Antigens and allergens: proteins

ANTIGENS AND ALLERGENS: PROTEINS
One major group of antigens are the proteins, which are widespread in all living things (see p23). The chemical variety of proteins makes them good antigens - there are plenty of distinctive 'handles' for an antibody (itself a protein) to seize on. Some other chemicals found in living things are less distinctive chemically and they do not readily act as antigens - fats and oils, for example. Complex carbohydrates - which are made up of chains of sugar molecules - can act as antigens, although the sort that we eat in quantity (such as the starch found in potatoes and bread) are very dull chemically and unlikely to be antigenic. These foods also contain proteins, however, and it is mainly these that act as antigens.
The other potential source of antigens in food, apart from the proteins, are small molecules such as phenols, amines and carotenoids. Some of these give the food its colour and flavour, others are there to deter animals from feeding on that food, or prevent it being attacked by bacteria and fungi. The majority of these small molecules are natural compounds, but artificial colours, flavours and preservatives greatly increase the number present in modern food.
Most of these molecules are too small to be antigens in their own right, but can act as haptens. To do this they must combine with proteins in the food itself, or with proteins in our bodies - something they may do quite easily as they tend to be very reactive. The extent to which these small molecules can act as haptens is somewhat controversial, and the issue is clouded by the fact that many of these compounds also have toxic or pharmacological (drug-like) effects on the body.
*38\180\8*

Allergies

ŤCanada Online Pharmacyť