All samples included junctional and sulcular epitheliums and connective gingival tissue. The gingival biopsies were divided into two portions. One portion was immediately placed in microcentrifuge tubes containing 250 μl phosphate-buffered saline and protease inhibitor cocktail (Sigma-Aldrich), and homogenized (Kinematica Polytron PT3100, Littau-Luzern, Switzerland), and then centrifuged at 13,000 g for 5 min at 4 °C. The resulting supernatants, devoid of debris, were stored at −70 °C until subjected to cytokine measurements by ELISA. The additional portion was stored in a tube containing RNA later (Ambion Inc., Austin, TX, USA) and stored at −20 °C for subsequent assays. Enzyme linked
coated for 24 h at 4 °C with 2 μg/ml of goat IgG anti-human IgA (Southern Biotech, Birmingham, AL, USA) in carbonate-bicarbonate buffer, pH 9.6. After being coated, plates were washed and blocked for 1 h at room temperature with bovine serum albumin (0.1%) in phosphate-buffered saline (PBS), pH 7.5. Diluted saliva samples (1:200 in PBS) were applied in triplicate, and plates were incubated for 2 h at room temperature. All experiments included serial dilutions (1.0, 0.5, 0.25, and 0.125 μg/ml) of a standard sample of human IgA antibody purified from serum (Southern Biotech). The secondary antibody was biotin-conjugated goat IgG anti-human IgA (Southern Biotech) at a dilution of 1:14,500. After incubation with a solution of streptavidin, conjugated with alkaline phosphatase (Southern Biotech) (1:500 in PBS, pH 7.5), antibody reactions were revealed by incubation with the substrate p-nitrophenyl phosphate disodium. In order to obtain the A405 units, plates were read in an ELISA plate reader (Epoch, Biotek, Winooski, VT, USA). Negative controls included the uncoated wells without saliva and primary antibody. For determination of IgA concentrations, absorbance values were plotted
PD184352 (CI-1040) against the standard curve obtained for the serial dilutions of the purified human IgA within a linear range. IgA levels were expressed as pg/ml of saliva. The gingival biopsies were analyzed by ELISA for IL-4 and IL-10 using commercially available ELISA kits (Quantikine; R&D Systems Inc., MN, USA). Assays were carried out according to the manufacturer’s recommendations using human recombinant standards. The optical density was measured at 450 nm according to recommendation. Results are reported as total amount (pg/mg) of each cytokine. Sites with cytokine levels below the detection limit of assay were scored as 0 pg. RNA extraction. The gingival biopsies stored in RNA later (Ambion) were evaluated for mRNA levels of IL-4, IL-10, IL-21, IL-21R, CD40L and glyceraldehyde-3-phosphate dehydrogenase (GAPDH).