05_SISTEM IMUN_BD.02_2013

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

SISTEM IMUN HEWAN

Biologi Dasar 2. 2013


Pendahuluan

• Barriers yg dimiliki hewan membantu hewan mempertahankan dirinya thd berbagai pathogens yg ditemuinya

• The immune system mengenal benda asing dan merespon dengan menghasilkan sel-sel imun dan protein

• Dua tipe pertahanan tubuh : imunitas bawaan dan imunitas yg diperoleh

Fig. 43-1

1.5 µm


• Innate immunity ada sebelum bertemu patogen dan efektif sejak lahir

• Melibatkan respon non spesifik terhadap patogen

• Innate immunity terdiri atas barriers eksternal, sel-sel di dalam tubuh dan senyawa kimia pertahanan


• Acquired immunity atau imunitas adaptif, berkembang setelah pemaparan thd zat asing spt mikroba, toksin dan substansi asing lain

• Umumnya melibatkan respon yg sangat spesifik terhadap patogen

• Baik vertebrata maupun avertebrata terhantung pada respon imun bawaan

• Vertebrata juga mengembangkan sistem imun adaptif

Fig. 43-2

INNATE IMMUNITY

Recognition of traitsshared by broad rangesof pathogens, using asmall set of receptors

•

•Rapid response

•Recognition of traitsspecific to particularpathogens, using a vastarray of receptors

•Slower response

ACQUIRED IMMUNITY

Pathogens(microorganisms

and viruses)

Barrier defenses:SkinMucous membranesSecretions

Internal defenses:Phagocytic cellsAntimicrobial proteinsInflammatory responseNatural killer cells

Humoral response:Antibodies defend againstinfection in body fluids.

Cell-mediated response:Cytotoxic lymphocytes defendagainst infection in body cells.


Immunitas bawaan pd Avertebrata• Pd Arthropoda, exoskeleton dibuat dr chitin

membentuk barrier pertama thd pathogens

• Sistem digestive jg protected oleh pH rendah dan lysozyme, berisi enzyme yg mendigesti dinding sel mikroba

• Hemocytes yg bersirkulasi bersama within hemolymph jg melakukan phagocytosis, menelan dan mendigesti substansi asing, termasuk bakteri

• Hematosit jg mensekret peptida anti mikroba yg merusak membran plasma bakteri

Fig. 43-3

Microbes

PHAGOCYTIC CELL

Vacuole

Lysosomecontaining enzymes


• Sistem imun mengenal bakteri dan jamur melalui struktur dinding selnya

• Suatu respon imun bervariasi dengan klas patogen yg ditemui


Innate Immunity of Vertebrates

• Sistem imun mamalia adl yg paling dipahami dr vertebrata

• Pertahanan bawaan meliputi barrier defenses, phagocytosis, antimicrobial peptides

• Pertahanan tambahan adl unique to vertebrates: the inflammatory response and natural killer cells


Barrier Defenses

• Barrier defenses meliputi the skin and mucous membranes of the respiratory, urinary, dan saluran reproductive

• Mucus menangkap dan mengeluarkan mikroba

• Banyak cairan tubuh meliputi saliva, mucus, dan air mata jg untuk melawan microbes

• The low pH of skin and the digestive system prevents growth of microbes


• Sel darah putih menelan mikroba, lalu berfusi dgn lisosom untuk merusak mikroba

• Terdapat tipe berbeda dr sel fagositik :

– Neutrophils engulf and destroy microbes

– Macrophages are part of the lymphatic system and are found throughout the body

– Eosinophils discharge destructive enzymes

– Dendritic cells stimulate development of acquired immunity


Antimicrobial Peptides and Proteins

• Peptides dan proteins berfungsi dalam pertahanan bawaan dgn menyerang mikroba langsung atau menghalangi reproduksinya

• Protein Interferon menyediakan pertahanan bawaan melawan virus dan membentu mengaktifkan macrophages

• Kira2 30 proteins menyusun complement system, yg menyebabkan lisis sel-sel penyusup dan membantu memicu peradangan


Inflammatory Responses

• Bila ada luka, mast cells release histamine, yg mempromosi perubahan pembuluh darah; this is part of the inflammatory response

