-Inguinal
Deep groups
-Tracheobronchial
-Aortic
-Iliac
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 Lymph nodes: bean shaped organs along
lymphatic collecting vessels.
 Two basic functions:
 Filters: Macrophages remove and destroy
microorganisms and debris.
 Immune activation: Lymphocytes monitor the
lymph for invaders.
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 Surrounded by a fibrous capsule
 Connective tissue strands called trabeculae divide
up the node into compartments.
 There are three distinct regions histologically
 Cortex
 Medullary Cords
 Lymph Sinuses
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Lymph node anatomy
 The cortex contains densely packed
follicles that produce B-cells (a type of
lymphocyte).
 T-cells (another type of Lymphocyte) can
also be stored in the cortex.
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Lymph Node
 The Medullary Cords are thin projections
from the cortex deeper into the node.
 The cords can hold the lymphocytes, but
also plasma cells.
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Lymph Nodes
 The lymph sinuses are large reticular
fibers that span the node.
 They contain the macrophages that
consume debris and invaders.
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Lymphoid Organs
 Lymphoid organs
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Lymph nodes
Spleen
Thymus
Tonsils
Small intestine & appendix aggregated lymphoid
nodules
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Spleen
 The spleen provides a site for lymphocyte
proliferation.
 It also extracts damaged and aged blood
cells.
 Produces erythrocytes in a fetus.
 Stores blood platelets
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Thymus
 The thymus releases the hormones
thymosin and thymopoietin.
 These hormones cause T-cells to full
develop their their ability to kill certain
pathogens.
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Tonsils
 Tonsils have a variety of locations in and
near the pharynx.
 The oral tonsils are the most likely to get
infected.
 All tonsils house lymph follicles that
produce lymphocytes and filter lymph.
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Intestines and Appendix
 Peyer’s Patches are large clusters of
lymph tissue on the intestines.
 There are also similar patches in the
appendix.
 They destroy bacteria and generate
“memory lymphocytes” for immunity.
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Components of the immune system
Innate immune system
Adaptive immune system
 Response is non-specific
 Pathogen and antigen
specific response
 Lag time between
exposure and maximal
response
 Cell-mediated and
humoral components
 Exposure leads to
immunologic memory
 Found only in jawed
vertebrates
 Exposure leads to
immediate maximal
response
 Cell-mediated and
humoral components
 No immunological
memory
 Found in nearly all forms
of life (plants & animals)
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External Innate Defenses
 The skin secretions we produce are acidic
helping to fight fungus and bacteria.
 Mucus comes from a variety of
membranes and is meant to trap and filter
incoming particles.
 Salivia cleans and prtotects our oral cavity.
 Eyes produce lacrimnal fluid that contains
lysozyme a natural bacteria killer.
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Internal Innate Defenses
 When we get hurt or infected with a virus,
bacteria or fungi the body activates the
inflammatory response.
 The symptoms of the response are:
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Swelling
Redness
Heat
Pain
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Internal Innate Defenses
 Steps of Infalmmatory Rsponse
Step 1: A flood of inflammatory chemical are
released into the tissue.
Step 2: Epithelial cells and Macro phages
release cytokines that promote
inflammation and attract WBC’s
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Internal Innate Defenses
 Step 2 continued: At the same time other
cells (phagocytes, lymphocytes, etc.)
release other chemicals (histamine, kinins,
prostagladins and complement).
 All of these chemical have different roles
in inflammation, but they all cause more
blood flow to the area and capillaries
release clotting factors and antibodies.
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Internal Innate Defenses
 Step 3: The major players (lymphocytes,
antibodies, etc) of the adaptive immune
system are activated.
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Internal Innate Defenses
 Phagocytes: The main phagocyte is the
macrophage (big eater).
 They wonder through tissue looking for
debris and invaders to phagocytize (eat).
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Internal Innate Defenses
 Neutrophils: WBC that phagocitize
infectious material
 Eosinophils: WBC that phagocitize
parasites.
 Mast Cells: WBC that phagoitize bacteria.
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Internal Innate Defenses
 Natural Killer cells: a unique group of
defensive cells that patrol the blood and
lymph killing cancer cells and viruses.
 Not phagocytic. They release chemicals
called perforins that break down the cells
membranes and disintegrate the nucleus.
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Internal Innate Defenses
 Antimicrobial Proteins attack
microorganisms directly or keep them from
reproducing:
 Two most important antimicrobials
 Interferon
 Complement
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Internal Innate Defenses
 Infected cells produce small proteins
called Interferons.
 The interferons diffuse to healthy cells and
synthesize a protein that interferes with
the viruses ability to replicate.
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Internal Innate Defenses
 Complement is actually short for
Complement System.
 It is a group of over 20 plasma proteins
that circulate in the blood.
 Normally inactive, when inflammation
response is stimulated these chemicals
enhance every aspect of the response.
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Internal Innate Defenses
 Fevers are another form of natural
defense.
