Immunoglobulin levels and function in pre-school children with recurrent respiratory infections.

Thirty pre-school children with recurrent respiratory infections had a higher age adjusted mean serum IgG level than their siblings or a reference group. One index child had persistently low serum IgA, but mean serum IgA and IgM levels for the index children were normal. All of the 23 index children and 17 siblings studied had a four-fold or greater rise in virus neutralizing antibody titre. There was no correlation between serum immunoglobulin levels and frequency of infections. There was, however, a significant inverse correlation between salivary IgA levels when healthy and the number of infections experienced by each child in the study year. Salivary IgA levels rose considerably during acute infections.