IMUNITAS SELULER DAN HUMORAL a. Mekanisme Imunitas Seluler b. Mekanisme Imunitas Humoral Kuliah 7 Kriana Efendi, M.Farm., Apt.
Sep 22, 2014
IMUNITAS SELULER DAN HUMORAL
a. Mekanisme Imunitas Seluler
b. Mekanisme Imunitas Humoral
Kuliah 7
Kriana Efendi, M.Farm., Apt.
Tipe Respon Imunitas Spesifik/didapat
Limfosit B/ sel B Humor cairan tubuh Maturasi sumsum
tulang Menyerang patogen
ekstraseluler Plasma cell Antibodies
/immunoglobulins Memory B cells
Limfosit T / sel T Maturasi Thymus Pertahanan thd patogen
intraseluler, sel kanker dan jaringan transplantasi
CD8 –cytotoxic T cells CD 4 cells –Helper T Memory T
Humoral immunity Cell Mediated immunity
Humoral Immunity Antibody-mediated Immunity
Antibody-mediated Immunity Response of B cells Secrete antibodies which circulate in
lymphatic fluid and blood• Activation:
– Antigen binds to B-cell receptor– antigen-MHC complex-Recognized by helper T cells– T cells produce interleukins that activate B cells
• Differentiation: – B cells differentiate into plasma cells & memory cells – Plasma cells release antibodies
Activation & Differentiation of B Cells
Antibody-secreting plasma cells Secrete antibodies for 4 or 5 days Cells die
Some remain as memory B cells Each particular clone able to secrete only
one type of antibody
Antibodies Also known as immunoglobulins Globular glycoproteins The heavy and light chains are polypeptides The chains are held together by disulphide
bridges Each ab has 2 identical ag binding sites –
variable regions. The order of amino acids in the variable region
determines the shape of the binding site
Antibodies Effective against extracellular antigens including
bacteria, viruses, protozoans, fungi, parasites, and toxins when they are outside cells.
combine specifically with antigen - serves as trigger
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Variable regions differ in the a.a. sequences at the antigen-binding site & are responsible for the diversity of Ab specificity
BivalentAntibodies / Immunoglobins
Fc
Antibody / Immumoglobulin• Product of B cell (plasma cell) activation
– Immunoglobulin (Ig) or antibody• Structure
– Four polypeptides – Connected by disulfide bonds– Antigen binding fragment (Fabs)– Crystallizable fragment (Fc)
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Fab
Variable (N-terminal of the heavy and light chains)
Binds to the antigenic determinant Swiveling enables more efficient Held together by disulfide bonds
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Fc
Constant (C-terminal of heavy chain) Binds to macrophages Anchors Ig to lymphocyte Held together by disulfide bonds Responsible for class identification
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Classes
Isotypes – based on the Fc fragment Immunoglobulin (Ig)
IgG IgA IgM IgD IgE
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IgG
Monomer Primary response Memory cell response Most prevalent in tissue fluid and blood
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IgA
Monomer or dimer (secretory IgA) Dimer – held together by a J chain Secretory IgA (mucous and serous
secretions)Local immunitySalivary glands, intestine, nasal membrane,
breast, lung, genitourinary tract Protection for newborns
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IgM
Five monomers Held together by a J chain First to be synthesized during primary
immune response Associated with complement fixation Receptor for antigens on B cells Circulates in the blood
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IgD
Monomer Small amounts in the serum Receptor for antigens on B cells
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IgE
Allergies Parasite infections Fc portion binds to mast cells and
basophilsrelease chemical mediators that aid
inflammation
Different Immunoglobulins
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How Abs work Some act as labels to identify
antigens for phagocytes Some work as antitoxins i.e. they block toxins
for e.g. those causing diphtheria and tetanus Some attach to bacterial flagella making them
less active and easier for phagocytes to engulf Some cause agglutination (clumping together)
of bacteria making them less likely to spread
Antibody Actions
Neutralizes antigen Immobilizes bacteria Agglutinates and precipitates antigen Activates complement proteins Enhances phagocytosis
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Consequences of Antibody Binding
Cellular Immunity Cell-mediated Immunity
Cell-mediated Immunity
Activation of T cells by specific antigen Eliminate intracellular pathogens and cancer cells First signal TCRs – T cell receptors(CD4 and CD8 proteins)
recognize antigen –MHC complexes Second signal- costimulation
cytokins- Interlukins -2 –produced by helper T cells
Proliferation and differentiation of the T cell to acquire effector function
(Mature naive T cell)
The two signal model for lymphocyte activation(antigen alone is insufficient)
(Mature dendritic cell)
Signal 1 comes from recognition of antigenSignal 2 comes from another (activated) cells
Antigen+MHC TCRTH2 activation,
for example
Proliferation and differentiation of the B cell to acquire effector function
(Armed effector T cell)
B cell activation,
for example
Plas
ma
cell
Mem
ory
B ce
ll
Cell-mediated Immunity - T cells Functions: most effective against intracellular
microorganisms: viruses, fungi, intracellular bacteria, parasites
Types : Cytotoxic T cells: Helper T cells Memory T cells
Cytotoxic T cells CD8 Release cytotoxic
substancesGranzymes – cell apoptosis Perforins –cytolysisLymphotoxins- destroys
DNA of the target cell Recognize foreign antigen-
MHC complex on:Virus infected cellsTissue transplant cellsCancer/ tumor cells
Helper-T cells
Called CD4 Secrete cytokines Interlukin-2 activates
T cells , B cells NK cells
Tumor necrosis factor (TNF)- inflammation
Positive feedback loop
Table 21.4
TERIMA
KASIH