The Adaptive Immune Response on line.ppt

The Adaptive Immune Response “Match me perfectly and I’m neutralized” Kathy Huschle Northland Community and Technical College

Adaptive Immune Response
in contrast to the innate immune response which we are basically born with, the adaptive immune response is an ever developing system
it continues to mature throughout our life

in most cases as each new microbial invader is encountered, our adaptive immune response initiates a specific attack against the invader
generally this invader is remembered and that “memory” is readily available in the case of a second or subsequent attack from the same invader

this system is an extremely complex system to which we will attempt to gain a basic understand
immunologists are continually discovering many facts about the adaptive immune response

the adaptive immune response
is learned or acquired
recognizes specific substances foreign to the body
is essential for life

other terms used for the adaptive immune response include
acquired immunity
specific immunity
though at one time thought to function exclusive of the innate immune system, research is now discovering a correlation between the two systems
regardless of a correlation or not, the failure of our immune system results in mortality

adaptive immune response is characterized by
specificity
memory
learned ability to recognize (acquired) pathogens which allows the body to usually only suffer once from that particular pathogen

Components of the Adaptive Immune System
antigens
antibodies
lymph system
lymphocytes
B cells
T cells
NK cell (Natural Killer)
Antigen Antibody B cell T cell NK cell

Antigens
the term antigen derives from the two words anti body gene rator
most antigens are proteins or large polysaccharides

Antigens
often a component of invading microbes, such as the capsule, cell wall, flagella, toxin
particular chemical that will activate the adaptive immune response
Antigens found in autologous tumor

Antigens
invading microbes can have many antigens on its surface
pathogen

Antigens
when and antigen elicits an immune response it is often referred to as a immunogen
epitope is the reactive portion of the antigen that reacts chemically with an antibody to form the antigen-antibody complex or immune complex

Antigens
two essential properties of antigens include
immunogenicity
the ability to stimulate immune system
antigen-antibody complex

Antigens
specific reactivity
the ability to react with effector molecules (antibody) to form an antigen-antibody complex
Antigens in red with green borders

Antibodies
glycoproteins that are also referred to as immunoglobiulins
basic structure is a Y shaped molecule with 2 functional parts
Fab region
Fc region
Fab region Fc region

Antibodies
Fab region
this is the part of the antibody that binds to the antigen
Fc region
the stem of the antibody that functions as a “red flag”
notifies the rest of the immune system: “here I am, come and help”

Fab regions The Fab portion of IgG binds to epitopes of a capsule. The Fc portion can now attach the capsule to Fc receptors on phagocytes for enhanced attachment. Once attached to the phagocyte by way of IgG, the encapsulated bacterium can be engulfed more efficiently and placed in a phagosome

Antibodies
protection gained from the formation of antigen-antibody complexes basically comes down to the tagging of foreign cells and molecules for destruction by phagocytes and complement
Antibodies shown in different stains

Antibodies
the antibody molecule is not damaging to the antigen
Melanoma antigens

Antibodies
foreign organisms and toxins are rendered harmless by
neutralization
immobilization and prevention of adherence
agglutination and precipitation
opsonization
complement activation
antibody-dependent cellular cytosis (ADCC)
Respiratory syncytial virus antigens

Antibodies
neutralization
blocks the adhesion of bacteria and viruses by bathing the surface of the cell with antibody
immobilization and prevention of adherence
antibodies binding to structures such as flagella and pili can interfere with mobility and attachment

Antibodies
agglutination and precipitation
enhances phagocytosis by gathering antigens into clumps
opsonization
coating an antigen with antibody enhances phagocytosis

Antibodies
complement activation
enhances cell destruction by cell lysis
antibody-dependent cellular cytotxicity
antibodies attach to target cells causing destruction by non-specific immune system cells

Antibodies

Antibodies
there are 5 classes of immunoglobulins
each class plays a different role in the immune response
IgG
IgM
IgA
IgD
IgE

Antibodies
IgG
enhances phagocytosis
neutralizes toxins and viruses
protects the fetus and newborn
only immunoglobulin that is transferred across the placenta

Antibodies
IgG
circulates in the blood, but can easily exit to the tissues
most abundant circulating antibody
IgG circulating in tissue

IgG IgG reacts with epitopes on the host cell membrane. Phagocytes then bind to the Fc portion of the IgG and discharge their lysosomes.

