Regulation- The MHC
The humoral system can generate antibody against anything, including self.
Regulation to prevent autoimmune disease involves T-helper cells and a set of cell
surface molecules first identified as playing a role in tissue rejection. The Major
Histocompatibility Complex (MHC) presents parts of antigens to T-cells.
- Called H2 in the mouse and HLA (for human lymphocyte antigen) in man.
- MHC gene products.
- Class I- present on the surface of all nucleated cells.HLA-A,B,C
- Class II- present on the surface of macrophages and B-cells.HLA-DR
- Antigens - processed to fragments, MHC molecules bind the fragments and
"present" them to T-cells which have the appropriate receptor.
- Hundreds of alleles, no two individuals alike.
- There are strong genetic pressures to keep our MHC as diverse as possible.
This pressure drives mate choice in many species, and some evidence suggests that
men and women are not indifferent to MHC type.
How to chose a mate.
Ref. Wedekind et al. Proc. Royal Soc Lond.B 260, 245(95).
- 49 Female and 44 Male students typed for HLA-A,B, DR.
- Men- wear cotton T-shirt Sunday and Monday night, remain odor neutral,
perfume free detergent for clothes and bed sheets, sleep alone,no tobacco,
no alcohol. Avoid sex and odor producing foods.
- Women- tested in the second week after the beginning of menstruation,
use nose spray during 14 days before the experiment, read P. Suskind's novel
'Das Pafum' to sensitize smell perception.
- On Tuesday, test women rate odors of six shirts, 3 worn by men with similar
MHC and 3 from dissimilar men.
- Shirts ranked for pleasantness and sexiness on a 1-10 scale.
- Repeat experiment using women on the pill.
Conclusions: as shown for animals, MHC differences are significant for
attraction. The preferences are reversed during pregnancy. Women should
avoid selecting a mate while on the pill. A pressure to select a mate with a different set of MHC proteins.
MHC- function to carry fragments of proteins on the cell surface.
Example 1- Exposed on cell surfaces, the space between the helicies can bind
peptides inside the cell and carry them to the cell surface
Example 2- HLA-A2 with a peptide from HIV
The immune response is controled by T-Cells.