Biology 432

Chapter 7 Lecture Notes

 

 

II. Genomic Map of MHC Genes (Reference Figure 7-15)

 

  1. Focus on Human HLA Complex

 

1.     Class I region spans 2000kb at the telomeric end

 

a.     Encodes classical class I MHC proteins

 

                                                              i.     HLA-A, HLA-B, HLA-C

 

b.     Encodes non classical class I MHC proteins

 

                                                              i.     HLA-E, HLA-F, HLA-G, HLA-J, HLA-X, HFE, MIC

                                                               ii.     Function is largely unknown

                                                                 iii.     Some ideas…

 

2.     Class II region spans 1000 kb at the centromeric end

 

a.     Encodes a and b chains of classical class II MHC

 

                                                              i.     HLA=DR, HLA-DP, HLA-DQ

                                                               ii.     Can be multiple a and b chain genes in some regions and all gene products can be expressed together in a given cell

                                                                 iii.     Net effect

 

b.     Encodes non classical class II MHC

 

                                                              i.     DM

1.     Encodes class II-like molecule (HLA=DM)

 

2.     Function

 

                                                               ii.     DO

1.     Expressed only in thymus and mature B cells

 

2.     Function

 

 

 

 

 

 

3.     Class III- located between Class I and Class II MHC

 

a.     Heterologous collection of genes encoding complement components, steroid hydroxylases, two heat shock proteins, and two cytokines (TNF a and TNF b)