Wednesday, August 15, 2012


Recent outbreak of a peculiar allergy syndrome in some parts of the US raised serious concerns among food safety experts because of its lack of resemblance to any other allergies known earlier. Popularly known allergies from foods are invariably attributed to proteins of different nature contained in them but it is for the first time that a polysaccharide was implicated in human allergy. Detailed investigation revealed that this allergy is caused only in consumers eating meat and attempts to use this as an excuse for advocating vegetarianism does not make any sense. After all meat was being eaten for ages without this allergy raising its head till recently. Fortunately scientific investigations were able to pin point the source of the allergen and it should be possible to avoid by taking adequate precaution in protecting the meat animals from infestation with certain species of ticks. Here is an expose on the above unusual allergy. 

"Fortunately for those inflicted by this mysterious allergy, one of the victims of this strange disease was Dr. Thomas Platts-Mills, a reknowned University of Virginia immunologist. Dr. Platts-Mills and his colleagues at UVA have been on a mission to figure out just what is going on. They reported initially in 2009 on what appeared to be a wholly new type of food allergy: cases of anaphylactic shock that were not occurring immediately after a food was eaten as is typical for food allergies, but which had its onset 3-4 hours after consumption of the trigger. In the spring of 2011, the team of researchers came to an even more surprising conclusion: tick bites are causing meat allergies. The trigger turns out to be an oligosaccharide (a complex sugar, galactose-alpha 1,3-galactose or alpha-gal, if you like scientific names) contained in the cell on non-primate mammals -- that means a molecule that is in beef, pork, lamb, and other meats that is not found naturally in human cells. Alpha-gal in the tick's saliva sensitizes susceptible people when they are bitten; hives or anaphylactic shock result when the person subsequently ingests alpha-gal in meat".

Unique features of this allergy include its polysaccharide nature and delayed manifestation of allergic symptoms taking as much as 3-4 hours after consumption of the infested meat. It is intriguing as to how a polysaccharide like alpha-gal can get entry into the human digestive tract to cause allergy as such complex carbohydrates are not known to be digested in human system. Also why it should take hours for the allergy to be manifested is another unanswered question in this episode. Though the number of people affected by this latest allergy episode is very few, as a scientific curiosity, further investigation may reveal interesting biochemical evolutionary developments involving polysaccharide metabolism in human beings.


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