In vitro sorption of IgG to cementum

The nature of the interaction between root surfaces and gingival fluid proteins has not been studied. Therefore, a series of in vitro investigations were undertaken to develop an assay to determine sorption of prominent gingival fluid proteins to the cementum. In initial studies extracted teeth were immersed in various concentrations of whole human serum and incubated with rabbit anti‐IgG, IgA, IgM, and C₃ followed by anti‐peroxidaseperoxidase bridging reagents. Of the proteins analysed IgG sorbed to the highest degree in gross and microscopic evaluations. Remaining studies focused on quantifying IgG sorption, and thus root segments of known surface area were prepared and immersed in ¹²⁵I‐IgG. Sorption of IgG was calculated as 21.5 ± 0.27 ng/mm² when IgG was added at concentrations found in gingival fluid. Root fragments immersed in non‐IgG human serum reconstituted with specific amounts of ¹²⁵I‐IgG, sorped only 3.4 ± 0.9 ng/mm² of IgG, and direct measurement of IgG sorption in whole serum by the ELISA method gave comparable results. Moreover, pre‐coating of root segments with non‐IgG serum followed by incubation with ¹²⁵I‐IgG resulted in 74% inhibition of IgG binding. Results suggest that serum protein sorption to root surfaces can be quantitated and may be non‐specific and concentration dependent with respect to IgG.