ABSTRACT
Antibodies are molecules that are capable of binding the target antigen with high affinity. The ability of the immune system to make antibodies with combining sites specialized to recognize different antigens arises from unique mechanisms that permit amino acid sequence diversification of the variable regions of antibody light-chain and heavy chain subunits. A rigid lock-and-key type of fit may not be conducive for catalysis. An imperfect surface alignment between a polypeptide and an antibody raised against a structurally related but different antigen could afford sufficient conformational freedom to permit facile catalysis. The tendencies toward increased airway smooth muscle constriction and inflammation in asthma are consistent with a deficit of Vasoactive intestinal polypeptide (VIP) brought about by autoanti-bodies. In experimental animals, VIP produces strong bronchodilation. The results with VIP administered to humans have been disappointing. It has been suggested that proteolytic breakdown and the presence of thicker cellular barriers may explain the low bronchodilator potency of VIP in the human.
