The Lymphatic System
Inflammation: is the response triggered whenever body tissues are injured.
It occurs following physical trauma, infection, or irritation, and effectively
delivers white blood cells to the area.
The purpose of inflammation is to:
1) Prevent the spread of damaging agents to nearby tissues
2) Dispose of pathogens and cell debris
3) Prepare for regeneration
The four signs of acute inflammation are
1) Redness
2) Heat
3) Swelling
4) Pain
Inflammation Continued
• Chemical messengers such as
Histamine, Bradykinin and
prostaglandins released by damaged
tissue and WBCs cause vasodilation
and increased capillary permeability
• This increases the delivery of
phagocytes to the injured area, that
ultimately leads to tissue clean-up
and healing
• Increased vasodilation causes Heat
and Redness at the site of
inflammation, while increased
capillary permeability causes Pain
and Swelling
Inflammation Continued
Tissue Injury
Release of Histamine,
Bradykinin and PGs
Vasodilation
Capillary
Permeability
Heat and
Redness
Capillaries
leak fluid
and protein
(exudate)
Increased
metabolic rate,
oxygen and
nutrient delivery
Pain and
Swelling
Release of
Leukocytosis
inducing factor
Chemotaxis
Increased WBCs
in blood
PMNs and
monocytes
migrate to
injured area
Blood clot
‘walls-off’ injured
area
Healing
Phagocytosis
by PMNs and
macrophages
The Complement System
Antibody bound
to an antigen
Bacterial
surface
Classical
Pathway
Alternative
Pathway
Complement Proteins
Stimulate
Inflammation
Enhance
Phagocytosis
(Opsonins)
Bacterial
Lysis
• The complement proteins
are blood plasma proteins
that help us defend against
bacterial infections
• The complement proteins
are activated by an
antibody-antigen complex
(Classical pathway) or by
the surface of a bacterial
membrane (Alternative
pathway)
• Once activated,
complement proteins
stimulate inflammation,
enhance phagocytosis, and
lysis bacteria
Immunity
Antigen: Substances that can mobilize our immune systems, leading to an
immune response. Most often antigens are large molecules (natural or
artificial) that are not normally present in our bodies. They are the ultimate
target of the immune system.
Antibody: Also called immunoglobulins (Ig), antibodies are soluble proteins
secreted by activated B cells or plasma cells in response to exposure to
an antigen. Antibodies are capable of binding with high specificity to that
antigen.
The 3 Principles of Immunity:
1) It is antigen-specific
2) It is systemic
3) It has ‘memory’
Our immune systems are divided into 2 different branches:
1) Humoral (antibody-mediated) immunity involving B cell lymphocytes
2) Cellular immunity involving T cell lymphocytes
Differentiation of Lymphocytes
• Lymphocytes begin their lives as stem
cells in the red bone marrow.
• They enter the blood before they are
fully mature.
• B cells (plasma cells) mature in the
blood and form the Humoral or antibodyproducing arm of our immune system.
Most mature B cells reside in the lymph
organs.
• T cells complete their maturation in the
thymus gland. Following maturation they
reside in lymph organs and some in the
blood. T cells comprise our Cellular
mediated immune system.
• Natural killer cells are similar to T cells,
but do not require the thymus for
maturation.
(2)
Humoral Immunity
• When a B cell is exposed
to an antigen, the B cell
proliferates (clones) and
becomes a Plasma Cell or
a Memory Cell
• Plasma Cells are
antibody ‘factories’ that
release antibodies in the
blood
• On the subsequent
exposure, the Memory
Cells rapidly produces
many more antibodies
• The Secondary response
is greater than the Primary
Response
Antibodies
• Once released into the blood, antibodies can bind
to the antigen and/or the invading organism
• This leads to phagocytosis, inflammation or cell
lysis of the invading organism
(2)
•
Antibodies
achieve these
effects by:
1) Neutralization
2) Enhancing
inflammation
3) Activating the
complement
system or Natural
Killer (NK) cells
Cellular Immunity
(2)
• In cellular immunity, an antigen is engulfed by a macrophage, which then
presents the antigen to a Helper T cell. The Helper T can then ‘activate’ a
Cytotoxic (Killer) T cells and B cells. Cytotoxic T cells then seek viral infected
cells. T cells also form ‘memory cells’.
• Cellular immunity is particularly important in defending against a viral
infection and cancerous cells .
Cellular Immunity Continued
(7)
• Cytotoxic T-cells are activated by interleukin 2
(IL-2).
• Activated T-cells search the body for an
infected cell that is presenting an antigen that
matches their receptor.
• Once the T-cell receptor binds to the viral
antigen, the infected cell initiates ‘programmed
cell dealth’, also called apoptosis. This is
achieved by the insertion proteins called
perforins into the viral infected cell’s membrane,
creating a pore so that the cytotoxic T-cell can
insert enzymes into the infected cell or by the
binding of a cell surface protein called Fas.
(7)
Lymph Vessels
• Lymph vessels begin as openended capillaries that are
interspersed between the blood
capillaries
• The lymph vessels drain the
excess ISF and return this fluid
to the systemic circulation, thus
helping to maintain the blood
volume
• Proteins, bacteria, viruses, and
cell debris are carried in the
lymph, especially in areas of
inflammation
• Before returning to the blood
stream, the lymph is passed
through Lymph Nodes, to be
cleansed by white blood cells
(1)
Lymph Nodes
• Before entering the blood
stream, lymph is passed
through Lymph Nodes to be
cleansed.
• Lymph Nodes contain
Macrophages and
Lymphocytes which remove
bacteria, viruses, cell debris,
and even cancerous cells
• During infection Lymph
Nodes can become swollen
as they ‘trap’ incoming
lymph while pathogens are
destroyed
• The Nodes are localized in
three regions of our body:
Cervical, Axillary, and
Inguinal
(2)
Other Lymph Organs
Tonsils: The tonsils are similar to lymph
nodes, as they contain white blood cells.
The tonsils act to cleanse bacteria,
viruses and debris that enter our oral
cavity. There are 3 pairs of tonsils and
they are named according to there
location: Palatine, Lingual, and
Pharyngeal (adenoids)
Spleen: In addition to destroying old
RBCs, the spleen acts to filter bacteria,
viruses and other debris by containing
macrophages and lymphocytes
Thymus: The thymus gland function to
release Thymosin, a hormone that aids
in T cell differentiation
MALT: mucosa-associated lymphatic
tissue serve a similar function as Nodes
(eg. Tonsils, Peyer’s patches, the
appendix and bronchi nodules)
(2)
The Tonsils
Pharyngeal
(Adenoid)
Palatine
Lingual
(1)