Antibodies
IgA
provides localized protection on mucosal surfaces
found in mucus, tears, saliva, sweat, blood, human milk
protects surface tissues and prevents adherence of microorganisms
this is important in respiratory, gastrointestinal and genitourinary tract infections

Antibodies
IgM
especially effective against microorganisms and clumping antigens
these are the first antibodies produced in response to a mild infection
are circulating antibodies found in the circulatory system with IgG

IgM IgG or IgM reacts with epitopes on the host cell membrane and activates the classical complement pathway. Membrane attack complex (MAC) then causes lysis of the cell.

Antibodies
IgD
function of these antibodies is not yet fully defined
it’s presence on B cells functions in the initiation of an immune response

Antibodies
IgE
antibodies responsible for allergic reaction
possibly involved in the lysis of parasitic worms
found in the blood serum
plays a role in the initiation of the inflammatory response

Lymphoid System
in regards to the immune system the lymphatic system consists of tissues and organs that are designed and located to convey the B and T cells into contact with all antigens that enter the body

Lymphoid System
this process is accomplished with the
lymphatic vessels
fluid of the lymphoid system called lymph
secondary lymph organs such as tonsils, spleen, lymph nodes

Lymphoid System
primary lymph organs
bone marrow: the location of stem cells that will eventually become B and T cells, B cells mature in the bone marrow
thymus: maturation of the T cells
Healthy bone marrow Bone marrow with leukemia Lymph node

Lymphoid System
notice how completely our body is covered by the lymphoid system

Lymphocytes
critical part of immune system responsible for
detection of foreign antigens
activate immune system
B lymphocytes
T lymphocytes
natural killer cells (NK cells)

B lymphocytes: B cells
antibody producing cells that respond to an antigen stimulation
develop from stem cells located in the red bone marrow of adults and the liver of a fetus
B Cells dividing

following maturation, they migrate to the lymphatic tissue
B cell in lymph node

once in place in the lymphoid organs, the B cells recognize antigens by means of the antigen receptors found on their cell surfaces
basis for antibody-mediated immunity
B indicates a B cell HIV antigens in yellow B cells in red

B cells

T lymphocytes: T cells
key cellular component of immunity
develop from stem cells found in the bone marrow
precursors to T cells migrate to the thymus, where they reach maturity
human T cells

T lymphocytes: T cells
following maturity, T cells migrate to various lymph organs where they await contact with antigens
basis for cell-mediated immunity
T cells (on left – orange, on right – gray) killing cancer cells (on left- mauve. on right – red)

T cells

Natural Killer Cells
these cells are not immunologically specific
they do not need to be stimulated by an antigen

Natural Killer Cells
capable of destroying other cells, particularly viruses-infected cells and tumor cells
also can attack large parasites

Clonal Selection of Lymphocytes
speaks to the ability of B cells and T cells to differentiate to a population of cells capable of recognizing an infinite number of antigens
it is estimated that the human body has approximately 1 billion B cells, yet each individual cell is only capable of recognizing and responding to one antigen
B cell differentiation

terms used to define various stages of clonal selection include
immature
naïve
activated
effector
memory

immature lymphocytes
have not fully developed their antigen-specific receptor
naïve lymphocytes
have an antigen receptor, but have not encountered the antigen
immature lymphocyte

activated lymphocytes
have received confirmation of the danger of the antigen and are able to proliferate more lymphocytes specific for that antigen
effector lymphocytes
descendents of activated lymphocytes
Activated lymphocyte

memory lymphocytes
long-lived descendents of activated lymphocytes
can revert back to activated lymphocytes with stimulation from the same antigen

