Humoral immunity and bronchiectasis.

Area of Science:

• Immunology
• Pulmonology
• Medical Diagnostics

Background:

• Bronchiectasis is a known complication of primary antibody deficiency.
• The frequency of antibody deficiency as a cause of bronchiectasis is not well-defined.
• Assessing the need for immunological investigation in bronchiectasis patients is important.

Purpose of the Study:

• To investigate the humoral immune status of bronchiectasis patients.
• To determine the frequency of significant antibody deficiency in this cohort.
• To assess the appropriateness of routine immunological investigations for bronchiectasis.

Main Methods:

• Serum immunoglobulins, IgG subclasses, and specific antibodies to Haemophilus influenzae and Streptococcus pneumoniae were measured in 56 outpatients.
• Vaccination responses were quantified in patients with low antibody levels.
• Patients had a mean age of 59.6 years.

Main Results:

• Three patients (3/56) had low total serum IgG.
• Thirteen patients (13/56) had IgG subclass deficiencies, most commonly IgG4 (9/56).
• Twenty-nine patients (29/56) had low basal specific polysaccharide antibody levels, with one showing a specific defect in response to pneumococcal polysaccharide vaccine.

Conclusions:

• Antibody deficiency is an uncommon etiological factor in bronchiectasis beyond the fourth decade.
• Routine detailed investigation of humoral immune status is not generally justified in adult bronchiectasis patients.
• The findings suggest a selective approach to immunological testing in this population.