RESPON IMUN TERHADAP ANTIGEN

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DOSEN IMUNOLOGI FAKULTAS FARMASI UNIVERSITAS PANCASILA JAKART A RESPON IMUN TERHADAP ANTIGEN

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RESPON IMUN TERHADAP ANTIGEN. Dosen Imunologi Fakultas Farmasi universitas Pancasila Jakart a. Antigen. Suatu substansi yang menyebabkan timbulnya respon imun bila masuk kedalam jaringan hewan/manusia yang peka dan mampu mengikat antibodi yg spesifik (biasany BM nya besar) - PowerPoint PPT Presentation

Transcript of RESPON IMUN TERHADAP ANTIGEN

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DOSEN IMUNOLOGIFAKULTAS FARMASI

UNIVERSITAS PANCASILAJAKARTA

RESPON IMUN TERHADAP ANTIGEN

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Antigen

Suatu substansi yang menyebabkan timbulnya respon imun bila masuk kedalam jaringan hewan/manusia yang peka dan mampu mengikat antibodi yg spesifik (biasany BM nya besar)

Bentuk protein, polisakarida, lipida, asam nukleat atau material lainn yang juga dapat bersifat antigen

Mikroba adalah antigen dan ia dapat memproduksi antigen

Antigen mempunyai lokasi yg spesifik untuk mengikat antibodi disebut “epitope”

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Immuniti dan Respon Immun

Di bangun dari dua komponen sistem imun:

Humoral atau circulating antibody systemSel B

Cell mediated immunity Sel-T

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Immuniti dan Respon Immun

Sistem imun mengidentifikasi antigen (protein asing dan polisakharida) Komponen dr mikroba atau bagian partikel produk dr

mo tersebut dan protein asing lainnya dan polisakharida. (termasuk asam nukleat)

Hospes (manusia dan hewan) antigen tdk di bentuk oleh individu juga sebagai antigen Result: in graft, transplant rejection

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Sistem imun

Sistem imun manusia di mulai dari saat perkembangan embrio

Di mulai pd saat proses hematopoietic stem cells. Stem cells differentiate menjadi sel yg penting dalam sistem

imun granulocytes, monocytes, dan lymphocytes

Stems cells juga ber defernsiasi menjadi sel darah lain yg tdk terlibat dalam sistem imun, yaitu sel darah merah dan megakaryosit (fibrin)

Stem cells terus menerus diproduksi dan berdeferensiasi sepanjang suatu masa kehidupan manusia

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Produksi sel darah dan leukosit

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Komponen sistem imun manusia

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Sistem imun

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Immuniti dan respon sistem imunm

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Immuniti dan respon sistem imun

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Seleksi clonal dr sel B krn stimulus antigenik

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Klasifikasi Antibodi (Immunoghlobulins)

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Re sp o n im u n terh ad a p an tig en p d m an u sia

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Respon imun terhadap antigen

First exposure to antigen "A”: begin to make low levels of antibody in about a week

Second exposure to antigen "A”: produces a much faster response, and several orders of magnitude higher levels of antibody. Ability of antibody to bind antigen also increases

dramatically in the secondary response. Injecting a new antigen "B” with "A"

Elicits only a primary response Shows that a memory or prior exposure is required for the

accelerated response.

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Humoral Mediated Immune ResponseProduces secreted antibodies (proteins)Bind to antigens and identify the antigen complex

for destruction. Antibodies act on antigens in the serum and

lymph B-cell produced antibodies may be

attached to B-cell membranes or Free in the serum and lymph.

Each B lymphocyte makes a unique antibody molecule (immunoglobulin or Ig)

Over a million different B lymphocytes are produced in each individual So, each individual can recognize more than a

million different antigens

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Immuoglobulin G (IgG)

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Reaksi Immunoglobulin terhadap antigen

IgG antibody molecule Composed of 2 copies of 2 different proteins Two copies of a heavy chain

>400 amino acids long Two copies of a light chain -

>200 amino acids longeach IgG antibody molecule can bind 2

antigens at one time A single antibody molecule can bind to 2 antigens

(e.g., viruses, bacateria or other particle), which leads to clumping

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Pengaruh ukuran antgen terhadap respon antibodi

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Fate of Antigen-Antibody Complexes

Ag-Ab complexes engulfed into the B-cell and partially digested

Antigen is displayed on the B-cell surface by a special receptor protein (MHC II) fo recognition by helper T-cells

B-cell is activated by the helper T-cell to divide and produce secreted antibodies Abs circulate in the serum and lymph

