MHC Numbers Videos

Major Histocompatibility Complex (MHC) Overview

MHC Class 1

• Key Components:

  • HLA-A, HLA-B, HLA-C.

  • One allele inherited from each parent (maternal and paternal).

• Protein Structure:

  • Composed of a single alpha chain that is divided into three domains (alpha 1, alpha 2, and alpha 3).

• MHC Class 1 Functionality:

  • Each MHC class 1 molecule can present around 10,000 different peptides.

  • Total potential for heterozygous individuals: 6 distinct MHC Class 1 molecules (3 from each parent).

  • In homozygous conditions, only 3 different presenting molecules exist due to identical alleles from both parents.

MHC Class 2

• Key Components:

  • HLA-DP, HLA-DQ, HLA-DR.

  • This system requires two genes: one for the alpha chain and one for the beta chain from each parent, creating a combination of alleles.

• Protein Structure:

  • Each MHC Class 2 molecule consists of both an alpha chain and a beta chain.

• MHC Class 2 Functionality:

  • Similar to MHC Class 1, but since alpha and beta chains can pair differently, the number of combinations is doubled.

  • Total potential for heterozygous individuals: 12 distinct MHC Class 2 molecules available for peptide presentation.

  • If homozygous, similar to MHC Class 1, fewer MHC Class 2 molecules will be produced due to identical alleles.

Peptide Presentation Capacity

• MHC Class 1 and Class 2 can together present a total of:

  • MHC Class 1: 6 molecules x 10,000 peptides = 60,000 peptides.

  • MHC Class 2: 12 molecules x 10,000 peptides = 120,000 peptides.

• Total Peptide Presentation Potential:

  • Combine both classes: 60,000 (Class 1) + 120,000 (Class 2) = 180,000 different peptides.

Summary

• Understanding the genetic makeup of MHC Class 1 and Class 2 is crucial in immunology as it illustrates the diverse capabilities in presenting peptides from different pathogens to T cells.

• This diversity plays an important role in the body's adaptive immune response.