• Perubahan ini menngkatkan suplai darah lokal dan memungkinkan lebih banyak phagocytes and antimicrobial proteins masuk jaringan

• Pus, suatu cairan yg kaya sel darah putih, dead microbes, and puing2 cell, accumulates at the site of inflammation

Fig. 43-8-3

Pathogen Splinter

Macrophage

Mast cell

Chemicalsignals

Capillary

Phagocytic cellRed blood cells

Fluid

Phagocytosis


• Inflammation can be either local or systemic (throughout the body)

• Fever is a systemic inflammatory response triggered by pyrogens released by macrophages, and toxins from pathogens

• Septic shock is a life-threatening condition caused by suatu penyebaran inflammatory response


Imunitas diperoleh

• Sel darah putih lymphocytes, mengenal dan merespon thd, foreign molecules

• Lymphocytes that mature in the thymus above the heart are called T cells, and those that mature in bone marrow are called B cells

• Lymphocytes contribute to immunological memory, suatu peningkatan respon thd molekul asing yg telah ditemui sebelumnya

• Cytokines are secreted by macrophages and dendritic cells untuk menarik dan mengaktifkan lymphocytes


• B cells and T cells memp protein receptor yg dapat mengikat molekul asing

• Tiap individu lymphocyte terkhususkan untuk mengenal molekul spesifik

• Suatu antigen adl molekul asing yg dpt membangkitkan respon suatu lymphocyte

• A single B cell or T cell memiliki kira2 100,000 reseptor antigen yg identik

Fig. 43-9

Antigen-bindingsite

Antigen-binding site

Antigen-bindingsite

Disulfidebridge

Variableregions

Constantregions

Transmembraneregion

Plasmamembrane

Lightchain

Heavy chains

T cell

chain chain

Disulfide bridge

Cytoplasm of T cell

(b) T cell receptor

Cytoplasm of B cell

(a) B cell receptor

B cell

V

V

C C

V

V

C C C C

VV


• All antigen receptors on a single lymphocyte recognize the same epitope, or antigenic determinant, on an antigen

• B cells give rise to plasma cells, which secrete proteins called antibodies or immunoglobulins

Fig. 43-10

Antigen-binding sites

Antigen-bindingsites

Epitopes(antigenicdeterminants)

Antigen

Antibody B

Antibody CAntibody A

CC

CV

V

V

V

C


• The first exposure to a specific antigen represents the primary immune response

• During this time, effector B cells called plasma cells are generated, and T cells are activated to their effector forms

• In the secondary immune response, memory cells facilitate a faster, more efficient response

Animation: Role of B CellsAnimation: Role of B Cells

Fig. 43-15

Antibodiesto A

Antibodiesto B

Secondary immune response toantigen A produces antibodies to A;primary immune response to antigenB produces antibodies to B.

Primary immune responseto antigen A producesantibodies to A.

An

tib

od

y co

nce

ntr

atio

n(a

rbit

rary

un

its)

Exposureto antigen A

Exposure toantigens A and B

Time (days)

104

103

102

101

100

0 7 14 21 28 35 42 49 56


Dua tipe imunitas diperoleh

• Acquired immunity has two branches: the humoral immune response and the cell-mediated immune response

• Humoral immune response involves activation and clonal selection of B cells, resulting in production of secreted antibodies

• Cell-mediated immune response involves activation and clonal selection of cytotoxic T cells

• Helper T cells aid both responses

Fig. 43-16

Humoral (antibody-mediated) immune response

B cell

Plasma cells

Cell-mediated immune response

Key

Stimulates

Gives rise to

+

+

++

+

+

+Memory B cells

Antigen (1st exposure)

Engulfed by

Antigen-presenting cell

MemoryHelper T cells

Helper T cell Cytotoxic T cell

MemoryCytotoxic T cells

ActiveCytotoxic T cells

Antigen (2nd exposure)

Secretedantibodies

Defend against extracellular pathogens by binding to antigens,thereby neutralizing pathogens or making them better targetsfor phagocytes and complement proteins.

Defend against intracellular pathogensand cancer by binding to and lysing theinfected cells or cancer cells.

+

+ +

05_SISTEM IMUN_BD.02_2013

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