•Briefly outline the major role of the thymus gland
in immunity.
•Briefly outline the role of the spleen.
•List the 7 non-specific defence mechanisms and
briefly describe how they work.
•Discuss complement activation.
•List and briefly describe the components of
specific immunity.
•Differentiate between innate and acquired
immunity and discuss further classification of
acquired immunity.
•The lymphatic system consists of a pale yellow
fluid called lymph, lymphatic vessels, lymphatic
tissue and red bone marrow.
• Functions: 3 Primary Functions• (I) Draining excess interstitial fluid.
• (II) Transporting dietary lipids.
• (III) Carrying out Immune Responses.
Figure 22.1 Tortora, G.J. & Derrickson, B. 2006. Principles of
Anatomy and Physiology, 11th edition.
•Lymphatic Vessels and circulation
•Lymphatic capillaries
•Lymph trunks and Ducts
•Formation and flow of Lymph
Figure 22.2; Figure 22.3 Tortora, G.J. & Derrickson, B. 2006.
Principles of Anatomy and Physiology, 11th edition.
•Primary Lymphatic Organs: Red bone marrow
and Thymus
•Secondary Lymphatic Organs: Lymph nodes,
Spleen and Lymphatic nodules.
•Bi-lobed organ located between the sternum and
aorta.
•Each thymic lobule consists of an outer cortex
and central medulla.
•Located along lymphatic vessels are about 600
bean shaped lymph nodes.
•Lymphatic nodules: Primary and Secondary
•Largest single mass of lymphatic tissue in the
body, located between the stomach and the
diaphragm.
• The parenchyma of the spleen consists of two
different kinds of tissue: White pulp and red pulp.
•Egg shaped masses of lymphatic tissue.
•Scattered throughout the connective tissue of
mucous membranes lining the GI tract, Urinary
and Reproductive and Respiratory airways.
•Present at birth and offer immediate protection
against a wide variety of pathogens and foreign
substances.
• External
physical and chemical barriers
•Internal non-specific defenses: antimicrobial
proteins, natural killer cells and phagocytes,
inflammation and fever.
•First Line of Defense: Skin and mucous
membranes:
• (I) Epidermis
• (II) Mucous membranes
• (III) Lacrimal apparatus (lysozyme)
•Second line of Defense: Internal Defenses:
• (I) Antimicrobial proteins: 3 main types
• (a) Interferons
• (b) Complement
• (c) Transferrins
• (II) Natural Killer cells and Phagocytes
• (a) Perforins (bursting)
• (b) Granzymes (apoptosis)
• (c) Macrophages (fixed) e.g. Kupffer cells, tissue
macrophages in the spleen; Neutrophils.
•Occurs in 5 phases:
• (I) Chemotaxis: the stimulated movement of phagocytes to a
site of damage.
• (II) Adherence: Attachment of the phagocyte to a microbe or
foreign material.
• (III) Ingestion: Engulfing of the microbe by pseudopods
(phagosome).
• (IV) Digestion: Lysosomes release lysozymes, and additional
digestive enzymes, break down microbial cell walls .
• (V) Killing: The chemical onslaught provided by the lysozyme,
digestive enzymes and oxidants quickly kill many types of
microbes.
•Two properties distinguish specific immunity
from non- specific immunity:
• (a) specificity for particular foreign molecules
(allow self to distinguish between non-self).
• (b) Memory for most previously encountered
antigens so that a second encounter prompts an
even more rapid and vigorous response.
•Maturation of T cells and B cells
•Types of Immune responses
•Antigens
•Complement and Immunity
•The cells that develop immunocompetence are
lymphocytes called B cells and T cells.
•Develop in primary lymphatic organs (red bone
marrow and thymus).
• B cells complete their development in red bone
marrow.
•T cells develop from pre-T cells that migrate from
red bone marrow into the thymus, where they
mature.
•T- cells exit the thymus as either CD4 or CD8
cells.
•Most T-cells are inactive.
•T-cell becomes activated only if it binds to a
foreign antigen and at the same time is costimulated by either a cytokine or plasma
membrane molecule.
•Three main types of differentiated T cells:
(I) Helper T Cells
(II) Cytotoxic T Cells
(III)Memory T Cells
•The body contains millions of different B cells,
each capable of responding to a specific antigen.
•During activation of a B cell, an antigen binds to
B-cell receptors (BCR’s).
•Cell mediated immunity: CD8 cells proliferate
into cytotoxic T cells that directly attack the
antigen.
•Antibody mediated immune responses: B cells
transform into plasma cells, which synthesise and
secrete proteins called antibodies.
•Antigens have two important characteristics:
• (I) Immunogenicity: provoke an immune
response
• (II) Reactivity: ability to react specifically with
antibodies or cells it provoked.
•Epitopes: small parts of a large antigen molecule
act as triggers for immune responses. An antibody
can combine specifically with the epitope on an
antigen that triggered its production.
•Located in the plasma membrane of body cells
are self antigens, the major histocompatibility
complex (MHC) antigens.
•Two classes of MHC: Class I and Class II
•All 5 classes of antibodies (IgG, IgA, IgM, IgD
and IgE) act to disable antigens.
• (I) Neutralise antigens
• (II) Immobilising bacteria
• (III) Agglutinating and precipitating antigens
• (IV) Activating complement
• (V) Enhancing phagocytosis
•The complement system is a defensive system
made up of over 30 proteins produced by the liver
and found circulating in blood plasma and within
tissue throughout the body.
•Collectively the complement proteins destroy
microbes by causing phagocytosis, cytolysis, and
inflammation: they also prevent excessive damage
to body tissues.
•To function properly your T cells must have two
traits:
• (I) Recognise MHC proteins: self-recognition.
• (II) Lack reactivity: self-tolerance.
•Microbiology is the study of microbes. An
organism that is visible only with a microscope.
• Microbes are either autotrophic or
heterotrophic.
•Prokaryotic and Eukaryotic
•Types of microbes: Viruses, Bacteriophages,
Slime moulds, Bacteria, Fungi, Protozoa and
Prions.