ab production theories.pptx

7/30/2019 Ab Production Theories.pptx

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THEORIES OF ANTIBODYPRODUCTION

IMMUNOLOGY


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MANY HYPOTHESIS REGARDING THE

ANTIBODY PRODUCTION WERE MADE


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1.THE INSTRUCTIVE THEORY

2.THE SELECTIVE THEORY

There are two theories of antibody

production mainly:-


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INSTRUCTION VERSUS SELECTION Precursor of an antibody-forming cell

(AFCP) is not precommitted, but has thepotential of making any one of a millions of

different antibodies.

AFCP are precommitted to

producing antibody of a

particular specificity.


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INSTRUCTIVE THEORY These theories postulate that an immuno-

competent cell is capable of synthesizingantibodies of any specificity. The antigenencounters an immuno-competent cell andinstructs it to produce the complimentaryantibody, e.g.-DIRECT TEMPLET THEORY andINDIRECT TEMPLET THEORY.


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DIRECT TEM PLET THEORYThese theories were

proposed by Breinl &

Haurowitz (1930) and

Alexander(1931) Mudd(1932).

It is proposed by Breinl and

Haurowitz in 1930. Accordingto this theory, antigen enters

into B cell and act as

template for the production

of antibody. Since thisantibody is produced from

antigen, it is specific for

antigen. But in reality, the

antibody specificity is

predetermined before


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Burnet and Fenner-1949 proposed thisinstructive theory to explain the synthesis

of antibody as an adaptive protein.

According to this theory, antigen enters

into B cell and it binds to its DNA andmodifies it and forms this modified DNA,

antibodies are produced against antigen

and it also specific for it. But in nature,

there is no need for an antigen to enter

into B cell and modify DNA for antibodyproduction because soluble antigen can

activate B cell by binding to its cell

surface receptor BCR. Because of this

reason, this theory also disproved.

INDIRECT TEMPLATE THEORY:

Sir Burnet


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SELECTIVE THEORIESThese theories shift the emphasis from the antigen tothe immuno-competent cell. They postulate thatimmuno-competent cells have only a restrictedimmunological range. The antigen exerts only aselective influence by stimulating the appropriateimmuno-competent cell to synthesis an antibody, e.g.-Side Chain Theory, Natural Selection Theory\ andClonal Selection Theory.


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It is proposed by Ehrlich in1897. According to this theory, Bcell contains different side chains i.e.antibodies with differentspecificity. When antigenencounters naive B cell, it caninteract with the side chains andselect one of the side chains. Itinturn activates B cell. Activated Bcell then produces antibodies ofselected side chain type . But inreality, each B cell possesses only onetype of BCR with single specificity.Because o f this, this theory disproved

SIDE CHAIN THEORY:


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Paul Ehrlich

(1854-1915)

Germany

Nobel price

Medicine

1908

he hypothesized that receptors (described as side chains)

on the surface of cells could bind specifically to toxins in a

"lock-and-key" interaction (Emil Fischer) - and that this

binding reaction was the trigger for the production of

antibodies.

KeypointsAll cells express on their surface sidechains (receptors) that bind toxin.

Side chains physiologic function is to to take up food. (A ff)

Cell overproduces the partcular sidechain (B) and releases it into thebloodstream (C)

Soluble sidechain neutralises toxin (C), or recruits complement (D),

agglutinates pathogens (D as membrane-bound form) or even opsonises

pathogen (activity only known since 1905)

Explains

all oberserved activities of antibodies (agglutinins, lysins, antitoxins andprecipitins and even opsonins)

Inducibility (only present in blood is soluble form after immunisation)

Specificity (only antibodes to particular pathogen)

Problem

Enough space on a cell for all possible toxinsandpathogens?


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NATURAL SELECTION THEORY:This theory is proposed by Jerne in1955. According to this theory serumwill contain antibodies for all antigensand these antibodies are known asnatural antibodies. Antibodies forblood group antigen A and B can begiven as an example for thistheory. But naturally serum will notcontain secreted antibodies for specificantigen till it enters host and activates Bcell. Because of this valuable reason,this theory also rejected.

Niels Kaj Jerne


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CLONAL SELECTION THEORY:This is the present day theory which is also accepted

one. Proposed byBurnetin 1957. According thi s theory, theantigen specif icity i s predetermined one i.e. B cel l is matur ed with

single antigen specif icity in bone marrow and B cel ls with same

specificity is referred as B cell clone for a specific

specif icity. After they matured, they moved to per ipheral

lymphoid organs. When anti gen enters, i t moved to per ipheral

lymphoid organs for activation. I n thi s process, antigen selects a

single clone from multiple B cell clone with different

specif icity. Thus this theory named as clonal selection

theory. Af ter a clone is selected by antigen, B cel l is activatedand proli ferated. Af ter prol i feration, selected B cel ls undergo

differentiation to form plasma cell and memory B cells for

specif ic antigen. Plasma cel ls secrete antibodies and they

par ticipate in anti gen removal and memory cel ls wai t for future

anti gen encounters. Thi s theory is also practical ly proved.


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clonal expansion differentiation

MemoryB cell

MonospecificB cells

Antibody

B cellreceptor

Antigen

(Ant ikrpergenerierend)

Clonal Selection Theory (Burnet 1957)

o Each AFCP is pre-committed to produce one antibody (monospecific)

o Each AFCP carrys membrane-bound immunoglobulin

o B cell that binds Ag gets expanded and differentiates into AFCo Explains - Specifity

- Induciblity

- Secondary response

- Tolerance to self-antigens (clonal deletion, 1949)

Plasma cell


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REFRENCES:- SPECIAL THANKS TO-Ms.Tanurmi Ghosal (M.Sc.Microbiology2012 Batch) Textbook of Microbiology-By R. Vasanthakumari

Websites-www. http://biosiva.50webs.org/plasmacell.htm http://en.wikipedia.org/wiki/File:Burnet_2jpg.jpg

https://www.google.co.in/search?q=clonal

http://trove.nla.gov.au/people/508234?c=people
http://biosiva.50webs.org/plasmacell.htmhttp://en.wikipedia.org/wiki/File:Burnet_2jpg.jpghttps://www.google.co.in/search?q=clonalhttp://trove.nla.gov.au/people/508234?c=peoplehttp://trove.nla.gov.au/people/508234?c=peoplehttp://trove.nla.gov.au/people/508234?c=peoplehttps://www.google.co.in/search?q=clonalhttps://www.google.co.in/search?q=clonalhttp://en.wikipedia.org/wiki/File:Burnet_2jpg.jpghttp://en.wikipedia.org/wiki/File:Burnet_2jpg.jpghttp://biosiva.50webs.org/plasmacell.htmhttp://biosiva.50webs.org/plasmacell.htm


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By-TANURMI GHOSHALMsc.Microbiology Iind Sem

THANK YOU:-

ab production theories.pptx

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