The Adaptive Immune Response.The Adaptive Immune Response.

BY: Ahmed Khalil Ibrahim BY: Ahmed Khalil Ibrahim University of GeorgiaUniversity of Georgia

Adaptive Immune ResponseAdaptive Immune Response

in contrast to the innate immune response which we are in contrast to the innate immune response which we are basically born with, the adaptive immune response is an basically born with, the adaptive immune response is an ever developing systemever developing system– it continues to mature throughout our lifeit continues to mature throughout our life– in most cases as each new microbial invader is in most cases as each new microbial invader is

encountered, our adaptive immune response initiates encountered, our adaptive immune response initiates a specific attack against the invadera specific attack against the invader

– generally this invader is remembered and that generally this invader is remembered and that “memory”“memory” is readily available in the case of a second is readily available in the case of a second or subsequent attack from the same invaderor subsequent attack from the same invader

Adaptive Immune ResponseAdaptive Immune Response

the adaptive immune response the adaptive immune response – is learned or acquiredis learned or acquired– recognizes specific substances foreign to the recognizes specific substances foreign to the

bodybody– is essential for lifeis essential for life

Adaptive Immune ResponseAdaptive Immune Response

other terms used for the adaptive immune response other terms used for the adaptive immune response includeinclude– acquired immunityacquired immunity– specific immunityspecific immunity

adaptive immune response is characterized byadaptive immune response is characterized by– specificityspecificity– memorymemory– learned ability to recognize (acquired) pathogens learned ability to recognize (acquired) pathogens

which allows the body to usually only suffer once from which allows the body to usually only suffer once from that particular pathogenthat particular pathogen

Components of the Adaptive Immune Components of the Adaptive Immune SystemSystem

antigensantigensantibodiesantibodieslymph systemlymph systemlymphocyteslymphocytes– B cellsB cells– T cellsT cells– NK cell (Natural Killer)NK cell (Natural Killer)

Antigen

Antibody

B cell

T cellNK cell

AntigensAntigens

the term antigen derives from the two words the term antigen derives from the two words antiantibody body genegeneratorratormost antigens are proteins or large polysaccharidesmost antigens are proteins or large polysaccharidesoften a component of invading microbes, such as the often a component of invading microbes, such as the capsule, cell wall, flagella, toxincapsule, cell wall, flagella, toxin– particular chemical that will activate the adaptive particular chemical that will activate the adaptive

immune responseimmune response

AntigensAntigens

two essential properties of antigens includetwo essential properties of antigens include– immunogenicityimmunogenicity

the ability to stimulate immune systemthe ability to stimulate immune system

antigen-antibody complex

AntigensAntigens

– specific reactivityspecific reactivitythe ability to react with effector molecules the ability to react with effector molecules (antibody) to form an antigen-antibody complex(antibody) to form an antigen-antibody complex

Antigens in red with green borders

AntibodiesAntibodies

glycoproteins that are also referred to as glycoproteins that are also referred to as immunoglobiulinsimmunoglobiulinsbasic structure is a Y shaped molecule with 2 functional basic structure is a Y shaped molecule with 2 functional partsparts– Fab regionFab region– Fc regionFc region

Fab regionFc region

AntibodiesAntibodies

Fab regionFab region– this is the part of the antibody that binds to the this is the part of the antibody that binds to the

antigenantigen

Fc regionFc region– the stem of the antibody that functions as a “red flag”the stem of the antibody that functions as a “red flag”

AntibodiesAntibodies

there are 5 classes of immunoglobulins there are 5 classes of immunoglobulins – each class plays a different role in the immune each class plays a different role in the immune

responseresponseIgGIgGIgMIgMIgAIgAIgDIgDIgEIgE

Lymphoid SystemLymphoid System

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

Lymphoid SystemLymphoid System

– primary lymph organsprimary lymph organsbone marrow: the location of stem cells bone marrow: the location of stem cells that will eventually become B and T that will eventually become B and T cells, B cells mature in the bone cells, B cells mature in the bone marrowmarrowthymus: maturation of the T cellsthymus: maturation of the T cells

Healthy bone marrow Bone marrow with leukemia

Lymph node

LymphocytesLymphocytes

critical part of immune system responsible forcritical part of immune system responsible for– detection of foreign antigensdetection of foreign antigens– activate immune systemactivate immune system

B lymphocytesB lymphocytesT lymphocytesT lymphocytesnatural killer cells (NK cells)natural killer cells (NK cells)

B lymphocytes: B cellsB lymphocytes: B cells

antibody producing cells antibody producing cells that respond to an that respond to an antigen stimulationantigen stimulationdevelop from stem cells develop from stem cells located in the red bone located in the red bone marrow of adults and the marrow of adults and the liver of a fetusliver of a fetus

B Cells dividing

B lymphocytes: B cellsB lymphocytes: B cells

following maturation, they following maturation, they migrate to the lymphatic migrate to the lymphatic tissuetissue

B cell in lymph node

T lymphocytes: T cellsT lymphocytes: T cells

key cellular component of key cellular component of immunityimmunitydevelop from stem cells develop from stem cells found in the bone marrowfound in the bone marrowprecursors to T cells precursors to T cells migrate to the thymus, migrate to the thymus, where they reach maturitywhere they reach maturity

human T cells

T lymphocytes: T cellsT lymphocytes: T cells

following maturity, T cells migrate following maturity, T cells migrate to various lymph organs where to various lymph organs where they await contact with antigensthey await contact with antigensbasis for cell-mediated immunitybasis for cell-mediated immunity

T cells (on left – orange, on right – gray) killingcancer cells (on left- mauve.on right – red)

Natural Killer Natural Killer CellsCells

these cells are not immunologically specificthese cells are not immunologically specific– they do not need to be stimulated by an antigenthey do not need to be stimulated by an antigen

capable of destroying other cells, particularly viruses-capable of destroying other cells, particularly viruses-infected cells and tumor cellsinfected cells and tumor cellsalso can attack large parasitesalso can attack large parasites

Clonal Selection of LymphocytesClonal Selection of Lymphocytes

terms used to define various stages of clonal terms used to define various stages of clonal selection includeselection include– immatureimmature– naïvenaïve– activatedactivated– effectoreffector– memorymemory

Antibody-Mediated ImmunityAntibody-Mediated Immunity

humoral or antibody-mediated immunity involves humoral or antibody-mediated immunity involves antibodies that are produced by B cellsantibodies that are produced by B cells– the term humoral is derived from the word “humors”, the term humoral is derived from the word “humors”,

which is Latin for fluidwhich is Latin for fluidin response to foreign antigens, the B cell is activated to in response to foreign antigens, the B cell is activated to produce a clone of plasma cells and memory cellsproduce a clone of plasma cells and memory cells– plasma cells secrete antibodiesplasma cells secrete antibodies– memory cells recognize pathogens from previous memory cells recognize pathogens from previous

encountersencountersB memory cells are long lived and are ready to B memory cells are long lived and are ready to mount an attack the next time that specific antigen mount an attack the next time that specific antigen presents itselfpresents itself

Primary & Secondary ResponsePrimary & Secondary ResponseThe 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

Antibody-Mediated ImmunityAntibody-Mediated Immunity

the antigen-antibody the antigen-antibody complexes that are formed as a complexes that are formed as a result of antibodies produce by result of antibodies produce by B plasma cells attract B plasma cells attract phagocytesphagocytes

Bacteria in green

Antibody-Mediated ImmunityAntibody-Mediated Immunity

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

Bacteria