Download Acquired Immunity Defends Against Infection of Body Cells and Fluids

Acquired Immunity
Defends Against
Infection of Body
Cells and Fluids
By: Jonah Harrington, Josh Yi
Introduction
• Acquired immunity is based on both a humoral
immune response a cell-mediated immune
response.
• Humoral immune response involves the activation
and clonal selection of effector B cells, which
secrete antibodies that circulate in the blood and
lymph.
Critical Parts
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Helper T cells
Cytotoxic T Cells
Antibody Classes
The Role of Antibodies in Immunity
Active and Passive Immunization
Immune Rejection
Blood groups
Tissue and Organ Transplant
Helper T Cells
• Helper T Cells are a type of T cells that play in important
role in the immune system like helping the activity of
other immune cells by releasing T cells cytokines
• They are activated by encounters with antigenpresenting cells, helper T cells play a central role in
enhancing humoral and cell-medicated responses.
• Three Principal types of antigen-presenting cell and
interact with helper T cells in different contexts:
o Dendritic cells
• Important in triggering a primary immune response.
o Macrophages
• Initiates a secondary immune response by presenting antigens to memory
helper T cells.
o B Cells
• Humoral response relies mainly on B cells to present antigens to help T cells.
Cytotoxic T Cells
• Cytotoxic T cells are the effector cells in a cell-mediated
immune response.
• They require signaling molecules from helper T cells as
well as interactions with antigen-presenting cells.
• When they are activated, they eliminate cancerous
body cells and body cells infected by viruses or other
intracellular pathogens.
• A surface protein called CD8, found on most cytotoxic T
cells, enhances the interaction between a target cell
and a cytotoxic T cells.
• They are best known as the “killer cell” because they kill
cancer cells, cells that are infected or damaged cells.
Cytotoxic T Cells (Cont’d)
• B Cells produce antibodies.
Antibody Classes
• The antibodies produced differ from the B cell
receptor only in the constant region of the heavy
chain.
• 5 Major types of heavy chain C regions determine
the five major classes of antibodies
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IgM
IgG
IgA
IgE
IgD
IgM
• They are the first Ig class produced after initial
exposure to antigen; then its concentration in the
blood declines.
• Its function is to promote neutralization and
crosslinking of antigens; they are very effective in
complement system activation.
IgG
• They are the most abundant Ig class in blood; also
present in tissue fluids
• Their function is to promote opsonization,
neutralization, and crosslinking of antigens; less
effective in activation of complement system than
IgM
IgA
• They present themselves in secretions such as tears,
saliva, mucus, and breast milk.
• Their function is that they provided localized
defense of mucous membranes by cross linking and
neutralization of antigens.
• Their presence in breast milk confers passive
immunity on nursing infant.
IgE
• IgE are present in blood at concentrations.
• They triggers release from mast cells and basophils
of histamine and other chemicals that cause
allergic reactions.
IgD
• IgD are present primarily on surface of B cells that
have not been exposed to antigens
• They act as antigens receptor in the antigen
stimulated proliferation and differentiation of B cells.
The Role of Antibody in
Immunity
• The binding of antibodies to antigens can interfere
with pathogen function in many ways.
• Neutralization: The binding to surface proteins of
virus or bacterium, thereby blocking the pathogen’s
ability to infect a host cell.
• Opsonization: Antibodies abound to antigens
present a readily recognized structure for
macrophages and therefore increase
phagocytosis.
Active and Passive
Immunization.
• Active Immunity: A type of immunity or resistance
developed in an organism by its own production of
antibodies in response
• Passive immunity: A type of immunity acquired by
the transfer of antibody from one individual to
another
• Vaccination/Immunization: introduction of antigens
into the body causing active immunity to develop
Immune Rejections
• Like pathogens, cells from another person can be
recognized and attacked by immune defenses.
• Example: Skin transplanted from one person to a
genetically non identical person will look healthy for
a week or so but then will be destroyed by the
recipient's immune response.
• Keep in mind that the body’s hostile reaction to a
transplant of other tissues or whole organs or to an
incompatible blood transfusion is the expected
reaction of a healthy immune system exposed to
foreign antigen.
Blood Groups
• To avoid harmful immune reactions in human blood
transfusions, there are different blood groups (types
• Red cells are designated as type A if they have A
antigen molecules on their surface. Similarly, the B
antigen is found on type B red blood cells; both A
and B antigens are found on type AB red bloods;
and neither antigen is fond on type 0 red blood
cells.
• Transfusions with different bloods can cause chills,
fever, hock, and kidney malfunction.
Tissue and Organ
Transplants
• In the case of tissue of organ transplants or grafts, it
is MHS molecules that stimulate the immune
response that leads to rejection.
• To minimize rejections, physicians try to use donor
tissue bearing MHC molecules that match those of
the recipients as closely as possible.
• In addition, the recipient takes medicine that
suppress the immune responses. However these
medicine can leave the recipient more susceptible
to infections during the course of the transplant and
treatment.