antigen capture and presentation to lymphocytes

Question 1

how antigens are taken to secondary lymphoid organs

Answer 1

microbes or their ag enter blood and go to lymph nodes or spleen and are captured by DCs and presented to T and B cels
DC cells in epithelial and CT and organs transport the ag to lymphoid organs

Question 2

types of Dentritic Cells

Answer 2

1- Conventional: epidermal DC ( langerhans cells) and secrete IL6, IL12, IL23 and TNF and it induces T cell response
2- Plasmacytoid DC: found in blood and secrete INF1 and induces T cell againt virus

Question 3

sturcutre of MHC1`

Answer 3

contain alpha chain noncovalntly associated with beta2 and the aminoterminal contain alpha1, 2 domains and peptide binding cleft accomdating 8-9 amino acids and contact with TCR
the alpha 3 domain is invariant and binds to CD8 T cell receptor

Question 4

Structure of MHC2

Answer 4

contain 2 transmembrane alpha and beta and each chain contain 2 extracellular domain and transmembrane and cytoplasmic region
alpha1 and beta1 contain polymorphic residues accomdating 10-30 residues in the cleft
alpha2 and beta 2 is binding site of CD4 T coreceptor

Question 5

properties of MHC genes

Answer 5

class 1 MHC is presented on all nucleated cells
Class 2 is expressed on DC, macrophages and B cells and thymic epithelial and endothelial cells and induced by IFNy

Question 6

processing and presentation by MHC1 steps 1
MHC1 made by chromosome 6

Answer 6

1- proteolysis of cytosolic protiens by ubiquetin proteasome pathway and the protiens are tagged by ubiquetin and threated through proteasome which degrade protiens into peptides
2-peptide is transported to ER and TAP ( transport associated with antigen processing) binds to proteasome made in cytosol and pumps it to the interior of the ER where the new MHC1 is made and MHC 1 at that time will have tapsin, which links to TAP
3. Transport of peptide MHC complex to cell surface

Question 7

Processing of interniliation ag to MHC2

Answer 7

1- internlization and protealysis from ECM and DC and macrophage ingest microbes and inside of the cells they make phagolysosome which breakdown the protiens to peptides
2- peptides bind to MHC2 and each new MHC contain invariant chain which contain 2 CLIP which binds ot peptide binding cleft to prevent it from inding to peptides in ER which are for MHC1
3- CLIP is exchanged in peptide binding cleft with peptides by help of HLA-DM
4- Transport peptide MHC complex to cell surface