Functional maturation of nasal mucosa: role of secretory immunoglobulin A (SIgA)

Secretory IgA (SIgA) plays an important role in defending the mucous membranes of the upper respiratory airways from common infection. Studying and comparing the values and the daily variation of SIgA in nasal secretion could explain the largest number of upper respiratory infection, especially in children. Moreover, the ELISA dosage of SIgA in nasal secretion, sampled by cotton swabs positioned between septum and middle turbinate for 20 minutes every 4 hours 5 times in a day, can be easily performed and shows significant differences between the healthy child and the healthy adult. Nasal secretion SIgA mean value is lower in the healthy child than in the healthy adult. Circadian variation for healthy child showed the highest value at 7.00 a.m., while in adult the highest value was at 4.00 a.m. These knowledge on SIgA may help to explain the highest number of upper airway infection during childhood and clarify the physiological cycle of production. Thus, in performing a SIgA dosage the time of sample must be considered and preferably it should be made at a standardized time of the day.