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Soluble proteins secreted by activated B cells or by their plasma-cell offspring (in response to an antigen)

They are capable of binding specifically with that antigen

Also known as immunoglobulins or Igs

B lymphocyte activation and clonal selection:First they bind to a specific antigenclonal selection creates copies of the activated cell

this is called the primary humoral responsemost clones become antibody producing plasma cellsother clones become memory cells

memory cells provide the secondary humoral responsea much faster, effective, and more prolonged response

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Primary response(initial encounterwith antigen)

Secondary response(can be years later)

Activated Bcells

Plasmacells

Secretedantibodymolecules

Secretedantibodymolecules

Plasmacells

Clone of cellsidentical toancestral cells

Proliferationto form a

clone

MemoryB cell

MemoryB cells

AntigenAntigen bindingto a receptor on aspecific B cell(B cells withnon-complementaryreceptors remaininactive)

Subsequentchallengeby sameantigen resultsin more rapidresponse

Primaryresponse

Secondaryresponse

Antigeninjected

Antigeninjected

Rel

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Time (weeks)

0 1 2 3 4 5 6

Active immunitywhen B cells encounter antigens and

produce antibodiesacquired naturally from infection or from

vaccines Most vaccines contain dead or weakened

pathogens

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Passive immunity (temporary protection)Antibodies are obtained from an immune

human or animal donor Naturally by mother to fetus via placenta; child

via breast milk Artificially by way of an immune serum

containing antibodies (antivenoms, antitoxins, gamma globulin)

No immunological memory is established

Four amino acid chains linked by disulfide bonds to form a T- or Y-shaped moleculeEach polypeptide

chain has a variable and a constant region Constant regions

determine antibody function and class

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Five major immunoglobulin classes (MADGE):1. IgM—can fix complement2. IgA—found mainly in mucus3. IgD—important in activation of B cell4. IgG—can cross placental barrier; fixes complement5. IgE—involved in allergies

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T lymphocytes are activated indirectly:Antigens must be presented by APCs

This is known as antigen presentationT cell recognizes and binds to the antigen fragmentT cell also recognizes and binds to “self”

glycoprotein on APC

Clonal selection occurs

Clones differentiate into various T cell classes

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Cytotoxic (killer) T cells Binds, releases lethal chemicals that degrade membrane and

digest proteins Helper T cells

Direct/manage cloning, signal with APCs, release chemicals called cytokines which increase efficiency of response

Regulatory (suppressor) T cells Release chemicals that slow down B and T cell activity; cease

the response after removal of antigen Memory cells

Remember each unique antigen second response is harder, better, faster, stronger…

that’s where Kanye got that song!!

HUMORAL (ANTIBODY-MEDIATED) ADAPTIVEIMMUNE RESPONSE

CELLULAR (CELL-MEDIATED) ADAPTIVEIMMUNE RESPONSE

Antigens displayed byinfected cells activate

CytotoxicT cell

Macrophage

Antigen-presentingcell

Antigen (1st exposure)

Engulfed by

Becomes

Stimulates

Stimulates

Free antigensdirectly activate

B cellT cell

Gives rise to Stimulates Stimulates

Plasmacells

Secrete

Antibodies

MemoryB cells

Defend against extracellular pathogens bybinding to antigens and making them easiertargets for phagocytes and complement.

Stimulates

Defend against intracellular pathogens andcancer by binding to and lysing the infectedcells or cancer cells.

Antigen (2nd exposure)

Stimulates

MemoryT cells

StimulatesHelper

Memory

T cell

Gives rise to

ActivecytotoxicT cells

Class II MHC: The main function of major histocompatibility complex (MHC) class II molecules is to present processed antigens which are derived from exogenous sources; they are critical for the initiation of the antigen-specific immune response.

T cell dependent antigens http://highered.mheducation.com/sites/0072507470/student_view0/

chapter22/animation__t-cell_dependent_antigens__quiz_1_.html

Clonal Selection http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?

it=swf::600::480::/sites/dl/free/0073532215/788107/Clonal_Selection.swf::Clonal%20Selection

Cell mediated Immunity https://smartsite.ucdavis.edu/access/content/user/00002950/bis10v/

media/ch23/cell_mediated.swf

Major types of tissue graftsAutografts—tissue transplanted on the

same person most successful

Isografts—tissue from an identical person (twin)

Allografts—tissue from unrelated person most common

Xenografts—tissue from a different animal species (whole organs unsuccessful)

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Blood group and tissue matching is doneensures the best match possible

Cell membrane antigens must have a 75% match (or better) to continue with transplant

immunosuppressive therapy follows

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