The Lymphatic System Immunity
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Transcript The Lymphatic System Immunity
The Lymphatic System and
Immunity
Lymph, lymph capillaries, ducts,
nodes and other lymphoid organs
Functions
Filter and absorb excess tissue fluid and
return it back into circulation
Transport of dietary lipids via lacteals
Carry out immune responses
Lymph and Lymph Capillaries
Lymph - clear, watery fluid resembling
interstitial fluid
Lymph capillaries - begin as blind-ended
capillaries consisting of simple
squamous epithelium allowing one-way
movement of fluid
Lymph Vessels
Formed from merging capillaries
Have thin walls and posses valves
Thoracic duct originates as cisterna
chyli draining abdomen, extremities,
and left side of body
Right lymphatic duct - drains lymph
from the right arm and upper right side
of body
Elephantiasis
Blockage of the lymphatic system by
parasitic worms
Transmitted by mosquitos
Causes severe swelling
Lymph nodes
Oval structures clustered along
lymphatic vessels that serve to filter
lymph
Consists of capsule, cortex, and medulla
Cortex contains mostly lymphocytes
Medulla filled with macrophages
Accessory Structures
Spleen
Thymus
Tonsils
pharyngeal
palatine
lingual
Spleen
Size of a fist
Located in left superior abdominal cavity
Functions:
Lymphocyte storage & surveillance
Blood cleansing
Recycles blood products
Fetal erythrocyte production
Stores blood platelets
Thymus
Located in lower neck, upper thoracic
region
Secretes hormones, thymosin &
thymopoietin
Function: T-cell maturation
Decreases in size with age
Tonsils
Form ring around entrance to throat
Epithelial surface invaginates to form crypts
that trap bacteria & particulate matter
Types:
Palatine tonsils - visible tonsils
Pharyngeal tonsil (adenoids)
Lingual tonsil - at base of tongue
Tubal tonsils - surround the openings to the
auditory tubes
Other aggregates of lymphoid
tissue
Peyer’s patches - nodules located in the
ileum portion of the small intestine
Appendix
Destroy bacteria in the digestive system
Belong to MALT (Mucosa-Associated
Lymphatic Tissue
Disorders of the Lymphatic
System
Hodgkin’s disease - malignant cancer of the
lymph nodes
Lymphoma - any tumor of the lymphoid
tissue (benign or malignant)
Non-Hodgkin’s lymphoma - all cancers of
lymphoid tissues except Hodgkin’s disease
Tonsilitis - inflammation of the tonsils
Mononucleosis - caused by Epstein-barr
virus attacking the B-lymphocytes which
are in turn attacked by oversized Tlymphocytes. These were misidentified
orginally as monocytes.
Nonspecific Resistance
Mechanical Barriers
Skin - epidermis
Mucous membranes
Cilia - hair, mucus
Flushing mechanisms
Chemical Protection
Lysozymes - in tears & saliva
Sebum Gastric juice
Body secretions
Acid = pH 3-5
Mucus
Antimicrobial substances
Interferons
defend against viruses, suppress tumors and
enhance phagocytosis;
stimulates production of PKR which interferes with
viral replication
Complement
>20 proteins that attach and “lyse” the cell
opsonization (enhances phagocytosis)
enhances the inflammatory response
Non-specific Immunity
Phagocytosis
Macrophages, Neutrophils
chemotaxis, adherence, ingestion, destroy
Natural Killer Cells (NK)
Large granular lymphocytes
Attach and release “perforins”
Inflammation
swelling, redness, pain, heat
histamines = promote dilation & permeability
Phagocyte mobilization
Leukocytosis leukocyte production
Margination - neutrophils collect inside
nearby capillaries
Diapedesis - neutrophils squeeze out of
capillaries into tissues
Chemotaxis - neutrophils are attracted to
injury
Monocytes follow; become Macrophages
Fever
Pyrogens released by leukocytes &
macrophages raise body temperature
Inhibits growth of microorganisms
Increases metabolic rate of cells
Can denature enzymes
Specific Immunity
Characteristics: specificity
memory
self recognition
Types of Cells
Lymphocytes arise from hemocytoblasts
in the bone marrow
B cells develop immunocompetence in
the bone marrow
T cells - mature in thymus
Types of Immunity
Antibody-mediated immunity
humoral immunity
involves B cells and the production of
antibodies
Cell - mediated immunity
cellular immunity
involves the destruction of intracellular
pathogens by T cells
Antigens
Any substance that can elicit an immune
response
Immunogenicity - “antibody-generating”
Haptens - incomplete antigens (allergens)
Major histocompatibility complex antigens
(MHC-I, MHC-II) ; “Self”-proteins
Class I - found on all cells
Class II - found only on certain cells
Antibodies = immunoglobulins
Highly specific soluble proteins secreted by
plasma cells in response to an antigen
Structure of an antibody
Heavy and light chains
Variable and constant regions
Up to a Billion different variables
Antigen-binding sites
Antibodies
Five classes of antibodies
IgM - first released; can fix complement
IgA - usually found in secretions
IgD - B-cell receptor
IgG - most abundant; crosses placenta;
can fix complement
IgE - causes allergic reactions
Antibody - Mediated Immunity
B cells are activated by the presence of a
foreign antigen which is taken into the B cell,
processed and then displayed in combination
with an MHC-II molecule the on the cell’s
surface
Activated B cells develop into clones of
antibody producing plasma cells
Plasma cells produce antibodies (2,000/sec)
Costimulation by Helper T cells useful
Functions of Antibodies
Agglutination
Precipitation
Neutralization
Enhanced phagocytosis
Complement activation
Immunological Memory
Primary response - first exposure
Secondary response - 2nd, 3rd, 4th, etc.
Faster
Higher Levels
More efficient
Active & Passive Immunity
Active = caused by encounter with antigens
Natural - acquired by infection & disease
Artificial - acquired by vaccination
Passive = caused by encounter with
antibodies
Natural - acquired from Mom; antibodies cross
placenta
Artificial - acquired from immune sera such as:
gamma globulin, antivenom, antitoxins
Cell - Mediated Immunity
T cells recognize and respond only to
processed antigen presented by an APC
(antigen presenting cell)
Binding of T cell to macrophage causes
secretion of interleukin-I which helps activate
T helper cells (also called CD4 or T4 cells)
TH cells secrete IL-2 which enhances B cell
activity and costimulates cytotoxic T cells
(CD8 or T8 cells)
Types of Lymphocytes
Helper T cells - TH
Cytotoxic (killer)T cells - T8
Stimulates macrophages
Suppressor T cells - TS
Kills invaded cells, cancer cells, rejects tissue
Delayed Hypersensitivity T cells - TDH
Stimulates other B & T cells (co-stimulation)
Slows or stops B & T cells
Memory T cells
remain in body for years for secondary response
Cytokines
Interferons
Interleukins
Lymphotoxins
Macrophage migration inhibitory factor
Perforins
Supressor factors
Complement
Immunodeficiencies
SCID - Severe Combined Immunodeficiency
Syndrome
Acquired Immunodeficiencies
Disease induced; Hodgkins, Leukemia
Chemically induced; immune suppressing
drugs
AIDS
Diagnosed 1981; Began ?
AutoImmune Disorders
Multiple Sclerosis - affects white matter of CNS
Myasthenia Gravis - destroys Ach receptors
between nerves & muscles
Graves’ Disease - causes hyperthyroidism
Type I Juvenile Diabetes - destroys insulinproducing cells
Systemic Lupus Erythematosus Rheumatoid Arthritis - attacks joint tissues