OBJECTIVETo study the possible role of human β-defensins 1 (Hbd-1) and immunoglobulins A, G and M (IgA, IgG and IgM) in the development of recurrent pneumonia by measuring serum concentrations of the above indexes in infants with recurrent pneumonia and healthy infants.

METHODSSerum samples were obtained from 35 healthy children and 35 children aged from 2 to 24 months with recurrent pneumonia. Serum Hbd-1 concentration was measured using ELISA. Serum IgA, IgG and IgM concentrations were measured by immunonephelometry. The correlation of hBD-1 with IgA, IgG and IgM was evaluated.

RESULTSThe serum concentration of hBD-1 in infants with recurrent pneumonia (14±11 μg/mL) was significantly lower than in controls (18±11 μg/mL) (P<0.05), as was the serum concentration of IgA in infants with recurrent pneumonia (1.3±0.6 g/L vs 1.5±0.8 g/L; P<0.05). The serum concentration of IgG in infants with recurrent pneumonia was also significantly lower than in controls (9±3 g/L vs 13±5 g/L; P<0.05). There were no linear relationships between serum Hbd-1 and IgA, IgG and IgM (P>0.05).

CONCLUSIONSThe serum levels of hBD-1, IgA and IgG decrease in infants with recurrent pneumonia, suggesting disorders in the immune defensive function of the respiratory tract, and this may be one of the immunity related reasons for recurrent pneumonia in infants. It is of great clinical value to measure serum levels of Hbd-1, IgA, IgG and IgM in infants with recurrent pneumonia.