Clinical and immunological evaluation of patients with mild IgG1 deficiency.

Serum IgG subclass concentrations were determined in patients visiting, the pulmonology out-patient clinic with chronic respiratory tract problems. A total of 24 patients with a serum IgG1 concentration < 4.9 g/l (i.e. below the reference range) and normal values for IgG2, IgM and IgA were included. Patients with a selective IgG1 deficiency were vaccinated with a 23-valent pneumococcal polysaccharide vaccine. There were nine patients with a poor antibody response to pneumococcal capsular polysaccharide antigens. Responsiveness to protein antigens was intact in all patients. Patients with pneumonia showed a significantly lower anti-polysaccharide response in the IgG2 subclass than patients without pneumonia. Patients with recurrent sinusitis showed a significantly lower response in the IgA isotype after vaccination with pneumococcal polysaccharide vaccine compared with non-sinusitis patients. It can be concluded that patients with recurrent sinopulmonary infections and a mild IgG1 subclass deficiency have an impaired IgG1 anti-polysaccharide response, which can extend to decreased IgG2 and IgA anti-polysaccharide responses.