A component of pigeon dropping extract that reacts specifically with sera of individuals with pigeon breeder's disease.

A component of pigeon droppings has been demonstrated to react with sera of individuals with pigeon breeder's disease, a form of hypersensitivity pneumonitis, by crossed isoelectric focusing. Similarly, exposed but asymptomatic pigeon breeders do not exhibit antibody to this component, even though they possess significant levels of antibody to other components of pigeon droppings. Purification of this disease-specific component of pigeon dropping was attempted by preparative isoelectric focusing, gel filtration, and affinity chromatography on an immunoadsorbent prepared with asymptomatic antibody. After repeated passage over the affinity column, complete purification could not be achieved. A rabbit antiserum made against the partially purified component revealed the presence of at least one other component that did not react with either symptomatic or asymptomatic sera. Despite these contaminants, the disease-specific component was characterized as a single polypeptide having a molecular weight of approximately 50,000 daltons and having an isoelectric point between 3.5 and 5.1.