Antibodies &Immunoglobulins

8/17/2019 Antibodies &Immunoglobulins

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Immunoglobulins and antibodies


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ImmunoglobulinsImmunoglobulins or antibodies are

glycoproteins present in the serum andbodyfluids, that are induced whenimmunogenic molecules are introduced into

the host’s lymphoid system.

They specifically bind to the antigen that

induced their formation.


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• WHO Definition proteins of animal

origin endowed with !nown antibodyacti"ity and certain proteins related tothem by chemical structure

• #ntibody globulins, abnormal proteins,sub units of Igs.

• #ntibody$%&'th carbohydrate andpolypeptide

• #ntibody binds to antigen specificallyand initiate secondary biologicalphenomena$(i$functional molecule


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• )on (erhing and *itasato$+%- /0ro"edtheir physical presence

• Tiselius and*abat +%-1- / 2identifiedantibody molecule

• 0orter+%-'- / clea"ed the antibody

molecule by papain• WHO +%-3-/coined the term 4Ig5

• The immunoglobulins include antibodies

and abnormal proteins


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6unctions of immunoglobulins

%. 0re"ent attachment of microbes to

mucosall surfaces of the host7. 8educe the "irulence of

microorganisms by neutrali9ing to:ins

and "iruses1. 6acilitate phagocytosisby

opsoni9ationof microbes

;. #cti"ate compliment


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• 0orter,


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Immunoglobulin antigenic determinants

Isotypes the particular constant regionof light or hea"y region of Ig

Immunoglobulins are classified on basis ofhea"y chains isotypes

>ight chains ha"e isotype mar!ers !appa

and lamdaIsotypes are present in all members of aspecies


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Ig?@tucture pentamer• @erum conc. %$%'A

• >ocation

• @edimentation coefficient %-• ?W-,

• Barbohydrate content%7

• @erum concC+mg&ml/ %.7

• Half life'days

• Bomplement bindingclassical pathway

• 0lacental transfer$

• 0resent in mil!$• @eromucous secretions$

• Heat stability+'3.c/ stable. Hea"ychainmu

• @usceptibility to mercatoethanolsusceptible


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Ig@tucture ?onomer0ercentage in total serumA>ocation Intra and e:tra "ascular

@edimentation coeffientE?W %',Barbohydrate A1@erum conc.+mg&ml/ %7

Half life71daysHea"y chain gamma %,7,1,;Bomplement binding classical pathway0lacental transfer F

0resent in mil! FHeat stabilityF@usceptibility to mercaptoethanol not susceptible


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IgA:@tructureDimer in mucosal surfaces and monomer in

serumA of total serum '$%A@edimentation coefficient E?W %3,

Barbohydrate contentA@erum conc.+mg&ml/ 7Hea"y chain alphaBomplement binding #lternate pathway

0lacental transfer $0resent in mil! F@eromucous secretion FHeat stability+'3.c/


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Ig


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• 0lacental transfer no

• @usceptibility to .7 mercaptoethanolsusceptible

• Increased le"els are seen hea"y

parasitic infestations• Half life %$' days• #ction by release of inflammatory

mediators by mast cell degranulation IgD structurally resembles Ig mostly

intra"ascular with half life 1 days.• 0resent on the surface of ($cells as

antigen receptor


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• Ig protects body fluids

• Ig#body surfaces

• Ig? blood stream• Ig


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• eneration of ab. di"ersity #ntibodiesproduced in an indi"idual are more than total

no. of proteins in the body• B,and) regions code for > chain and B,D,and ) code for H chain

• 6ew genes code for B$region,many genes code

for )$region• Immunoglobulin specifities The specific ag.

Determinants on paratope are calledidiotopes. The sum total of idiotopes on

antibody molecule is idiotype• Three categories of antigenic determinants

are present on Igs.


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• The antigenic specificities whichdistinguish different classes and sub

classes of Igs. in normal indi"idual$I@OT0< specificities

• The antigenic specificities which

distinguish of the same class betweendifferent groups of indi"iduals of thesame species 2#>>OT0IB specificities

m system+gamma,alfa,epsilonJ* chains/and In) system +!appa light chains/


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Abnormal immunoglobulins:

• ?ultiple myeloma # plasma cell tumourproducing e:cess amounts of single class ofIgs. with Ig,Ig?

