antigen & antibodies

7/24/2019 Antigen & Antibodies

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Antigen & Antibodies


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What is antigen?

Foreign molecule recognised by lymphocytes -produceantibodies.

Macromolecules carried on the surface of pathogen ortransplanted cells

Toxins hich secreted by phatogen also act as antigen. !ymphocytes recognise speci"c portions of antigens# called

epitopes $$ antigetic determinants

Antigen may ha% se%eral dierent epitopes as dierentantibodies may bind to a single antigen.


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!'M()*+'T,

(roduce

same basic structure/

ecretedAntibodies$$immunoglob

ulin

MembraneAntibodies


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Antibodies or immunoglobulins

- '-shaped

- Made up of four polypeptide chain

- To identical hea%y chain & to identical light chain- !in0ed by disulphide bridge

- 1o transmembrane region

- Amino acid se2uence of both type of

chain ha%e %ariable region and constant3egion

+onstant region amino acid se2uence hich are

same for all antibodies ithin the same class

4ariable region dier from antibody to antibodyAct as antigen binding site.


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Membrane Antibodies- Function as 5 cell receptors

-

Tail region anchor in plasma membrane of 5lymphocytes

- 3ecognised free unprocessed antigens.

- )a%e transmembrane region


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lg M

Fi%e ' shaped monomer lin0ed together

Many antigen binding sites agglutinationreactions

First class antibody produced 6oes not cross the placental barrier

7n%ol%ed n complement acti%ation


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7g 8

mall monomer hich easily mo%e out ofblood %essels into tissue 9uid.

+ross the placenta# conferring the passi%e

immunity on fetus :;< antibodies circulating in body 9uids

(romote opsonisation# neutralisation

& agglutination.


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7g A

mall molecule made up of to monomer

(roduced mainly in mucous membrane

Founds in tears# perspiration# sali%a#

colostrum (re%ent bacteria & %irus attrach to

epithelial surface of respiratory passages#

alimentary canal# urinary and reproducti%etract


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7g 6

Found on the membrane of 5 cels herethey function as antigen receptor.

+annot cross placental barrier

3esponsible for stimulating thedierentiation of 5 cell into plasma celland memory cells.


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7g ,

*nly small amount producedcompare to other antibodies.

5inds to mast cell and basophils tostimulate them to producehistamines.

Allergic response

7mmunity to parasitic orms


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6e%elopment and roles of Macrophages# 5 cellsand T cells.

Macrophages are cells de%elop from monocytes#type of hite blood cell.

Migrates into body tissue here dele%op intolarge# long li%ed amoeboid macrophages.

ome reside permanently in organ and tissues#example= >uppfer cells in the li%er/

*thes patrol in bodys tissues# ingesting foreignmatter bateria# proto@oan parasites and old redblood cells/


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Macrophages has surface receptors+lass 77M)+/

ynthesis

M)+ molecules

binds

Fragment of ingested antigens

mo%e toard

(lasma membrane

- 5ecome antigen presenting cell A(+/

-

7mportant in producing the speci"c immunesystem

M)+ B MAC*3 )7T*+*M(AT757!7T' +*M(!,D


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!ymphocytes

made in bone marro/

T cells 5cells migrates to thymus gland completede%elopment in

to complete maturation/ bonemarro/


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T cells ha%e receptor that consist E dierent polypeptide chain

-alpha chain

-beta chain

-lin0ed by disulphide bridge

These receptor recognise speci"c antigens

T - cells

+6 urface protein +6G

- helper T-+ells T)/ - cytotoxic T cellTc/

secrete

cyto0ineschemical/ recognise and destroycells

acti%ate ith foreign antigenon

+ell- mediated and humoral their surface %irus infected

7mmume responses cells# cancer cells and graftedtissue/


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5 cells

)a%e surface receptors 0non as

Membrane antibodies.

Main function=

(roduction and secretion of antibodies

That is humoral immune responses

antigen & antibodies

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