IgG4-Positive Plasma Cells Are More Often Detected In Chronic Periapical Lesions Arising From Permanent Rather Than Primary Teeth.

AIM To characterize plasma cell subsets in chronic periapical lesions affecting permanent and primary teeth. METHODOLOGY Only chronic periapical lesions without root canal treatment were selected. Twenty-one radicular cysts and 7 periapical granulomas affecting permanent teeth and 19 radicular cysts and 4 periapical granulomas affecting primary teeth were assessed for immunoglobulin (Ig) light chain (kappa and lambda), Ig heavy chain (IgG, IgG4, IgA, IgM, and IgD), as well as plasma cell IHC markers (MUM1/IRF4, EMA, and CD138). The data acquired were analyzed by Student's t test, Mann-Whitney U, Friedman test followed by Dunn's multiple comparison test and Spearman's rank correlation. RESULTS All cases were polyclonal (having similar kappa/lambda light chain ratio). IgG was most abundant compared to other Ig heavy chains (all, p<0.001); like Ig light chains, but unlike IgA, there was greater expression of IgG in the primary compared to the permanent dentition, for both radicular cyst (p<0.001) and periapical granuloma (p=0.53). Notably, IgG4 expression was greater in the permanent than the primary dentition, for both radicular cyst (p<0.05) and periapical granuloma (p=0.65). IgM and IgD expression was scarce and variable, whereas plasma cell populations were detected efficiently through EMA, CD138, and MUM1/IRF4 markers, the latter being more sensitive in both dentitions. CONCLUSIONS There were slight variations in the Ig light and heavy chain profiles in chronic periapical lesions when comparing the permanent and primary dentitions. The ability of IgG4+ plasma cell infiltration to modulate inflammatory responses in chronic periapical lesions arising from permanent as opposed to primary teeth should be considered in future studies.