Major Histocompatibility Complex

MHC introduction

What are MHCs? Normal cell surface proteins produced by most

cells. They are like ID tags for cells. They are involved in allowing T cells to

recognize self vs. nonself.

What do MHCs do? MHCs bind to peptide fragments (parts of

chopped up proteins) and display/present them on the surface of the cell.

The T cells monitor the MHCs for evidence of an invasion of a cell or for foreign cells

*B cells do not interact with MHCs.

What types of MHCs exist? Class I MHC molecules

Found on almost all nucleated cells (not RBCs) Bonds to portions of antigens (peptide fragments) Presents them on the cell surface. Cytotoxic T cells can recognize and begin specific

defense

What types of MHCs exist? Class II MHC molecules

Found on dendritic cells, macrophages, & B cells (aka Antigen-presenting cells)

Bonds to portions of antigens (peptide fragments) that have been ingested and broken down.

Presents them on the cell surface. Helper T cells can recognize and begin specific

defense

Dendritic Cell

Macrophage

Macrophages

Are my MHCs similar to others? There are many different alleles for MHCs. Most of us are heterozygous for all of our

MHCs and therefore unique (except identical twins).

Class I MHC