Some B-cells become memory cells to produce antibody at a low rate for a long time (long term immunity) They respond quickly when the antigen is encountered again the response is regulated by a class of T-cells called

suppressor T-cells

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Cell-Mediated Immunity and T Cells

T cell receptors are cell surface receptors that bind nonself substances on the surface of other cells

 Major histocompatibility complex (MHC) proteins protrude from the surfaces of most cells in mammals They help to distinguish self from nonself They coordinate interactions among lymphocytes and

macrophages Cytokines are soluble signal proteins released by

T cells They bind and alter the behavior of their target cells

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Cell Mediated Immune System: T lymphocytesT-cells mature in the thymus (thus the name T-cell) Act on antigens appearing on the surface of individual

cells.Over a million different kinds of T-cells

Each produces a different receptor in the cell membrane Each receptor is composed of 1 molecule each of two

different proteins Each receptor binds a specific antigen but has only one

binding site Receptor only recognizes antigens which are "presented" to

it within another membrane protein of the MHC type (major histocompatibility complex) Recognizes specific antigens bound to the antigen-

presenting structures on the surface of the presenting cell. Recognizes antigens presented by B-cells, macrophages, or

any other cell type

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T Cells and their Functions

Have a specific receptor for a fragment of antigen Cytotoxic T-cells:

Contain a surface protein called CD8 Destroy pathogen infected cells, cancer cells, and

foreign cells (transplanted organs)Helper T-cells:

Contain a surface protein called CD4 Regulate both cellular and humoral immune systems This regulation reduces autoimmunity.

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Autoimmune disease

Self immunity Some examples:

rheumatic fever rheumatoid arthritis ulcerative colitis myasthenia gravis Lyme disease (microbial etiology) Guillan-Barre syndrome (microbial etiology) Reiter’s syndrome or reactive arthritis (microbial etiology) Insulin dependent diabetes mellitus (IDDM) (microbial etiology?)

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Respon Interaksi diantara komponen sistem imun

T-cells, B-cells, and macrophages use MHC-II receptors for presentation;

All other cells use MCH-I (responsible for most of tissue graft rejection)

When a T-cell is presented with an antigen: its receptor binds to the antigen and it is stimulated to divide and produce helper T-cells

activate B-cells with bound antigen suppressor T-cells

regulate the overall responseCytotoxic "killer" T-cells

kill cells with antigen bound in MHC-I

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Peran Immuniti terhadap infeksi lokal

• Immunity to infection is usually short-term and transient– Mucosal (secretory or IgA) immunity in the gut or

respiratory tract wanes over time• Proof of concept: live, oral rotavirus vaccine:

– immunity declines over time and reinfection with “wild” type rotaviruses occurs

• Repeated localized (e.g., gastrointestinal) re-infection is possible. Examples:– Viruses: rotaviruses, noroviruses, adenoviruses and some

enteroviruses.– Salmonella spp, Shigella spp., Campylobacter spp, and E. coli spp.

cause localized infections– Giardia lamblia and Cryptosporidium parvum

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Peran imuniti terhadap infeksi sistemik • Immunity against generalized/systemic/disseminated

infection is usually lifelong, unless immune system is severely compromised

• Localized (e.g., gastrointestinal) re-infection is possible• Hepatitis A and E and many enteroviruses are viruses

causing systemic/generalized/disseminated infections• Salmonella typhi is a bacterium causing systemic infection• Typically, immunity against severe illness is long-term and

probably lifelong– Proof of concept: live, oral poliovirus vaccine and poliomyelitis

eradication; susceptibles are newborns and infants• Antigenic changes in microbes may overcome long-term

immunity and increase risks of re-infection or illness

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Seleksi infeksi mikroba strain baru thdp kepekaan dan terjadinya penyakit

• Antigenic changes in microbes overcome immunity, increasing risks of re-infection or illness– Antigenically different strains of microbes appear and are

selected for over time and space– Constant selection of new strains (by antigenic shift and drift)– Partly driven by “herd” immunity and genetic recombination,

reassortment , bacterial conjugation, bacteriophage infection and point mutations

• Antigenic Shift:– Major change in virus genetic composition by gene substitution

or replacement (e.g., reassortment)• Antigenic Drift:

– Minor changes in virus genetic composition, often by mutation involving specific codons in existing genes (point mutations)• A single point mutation can greatly alter microbial

virulence

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Perubahan sifat antigenik (mutasi) pada virus influenza H5N1

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