Antibody-Mediated Immunity
humoral or antibody-mediated immunity involves antibodies that are produced by B cells
the term humoral is derived from the word “humors”, which is Latin for fluid
in response to foreign antigens, the B cell is activated to produce a clone of plasma cells and memory cells
plasma cells secrete antibodies
memory cells recognize pathogens from previous encounters
B memory cells are long lived and are ready to mount an attack the next time that specific antigen presents itself

Primary & Secondary Response The body can make low levels of soluble antibody about one week after exposure to antigen. However, a second exposure to antigen produces a much faster response, and several orders of magnitude higher levels of antibody. The ability of antibody to bind antigen also increases in the secondary response. The memory of antigen and stimulated response is the basis for vaccination

the antigen-antibody complexes that are formed as a result of antibodies produce by B plasma cells attract phagocytes
Bacteria in green

phagocytosis destroys the pathogen and control of the disease is accomplished
Bacteria

Cell-Mediated Immunity
cell-mediated immunity involves specialized lymphocytes that respond to intracellular antigens
T cells are responsible for managing cell-mediated immunity
after maturation in the thymus, T cells differentiate into 2 groups
T-cytotoxic cells and T helper cells
Cytotoxic T cells Helper T cell

recognizes modified host cells (abnormal cells)
cell-mediated immunity is critical to controlling infections where pathogens reproduce in human cell
viruses, bacteria (rickettes), protozoa
important role in recognizing and destroying abnormal cells, such as tumor cells
T cells attacking cancer

T cells do not recognize free antigens, the antigen must be presented by a modified host cell
augments antibody-mediated immunity
eliminates cells infected with viruses
antibodies can’t penetrate a virus within a host cell
T cells

response to intracellular agents includes
antigen presentation
the antigen must be processed (degraded) and then individual peptides are displayed on the surface of a glycoprotein called a major histocompatibility complex (MHC) molecule
this antigen processing is done by antigen presenting cell (APC)

cytotoxic T cells recognize the non-self cell and induce apoptosis (cell self death) in the viral infected or other microbial infected cell
this process also recognizes cancer cells and destroys them
unfortunately this process also recognizes and destroys non-self tissue or organ transplants

T-helper cells, often referred to as CD4 cells, are responsible for the “second opinion” in immunity
T-helper cells judge the significance of the antigen presented by the antigen-presenting cells (APC)

after binding to an APC, T- helper cells secrete cytokines that activate other T cells and B cells
interleukin-2
macrophage chemotactic factor
migration inhibition factor
macrophage activating factor
macrophage colony stimulating factor

interleukin-2
stimulates the production of more T cells
macrophage chemotactic factor (MCF)
attracts macrophages (phagocytes) to the site of infection or abnormality
migration inhibition factor (MIF)
once at the infection site, MIF inhibits the macrophages from migrating elsewhere in the body
T cell (yellow) attracting Macrophage (blue)

macrophage activating factor (MAF)
once at the infection site, MAF alters the function of the macrophages
increases their lysosomal activities
increases their ability to kill
Macrophage using pseudopodia to grab pathogen Macrophage ingesting bacteria

macrophage colony stimulating factor (CSF)
regulates the production of macrophages at the site
Macrophage and T cell Macrophage & E.coli

T-Helper Cells T helper cells also play a role in activating B cells in antibody-mediated immunity

Helper T cells Click icon to learn more about T-cell dependent antigens

Overview of Antibody-Mediated Immunity
initial response (bacteria with antigens enters the body)
B cells recognize
differentiate into plasma and memory cells
memory: recurring exposures
plasma produce antibodies
antigen/antibody complex forms
phagocytosis
control of disease

Overview of Cell-Mediated
modified host cell arrives
T cells activated
secrete cytokines
increase of T cell reproduction
attraction of macrophages (MCF)
inhibit migration (MIF)
activate phagocytosis (MAF)
control of disease

Overview of Immunity

Summary

The Adaptive Immune Response on line.ppt

by many87 on Oct 19, 2010

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