5-major his to compatibility complex (mhc)
TRANSCRIPT
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
1/12
Major HistocompatibilityMajor HistocompatibilityComplex (MHC)Complex (MHC)
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
2/12
There are three major histocompatibilityantigens; class I, classII, and class IIIMHC antigens .These antigens are
genetically determined by a set of genescalled the major histocompatibility genecomplex , which lie on a portion of the shortarm of human chromosome 6.These genesoccupy four regions ( A,B,C and D).
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
3/12
HLA (MHC) geneHLA (MHC) gene
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
4/12
R egions B,C and A determine the antigenicspecificities of class I MHC surfacemolecules.R egion D determines the antigenic
specificities of class II MHC surfacemolecules.The region between D and B codes for certain complement components ( C 2,C 4,
factor B), and is not concerned with graftrejection. It is called class III MHC .
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
5/12
Class I MHC antigens: are glycoproteins and
include HLA-A,HLA-B, and HLA-C . They arefound on all nucleated cells. Class I MHCenables cytotoxic T cells (Tc) to recognizeforeign antigen on the surface of graft cells,
tumour cells or virus infected cells and kill thesecells. In other words Tc cells ( CD8 )are triggeredonly when they recognize both antigen and classI MHC molecules in close association on the
surface of cells. This is known as MHC-restriction .
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
6/12
Class II MHC-antigens: or HLA-D antigens are
glycoproteins, and include HLA-DP, HLA-DQand HLA-D R .These are found chiefly on the surface of Tlymphocytes, and antigen presenting cells(APCs) such as monocytes, macrophages,dendritic cells and B lymphocytes.Helper T cells (Th) ( CD4 ) will recognize foreignantigen on the surface of APC only if they areassociated with class II MHC molecules (MHCrestriction ).
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
7/12
HLA (MHC)HLA (MHC)
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
8/12
Class - I MHC Class - II MHC1- They include classical 1- They include classical
HLA- A ,B , C HLA- DP ,DQ , D Rnon classical non classical
HLA- G , E HLA - DM, DO2 - F ound on all nucleated cells 2 -F ound on certain cells
e.g. T - cells,and APCs.
3 -Presents the Ag to Tc 3 -Presents the Ag to Th
4 -Determined by serologic tests 4 -Determined by cellular testse.g. Microcytotoxicity tests e.g. Mixed lymphocyte reaction
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
9/12
Both classes could be typed by:ELISA , F low cytometry or molecular
techniques such as PC R .
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
10/12
Importance of MHCImportance of MHC
1 .Organ transplantation and graft rejection.2.MHC restriction :
a) Tc cells recognize the Ag in associationwith MHC I.b) Th cells recognize the Ag in association
with MHC II.
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
11/12
3.Disease association : It is found that thepresence of certain HLA antigens is oftenassociated with a particular disease;
- HLA- B27 with ankylosing spondylitis.- B8 with myasthenia gravis.-DR2 with multiple sclerosis.-DR4 with rheumatoid arthritis
-
8/8/2019 5-Major His to Compatibility Complex (MHC)
12/12
4.Paternity testing and forensicinvestigations
( An individual inherits one maternal andone paternal chromosome 6).