Immunoglobulin isotypes in human minor gland saliva

Lower labial, upper labial, palatine (minor), and parotid (major) gland saliva samples from 18 young adult males were quantitatively assayed for the presence of IgA1, IgA2, IgM, and IgG. The mean (+/- standard deviation) concentrations of IgA (sum of IgA1 + IgA2) were 79 +/- 42 micrograms/mL (parotid), 111 +/- 42 micrograms/mL (lower labial), 69 +/- 72 micrograms/mL (upper labial), and 88 +/- 68 micrograms/mL (palatine). Total IgA concentrations were positively correlated among different minor-gland samples from the same subject, although these correlations did not reach significance. Upper-labial-gland saliva samples contained significantly (at least p less than 0.05) lower concentrations of IgA1 than those found in parotid or lower-labial minor-gland secretions. All three minor-gland sources of saliva contained significantly (p less than 0.002) higher levels of IgG than did parotid saliva. Upper-labial fluids had significantly (p less than 0.02) higher IgG concentrations than lower-labial saliva. IgM could be detected in 89% of parotid saliva samples and 75% of the palatine saliva samples. Palatine IgM concentrations (8.2 +/- 17.8 micrograms/mL) were significantly (p less than 0.05) higher than parotid IgM concentrations (0.6 +/- 0.4 micrograms/mL). IgM was detected much less frequently and at lower concentrations in lower- and upper-labial-gland saliva. These data reveal that minor-gland saliva from different oral sites may contain distinctive immunoglobulin isotype patterns, and expressions of host defense may vary within each micro-environment.