ABSTRACT Background: The immune response to bacterial antigens on mucosal surfaces may be modified in individuals allergic to aeroallergens due to a maturational or genetic difference or from the interaction between inhaled allergens and bacteria at the mucosa. Methods: Plasma from aeroallergen-allergic (n=97) and non-allergic (n=54) children and adults were initially tested for IgG1 (Th1) and IgG4 (Th2) reactivity to P6, a conserved outer membrane protein of H. influenzae. IgE binding was measured for some allergic donors. The development of the antibody responses to P6 was subsequently examined in the plasma from 1, 2 and 5 year old infants (n=35) taken from a prospective birth cohort. Results: IgG4 antibodies to P6 were readily detected in allergic people compared to non-allergic people (p<0.001), with a strong bias to the male gender. Some allergic subjects (35%) also had IgE antibody (1-10 ng/ml) that was not associated with IgG4 or gender. In the cohort study of infants, subjects who developed skin prick test positively to mite allergens by 5 years had an 85% reduction of the IgG1 anti-P6 antibody at year 2 (p<0.05), and unlike skin test negative infants this group showed IgG4 anti-P6 antibodies at 5 years of age. Conclusions: The antibodies of allergic people to a bacterial antigen included IgE and particularly for males IgG4 compared to the almost exclusive IgG1 response of non-allergic subjects. The IgG1 responses of 2 year old children who became skin test positive was markedly reduced and P6-specific IgG4 became detectable at 5 years.
- Th1 and Th2