MEMBRANE RECEPTOR FOR ANTIGEN Ninda Sahriyani Ganys Tri S.

Agatha Mia Vita Agustina Kelompok : 4 (105090100111010) (115090107111020) (115090101111010) (115090100111011) Jurusan Biologi Fakultas Matematika dan Ilmu pengetahuan Alam Universitas Brawijaya 2013

THREE LIMBS OF IMMUNE RESPONE Fig 1. Three Limbs Immune Respone

Major Histocompatability Complex (MHC)

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Group of genes that code for proteins that found on the surfaces of cells that help the immune system recognize foreign substances

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Also known as HLA (Human Leukocyte Antigen) Two types:

Class I • Found in every nucleated cell • Bound to cytotoxic T cell (CD8) Class II • Found in special cell such as macrophage, dendritic cell, B cell, and thymus • Bound to Helper T cell

Function of MHC

1. Determinate between the self and nonself antigens 2. Presenting antigen to T cells 3. Determinate interaction between B cells, T cells and other cells.

Degradation Process (Processing and Presentation) Antigen

There are 3 ways of processing and presentation antigens : 1. Protein from extracellular pathogen broken down and processed by exogen pathway 2. Protein from self-protein and virus protein processed by endogen pathway 3. Lipid and derivate processed like extracelular protein and endosom, with CD1, that similiar to MHC and presented to CD8 T cell.

Function of MHC

Fig 2. MHC Structures

TABLE 1. DIFFERENCES BETWEEN CLASS I AND CLASS II MHC Variable Bound to Enzyme to form peptide Class I MHC CD8 T cell Cytosolic protease

Peptide binding site in cell

Reticulum endoplasmic

Peptide size

Expression and Presentation 8-9 amino acid • Expressed to hematopoietic cells • Presented by all nucleated cells. Class II MHC CD4 T cell Endosome and lysosom protease Vesicle specialized compartment 13-17 amino acid • Expressed to hematopoietic cell and stromal cell at thymus • Presented by macrophage, dendritic cell, B cell

SIMILARITIES OF ANTIGEN PRESENTING BY MHC MOLECULES

• Presented to T cell on the surface of APC (Antigen Presenting Cell) • Every MHC can only bind to single antigen fragment at one time, at the peptide binding cleft • The presented antigen fragment is only amino acid chain • The binding is done intracellular

Fig 2. Class I MHC Antigen Presenting Pathway

Fig 3. Class II MHC Antigen Presenting Pathway

• Mature T cell have thousands identical receptor on the cell surface • 2 kinds of receptor: – Alpha/beta (αβ) chain T cell (95%) – Gamma/delta (γδ) chain T cell (5%) • Co-receptor : CD4 and CD8

T Cell Receptor Complex: TCR-CD3

• • TCR binding to MHC-antigen

Fig 5. TCR-CD3

The long cytoplasmic tail of the CD3 functions in signal transduction.

Role of co-receptors in TCR binding affinity Fig. 6 Role of co- receptor

CD 4 and CD8 : they may act as adhesion molecule helping the T cell bind to the APC during antigen presentation for duration that is sufficient for antigen recognition or act as signal transducers.

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VIDEO

Link : T Cell Dependent Antigens http://highered.mcgraw-hill.com/olc/dl/120 110/micro33.swf

Cytotoxic T Cell http://highered.mcgraw hill.com/olc/dl/120110/micro34.swf