C-15B Free Communication/Slide Immune Function
During the last decade a surge of exercise immunological research examined the relationship between Imunoglobulin A (IgA) levels and incidence of upper respiratory tract infections (URTI). Early studies, for the most part, only reported the absolute values of salivary IgA that were observed. More recent reports attempt to account for the amount of IgA actually available on mucosal surfaces by reporting the secretion rate of IgA (s-IgA) or expressing IgA relative to total protein (IgA: protein) or osmolality (IgA: osmolality).
The purpose of this study was to determine which of the above standard IgA methods, either in combination or alone, serves best to predict the incidence of URTI.
A convenience sample of 100 college students (aged 18 – 24) participated in this study and reported to the lab every 6 weeks for 48 weeks (total number of lab visits = 8). Each time, unstimulated saliva was collected for 4 minutes at rest, measured for volume and frozen at −70 degrees C until analysis. In addition, subjects turned in standard study forms indicating the incidence of URTI in the preceding 6 weeks. Saliva was analyzed for IgA, protein and osmolality and s-IgA, IgA: protein and IgA: osmolality were calculated. Using two data collection points per season, Discriminant Function Analysis was employed to predict the number of colds. In each season, the variables IgA, s-IgA, flow, IgA: protein and IgA: osmolality all contributed to the prediction but s-IgA was the only variable with a significant relationship to URTI (p = 0.000) at all time points.
These findings suggest that among the various methods commonly employed to express IgA levels, the secretion rate of IgA may be the most useful clinical biomarker to predict the incidence of URTI.