The concentration and distribution of immunoglobulin isotypes (IgG, IgM, sIgA) and IgG‐subclass levels (IgG‐1–4) were measured in bronchoalveolar lavage fluid (BALF) in 47 children with chronic chest disease (age range 1.0–9.9 years) and 18 healthy controls (age range 1.0–6.25 years). Of these patients, 19 had nonallergic asthma (Group A), 19 suffered from recurrent pneumonia or chronic bronchitis (Group B), and 9 patients had IgG‐2 deficiency (Group C).

In all individuals, IgG was the predominant immunoglobulin in the lower respiratory tract, followed by IgA and IgM. In patients of Group A and B, IgG, IgM and IgA levels in BALF were significantly elevated when compared to controls. Assessment of IgG‐subclass concentrations in BALF revealed that IgG‐1 levels were increased in Group A and B when compared to controls (P < 0.05). Since this difference could not be explained by difference in age, it is possibly due to the inflammatory process at the mucosal level. IgG‐2 levels were elevated in all patients except those with IgG‐2 deficiency. IgG‐2 concentration in the IgG‐2 deficent group was lower compared to controls (P < 0.005) and patients in Group A (P < 0.0005) and B (P < 0.005). IgG‐3 levels were elevated in asthmatics in group A compared to healthy controls (P < 0.005). IgG‐4 concentrations were the same in all study groups.

Since IgG‐subclasses in percentage of total IgG were similar in BALF and serum, our results do not indicate a local production of any of the IgG‐subclasses in the respiratory tract. Pediatr Pulmonol. 2000; 29:443–451. © 2000 Wiley‐Liss, Inc.