Determination of secretory IgA and albumin in saliva of newborn infants.

As a first line of defence against microbial invasion, secretory IgA (sIgA) is the dominant immunoglobulin on all mucosal surfaces. In this study sIgA was determined by radial immunodiffusion in saliva samples of 63 newborn infants divided into the following age groups: (1) 1 day and younger, (2) 2-10 days. Concentrations of sIgA and albumin as well as their relation to age, postprandial time, gestational age and birth weight were analysed. sIgA could be detected in 75.0% (group 1) and 77.1% (group 2) of the saliva samples with a mean concentration of 190.2 mg/l (group 1) and 216.4 mg/l (group 2). Differences failed to reach significance. Concentration of sIgA was found to be independent of age but positively related to the concentration of albumin in the same saliva sample. In conclusion, this study provides evidence that high levels of sIgA are found in saliva of newborn infants, indicating the existence of a competent oral mucosal immune system as early as within the first 10 days of life.