Changes

Jump to navigation Jump to search
Line 20: Line 20:  
==MHC II==
 
==MHC II==
 
[[Image:MHC II presentation.jpg|thumb|200px|right|'''MHC II presentation, courtesy of Janeway, et al. 2008''']]
 
[[Image:MHC II presentation.jpg|thumb|200px|right|'''MHC II presentation, courtesy of Janeway, et al. 2008''']]
 +
===Structure===
 +
MHC class II is expressed mainly on [[Macrophages|macrophages]], [[T cell differentiation#Antigen Presentation by Dendritic Cells|dendritic cells]] and [[B Cells|B-lymphocytes]]. MHC class II consists of membrane-associated α and β chains; each chain is a transmembrane glycoprotein. The extracellular parts of each chain have two Ig-like domains - α1 and 7alpha;2, β1 and β2. The outer domains (α1 and β1) are variable and the inner domains (α2 and β2) are constant.
   −
===Structure===
+
The 3-dimensional structure of MHC class II is similar to MHC class I; the outer domains of the α and β chains fold in a similar way to the α1 and α2 domains of class I to produce the antigen-binding groove.
* MHC class II is expressed mainly on [[Macrophages|macrophages]], [[T cell differentiation#Antigen Presentation by Dendritic Cells|dendritic cells]] and [[Lymphocytes#B Cells|B-lymphocytes]]
  −
* MHC class II consists of membrane-associated α and β chains
  −
**  Each chain is a transmembrane glycoprotein
  −
** The extracellular parts of each chain have two Ig-like domains
  −
*** α1 and 7alpha;2, β1 and β2
  −
**** The outer domains (α1 and β1) are variable-like
  −
**** The inner domains (α2 and β2) are constant-like
  −
* The 3-dimensional structure of MHC class II is similar to MHC class I
  −
** The outer domains of the α and β chains fold in a similar way to the α1 and α2 domains of class I
  −
*** Produce the antigen-binding groove
   
[[Image:MHC II Structure.jpg|thumb|right|200px| Structure of MHC II molecule - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]
 
[[Image:MHC II Structure.jpg|thumb|right|200px| Structure of MHC II molecule - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]
    
===Presentation Pathway===
 
===Presentation Pathway===
*MHC II presents '''exogenous''' (that is, derived from the ECF) peptides
+
MHC II presents '''exogenous''' (ECF) peptides. Endocytosed antigen interacts with MHC II in the cytoplasm to form a complex:
*Endocytosed antigen interacts with MHC II in the cytoplasm to form a complex:
+
*Antigen is endoycotsed from the ECF
**Antigen is endoycotsed from the ECF
+
*Lysosomes fuse with primary endosomes to digest the antigen to peptides
**Lysosomes fuse with primary endosomes to digest the antigen to peptides
+
*MHC II is meanwhile being produced by the endoplasmic reticulum, along with an invariant chain chaperone
**MHC II is meanwhile being produced by the endoplasmic reticulum, along with an invariant chain chaperone
+
*These pathways (endoytotic and secretory) merge to allow interaction between the antigen and MHC II and the invariant chain is digested, leaving a CLIP peptide in the binding groove.
**These pathways (endoytotic and secretory) merge to allow interaction between the antigen and MHC II:
+
*Foreign antigen then replaces the CLIP peptide
***The invariant chain is digested, leaving a CLIP peptide in the binding groove
+
*The MHC II-antigen complex is then secreted to the cell surface for presentation to [[T_cells#Helper_CD4.2B|CD4+ T-cells]]
***Foreign antigen then replaces the CLIP peptide
  −
*The MHC II-antigen complex is then secreted to the cell surface for presentation to [[Lymphocytes#Helper CD4+|CD4+ T-cells]]
      
=Interaction of MHC With Antigen=
 
=Interaction of MHC With Antigen=
5,582

edits

Navigation menu