Monday, April 25, 2011

Major Histocompatibility Complex: Fighter and Matchmaker

     Permit me to introduce myself.  My name is Major Histocompatibility Complex.  I am a protein and a strange paradox, both fighter and matchmaker.   I am on duty day and night, 365, working as the second line of defense against pesky and sometimes deadly viruses.  I am also a player, not in the naughty sense, in the immune response to autoimmune, bacterial, and parasitic infections.  Because I am the amazing protein that I am, my very presence elicits male and female human sexual attraction. I doubt there is any other protein that can claim to be both a protector and a matchmaker.
      When cells break down old proteins, they place the peptide fragments on the outside of the cell surface.  I pick up the fragments and display them for the immune system to inspect. If the fragments are normal, the immune system ignores them. If the fragments are abnormal, however, the immune system kills the cell.
     When certain foreign invaders activate me, such as poison ivy, I tend to cause a rather dramatic reaction. You will notice this reaction as a bright red, itchy rash. For that I apologize. On a more positive note, if I come across a dangerous mutation, such as cancer cells, I recruit my troops to come and destroy them.
     Now on to my role as cupid. Research studies demonstrate that men prefer the t-shirts of women with MHC scent dissimilarity. On the other hand, women prefer the scent of MHC heterozygosity and show no preference for dissimilarity. Since the majority of people are not aware of my existence or importance in the immune response, I believe I can move into a higher place of significance by marketing my attributes in human sexual attraction.

Thursday, March 17, 2011

What does the major histocompatibility complex do?
The major histocompatibility complex is a key player in the human body’s fight against viruses. The human body defends against the invasion of foreign viruses by recruiting antibodies, which attack and destroy the viruses. If a virus is sneaky enough to get past these initial antibodies of the immune system and enter a cell, another defense mechanism is required. This is when the major histocompatibility complex comes into action. In order to maintain their health, cells consistently break down old proteins and place the peptide fragments on the outside of the cell. The MHC comes in, picks up these peptide fragments, and displays them for the immune system to see. If all of the fragments are normal, without any viral peptides, the immune system moves on inspect another cell. However, if the fragments contain abnormal, viral peptides, the immune system attacks and kills the cell.

MHC is present in all mammals, and it is the primary set of genes that function in immune response, and further in disease resistance. Specifically, MHC encodes for proteins that are used by T-lymphocytes of the immune system. MHC has also been shown to play a role in resistance to viral, autoimmune, bacterial, and parasitic infections, in addition to its role in the immune response.

What are the diseases associated with MHC?
There are countless illnesses and diseases associated with MHC, because it is a key player in the immune response. One disease associated with MHC is HIV. In HIV infected cells, the expression of MHC is down modulated by the virus, which inhibits the cell destruction that would typically occur by the T-lymphocytes once the virus was detected. An example of MHC functioning in an illness that you may have encountered once or twice before is in your body’s response to poison ivy. The poison ivy toxins enter our skin cells and infect them. The cells breakdown some of the proteins within them and place the peptide fragments on their surface for the MHC to pick up. The MHC holds the fragments as the immune system examines them, determines that the peptide fragments are foreign and that the cells need to be destroyed. The itchy rash that occurs from contact with poison ivy is the direct result of the immune system attacking the cells! These are just two examples of the thousands of functions of MHC in illness and disease. It is amazing how one protein has such a large responsibility in the human body for maintaining health.  A defect in this protein can result in serious illness and/or death.

Looking for your soul-mate?!
Research was done to determine if the scent of dissimilarity in MHC genes played a role in human mate selection. It was found that men preferred t-shirts of women with the scent of MHC dissimilarity. Women, however, did not show a preference for the scent of MHC dissimilarity or allele frequency, but rather showed preference for the scent of MHC heterozygosity. It was also shown that men prefer the scent of women with common MHC alleles, rather than rare alleles. So, ladies and gentlemen, here is a new dating tip for mate attraction!