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Immune System
1. Define the following:
a. B cells
b. T cells
c. Macrophages
2. Provide 3 cells and/or molecules
involved in specific defense.
3. Provide 3 cells and/or molecules
involved in non-speccific defense.
Innate Immunity
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What is innate immunity?
Present from birth
Non specific
External
– Skin
– Mucous membranes
• Internal
– Macrophages
– phagocytes
Phagocytic cells
• Phagocytes bind to non-self surface
carbohydrates
• microbe is engulfed forming a vacuole
• lysosome fuses with vacuole
• Evolution of microbes:
– Extra capsule hides non-self surface
carbohydrates
– Resistant to destruction by lysosomes
Pahgocytic Leukocytes
• Neutrophils: most abundant
– Phagocytes that engulf and destroy microbes
– Self destruct  pus
• Monocytes: more effective
– Macrophages
– Reside mainly in lymph nodes, spleen and lymph
tissues
• Eosinophils: less abunadant limited role
– Fight multicellular parasites
• Dendritic cells:
– Stimulate aquired immunity
Antimicrobial Proteins
• Complement system
• Interferons
– Secreted by virus infected cells
– Induce other non-infected cells to release viral
inhibitors
• Defensins
– Secreted by macrophages
– Damage pathogens
Responses
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Localized inflammatory response
Fever
Septic shock – systemic inflamation
Natural killer cells
– Attack cancer and virus-infected cells
Lymphatic System
Acquired Immunity
Antigen Recognition
• What are the two main types of
lymphocytes?
– B cells
– T cells
• There are antigen receptors on these cells
• Antigen receptors are specific for an
epitope
B cell Receptors
• Y shaped with
– 2 heavy chains
– 2 light chains
• Recognize
intact antigens
T cell Receptors
• Recognizes self/non
self complexes
– Pieces of antigens
– MHC
• Class I MHC
• Class II MHC
Lymphocyte development
• How do
lymphocytes
develop?
• Pleuripotent stem
cells in bone marrow
• T cells migrate to
thymus
• B cells mature in
bone marrow
Lymphocyte Diversity
• 40 V chain
options
• 5 J chain
options
• How many
different
combinations of
V/J
arrangements
are possible?
• 40 V x 5 J =
200
• How do we avoid auto immune issues?
• Before B cells and T cells mature, they are
checked for class I and class II MHC
compatibility.
• If they are compatible they are destroyed
Clonal Selection of Lymphocytes
• B cells, TH, and TC cells may be activated
by finding their antigen in the body
• Binding of the antigen stimulated the cell
to:
– Generate short-lived clone of effector cells
– Generate long-lived memory cells
Primary and Secondary Immunity
Humoral and Cell mediated Immunity
Helper T cells
Clone of
TH cells
Clone of
TH cells
Cytotoxic T cells
Humoral Immune Response
Antibodies
Role of Antibodies
Active and Passive Immunity
• What is the difference between active and
passive immunity?
• Active immunity
– Natural exposure to antigen
– Immunization
• Passive immunity
– Transferred antibodies
– Seen with pregnant and nursing women
– Also with anti-venom injections
Blood Groups
• Why would a person with type A blood have anti
– B antibodies?
• There are bacteria with similar antigens
• The immune response produced by blood group
antigens has no memory
• Blood mixing at birth causes no problems fro
future pregnancies
• Rh factors, however, do have memory so there
is a problem here
• How do Rh negative mothers deal with blood
from Rh positive babies?
Allergic Response
Autoimmune Diseases
• Found in most body
cells
• When infected or
cancerous presents
antigen fragments
• Identify the
self/nonself complex
• Recognized by Tc
cells
• Class II MHC found
on
– Dendritic cells
– Macrophages
– B cells
• Known as antigen
presenting cells
Macrophage ingesting a yeast cell
Lining of trachea with orange mucus producing cells and yellow cilia