Chapter 14
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Lymphatic System
and Immunity
Peanuts are a common
food allergy and the
amount of individuals
with this type of
allergy is on the rise.
THE LYMPHATIC SYSTEM
Similar to the cardiovascular
system
Transports fluid made of cells
and biochemicals called lymph
1st major function: transport
of excess fluid from interstitial
space to return it to the blood
stream
2nd major function: attack
foreign invaders, toxins and
cancer cells
MICROVIEW OF
LYMPH CAPILLARIES
Many capillaries in the skin as
a first defense against invaders
Form complex closed ended
tubes that parallel vessels and
extend into the interstitial
space
The walls have a single layer
of squamous epithelium to
allow of tissue fluid entry
Have valves like veins
Large lymph vessels lead to
lymph nodes
LYMPH TRUNKS AND
COLLECTING DUCTS
Lymph trunks - drain
lymph from
lymphatic vessels
Right lymphatic duct
- collects from area
highlighted in red
Thoracic duct collects
everything else
After leaving the
ducts the lymph
becomes part of the
plasma before blood
returns to the right
atrium
LYMPH PATHWAY
Lymph returns small proteins and
foreign particles to lymph nodes
Hydrostatic pressure drives entry of
lymph into lymph capillaries
Lymph vessels pump lymph with help
from smooth muscles, skeletal muscle
contractions and breathing
LYMPH NODES
Contain large numbers of
lymphocytes and macrophages
Afferent vessels “in”
Efferent vessels “out” from
hilum
Enclosed in connective tissue
capsule
Sinuses - lots of macrophages
Lymph nodules - masses of B
cells and macrophages in the
cortex
Nodules occur in groups or
singly ex: tonsils or Peyer’s
Patches
LYMPH
NODE
IN
A
HUMAN
LYMPH NODE LOCATIONS
They follow large vessel
patterns
Filter harmful particles from
lymph before return fluid to
blood
Swollen lymph nodes =
lymphadenitis - painful, occurs
while body is fighting infection
or downstream of an injury
Streaking - inflamed lymph
vessels secondary to bacterial
infection - treated with
antibacterial medications
THYMUS AND SPLEEN
THYMUS - immune
organ
- shrinks after puberty &
by 70 it’s only 25% as
powerful as when young
-filled with Tlymphocytes (T Cells)
-Thymosins released to
mature T cells
SPLEEN - largest
lymphatic organ
-filters blood
-Sinuses filled with blood
versus lymph
WHITE PULP - has lymph
nodes filled with
lymphocytes
RED PULP - has RBCs,
lymphocytes and
macrophages
In the spleen RBCs are
recycled by macrophages
Macrophages - engulf and
destroy foreign particles
BODY DEFENSE AGAINST
INFECTION
Pathogens invade &
replicate in the body to
cause infection
Innate response: species
resistance, mechanical
barriers, chemical
barriers, NK cells,
inflammation,
phagocytosis and fever
(fast responders)
Adaptive response: aka
immunity - targeting
specific pathogens antibody production
(slow responders)
Both responses work at
the same time
T Cell Activation Response
INNATE DEFENSES
1) Species resistance - we can’t develop a dog disease and we have
diseases specific to us (measles, gonorrhea and syphilis)
2) Mechanical barriers - skin and mucous membranes that line the
respiratory, digestive, urinary and reproductive system
- hair traps pathogens
- Sweat and mucus - rinses away microorganisms
3) Chemical barriers - enzymes (gastric enzymes HCl and pepsin) lethal
to stomach pathogens
- Lysozyme in tears kills bacteria
- Salt from sweat kills skin bacteria
- Interferons hormone-like peptides produced by lymphocytes and
fibroblasts
- Released from virus infected cells to stimulate surrounding uninfected cells to produce proteins that block viral replication
- Stimulate phagocytosis to enhance cell activity to resist infection
INNATE DEFENSES CONTINUED…
4) NK CELLS - lymphocytes that secrete performs that lyse cell membranes of
viruses and cancer cells yet, secrete chemicals that enhance inflammation at the same
time
5) INFLAMMATION - tissue response to injury or infection leads to redness,
swelling, heat and pain
-infected cells send chemical messages to WBCs to eat pathogens
6) PHAGOCYTOSIS - neutrophils - small invaders; monocytes - large invaders both called to injured areas via chemotaxis and leave vessels via diapedesis
7) FEVER - high body temperature maintained to fight infection
-liver and spleen hold iron which prevents extra iron in the blood because bacteria
and fungi require iron to survive
-Phagocytic cells attack better with increased temperature
LYMPHOCYTE FUNCTION
T Cells - attach directly to foreign antigen bearing cells
-can secrete cytokines ex: IL 1& 2 that cause T Cell proliferation
and cytotoxic T Cell activation
B Cells - divide into plasma cells which produce antibodies (aka
immunoglobulins)
-antibodies are carried in body fluid to destroy specific particles
with antigens
-T and B Cells with lots of varieties and each variety all come
from a clone
LYMPHOCYTE ORIGIN
Thymus - T Cells
aka T lymphos 70-80%
lymphocytes in
circulation
-lymphocytes are
