Transcript Chapter 43: The Immune System

Chapter 43: The Immune System
Disease
A departure from health
Types:
Deficiency
diseases
Genetic diseases
Communicable diseases
Contagious
disease
Infectious disease
Host
provides metabolic needs of pathogen or parasite
Infectious disease
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Transmission
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Contact
Droplet infection
Vector
Common vehicle transmission
Types
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Sporadic disease
Endemic disease
Epidemic disease
Pandemic disease
Adaptations of pathogen to resist
host defense
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Cell wall
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Sticky capsule
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Contain proteins to resist host &/or antibiotics
Counters phagocytosis; increases virulence of
pathogen
Production of enzymes or metabolic toxins
Manipulates host cell’s metabolic structure
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viruses
Adaptations of the Human Body
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1st line of defense
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Physical shield
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Skin, mucus, ciliated cells, tears, urine flow,
coughing, sneezing, ear wax
Chemical shield
Stomach acids kill bateria
 Enzymes (lysozyme) in tears etc.
 Skin acids
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2nd line: inflammatory response
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Increased blood flow
Promotes healing
 Swelling insulates tissues
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Macrophages, neutrophils, Eosinophils, &
Dendritic cells
Phagocytic activity to engulf pathogen
 Macrophages:
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Neutrophils:
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Enter infected tissue to engulf microbes
Self destruct
Eosinophils:
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Develop from monocytes
Migrate through the body or reside permanently in some
organs (i.e. spleen)
Position against multi-cellular parasite & release enzymes
to destroy
Dendritic cells:
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Can act like macrophages but are usually involved in
acquired immunity
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Injured, circulating basophils release
histamines & prostaglandins
Promotes vasodilation
 Capillaries become “leaky”
 Attracts phagocytic cells
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Neutrophil engulfs bacteria macrophage engulfs
neutrophil
Infected cells release interferon
Stimulate adjacent cells to produce proteins that
prevent viral replication
 Activates phagocytes
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3rd line: Immune response
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Production of Lymphocytes
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Circulate in blood & lymph
Concentrated in spleen, lymph nodes, & lymphoid
tissue
Each lymphocyte is specific to a particular foreign
antigen
Originate in stem cells of bone marrow
Types:
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B cells
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T cells
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Mature in bone marrow
Mature in thymus gland
Maturing B cells & T cells tested for self-reactivity &
destroyed if self reactive
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Production of specific antibodies by
lymphocytes
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Antitoxins
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Agglutinins
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Stimulate phagocytosis of clumped bacteria
Lysins
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Clumping of bacteria
Opsonins
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Neutralize bacterial toxins
Dissolve cell walls of bacteria
Precipitins
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Coagulation chemicals of bacteria
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Immunoglobins (antibodies)
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Specific antigen binding immunoglobulins
Generated by B cells
Types
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IgM
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IgC
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Antibodies found in body secretions (saliva, sweat)
IgE
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Most abundant antibodies in blood & lymph
IgA
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First antibodies to arrive at infection site
Trigger release of histamines & other chemicals by mast
cells & basophils to cause allergic reactions
IgD
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On naïve B cells (not yet exposed to foreign antigen)
Receives antigen that leads to clonal selection
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Self/non-self
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Immune system must be able to distinguish
foreign from non-foreign proteins
Major histocompatability complex (MHC)
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Group of glycoproteins embedded in cell
membrane
Two major classes of MHC
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Class I MHC
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Bind to cytotoxic T cells
Class II MHC
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Known as antigen presenting cells
Bind to specialized cells (macrophages, B cells) &
activate T cells
Action of lymphocytes
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Humoral Response
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B cells
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Enter blood & produce specific antibodies to counter specific
antigens
Antigen-antibody complexes are formed
Helper T cells
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Secrete interleukins
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B cells into memory cells (M cells)
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Stimulate clonin of B cells to memory cells
Long lived cells
Recognize specific antigen
Basis of active immunity
Plasma cells (P cells)
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Short lived cells
Produce additional antibodies with initial exposure to antigen
Antibodies draw phagocytic cells in to destroy
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Cell mediated response
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Cytotoxic T cells
Stored in thymus gland prior to moving into blood
 Activated when CD8 receptors recognize antigen
on Class I MHC; helper T cell releases cytokines to
promote activation
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Do not produce antibodies
Attack & kill antigen-bearing cells
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Stimulate the production of B cells
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Secrete proteins that destroy infected cells
Dispose of infected cells
Suppress B cell reproduction when infection
has been suppressed
Secrete interferon which defends healthy cells
from virus
Primary vs. Secondary immune
response
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Primary immune response
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First exposure or vaccination to antigen
Results in formation a specific antibody to
inactivate an antigen
Requires time to occur
Secondary immune response
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Rapid reproduction of specific antibodies to
inactivate & destroy antigen (immediate)
Types of Defense
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Innate immunity
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Present at birth without any exposure
Non-specific
Acquired immunity/adaptive immunity
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Develops after exposure
Highly specific
Recognition by lymphocytes
Types of immunity
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Natural immunity
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Inherited immunity (parent to child)
Active immunity
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Long term immunity due to
Exposure (i.e. chicken pox, mumps, measles)
 Vaccination
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Intentional exposure to weakened/dead pathogen or
pathogenic toxin
Immunization
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Polio...
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Passive immunity
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Borrowed or temporary immunity through
Injection of antibodies
 Blood serum or gamma globulin injections
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Immediate immunity
Short term immunity
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Memory cells are not produced
Blood Groups effect on transfusions &
transplants
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Antibodies present against non-self blood
types without exposure
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result of reaction to bacterial antigens
MHC molecules stimulate immune
response leading to tissue rejection
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each person has a unique polymorphic
combination of MHC molecules
Exaggerated, self-directed or diminished
immune response & disease
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Allergies
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Hypersensitive response to antigens on
allergens
Often involve IgE antibodies
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Anaphylactic shock
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Attach to mast cells to induce histamine release
Whole body, life threatening allergic reaction
Autoimmune disease
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Body generates antibodies against self
Ex. Lupus, rheumatoid arthritis, multiple
sclerosis, diabetes mellitus
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Immunodeficiency diseases
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Inborn or primary
Caused by genetic or developmental defect
 Defect in production of immune cells or specific
proteins
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Acquired or secondary
Develops later in life
 Caused by exposure to agents or disease
 Ex. Hodgkin's, AIDS
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