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RESPON IMUN TERHADAP ANTIGEN DOSEN IMUNOLOGI FAKULTAS FARMASI UNIVERSITAS PANCASILA JAKARTA

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(1)

DOSEN IMUNOLOGI

FAKULTAS FARMASI

UNIVERSITAS PANCASILA

JAKART

A

RESPON IMUN

TERHADAP ANTIGEN

(2)

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

(3)

Immuniti dan Respon Immun

Di bangun dari dua komponen sistem imun:

Humoral atau circulating antibody system

Sel B

Cell mediated immunity

Sel-T

(4)

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

(5)

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

(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)

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.

(15)

Humoral Mediated Immune Response

Produces 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 beattached 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

(16)
(17)

Reaksi Immunoglobulin terhadap antigen

IgG antibody molecule

Composed of 2 copies of 2 different proteinsTwo copies of a heavy chain

>400 amino acids long

Two copies of a light chain

- >200 amino acids long

each 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

(18)

Pengaruh ukuran antgen terhadap respon

antibodi

(19)

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

(20)

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

(21)

Cell Mediated Immune System: T lymphocytes

T-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 membraneEach 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 antigen-presenting cell.

Recognizes antigens presented by B-cells, macrophages, or any other cell type

(22)

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 systemsThis regulation reduces autoimmunity.

(23)

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)

(24)
(25)

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 response

Cytotoxic "killer" T-cells

(26)

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

(27)

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

(28)

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

(29)

Perubahan sifat antigenik (mutasi) pada

virus influenza H5N1

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