 A mild fever causes the body stores zinc
and iron instead of producing them.
Bacteria require large amounts of both.
 It also speeds up the metabolic rate, which
speeds up tissue repair.
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Components of the immune system
Innate immune system
Adaptive immune system
 Response is non-specific
 Pathogen and antigen
specific response
 Lag time between
exposure and maximal
response
 Cell-mediated and
humoral components
 Exposure leads to
immunologic memory
 Found only in jawed
vertebrates
 Exposure leads to
immediate maximal
response
 Cell-mediated and
humoral components
 No immunological
memory
 Found in nearly all forms
of life (plants & animals)
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Adaptive Immunity
 The adaptive immune response is more
complex than the innate.
 The antigen first must be recognized.
 The three crucial cell types include:
 Antigen – presenting cells
 B Cells
 T Cells
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Antigens
 Antigens are anything that can provoke an
immune response.
 There are two types of antigens
 Complete: ability to stimulate proliferation of
and react with specific lymphocytes and
antibodies.
 Incomplete: small molecules that have
hooked up with the bodies own proteins and
the immune system does not recognize them.
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“Humoral” vs “Cell mediated”
 Antibody-mediated (humoral) immunity – attack
by circulating antibodies released by the plasma
cells derived from activated B cells.
 This response is only good for non complicated “obvious”
bacteria or invaders.
 Cell-mediated immunity - direct attack by activated
T cells (react with foreign antigens on the surface of
other host cells).
 This response deals with more complicated or unknown
invaders.
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Antigen-Presenting Cells
 APC’s engulf anitgens and display
fragments of the antigen on their cell
membrane for identification by T-cells or
B-cells.
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B Cells (humoral response)
 The B-cell with the correct receptor complex is
duplicated many times. Called Colonial
Selection.
 Differentiate into plasmocytes (plasma cells)
when stimulated by exposure to an antigen.
 Most of the clones produce antibodies that kill
the antigen .
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B -Cells
 Memory B cells: produced by activated B
cells that do not turn into plasma cells.
 Upon re-exposure the memory B cells go
into immediate action and your body is
able to handle the invader faster, more
efficiently and actually produces way more
of the correct B-cells.
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Passive and Active Humoral
Immunity
 Active Immunity: The proliferation of Bcells and their production of antibodies by
your own body.
 Passive Immunity: When those antibodies
and B-cells are acquired from an outside
source.
 A fetus has the same immunity as his/her
mother for the first few days after birth.
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Cell mediated response
 What the B-cells miss or are not
programmed to deal with T-cells are able
to handle.
 Usually
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T Cells
 80% of circulating lymphocytes.
 Much more complex structure.
 All T cells get “primed” to fight a certain
antigen in the Thymus gland.
 Some of the types:
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Regulatory T cells
Cytotoxic T cells
Memory Cells
Suppressor T cells
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T Cell response
 How T-cells respond is similar to B-cells.
 They identify the antigen
 The correct T-cell goes through colonial
selection and proliferation.
 Then the correct T-cell performs it’s specific
function (phaocytosis, chemical secretion, or
signaling other cells)
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Regulator T-Cells
 Once regulatory (helper) T-cells have
bound with an antigen they stimulate
proliferation of B cells and other Tcells.
 Without helper T-cells your body would not
know to send out the killer Tcells nor what
antigen to fight.
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Cytotoxic T cells
 Cytotoxic (killer) T cells: attack foreign cells or
body cells infected by viruses (“cell-mediated
immunity”).
 They roam freely around the body looking for
infected cells to chemically Kill.
 They can be called to action in a certain area by
helper T-cells.
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Memory Cell
 Memory T cells: produced by the division
of activated T cells following exposure to a
particular antigen (remain on reserve, to
be reactivated following
 Basically they remember the shape of a
certain antigen and upon coming in
contact know exactly which immune cell to
call.
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Suppressor T Cells
 Also a type of regulator cell, but this one
releases the chemical signal that stops the
production of B and T cells.
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Development of lymphocytes
Originate in bone marrow from lymphoid stem cells
B cells stay in bone marrow, hence “B” cells
T cells mature in thymus, hence “T” cells
These divide rapidly into families
Each has surface receptors
able to recognize one
unique type of antigen=
immunocompetence
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The immune system protects organisms with
layered defenses of increasing specificity
 Most simply, 1. physical barriers prevent pathogens such
as bacteria and viruses from entering the body
 If a pathogen breaches these barriers, the 2. innate
immune system provides an immediate, but non-specific
response
 Innate immune systems are found in all plants and animals
 If pathogens successfully evade the innate response,
vertebrates possess a third layer of protection, the 3.
adaptive immune system
 Here, the immune system adapts its response during an infection to
improve its recognition of the pathogen
 This improved response is then retained after the pathogen has been
eliminated, in the form of an immunological memory, and allows the
adaptive immune system to mount faster and stronger attacks each
time this pathogen is encountered
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