The IgG subclasses of antibodies to castor bean allergen in patients with allergic asthma: detection of a high incidence of antibodies of the IgG4 subclass.

Sera from patients with allergic asthma to castor bean dust were tested for specific antibodies in the red cell linked antigen-antiglobulin reaction (RCLAAR) using antiglobulin sera specific for IgE and the four subclasses of IgG. Approximately one-third of the patients with specific IgG antibodies had an antibody response that was predominantly in the IgG4 subclass. Two patients who were thought not to be sensitive to castor bean allergen, despite long exposure to the dust, did not have detectable IgE antibodies, but had high titres of IgG antibodies that were predominantly IgG4. Specific IgG4 antibodies to castor bean allergen were heat stable, did not appear to passively sensitize monkey skin in the PCA reaction and did not passively sensitize human basophils for the rosette reaction with castor bean-coated red cells.