• Ig< myelomas are e:tremely rare

• (ence$ones proteinslight chains ofimmunoglobulins either * or >. coagulate at' degrees and re dissol"e at Edegrees

• Hea"y chain disease abnormal proliferation of6c portion of hea"y chains

• Bryoglobunaemia presence of cryoglobulin


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• Immunoglobulin class switching: Initial

antibody is Ig? fallowing primary orinitial antigenic challenge and ($ cellproliferation

• Blass switch occurs later with generearrangement producing either Ig orIg# with the same specificity

• @ame )H genes associated withdifferent BH genes


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? l l tib di


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?onoclonal antibodies

• #ntibodies directed against singleepitope single clone of cells getacti"ated producing monoclonalantibodies with single antigenicspecificity

• ?icrobial infection and immuni9ationleads to polyclonal antibody production

• =aturally occurring monoclonalantibodies are myeloma proteins


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• ?ilstein and *ohler de"ised a techniGueof hybridoma production for largescale production of monoclonalantibodies artificially

• Hybridoma somatic hybrids arede"eloped by fusing antibody formingspleen cells with myeloma cells

%. @pleen cells are immuni9ed withdesired antigen

7. ?yeloma cells do not produce and

deficient in H08T en9yme


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•


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• Blea"ed 6ab fragment coupled to "arious to:icsubstances and en9ymes

• (y fusing genes coding for abs.fragments tobacteriophage genes

• #d"antages limitlessgrowthand%,moleculesof Ig &min.

#pplications Diagnostic leucocyte identification

H># typing"iral detection 2sub typing

parasitic ag. Identification detection of tumor related ags.


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Therapeutic 8adiotope tagging

antitumor therapy

immunosuppresion treatment of auto immune

and Hyper sensiti"ity diseases

treatment of )H

Identification and purification ofmicrobial products


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?O=OB>O=#> #=TI(ODI


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A$TI%&$' A$TI()D*

!&A+TI)$S

• #gs.and #bs. combine with eac otherspecifically and in obser"able manner

• Ini"i"o #?I is effecti"e in e:tracellularpathogens mainly resulting in immuneelimination or in tissue inKury eitherhypersensiti"ity or autoimmunity

• In"itro ag$ab reactions 2serological reactionsuseful in$

Identification of I.agents purification of ags and

abs. Diagnosis of diseases

epidemiological sur"eys


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• #g$#b reactions occur in three stages• 0rimary stage reactions are rapid and occur at

low temp. detected byusing mar!ers

• @econdary reactions some primary reactionslead to secondary reactions 2demonstrable by

precipitation agglutination

lysis of cells !illing of li"e antigens neutrali9ation fi:ation of complement immobili9ation of motile cells enhancement of

phagocytosis


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Tertiary stage some ag$ab reactions in"i"oleadto chain of reactions

neutrali9ation or destruction of inKurious ags.or to tissue inKury resulting in #?I orclinical allergy

or other immunological diseases.

eneral features of ag$ab reactions%. @pecific7.


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,- (oth ag and ab participate in formationof ag$ab comple:es

E. )alency for ag or ab are not fi:ed ?easurement of ag$abin terms of

mass of nitrogen or in units

#b titre of the particular test titre ofserum is the highest dilution of serumwhich gi"es obser"able reaction.=ature and Guantity of the #g

influence the titreTwo parameters of serological test are

sensiti"ity and specificity

#nother parameter is reproducibility


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@ensiti"ity

ability of the test to detect e"en "ery

minute amounts of #g or #b@pecificity

ability of the test to detect reactions

between homologous #g and #b onlyIna serological test the sensiti"ity,

specificity and reproducibility depend

on the standard of #g and #b andfacilities in the laboratory


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@OIB#> reactions detected by%. 0recipitation

7.#gglutination 1. Bomplement fi:ation ;.=eutrali9ation

'. Opsoni9ation 3.I6 E.8I# .


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08OBBL>#TIO= remains as a floccule.

0recipitation can ta!es place in liGuidmedia or in gels such as agar, agaroseand polyacrylamide


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#mount of precipitation is influenced byrelati"e proportions of #g and #b.

>#TTIB< H0OTH


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Antibodies &Immunoglobulins

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