in lymph nodes,
thoracic duct,
white pulp of the
spleen
-B-lymphocytes
aka B-Cells - in
red bone marrow
till mature - go to
lymph organs (2030% lymphocytes
in circulation)
B Cells respond quickly to invaders they
have seen before
TYPES OF ANTIBODIES
IMMUNOGLOBULIN G (IgG) - in plasma and tissue fluids - effective
against bacteria, viruses and toxins; activates complement
IMMUNOGLOBULIN A (IgA) - in exocrine gland secretions, breast
milk, tears, nasal fluid, gastric juice , intestinal juice, bile and urine
IMMUNOGLOBULIN M (IgM) - antibody present in plasma in
response to contact with certain antigens in foods or bacteria; activates
complement
-ex: antiA and antiB antibodies in blood are IgM
IMMUNOGLOBULIN D (IgD) - surfaces of B cells, activates B cells
IMMUNOGLOBULIN E (IgE) - in exocrine secretions and associated
with allergic reactions
ANTIBODY ACTIONS
Antibodies attack antigens
Activate complement or stimulate inflammation
Prevent spread of pathogens
Direct attack: antibodies combine with antigens causing them to
clump so that phagocytic cells recognize and eliminate cells displaying
antigens
-antibodies can also cover toxic portions of antigen displaying
molecules and neutralize their effects
-Complement is activated when IgG or IgM antibodies bind to
antigens
-What does complement activation do? Lets see the next slide…
COMPLEMENT
ACTIVATION
Figure 14.16
All memory B and T Cells
here
Activation of B and T cells after 1st
encounter an antigen
THE MAKING OF AN
ANTIBODY
CLASSIFYING IMMUNE SYSTEM RESPONSES
ALLERGIC REACTIONS
ALLERGENS - antigens that trigger allergic responses
Delayed reaction allergy - occurs due to repeated exposure of skin to certain chemicals usually after 48 hrs; ex: detergents, lotions
-after repeated exposure - the foreign substance activates T cells and macrophages which
cause eruptions and inflammation (dermatitis)
- can affect anyone - do not need genetic tendency
-Immediate reaction allergy - occurs within minutes of contact with an allergen
-Affects those with inherited tendency to over produces IgE antibodies in response to
certain antigens
-Activates B Cells
-IgE attaches to mast cells and basophils and histamine, prostaglandin and leukotrienes are
released
-Vessels dilate, become permeable and edema occurs
-Contraction of bronchial and intestinal smooth muscles as well as increased mucus
production occur
-ANAPHYLACTIC SHOCK - severe immediate reaction allergy where mast cells release
histamine throughout the body causing itching, hives, vomiting, diarrhea, swelling of the
face, tongue and larynx
Treatment: epinephrine needed within 5 minutes
Common causes: penicillin, insect stings and peanuts
TRANSPLANTATION AND TISSUE REJECTION
Tissue rejection reaction - recipient’s immune system
recognizes the donor’s cell surfaces as foreign and tries to
destroy the transplanted tissue
-similar to cellular immune response against non-self antigens
-The greater the difference between cell surface molecules the
quicker and severe the reaction
-Matching up donor and recipient tissues better prevents
severe reactions
-Immunosuppressive drugs are given to decrease rejection
-T cells and the formation of antibodies are suppressed to
prevent humoral and cellular immune responses
AUTOIMMUNITY
Occurs when the immune system fails to differentiate between self
and non-self thus making antibodies to it’s own cells
Ex: type I diabetes mellitus, rheumatoid arthritis, systematic lupus
erythematosus
Why would the body do such a thing?
- A virus while replicating “borrowed” proteins from the host cell
and put it into it’s surface so when the immune while attacking
viral invaded cells also attacks self-cells that have the same protein
- T cells may never learn to distinguish self from non-self or a
non-self antigen resembles a self antigen as in the case of the
bacterium streptococcus triggering inflammation of the heart
valves
HIV AND AIDS
-the immune system gradually
shuts down as infected T cells
die
-When T cells die bacterial
infections set in
-Later in the infection the
virus kills cytotoxic T cells
-1st HIV enters macrophages
-2nd the virus adheres to
gp120 on CD4 and CCR5
cells
- reverse transcriptase makes
a strand of DNA just like the
viral RNA and it is
incorporated in to that cell’s
DNA
HIV TREATMENT
HIV replicates, mutates and hides often making it tricky to treat
For a few years after infection one can produce enough new B and T Cells
to counter the ones that are infected - thus one may show no symptoms
TREATMENTS AVAILABLE:
Generally it is a combination of the following:
those that block viral replication
Protease inhibitors to prevent HIV from making it’s proteins
Entry inhibitors - block binding and/or fusing of HIV to T Cells
VACCINES ARE BEING TESTED - to target molecules on it’s viral
envelope or proteins that the virus uses to package itself for replication
CURRENT GOALS: keep viral levels low so health and life span
improved